Chapter 7  Reproduction

7.1 Reproductive Physiology and Behavior

It is important to have a comprehensive understanding of the reproductive physiology and behaviors of the animals in our care. This knowledge facilitates all aspects of reproduction, artificial insemination, birthing, rearing, and even contraception efforts that AZA-accredited zoos and aquariums strive to achieve.

A. cinereus: These otters are non-seasonal and thought possibly to be spontaneous ovulators (Bateman et al. 2009). The estrous cycle lasts 30-37 days, with breeding occurring year round. Some facilities report this cycle extending to every few months with older animals. Estrus lasts from 1-13 days. Behavioral signs of the onset of estrus may include increased rubbing and marking. Sexual behavior has been observed in pups as young as 6 months, with breeding behavior having been noted in animals (males and females) as young as 11/2 years. Successful breeding has been reported for 2.1-year-old females and 2.8-year-old males. There do not appear to be any significant environmental cues that are involved with the onset of estrus. Breeding pairs have been introduced at various ages and have been together for varying lengths of time before successful breeding occurs. It has been reported that pups from previous litters have interfered with copulation, but their presence had no bearing in any other way (Lombardi et al. 1998).

Recent work has shed light on litter intervals; Bateman et al. (2009) report: "In one female having three consecutive pregnancies during [their] study, the interval between the first parturition and subsequent progesterone increases owing to the next pregnancy was 169.25±11.15 days. This female was observed nursing her pups from the first pregnancy for the first 122 days of this intergestational time period."

Breeding pairs need to establish a bond for successful reproduction. The male pursues the female in courtship and most breeding occurs in shallow water. A single copulation can last from 5-25 minutes. Courtship behavior has been recorded from 1-3 days, at one-month intervals. Gestation is roughly 60-74 days (67-77 range, average 71.17±1.49 days reported by Bateman et al. 2009).

Pseudopregnancies do occur in this species, including in females housed in single sex groups (5 of 6 females housed together exhibited pseudopregnancy) (Bateman et al. 2009). Bateman et al. (2009) report: "...a mean duration of pseudopregnancy of 72.45±1.37 days (range: 62-84 days). The average interval length between sequential pseudopregnancies and/or pregnancies was 39.86±3.86 days (range: 17-92 days) in paired females and 134.50±48.94 days (range: 62-279 days) in the single gender group."

The sire plays a very active role in rearing the pups and should not be removed prior to their birth. Male behaviors include nest building, carrying pups, and bringing food to the pups during weaning.

Table 7.1.1: Ex situ population breeding parameters of Aonyx cinereus in North American zoological facilities 1980's and 1990's (Reed-Smith & Polechla 2002, Bateman et al. 2009)

A. capensis: This species does not appear to have a specific reproductive season (Mead 1989). Breeding in the northern hemisphere has been observed in November, January, March, and April (R.Meyerson, personal communication), with pups born in January-March and June-September (R.Meyerson, personal communication). Gestation length ranges from 63-80 days depending upon the source (Estes 1989; Reed-Smith & Polechla 2002; R.Meyerson, personal communication). In one ex situ population breeding situation, receptivity by the female lasted one day (Personal communication); in another, breeding occurred for 2-3 days (R.Meyerson, personal communication). Generally, 1-2 days before a female is receptive, the male will start following her around. All ex situ population pairs have shown an increase in the level of interactive play behavior for several days before and after breeding. All observed copulations have occurred in the water.

Table 7.1.2: Ex situ population breeding parameters of Aonyx capensis in North American zoological facilities 1980's and 1990's (Reed-Smith & Polechla 2002)

L. canadensis: These otters are seasonal breeders. Females mature reproductively as early as 12-15 months (rare reports of successful breeding at this age) to two years of age (typical). They are believed to be induced ovulators and experience delayed implantation (Chanin 1985; Reed-Smith 2001, personal observation). Recent evidence suggests that this species also may be capable of spontaneous ovulation (Bateman et al. 2009).

There is evidence that breeding season varies somewhat with latitude (Reed-Smith 1994, 2001; Bateman et al. 2005, 2009) and also may be influenced by seasonal availability of food resources (Crait et al. 2006); however, the authors of the one study (Crait et al. 2006) speculating on the influence of food availability acknowledge there could have been other things occurring, and their sample size was small. In general, breeding occurs in late spring (March-June) at northern latitudes and between November- February at more southern latitudes, with a gradient in between (Reed-Smith 2001). The estrus period lasts approximately 42-46 days, unless mating occurs (Chanin 1985). Bateman et al. (2009) found that "...peaks in fecal estrogen values occurred only during the defined breeding season from December to March". They also report, "...the estrus phase of their cycles [N=11] was observed just once per year with an average duration of 15.33±1.98 days (range: 6-54 days). The average duration of estrus elevation coincident with observed breeding (n=4) was 22.00±1.22 days (range: 19-24 days)." During this time, observations of ex situ populations suggest peaks of maximum receptivity are roughly 3-6 days apart with intervals of only mild receptivity during which the female may completely reject the male (Liers 1951; Reed-Smith 2001). The work done by Bateman et al. calls into question the estrus duration of 42 to 46 days traditionally cited; this is an area that should be researched further. Worth noting is the slightly longer estrus (21-23 days) reported in breeding versus non-breeding females (14-17 days); also the widely varying range of estrus duration (6-54 days) reported in the Bateman et al. study.

More recently, Bateman et al. (2009) have reported some additional interesting results from fecal hormone studies:

"In the observed pregnancies and pseudopregnancies (n= 12), the date of initial progesterone increase ranged from September 4 to January 14, and the timing was not correlated (r=0.53, P>0.05) with the female's geographic latitude (range: 27- 41°N) at the time of the pregnancy or pseudopregnancy. However, the date of the progesterone increase was correlated (r=0.66, P<0.05) with the female's geographic latitude at the time of her own birth (range: 27-42°N)."

The finding of a possible genetic component tying the timing of progesterone elevation in pregnant and pseudopregnant females to the female's birth latitude (instead of to their geographic location) is significant and requires further study. This impacts ex situ population management practices (transfers of animals to create breeding pairs) and the outcome of wild otter translocation/reintroduction projects (females may be giving birth too early or too late).

Males mature sexually at about two years; the production of male spermatozoa begins at this age. The male's testes begin to enlarge and spermatozoa production begins sometime in October/November, (or earlier at more southern latitudes) and testes remain distended until the end of the breeding season (Liers 1951; Reed-Smith 2001). Bateman et al. (2009) have shown that male testosterone levels increase seasonally to coincide "...with the increasing amount of daylight occurring after the winter solstice." Testosterone levels peaked at different times of the year corresponding with the male's latitudinal location; "As latitude increased, peak testosterone values appeared to occur later in the calendar year" (Bateman et al. 2009). They found that "for all NARO males, testosterone levels were elevated above baseline for an average of 101.8±78.97 days with peak levels being maintained for 25.50±7.51 days."

Females may show some, all, or occasionally none, of the following signs of estrus: increased marking of their territory, vulvular swelling, a slight pinking of the vulva area, increased rubbing, rolling and allo-grooming, increased interest in the male or the male's quarters, increased interaction between the female and the male to include chasing, tumbling, mutual grooming, sleeping together (obviously will only be apparent in pairs that do not normally do this), chuckling to the male, genital sniffing by the male of the female and vice-versa, and copulation. If male and female L. canadensis are housed alone, the pair should be introduced for breeding after the first signs of estrus appear or when the female shows unusual interest in the male's scent or enclosure. Absent any obvious signs, introductions should begin roughly four weeks prior to typical onset of estrus at the facilities latitude. Some facilities have reported a small amount of estrus-associated bleeding from the vulva, while others have not seen this. This is an area that requires further research. Female river otters also appear to be prone to urogenital infections, which frequently cause a milky, milky-blood-tinged, or slightly off colored discharge, which has been interpreted as a possible indicator of estrus or imminent parturition. If this kind of discharge is seen, the female should be closely observed and the condition monitored by a veterinarian.

Although copulation generally takes place in the water, it also can take place on the land. The copulatory act is vigorous, noisy, and can be lengthy with intromission lasting up to 60 minutes or more. A pair will copulate repeatedly over a period of an hour or two, then rest or forage for several hours before starting again. Copulation generally occurs several times over successive days. Copulations should be at least several minutes in duration to be successful. Short and/or infrequent copulatory bouts are generally not successful (Reed-Smith 2004b). Breeding activity may resume after a lull of 3-6 days throughout the course of a female's receptive period. During copulation, the male holds the female's scruff with his teeth, and positions the posterior part of his body around and below the female's tail (Liers 1951; Toweill & Tabor 1982). If the female is not receptive, or interested, she may roll on her back and paw at the male, nip and scream at him, or bite him and then run away.

Total gestation lasts from ~317 to 370 days reported by Liers (1951) and Reed-Smith (2001) or 302- 351 (average 333.3 ±15.7) days reported by Bateman et al. (2009); actual gestation is about 68-73 days (average 71.67±1.48) (Bateman et al. 2005, 2009). The parturient female may exhibit a number of different signs including: increased 'nest' building, swollen mammae, aggression towards exhibit mates or keepers, depressed appetite, frequent floating in the pool, refusal to leave the nest box, restlessness or lethargy. No pre-partum discharge has ever been noted. Parturition may occur from November through May, however, the peak time appears to be March through May in the northern latitudes (40-60 ̊N) and late December through February at more Southern latitudes (23-30 ̊N).

Estrus occurs soon after parturition lasting the same 42-46 days (recent hormonal work sets estrus as 15 to 22 days [Bateman et al. 2009]). Hamilton and Eadie (1964) record estrus as occurring not long after parturition. Most zoos that have observed postpartum estrus see behavioral signs 1-2 weeks after parturition.

The AZA North American River Otter PMP recommends that facilities interested in breeding should exchange one individual if the pair has been together since a young age and have not been successful at breeding. Based on previous hormone monitoring, the time of year in which each river otter's breeding season occurs is highly influenced by its geographic location/latitude (Bateman et al. 2005, 2009). Consequently, a possibility exists that some animals moved between widely varying latitudes may be physiologically out of synchrony and would require at least one breeding season to adapt physiologically to their new environmental cues, which are important for signaling the start of breeding season. This should be factored in when making transfer recommendations, but should not limit transfer options when creating new breeding pairs. The North American River Otter Husbandry Notebook (Reed-Smith 2001) provides greater detail on the breeding strategy and reproductive physiology of this species, and the AZA Otter SSP reproductive advisor (Helen Bateman, C.R.E.W., Cincinnati Zoo) is involved in on-going research.

In both NARO and ASCO, additional research is needed to improve endocrine monitoring of estrogen metabolites to further address these questions about ovarian cyclicity and ovulatory mechanisms.

Table7.1.3: Ex situ population breeding parameters of Lutra canadensis in North American zoological facilities 1980's and 1990's (Reed-Smith & Polechla 2002, Bateman et al. 2009)

L. maculicollis: Schollhamer (1987) reported that females came into estrus for the first time at about two years of age, but females typically do not conceive until they are three years old. Cycles vary between individuals, but average about 45 days, and estrus generally lasts 5-7 days. There is a postpartum estrus 2-3 weeks after parturition if pups are pulled or die soon after birth.
Males may attempt breeding at 1-2 years of age, but typically are not successful until they are 2-3 years old (Schollhamer 1987). Mating occurs in the water (Schollhamer 1987; R.Willison, personal communication) and involves the male neck biting the female and clasping her with his fore and hind limbs. Copulatory bouts may last up to 45 minutes, generally occur repeatedly over the course of several days (R.Willison, personal communication), and at any time during the day or night. There are no vocalizations associated with copulation in this species in zoos (R.Willison, personal communication) or in the wild (Reed-Smith in prep.). The rate of conception is increased if the male breeds the female for the entire 5-7 day cycle of a typical female; the conception rate is poor if the male only breeds the female for 2-3 days (Schollhamer 1987).

Gestation is roughly 60-63 days (R.Willison, personal communication). Ex situ population births in North America have occurred in January/February and April (R.Willison, personal communication). Births in the wild were recorded during September, based on one year of observation in Tanzania (Proctor 1963); ongoing research in Tanzania substantiates this observation with breeding observed twice in June (2006 and 2007), which would result in late August to mid-September births. However, work by Bateman et al. (2009) and observations of half-grown animals throughout the year in Tanzania indicate that births may occur anytime with a peak during August/September. Further research is required.

P. brasiliensis: Estrus generally occurs every three months, typically lasting 5-7 days with a range of 1- 11 days (Autuori & Deutsch 1977; Trebbau 1978; Hagenbeck & Wunnemann 1992; Wunnemann 1995b; Marcato de Oliveira 1995; Corredor & Muñoz 2004; Sykes-Gatz 2005, 1999-2006). The pair will begin exhibiting an increase in rough play and chasing behaviors a few days prior to breeding. These behaviors continue throughout the estrus period (S.Sykes-Gatz, personal observation). Copulation generally takes place in the water, but also may occur on land. The copulatory act is typically repeated several times a day over the course of 5-7 days and may last from 30 seconds to 30 minutes or more (Hagenbeck & Wunnemann 1992; V.Gatz, personal observation; S.Sykes-Gatz, personal observation).

There can be an estrus 5-7 days postpartum/post-loss of a litter that lasts for 3-5 days (Hagenbeck & Wunnemann 1992; Wunnemann 1995b). Delayed implantation occurs in zoos (Flugger 1997; Corredor & Muñoz 2004; Sykes-Gatz 2005, 1999-2006; V.Gatz, personal observation). Generally, this species produces one litter annually in the wild. In zoos, false or pseudo pregnancies are not uncommon in this species (Sykes-Gatz 2005). Typically, behavioral and physical changes associated with pseudo- pregnancy mimic those of actual pregnancy. These include: increased appetite and girth, aggression, changes in favorite fish, enlarged nipples and swollen vulva. It is unknown at this time how often presumed pseudo-pregnancies were actual pregnancies that resulted in the female consuming newborn pups (one known case) (Institution U reporting on institutional survey results). Gestation ranges from 64- 71 days, and in one case a gestation of 77 days occurred in a 9-year-old, although this was unusually long for this female (Autuori & Deutsch 1977; Trebbau 1978; Hagenbeck & Wunnemann 1992; Wunnemann 1995a,b; Corredor & Muñoz 2004; Sykes-Gatz 2005; V.Gatz, personal communication). Often the female's mammary glands become enlarged 30 days prior to parturition and the vulva may become swollen about 14 days prior. In zoos and aquariums, inter-birth intervals of 63 days, 74 days, and 94-103 days have been recorded in cases of pairs that lost litters at birth (Hagenbeck & Wunnemann 1992; Wunnemann 1995b).

Sexual maturity is reached at roughly 2 years of age. Females exhibit more obvious indicators of sexual maturity to include subtle physical changes such as some nipple enlargement, and obvious behavioral changes consisting of extreme mood swings, aggression towards or attacking siblings, and obvious attempts to try and assume the Alpha role within the group (Institution U). Other than testiclular development, which completes at roughly two years of age, males do not show similar behavioral changes (Institution U). Generally it is the sexually maturing females that present behavioral problems and cause social disruption in established family groups. Ex-situ population records show that at 2 years and 5 months, females can come into their first estrus, mate, and bear a litter at the age of 2 years 7 months. Males can mate at 2.5 years of age, with their first litter born when they are 2 years and 8 months. Due to limited records, it is not known if this is the earliest age at which giant otters can become sexually mature and bear litters. There is some indication that at least some giant otter females, from the age of 10-11 years, may experience a slowing or end to their reproductive capabilities. Females of this age may alternatively experience health problems or other difficulties during gestation and parturition. Whether this is due to their advancing age or a high number of previous litters is unknown. An 18 years and 9 month old male is the oldest successful sire on record (Sykes-Gatz 2005 & 1999-2006, V.Gatz, personal communication).

The International Giant Otter Studbook Husbandry and Management Information and Guidelines (Sykes-Gatz 2005) should be consulted for greater detail on management of this species, particularly their requirement for isolation and pupping den specifications.

Separation of Sexes/Conspecifics: 
If it is necessary to separate animals for reasons associated with reproduction (e.g., to promote or prevent it), a holding area connected to the exhibit is recommended; ideally this should include a pool with clean water available at all times, proper lighting, a sleeping or den box, enough floor space for grooming and drying areas, and at least one nest box that is heavily bedded to allow excess moisture to be removed from the animals' coats (Lombardi et al. 1998; Reed-Smith 2001). Holding pens should have non-climbable sides. If chain-link barriers are present, the sides should be covered with lexan or similar material to prevent animals from climbing too high and falling. See species- specific recommendations below.

A. cinereus: Females become very aggressive prior to parturition and remain so post-parturition. It is not necessary to separate them from the male or older siblings. It is necessary to provide multiple nest boxes. The sire plays a very active role in rearing the pups and should not be removed prior to their birth. Male behaviors include nest building, carrying pups, and bringing food to the pups during weaning. Access to pools and water sources should be strictly monitored to prevent newborns from drowning.

A. capensis: Pregnant females should be offered nest box choices and separated from the male to give birth (R.Meyerson, unpublished data). To date, records indicate two institutions have successfully bred this species in North America. One facility had one male with two females; both females bred and produced offspring. The other facility housed a pair. The animals were housed together 24 hours a day; females were separated to give birth at both facilities (Reed-Smith & Polechla 2002; R.Meyerson, personal communication). The male can be reintroduced to the female and pups when they are swimming well.

L. canadensis: There seems to be a mate preference for breeding, with some females showing a definite preference for particular male and lack of interest in others when they have a choice. Some successful zoos separate pairs for several months prior to the breeding season, introducing them every few days once the female's estrus begins. Others offer multiple mate selections to the females, and others have been successful keeping single pairs together year around. An extensive ex situ population study (N=13.14 animals) attempted to determine breeding associated behaviors in zoos and aquariums across the species over two years. The study's behavioral results show an increase in pair association, mutual grooming, and extended copulation in those pairs that reproduced successfully (N=3), but was inconclusive otherwise (J.Reed-Smith, data in preparation).

In the wild, males do not participate in pup rearing (Melquist & Hornocker 1983; Rock et al. 1994). In zoos and aquariums, parturient females should be given privacy (particularly for primiparous females) and nest box choices supplied with plenty of dry bedding (all females). Males have been successfully left in the exhibit with parturient females in large exhibits that provide numerous visual barriers and allow the male to stay out of the female's sight. In all other cases, the male and female should be separated prior to the birth to prevent injury to the male or neglect of the pups by the female. In multi-female groups, other females may also need to be separated from the parturient female. When separated, the male or non parturient female should not be required to pass the parturient female's den to enter the exhibit; if this cannot be done, the other animals should be removed entirely from the exhibit or the female sequestered away until she deems it time for the pups to meet the male (see below). Males can be reintroduced to the female and pups once they are swimming proficiently, as early as 60-75 days or more typically by 80 to 90 days (Reed-Smith 2001).

Actual gestation is calculated at roughly 68-73 days (Bateman et al. 2009.); pair separation should occur either when the female becomes aggressive towards the male or roughly 10-14 days prior to anticipated parturition date. Due to this species' delayed implantation and total gestation time of >10 months, it is often difficult to anticipate delivery date, particularly for primiparous females. In these cases, staff should base their management decisions on the female's behavior. If she becomes aggressive to the male or other exhibit mates, begins to show excessive nesting behavior, or spends increasing amounts of time in her nest box, the pair should be separated. It is important to remember that the female should be monitored for health issues during this time, as these behaviors also can be signs of illness.

Management change should be scheduled so that they do not interfere with the birth and rearing of the pups. Any modifications to the exhibit should be finished several months prior to possible pupping season. Denning/nest box choices should be introduced at least one month prior to possible pupping season. Changes in management routines, e.g., closing the female in holding at night, closing her in holding alone, etc. should be introduced to the female at least a month prior to the possible parturition period to allow her time to become comfortable with the new routine. If the male will have to be removed from the exhibit entirely, this should be done several weeks prior to possible parturition to allow the female a period of adjustment.

Generally, the best way to handle pair separation is setting up the female in off-exhibit holding (providing there is adequate space). Once the pups are old enough to begin swimming lessons (some females begin this instruction as early as 30 days, more typically at 40-50 days), the family group and the male can be alternated on exhibit. When the pups are swimming well, after about three months, the male can be introduced to the family group. This should be handled, as with any introduction, via olfactory, visual, and then physical introduction to the female alone first, and under controlled circumstances as far as possible (see Introduction/Reintroduction).

L. maculicollis: Females should be separated from the male at about gestation day 55 (gestation ranges from 60-63+ days calculating from the day of last observed breeding) (Schollhamer 1987), or when she shows signs of aggression towards the male (R.Willison, personal communication). Males should be separated from a pregnant/nursing female unless the exhibit is large enough for him to stay out of her line-of-sight. When separated, he should not be required to pass the female's den to enter the exhibit; if this cannot be done, he should be removed entirely from the exhibit or the female sequestered away until she deems it time for the pups to meet the male. Females with pups are more of a danger to the male than typical males are to the pups. Males can be reintroduced to the female and pups once they are swimming proficiently and eating on their own, typically when the pups are roughly four months of age (R.Willison, personal communication).

Females should always be given a choice of denning sites with bedding provided for them to use if it is wanted. Schollhamer (1987) states that at Institutin A female spotted-necked otters did not use bedding of any kind. Kruuk (1995) references the presence of soft, leafy substrate or pebbles in most dens he or other researchers located. Brookfield Zoo used a nest box made from molded plastic and fiberglass measuring 68.6 cm long x 51 cm wide x 38.1 cm high (27 in x 20 in x 15 in) with holes drilled in the bottom for drainage. The box was placed 4 cm (1.5 in) off the floor, and was accessed via a drop- guillotine door 25.4 cm high x 20.3 cm wide (10 in x 8 in) (Schollhamer 1987).

P. brasiliensis: This species lives in family groups with pairs and older offspring jointly raising new pups. Therefore, a pair should never be separated during pregnancy or pup rearing. Typically, animals should not be separated from the family group unless health problems, change in social status, or family friction develops. Removal of any member of a group during pup-rearing, or close to parturition, will likely cause litter loss. Animals separated for extended periods should be put through a standard introduction (see Chapter 4, section 4.3), including visual, acoustic, and olfactory contact at first, and then physical contact (Sykes-Gatz 2005). Even a few days of separation have been known to be long enough to cause difficulty, such as serious fighting, when reintroduction was attempted (K.Lengel, personal communication).

Secondary accommodations should be provided for giant otters to allow for the temporary separation of family members if needed. These secondary enclosures should provide husbandry conditions similar to primary enclosures.

Nursery Groups: 
Typically, nursery groups of neonates are not seen in river otter species. The following species-specific information is available:

A. cinereus: All otters of a family group take an active role in caring for the young. It is not uncommon for the sire and older offspring to be involved in all behavioral activities of the mother and her newborns.

A. capensis: Nursery groups are not typical for this species.

L. canadensis: Nursery groups are not typical for this species. Helper otters have been reported from the wild. In these cases, a female with partially grown pups is accompanied by another adult female (Rock et al. 1994; R.Landis, personal communication). There are reports of two adults with young animals, but the relational composition of these groups is unknown (Reed-Smith 2001).

L. maculicollis: Nursery groups are not reported for this species, but further research is needed. Adolescent groups (roughly one year or older) have been reported (Reed-Smith in prep.).

P. brasiliensis: As with the Asian small-clawed otter, generational groups are typical in the wild; true nursery groups are not reported for either species.

Separation of Mother and Offspring: 
The timing of mother-offspring separations can have long-term effects on the development of otter pups and on the reproductive success of adults. The following species-specific information is available:

A. cinereus: Adolescents are not forced from the group. In zoos and aquariums, it is necessary to remove older offspring, as the group size can become quite large in a year, leading to aggression resulting from over-crowding. Typically, the age at which older pups should be removed varies with the size of the exhibit and compatibility of the group.

A. capensis: The timing of emigration is unknown in the wild, but emigration of sub-adults at some point is presumed.

L. canadensis: Pups can be removed from the dam when weaned, if absolutely necessary. It is preferable that they be left with the family group until they are at least 8-9 months of age (Reed-Smith 2001) or six months old at a minimum. In the wild, pups will generally leave the female when they are 9 months to over one year of age (Melquist & Hornocker 1983; Melquist & Dronkert 1987).

L. maculicollis: No specific information on emigration is available, but pups should be left in the family group for at least 6-9 months and be removed before reaching sexual maturity. Roving groups of what appear to be young animals, possibly dispersing, and pups remaining with their mothers (or at least utilizing the same core area simultaneously for one year) has been reported in the wild (Reed-Smith in prep).

P. brasiliensis: Pups from previous litters up to the age of about two years generally stay with the family group (Schenck & Staib 1994); after this time, they emigrate to set up a new family group. In the wild, Duplaix (2002) reports that sub-adults may leave the family group after 2 years, before birth of the next litter, or be pushed out by the adults with a fight. Staib (2002) found that animals dispersed at the age of 2-3 years, and separations were gradual, without aggressive behavior. In zoos and aquariums, offspring should be left with the parents for at least the first 6-12 months of life, but preferably they should be left together until they reach sexual maturity at approximately 2 years of age (Sykes-Gatz 2005, 1999-2006; Corredor & Muñoz 2004; G.Corredor, personal communication; V.Gatz, personal communication). This provides a more natural social structure, and allows older siblings to gain experience helping to rear pups, which is highly beneficial towards developing their future parenting skills. Caution should be taken, as in one case three ex situ population-born otters between the ages of 6.5-8.5 months were suspected of competing for milk with their younger siblings. This behavior persisted over a two-month period, causing the death of a younger sibling and the necessary removal of the emaciated survivors for hand- rearing (Flugger 1997). In two other cases, sub-adults were suspected to have caused litter loss because of their over-zealous play with, and attention to, their younger siblings (Flugger 1997; G.Corredor, personal communication). However, experience has shown that removal of any member of a giant otter group during pup-rearing or close to parturition will likely cause litter loss due to the excessive stress caused to the parents by this human disturbance and unnatural social structure change (Flugger 1997; Sykes-Gatz 2005, 1999-2006). If it is necessary to remove a group member from a breeding pair, it should be done when the mother is not pregnant or at the latest in the early stages of pregnancy. Pups younger than 6 months of age should not be removed.

Reproductive Hormone Tracking: 
Research utilizing techniques to identify reproductive state in these species is ongoing. At this time, it appears that ELISA protocols for testing hormonal secretions in fecal samples is successful in determining pregnancy in Asian small-clawed and North American river otters (Bateman et al. 2005, 2009). The reproductive physiology advisor for the AZA Otter SSP should be contacted for more information.

Pseudopregnancy has been reported for most otter species and is an area that requires further research. For information on the status of current research into this and other reproductive physiology, behavioral, and health issues, contact the current AZA Otter SSP Chair for the most recent information. Institution T reported a possible pseudopregnancy accompanied by increased aggressiveness and voaclizations as well as decreased focus during training sessions. Physical symptoms included pinking and enlargement of nipples.

Facilities for Reproduction: 
All expectant females should be provided with nest box choices that are located away from pools, and these should be well stocked with dry bedding. The size of these dens should allow ample room for bedding, pups, and for the female to turn around (A. capensis, L. canadensis, and L. maculicollis). Highly social species (A. cinereus and P. brasiliensis) should be provided with a nest box or pupping den that allows enough room for the entire group. See species- specific information below and Sykes-Gatz for dimensions and recommendations on pupping dens and nest boxes.

A. capensis: Nest boxes 8-10 cm (3-4 in) wider and taller than those used for L. canadensis (see below) are suitable for this species. Nest box choices and plenty of bedding should be provided 2-3 weeks before expected parturition date to allow the female to become comfortable with them. At this stage, females show a weight gain in the axillary region (R.Meyerson, personal communication). Some females prefer to pup without the bedding, and will remove it from their nest box; in these cases, allow the female her choice.

L. canadensis: Due to delayed implantation (also known as embryonic diapause), it is difficult to determine when a female is near parturition; therefore, close attention should be paid to her behavior changes, appetite, and physical appearance. These may include, but are not limited to: aggression towards exhibit mates or keeper staff, refusal to leave holding or her den, increased or decreased appetite, obvious teat development, slow movements, more frequent floating in the pool, and lethargy.

Parturition boxes should be at least 50.8 cm long x 45.72 cm wide x 38.1 cm high (20 in x 18 in x 15 in), be large enough for an adult animal to move around in, and large enough to accommodate the pups. Slightly smaller boxes with entrance foyers have been used successfully. This box type allows the female to be secluded in a location near the pups but not actually with them. Females should be offered denning choices for parturition and den choices of different sizes to allow for the growth of the pups.

Dimensions for a sample nest box are as follows: total width = 68.58 cm (27 in), chamber width = 48.26 cm (19 in), chamber depth = 45.72 cm (18 in), entrance foyer = 20.32 cm (8 in), entrance diameter = 16.5 cm (6.5 in), and 26.67-38 cm (10.5-16 in) high, with a 16.5 cm (6.5 in) height at the end of the ramp, and a 36.83 cm (14 in) height at the entrance to the ramp. The top is hinged on one side for easy lifting and cleaning. The ramp floor is made of wire mesh and the chamber floor should have drainage holes.

L. maculicollis: Spotted-necked females should be separated from exhibit mates prior to parturition at roughly day 55 of a 60-63 day pregnancy (Schollhamer 1987), or when the female begins to show a tendency to keep the male or other group members away from her denning area (R.Willison, personal communication). Generally, females give birth to one pup, sometimes twins (Schollhamer 1987; R.Willison, personal communication).

Secured sleeping dens (R.Willison, personal communication) or nest boxes that are 68.6 cm long x 51 cm wide x 38 cm high (27 in x 20 in x15 in) have been successful (Schollhamer 1987). Typically, females do not use any nesting material, however, bedding should be offered to all females.


Females should be given rubber tubs in which to swim just prior to parturition (1-3 days), and for the first two months or so of the pup's life. The female will begin to bring the pup(s) out of the denning box when it is roughly 3-4 weeks old; at this point, she should start teaching pups to swim by placing them in the water tub for a few minutes at a time. It is important that the water level in tubs be kept high (which allows pups to hang on the lip), or that tubs/pools have a slopping ingress and egress so pups can get out of the water. While females are typically very vigilant, pups have suffered from hypothermia from being left too long in the water (Schollhamer 1987).

P. brasiliensis: Giant otters (especially mothers) are susceptible to any human disturbance, especially within the surroundings of the natal den, and to discomfort created by enclosure variables (see in Sykes- Gatz 2005; 2.1 & 6.7; Sykes-Gatz & Gatz 2007). Several steps have been recommended to increase the comfort of the reproductive pair and older siblings, and improve pup-rearing success (Sykes-Gatz 2005):

# Build a positive keeper-animal relationship and allow only familiar staff to work with the otters after parturition
# The provision of food and clean water should be accomplished with minimal disturbance to the otters during pup rearing.
# Cleaning should be minimal and not disruptive to the otters.
# Reduce stress as far as possible, including loud sounds, unfamiliar people, and the introduction
of anything new to the exhibit.
# Prohibit visitor and zoo staff (other than immediate caretakers) access to the enclosure area.
# Provide multiple nest box choices located in separate locations to allow parental choice according
to their comfort level.
# Provide appropriate substrate and exhibit conditions to include the recommended land/water
ratio, substrate depth, digging opportunities, and dry substrate conditions.
# Isolation of the natal den and limitation of all human activity in the vicinity at and prior to the birth
is very important.
# Monitoring of the natal den and early pup rearing should be done from a hidden location or
carried out via audio and video monitoring equipment with infrared capability.
Based on 15 years of experience Institution U offers these guidelines as key to their successful breeding of this species:
# High level of intelligence and ease of the otters willingness to participate in operant conditioning
# Keepers' ability to know personalities of individual otters and understand how each fits into the
group dynamic.
# Keeper/animal bond and noting observations of otters' cohesiveness through family bonding.
# Strong social bonds are key to the success of the group; this includes the keeper
# Maintaining consistency before, during and after pups (includes; keeper activity schedules,
routine noises (e.g. radio play, noise level in general), cleaning and operant conditioning.
# Allowing the giants to become accustomed to all keeper activies and multiple keepers.
# Close observation of postnatal development and family structure dynamics including changes
(sibling interactions, teaching young, and social status of each individual).

Exhibits should be provided with multiple den sites; these can include both natural (e.g., dug by the otters) and man-made dens. Dens are often 4.5-9.5 m2 (48-102 ft2) in size. Ideally, pupping boxes just large enough to hold the adults, older siblings, and pups should be placed within the dens to allow the parents choices and maximum privacy. Dens should be provided in locations where the animals are removed from all disturbances (Sykes-Gatz 2005). Nest box temperatures should stay above 20 °C (68°F). Den area temperatures (where nest boxes were located) were increased to 22-23 °C (71.6-73.4 °F) during pup-rearing at one institution (Flugger 1997). P. brasiliensis in ex situ populations have been observed to have a low heat tolerance (Carter & Rosas 1997; S.Sykes-Gatz & V.Gatz, personal observation), and pups can be very susceptible to overheating or becoming too cold. Very young pups especially do not thermo regulate well (Read & Meier 1996). Pups <5 months of age should not be exposed to air temperatures below 15 °C (59 °F), and pups >5 months of age should not be exposed to air temperatures below 10 °C (50 °F). Parents should be prevented from taking pups outside if temperatures fall below these parameters. Precise recommendations for enclosure and den design are provided by Sykes-Gatz (2005). This publication is available on the Otter Specialist Group website ( and going to the Otters in Captivity Task Force under Library.

In at least the first days after parturition, dams have been seen to be a little protective of the pups when the sire tries to become involved with them. This is not abnormal behavior. Soon afterwards, the sire will become equally involved (and his involvement will be accepted by his mate) in the care of the pups. Under normal situations, it may appear that both parents and older siblings sometimes treat their pups a little roughly. This kind of behavior may be carried out whether otters are in the nestbox, on the land, or in the water. This is especially evident when parents or older siblings are teaching pups to swim. This seems to be normal behavior for giant otters. However, the situation should be closely monitored to ensure that parents and older siblings are not actually too rough with their pups, as this is abnormal. Starting at 2-3 weeks of age, parents will push pups under the water then let them go to resurface on their own or with help. This may be repeated several times to teach them to submerge (Autuori & Deutsch 1977). Parents and older siblings have been known to teach ex situ population-born pups to submerge starting at 2-6 weeks of age by holding the pup with their front feet and rolling over sideways 360° a few times; this has been called 'Eskimo rolling' (Sykes-Gatz 1999-2006). Pups also may be gently pushed or pulled into the water to encourage swimming.

The following is a list of parental and older sibling behaviors observed ex situ that often resulted in pup death and may be a result of sub-optimal environmental or rearing conditions:

# Pups handled, carried, or moved to pools or new nest boxes very frequently. Generally, pups < 2 weeks of age should not be taken into pools, if this occurs it is rare. Pups 2 weeks old or older should not be taken into pools more than 1-2 times per day. Older pups may tolerate more frequent moving, generally no more than 3 times a day. In general, pups should not be moved to new nest boxes on a daily basis or at most more than once or twice a day. Frequent movement of pups should be closely monitored without disturbance to the parents.
# Too frequent entering of the nest box by the parents, e.g., 1-3 times per hour is normal, more can be abnormal.
# Excessively forceful pushing or throwing of the pups into pools or elsewhere may be indicative of a problem and should be monitored, again without disturbance to the parents. In general, excessively forceful, rapid, or uncoordinated interactions with pups are abnormal.
# Inappropriate mothering behavior by the dam. This may include: neglecting the pups, not lying still or lying incorrectly preventing pups from nursing, not staying long enough to allow for sufficient nursing by the pups, not visiting the pups frequently enough to allow for sufficient nursing, and pulling pups off their teats. These behaviors may indicate an inexperienced or stressed mother, or problem with lactation, such as insufficient milk production. This failure to produce sufficient milk amounts has been known to occur for varying periods of time as a reaction to stress.
# Biting, hitting, or laying on the pups; attempted drowning of, or eating pups

Further information on these abnormal occurrences can be obtained from Wunnemann (1995a,b), Flugger (1997, Autuori & Deutsch (1977), Corredor & Muñoz (2004), Sykes-Gatz (2005) and Sykes-Gatz and Gatz (2007).

7.2 Assisted Reproductive Technology

The practical use of artificial insemination (AI) with animals was developed during the early 1900s to replicate desirable livestock characteristics to more progeny. Over the last decade or so, AZA-accredited zoos and aquariums have begun using AI processes more often with many of the animals residing in their care. AZA Studbooks are designed to help manage otter populations by providing detailed genetic and demographic analyses to promote genetic diversity with breeding pair decisions within and between our institutions. While these decisions are based upon sound biological reasoning, the efforts needed to ensure that transports and introductions are done properly to facilitate breeding between the animals are often quite complex, exhaustive, and expensive. Also, conception is not guaranteed.

At this time AI is not used in any otter species but semen collection techniques and preservation are being researched by Bateman et al. (2005, 2009).

7.3 Pregnancy and Parturition
It is extremely important to understand the physiological and behavioral changes that occur throughout an otter's pregnancy. This information is contained in Section 7.1.

7.4 Birthing Facilities
As parturition approaches, animal care staff should ensure that the mother is comfortable in the area where the birth will take place, and that this area is "baby-proofed." This information is contained in Section 7.1.

7.5 Assisted Rearing
Although mothers may successfully give birth, there are times when they are not able to properly care for their offspring, both in the wild and in ex situ populations. Fortunately, animal care staffs in AZA- accredited institutions are able to assist with the rearing of these offspring if necessary.

Hand-rearing may be necessary for a variety of reasons: rejection by the parents, ill health of the mother, or weakness of the offspring. Careful consideration should be given as hand-rearing requires a great deal of time and commitment (Muir 2003). Before the decision to hand-rear is made, the potential for undesirable behavioral problems in a hand-reared adult should be carefully weighed (e.g., excessive aggression towards humans (rare in most otters), inappropriate species-specific behavior, etc.) and plans made to minimize deleterious effects on the development of natural behaviors as far as possible. This may require extensive time commitment on the part of staff, plans for fostering, relocation of the young to another facility, exposure to species-specific sounds, etc. At this time, the AZA Otter SSP is recommending hand-rearing of all otter species, if necessary.

Pups that have been abandoned by their mother should be removed as soon as possible to prevent infanticide. See Chapter 6, section 6.5 for a 'Neonatal Examination and Monitoring Protocol'. Offspring that are not receiving milk will be restless, possibly calling continuously, may be hypothermic, and scattered around the enclosure. Another indicator of trouble would be the female moving around the exhibit continuously while carrying the young; this could mean she is not comfortable with the denning provided, or there is a problem with her or the pups (Muir 2003). If it is necessary to remove offspring because of an exceptionally large litter, it is best to remove two of the largest pups. The temptation is often to take the smallest, but they stand the best chance if raised by their mother. Hand-rearing of singletons is more likely to lead to severe imprinting on humans than if they have a conspecific to play with (Muir 2003). The AZA Otter SSP recommends that singleton pups being hand-reared be placed together, if at all possible. To date, fostering has been attempted once with otter pups and was successful. A pup was taken from a female with no milk and sent to another facility where their female was already nursing pups. In these cases, the AZA Otter SSP management team should be consulted first. Other institutions have been successful at supplement feeding pups left with their mother. Young otters removed for hand-rearing should not routinely be reintroduced to the parents with an expectation of acceptance. Introductions of hand-reared animals should follow procedures specified in the Introduction/Reintroduction section.

Physical Care Protocol: 
Incubators provide the best source of warmth. Heat lamps are too intense and can be dehydrating. In an emergency, hot water bottles wrapped in a towel may be placed in a box with the pups nestled next to it, or they can be warmed slowly by placing them next to your body (Muir 2003). Pups may feel more secure if wrapped in layers of towels; this also aids in keeping them warm (Muir 2003). Pups should be dried after feeding/bathing to prevent hypothermia until they are proficient at self- grooming. The normal body temperature for pups is unknown, but the animal should feel warm to the touch.

Altricial young are unable to self-regulate their body temperature during the early postnatal period and require an external source of warmth. If an incubator is not used, it may be necessary to place a heating pad, set on low, under the housing container until the pups are able to thermo regulate. Meier (1986) and Wallach & Boever (1983) recommend 29.4-32.2 °C (85-90 °F) and 50-60% humidity as the desired incubator setting for neonate mustelids. The temperature should be gradually reduced to room temperature, 21.2-23.9 °C (70-75 °F), over the course of about three weeks (unless the neonate becomes ill). Litters of pups are less likely to need additional ambient heat since huddling together may provide an adequate amount of warmth. External temperatures should be closely monitored to prevent hyperthermia. Rapid and/or open-mouth breathing, restlessness, and hair loss are indication of an external environment that is too warm.

Pups should be stimulated to urinate and defecate at least 4-5 times each day for several weeks, generally before feeding. However, some animals may respond better to post-feeding stimulation. The genitals and anal area are rubbed gently with a finger, towel, or damp cotton to stimulate the pup to urinate and have a bowel movement. If pups do not urinate and/or defecate after two successive feedings, the formula should be reviewed and their health status evaluated immediately.

Specific environmental parameters, formula information, etc. for hand-rearing L. canadensis and P. brasiliensis pups can be found in the North American River Otter Husbandry Notebook, 2nd Edition (Reed- Smith 2001) and International Giant Otter Studbook Husbandry and Management Information and Guidelines (Sykes-Gatz 2005), respectively; these are available on the Otter Specialist Group web site ( The hand-rearing of giant otters (P. brasiliensis) is somewhat different than that of other otter species, because their development is slower. Detailed information on the types of records needed, signs of illness, etc. are available in the Giant Otter Husbandry Manual (Sykes-Gatz 2005).

Feeding Amount and Frequency: 
Initially, the animal should receive only an electrolyte solution for the first 2-3 feedings, depending on how compromised it is. This is to rehydrate the animal and clear the stomach of the maternal milk. The artificial formula should be started at a diluted concentration, generally at a 1:4 ratio (mixed formula: water) for another 2-3 feedings. It generally takes about 72 hours to get the animal on full-strength formula by gradually offering higher concentrations. Depending on the species, 4-5 feedings of each concentration level (1:2, 1:1, 2:1, full-strength) are required to allow for adaptation and to minimize the onset of digestive problems, particularly diarrhea. During the initial phase (24-36 hours), weight loss is to be expected, but the animal should quickly begin to maintain weight and then start gaining as the formula concentration increases. It is important that the pups are not given full strength formula too soon (in less than 48 hours after pulling for hand-rearing) because the likelihood of diarrhea is extremely high. Diarrhea is of particular concern with neonates less than one week of age, because they have very little or no immunity to infections.

Pups should have a normal body temperature and be properly hydrated before starting them on formula. Young mammals require a specific amount of calories per day for optimum development and growth. A nutritionally dense milk formula will allow for fewer feedings than more dilute formulas that are low in fat or protein. A method for calculating the volume of food to be offered per meal as well as total daily amount is presented below.

The Basal Metabolic Rate (BMR) or Basal Energy Requirement (BER) is the amount of energy (kcal) an animal needs for basic metabolic function at rest in a thermo-neutral zone. This represents the amount of calories it needs to stay alive, without having to use energy to maintain normal body temperatures (Grant 2004). Mustelids have a higher metabolic rate per body weight than many other placental mammals. For that reason, Iversen's equation of 84.6 x body weight (in kg) 0.78 (Iversen 1972) is used rather than Kleiber's equation of 70 x body weight (in kg) 0.75 (Kleiber 1947) typically used for other species. Therefore, for a 200g river otter, the BER would be: 84.6 x 0.2 0.78 = ~24 kcal/day.

Once the BER is established, the Maintenance Energy Requirement (MER) can be calculated. This measurement determines the amount of calories the animal needs to function in a normal capacity at its life stage. For adults in a maintenance life stage, the BER is multiplied by 2. For pups that have a higher metabolism and are developing and growing, the BER is multiplied by 3 or 4 (Evans 1985), depending on the species and other factors.

The stomach capacity for most placental mammals is 5-7% of the total body weight (Meehan 1994). Convert the body weight into grams to find the stomach volume in ml (cc). To calculate the stomach capacity in ounces, convert body weight into grams (30 g ~ 1 oz). It is important that units are the same for body weight and stomach volume. The stomach capacity is the amount of formula an infant can comfortably consume at one feeding. Offering much more than this value may lead to overfilling, stomach distension, and bloat. It also prevents complete emptying of the stomach before the next feeding, and promotes the overgrowth of potentially pathogenic bacteria, diarrhea, and enteritis (Evans 1985).

The following calculations will determine the total volume and kcal to feed/day, as well as the amount
of formula for each feeding and the total number of feedings daily. 0.78

# Calculate Maintenance Energy Requirement: 84.6 x body wt (kg)
# Determine stomach capacity (amount that can be fed at each meal): Body weight (in grams) x 0.05.
# Divide Maintenance Energy Requirement (number of calories required per day) by the number of
kcal/ml in the formula to determine the volume to be consumed per day (this can be converted into ounces by dividing it by 30).
# Divide ml of formula per day by volume to be consumed at each meal (stomach capacity). This gives the number of meals to offer per day.
# Divide 24 hours by the number of feedings/day to find the time interval between feedings.
# See Table 7.5.1.

Table 7.5.1: Calculations for formula volume and feeding frequency for neonate with an approximate birth weight of
135g (MER = Maintenance Energy Requirement) 

New calculations should be performed every few days so formula volume can be adjusted to accommodate growth. The general target average daily gain for infants is 5-8% increase of body wt/day while on formula feeding and 8-10% body wt increase/day on weaning diet (Grant 2005). Since neonates being hand-reared (less than one week of age) are typically severely compromised, they should be given smaller, more frequent feedings than calculated until roughly 2-4 weeks of age.

As a general rule, animals should have an overnight break between feedings that are no longer than twice the time period between daytime feedings (equivalent to missing one feeding). For example, if they are being fed every three hours during the day, they can go six hours at night without food. When they are eating every four hours, they can go eight hours at night. It is not advisable to go more than eight hours between feedings with species that typically nurse throughout the day when mother-raised. Intervals between feeding also will depend on how healthy or strong the infants are. Very weak neonates will probably need feedings every few hours even through the night; typically this is necessary for only a few days to a week. The AZA Otter SSP recommends that neonates be fed every two hours around the clock initially. Depending on how the animal is doing, these feedings may be stretched to every three hours after the first few weeks.

Otter pups should only be fed if the pup is hungry and suckling vigorously. Weak infants may be hypothermic, dehydrated and/or hypoglycemic. Do not offer anything by mouth until the body temperature is within the normal range for its age (i.e., warm, not hot, to the touch). Electrolytes can be offered orally if the pup is suckling, or subcutaneously if it is too weak; 2.5-5% dextrose can also be given to raise the pup's glucose level. More research is required to determine body temperature norms for young of all the otter species. This information should be collected by all facilities hand-rearing otter pups and submitted to the AZA Otter SSP. Young animals will be hungry at some feedings, less at others, but this is quite normal (Muir 2003). However, refusal of two feedings is a sign of trouble in young otters. Pups will not die from being slightly underfed, but overfeeding may result in gastrointestinal disease, which is potentially fatal.

If any animal's formula is changed abruptly, it is likely to cause diarrhea, which can dehydrate the pup quickly. Any formula changes should be made slowly, by combining the formulas and gradually changing the ratio from more of the first to more of the second. If an animal develops diarrhea or becomes constipated with no change having been made in the formula, consult the veterinarian. In general, adjusting the formula ratios should be attempted before medicating the animal. For diarrhea, increase the ratio of water to all the other ingredients. Be sure the water has been boiled or sterilized well, and the bottle is clean. Subcutaneous fluids (e.g., lactated ringers) may be needed if the infant dehydrates significantly.

Feeding Techniques: 
To bottle feed, hold the pup in the correct nursing position; sternally recumbent (abdomen down, not on its back), with the head up. Place the hand holding the bottle in such a way that it provides a surface for the pup to push against with its front feet. If milk comes through their nose, the nipple hole may be too large or the pup may be trying to eat too quickly. Make sure there is consistency with who is feeding the pups. Note any changes in feeding immediately. Decreased appetite, chewing on the nipple instead of sucking, or gulping food down too quickly can be signs of a problem (Blum 2004).

It is important to keep in mind that neonates are obligate nose breathers and incapable of breathing through their mouths and nursing at the same time. For this reason, respiratory infections can be life threatening because they may interfere with breathing and make nursing difficult or impossible (Meier 1985). Aspirated formula is frequently a contributing factor to neonatal respiratory infections; to avoid this, be sure to select the appropriate nipple. The nipple's hole needs to suit the neonate's sucking reflex. Also, if a nipple is too stiff, the pup may tire and refuse to nurse.

If an animal aspirates fluids the recommended protocol is to hold the infant with head and chest lower than the hind end. A rubber bulb syringe should be used to suck out as much fluid from the nostrils and the back of the throat as possible. If aspiration is suspected, or if fluid is heard in the lungs, the veterinarian should be contacted immediately; drugs should not be administered without the veterinarian's involvement. Body temperature should be closely monitored for the occurrence of a fever and a decline in the animal's appetite and general attitude. Depending on the condition and age of the animal, diagnostic procedures may include radiographs, CBC, and chemistry. It is possible to start a course of antibiotics while results from the bloodwork are pending, and the attending veterinarian can prescribe an appropriate antibiotic course.

Pups will need to be stimulated to urinate and defecate for the first six weeks of life, either immediately before or after feeding. Parent-reared giant otters of ex situ populations are reported to have required stimulation by their parents to urinate or defecate for up to 10 weeks of age. In at least one case, a hand-reared individual needed to be stimulated to urinate/defecate until it was 2.5-3 months old (Sykes- Gatz 1999-2006). In other cases (Corredor & Muñoz 2004), pups were reported using latrines on their own at 9 weeks of age. Some pups also may require "burping" to prevent gas build-up in the abdomen.

P. brasiliensis: One of the most reliable methods of determining if the young are nursing successfully is monitoring for what Sykes-Gatz (2005) calls the "nursing hum", which pups make when they are suckling. This hum is a somewhat higher pitched and faster vocalization than the contact hum described by Duplaix (1980), which has a twittering quality to it. The nursing hum is performed when a pup is nursing from the mother or a bottle. Sykes-Gatz (2005) also reports this call, when given by a caregiver, can encourage pups to feed. From birth, the pups also display "tail wagging" when they nurse, wagging their tails rather quickly and repeatedly from side-to-side. Some individuals may require "burping" to prevent gas build-up in the abdomen. For more detailed information refer to Sykes-Gatz (2005).

A. cinereus: Pups may be slow to learn how to suckle from a bottle, in one case taking eight days before suckling without aspirating (Webb 2008). Care should be taken to ensure that the nipple's hole is not too large and that pups are fed slowly at the beginning. For additional information see Webb 2008 (also available online at (

Hand-rearing Formulas: It is important that the artificial milk formula matches the maternal milk in protein, fat, and carbohydrate composition as closely as possible. Table 7.5.2 provides information on the nutritional content of otter milk, and Table 7.5.3 provides information on the nutritional composition of selected substitute milk formulas/replacers.

Table 7.5.2: Otter (Lutra spp.) Milk Nutrition Composition on As Fed (AFB) and Dry Matter Basis (DMB) (Ben Shaul 1962; Jenness & Sloan 1970)
アガベ チタノタ 白鯨Otter_CARE_MANUAL_table_7_5_2

Esbilac® (or Milk-Matrix® 33/40) is preferred as the base for milk formulas offered to otters and provides good pup growth. The addition of Multi-Milk® (or Milk-Matrix® 30/55) increases the total fat and protein content without adding substantially to the carbohydrate content of the formula. The maternal milk composition of otter milk only has a trace amount of milk sugars, so this component of the substitute formula should be kept as low as possible to prevent gastric upset and diarrhea. See Table 7.5.3 on the following next page.

Table 7.5.3: Nutritional analysis of commercial animal milk replacers
 Stussy x Our Legacy x Denim Tears jacketOtter_CARE_MANUAL_table_7_5_3

The addition of an anti-gas build-up product to the formula should be considered (milk sugars can cause the build-up of gas). Lact-aid® is an enzyme that has been used successfully with many species. Add two drops of Lact-aid® to 100 ml of mixed formula. The formula then should be refrigerated for 24 hours prior to feeding for the enzyme to perform correctly (Grant 2005). Lactobacillus spp., in Bene-bac® or Probios®, is a group of beneficial gut bacteria that also break down milk sugars in the digestive tract. Follow label instructions for these products.

Table 7.5.4: Substitute milk formulas for otters. Values taken from product composition documents available from PetAgTM (K.Grant, personal communication)
モヘアカーディガン M オレンジ アーガイルOtter_CARE_MANUAL_table_7_5_4

L. Canadensis: At this time, the preferred formula is canned Esbilac® due to palatability and good pup growth. Milk Matrix® based formulas also are nutritionally suitable but some facilities have had pups refuse this formula (Blum 2004) while others have had good success.

Weaning: Some of the following recommendations do not apply to P. brasiliensis (e.g. offering food in a bowl). The weaning process should be started when the pup shows interest in solid food, generally at about eight weeks of age. If the pup is not gaining enough weight on formula alone, solid food can be added at six weeks of age (this may need to be pureed or chopped). To begin, formula can be mixed with AD diet (canned cat food or similar), baby food, mashed up fish, rice cereal, or ground meat. New food can be added to the bottle; feed this mixture with a syringe, baby bottle, or offer it in a bowl. Milk formula in a bowl shoud not be provided to giant otters, as they tend to inhale liquids into the nose until they become proficient at eating solid foods (McTurk & Spelman 2005). Only one new food component should be added to their diet every couple of days until they are eating solids well. It is best to be creative, flexible, and not to rush the weaning process. In the case of problems, try different approaches, try them multiple times, and try foods in new ways like bottles, syringes, suction bulbs, bowls, etc. Do not cut back on bottle-feeding to make the pup "hungry". Offer new food at the beginning of the feeding and finish with the bottle (Blum 2004). Situations to watch for during the weaning process include (Blum 2004): weight loss, diarrhea and sucking behavior. If sucking on tails, feet, genitals, etc. is observed between feedings, an additional bottle-feeding should be offered for a few days. R. Green of the Vincent Wildlife Trust recommends putting orange oil on the genitals to discourage sucking; this worked well with Lutra lutra and is not harmful to the otter (G.Yoxon, personal communication).

Swimming, Terrestrial Activities, and Behavioral Stimulation: Otter pups are not born knowing how to swim and may even be scared of the water. They will usually start to take interest in the water at 4-8 weeks of age. The pups should be started off in shallow pools and watched carefully; once comfortable, they can gradually be introduced to deeper water. Pups should be dried off completely and warmed after their swim.

Enrichment is crucial to the development of the pups; toddler safe toys, grooming materials, dens, climbing structures, live food, etc. have all been used successfully. The more items that are introduced to otters at an early age, the more they will interact with as they age. All toys should be safe and approved by the veterinary staff. The suitability of toys should be regularly re-evaluated, as some may no longer be safe as the otter grows. Due to the tendency of all otters to take things into the water, the use of cardboard or other paper-type items, especially for young animals, is not recommended. Cases of these items becoming water logged and congealing in an animal's mouth or over their nose have been reported.

Pup Development: The following information provides a summary of pup development. More specific information can be found in the Otter Husbandry Manuals (Lombardi et al. 1998; Reed-Smith 2001; Sykes-Gatz 2005). See Appendix I for pup weight charts.

A. cinereus:
# Eyes begin opening at between 17 and 28 days, fully open by day 45
# Teeth begin erupting about day 20 and canines erupting ~ day 91 (Webb 2008)
# Thermo regulating well on their own about day 38 (Webb 2008)
# Moving on their own between day 39 and day 50
# Urinating and defecating on their own (hand reared animals) by day 59 (Webb 2008)
# Generally born with mostly grayish fur, darkens by 6-7weeks
# Solid food 7-8 weeks; weaned 82-120 days
# Hand reared animals eating solid well by day 92 and weaned on day 130 at a weight of 2336
grams (Webb 2008)

A. capensis: At this time there is no information available on pup development. More research is required.

L. maculicollis: Pups are born with white on their lips. After a few days, patches of white/orangish colored hair develop on their chest or groin area. These patches change to an orange color, before changing back to cream or white as the pups reach full growth or maturity. The age at which these color changes occur appears to be highly variable and is currently being documented (D.Benza, personal communication; R.Willison, personal communication).

# First spots seen ~6 days, whitish but turned orange in a few days. More orange spots developed by day 42
# Eyes open at 34-46 days
# First crawling at about 20 days, crawling well 42 days
# First teeth erupting at 23-29 days, all teeth in ~78 days
# Walking well at ~ 37 days, running 59 days
# Leaving den on own at about 57 days
# Playing in water bowl ~ 61 days
# First going in to water on their own at about 57-91 days; variation comes from water tub versus
pool exploration
# First pool swimming lessons ~ 86 days (timing may be due to when family is allowed into the


# First eat solids at about 60-73 days

L. canadensis: Consult the North American River Otter Husbandry Notebook 1st & 2nd editions for more detailed information (Reed-Smith 1994, 2001).
# Birth weight: 120-135g
# Born blind with dark brown fur
# External ears are flat against the head, and claws and toe webbing are well formed.
# Deciduous upper and lower canines erupt at about 12 days
# Eyes fully open at 28-35 days
# Walking at about 35-42 days, first swimming lesson generally at 28-56 days
# Beginning to play ~25-42 days
# Leaving nest box on their own ~49 days
# Pelt change 28-56 days, born with all dark fur
# First solid food taken at 42-56 days
# Localized latrine use ~49 days
# Pups should be weaned by 3-4 months of age

P. brasiliensis: Because this species requires complete isolation and privacy (particularly primiparous pairs), detailed information on pup development is taken from video and audio recordings. Note: Institution U does not believe in complete isolation but recommends maintaining the normal routine; this approach should be tailored to the individual female and situation.Sykes-Gatz (2005) provides more detail on pup rearing and development. McTurk & Spelman (2005) also provide information on hand-rearing and rehabilitation of orphaned giant otters. An outline of giant otter pup development is provided below (Wunnemann 1990, 1995a,b; McTurk & Spelman 2005; Sykes-Gatz 2005, 1999-2006; V.Gatz, personal communication; N.Duplaix, personal communication):

# Weight at birth - 150-265 g
# Birth pelt is grayish in color and darkens by 6-7 weeks of age
# Eyes begin opening at ~28 days and are fully open by ~45 days
# Pups should be moving on their own by 39-50 days
# First leave the nest box on their own at 63-67 days
# First swimming lessons at 20-60 days, or as early as 11 days
# Pups can be reliably sexed at 10 weeks
# Pups swim on their own for the first time at 63-67 days
# Pups will begin playing with solid food at roughly 56 days, but generally do not consume any until
about 70-90 days.
# Pups will begin weaning at roughly 4 months of age, but can nurse insignificant amounts (this
provides little nutritional value) at 6.5 to 8 months of age.
# Fish should first be offered pups at 2.5-4 months of age
# 100% of their required caloric intake should be offered in formula/mother's milk form until roughly
2.5 months of age
# Pups should be weaned from formula between 6.5-10 months of age
# Pups should be weaned on a fish based diet; rice cereal has been used successfully as a dietary addition for hand-reared pups. Formula should not be offered in a bowl, as giant otters tend to inhale liquids into the nose until they are proficient at eating solid foods.
# Pups are approximately 3/4 the size of adults at 10 months of age, although this will vary

7.6 Contraception

Many animals cared for in AZA-accredited institutions breed so successfully that contraception techniques are implemented to ensure that the population remains at a healthy size. In addition to reversible contraception, reproduction can be prevented by separating the sexes or by permanent sterilization. In general, reversible contraception is preferable because it allows natural social groups to be maintained while managing the genetic health of the population. Permanent sterilization may be considered for individuals that are genetically well-represented or for whom reproduction would pose health risks. The contraceptive methods most suitable for otters are outlined below. More details on products, application, and ordering information can be found on the Intstitution E webpage:

The progestin-based melengestrol acetate (MGA) implant, previously the most widely used contraceptive in zoos, has been associated with uterine and mammary pathology in felids and suspected in other carnivore species (Munson 2006). Other progestins (e.g., Depo-Provera®, Ovaban®) are likely to have the same deleterious effects. C.Osmann (personal communication) specifically recommends against using progestins in P. brasiliensis for the reasons mentioned above and because these side effects may compromise future breedings. For carnivores, one institution now recommends GnRH agonists, e.g., Suprelorin® (deslorelin) implants or Lupron Depot® (leuprolide acetate), as safer alternatives. Although GnRH agonists appear safe and effective, dosages and duration of efficacy have not been systematically evaluated for all species. GnRH agonists can be used in either females or males, and side effects are generally those associated with gonadectomy, especially weight gain, which should be managed through diet. Suprelorin® was developed for domestic dogs and has been used successfully in African clawless otters, North American river otters, Asian small clawed otters and sea otters.

Gonadotropin Releasing Hormone (GnRH) Agonists: 
GnRH agonists (e.g., Suprelorin® implants or Lupron Depot®) achieve contraception by reversibly suppressing the reproductive endocrine system and preventing production of pituitary (FSH and LH) and gonadal hormones (estradiol and progesterone in females and testosterone in males). The observed effects are similar to those following either ovariectomy in females or castration in males, but are reversible. GnRH agonists first stimulate the reproductive system, which can result in estrus and ovulation in females or temporary enhancement of testosterone and semen production in males. Then, down-regulation follows the initial stimulation. The stimulatory phase can be prevented in females by daily Ovaban administration for one week before and one week after implant placement (Wright et al. 2001).

GnRH agonists should not be used during pregnancy, since they may cause spontaneous abortion or prevent mammary development necessary for lactation. They may prevent initiation of lactation by inhibiting progesterone secretion, but effects on established lactation are less likely. New data from domestic cats have shown no effect on subsequent reproduction when treatment began before puberty; no research in prepubertal otters has been conducted.
A drawback of these products is that time of reversal cannot be controlled. Neither the implant (Suprelorin®) nor the depot vehicle (Lupron®) can be removed to shorten the duration of efficacy to time reversals. The most widely used formulations are designed to be effective for either 6 or 12 months, but those are for the most part minimum durations, which can be longer in some individuals.

Although GnRH agonists can also be an effective contraceptive in males, they are more commonly used in females. This is because monitoring efficacy by suppression of estrous behavior or cyclic gonadal steroids in feces is usually easier than ensuring continued absence of sperm in males, since most institutions cannot perform regular semen collections. Suprelorin® has been tested primarily in domestic dogs, whereas Lupron Depot® has been used primarily in humans, but should be as effective as Suprelorin® since the GnRH molecule is identical in all mammalian species.

If used in males, disappearance of sperm from the ejaculate following down-regulation of testosterone may take an additional 6 weeks, as with vasectomy. It should be easier to suppress the onset of spermatogenesis in seasonally breeding species, but that process begins at least 2 months before the first typical appearance of sperm. Thus, treatment should be initiated at least 2 months before the anticipated onset of breeding.

Progestins: If progestins (e.g., Melengestrol acetate (MGA) implants, Depo-Provera® injections, Ovaban® pills) have to be used, they should be administered for no more than 2 years and then discontinued to allow for a pregnancy. Discontinuing progestin contraception and allowing non-pregnant cycles does not substitute for a pregnancy. Use of progestins for more than a total of 4 years is not recommended. MGA implants last at least 2 years, and clearance of the hormone from the system occurs rapidly after implant removal. Progestins are considered safe to use during lactation.
Vaccines: The porcine zona pellucida (PZP) vaccine has not been tested in otters, but may cause permanent sterility in many carnivore species after only one or two treatments. This approach is not recommended.
Ovariectomy or Ovariohysterectomy: Removal of ovaries is a safe and effective method to prevent reproduction for animals that are eligible for permanent sterilization. In general, ovariectomy is sufficient in young females, whereas removal of the uterus as well as ovaries is preferable in older females, due to the increased likelihood of uterine pathology with age.
Vasectomy: Vasectomy of males will not prevent potential adverse effects to females that can result from prolonged, cyclic exposure to the endogenous progesterone associated with the pseudo-pregnancy that follows ovulation. This approach is not recommended for otters.
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