Weight as an indicator of enclosure suitability in Livingstone's fruit bats (Pteropus livingstonii).

Obesity is common in zoo animals, and both dietary management and the provision of adequate opportunities for exercise are needed to tackle it. We used 30 years of records from Jersey Zoo to compare the weight and forearm length of wild and captive-born Livingstone's fruit bats (Pteropus livingstonii), and to assess the impact on weight of enclosure space. The mean capture weight of wild-caught male Livingstone's bats was 657 g, significantly higher than that of females (544 g). In both wild and captive-born bats, males had significantly longer forearms than females, but there was no effect of birth location. Males weighed more in the mating season than at other times of year. Both sexes gained more weight during development if born in enclosures that restricted flight rather than a large aviary; this was particularly noticeable in females. After reaching maturity at 3 years, weights of bats born in restricted enclosures continued to increase, reached a peak of over 1000 g at 8-10 years, and then declined in both sexes. The weight of bats born in the aviary remained more stable after the age of three. Like wild bats, adult females born in the aviary weighed less than males. However, females born in restricted enclosures weighed more than males born in the same enclosures. Enclosure designs that maximize opportunities for flight can limit excessive weight gain in captive fruit bats and may therefore improve fitness and health, essential in planning for future reintroduction programs.

Successful treatment of infertility in a female Sumatran orangutan Pongo abelii.

In 2011, a female Sumatran orangutan housed at Durrell Wildlife Conservation Trust became infertile following a massive antepartum hemorrhage in labor and the delivery of a stillborn infant. The placenta was infected with Pantoea sp. Hysterosalpingography (HSG) revealed blocked fallopian tubes, and pressurized fallopian tube perfusion was used to reverse the tubal occlusion. She subsequently conceived and following an intensive training program, we were able to measure umbilical artery waveform analysis for fetal well-being and placental localization to exclude placenta previa, which could complicate pregnancy and lead to catastrophic hemorrhage. The female went on to deliver a healthy offspring. We suggest that these techniques should be considered for other infertile females in the global captive population.

Why do captive pied tamarins give birth during the day?

Diurnal primates typically give birth at night, when it is presumed that they are safer at a very vulnerable time, and this is reflected in an overwhelmingly nocturnal pattern of delivery in most species of Callitrichidae. However, over half (51.1%) of 88 births to pied tamarins (Saguinus bicolor) at Durrell Wildlife Park occurred during the day (0800-1700), almost always in the afternoon. Nearly three quarters of breeding females (17/23) had at least one diurnal birth, including females from all generations in captivity from wild-caught to fifth captive-born generation, and from all six matrilines represented at Durrell. The proportion of diurnal births has remained relatively stable over time despite management changes. We used generalized linear mixed modeling to investigate several factors that we hypothesized could affect time of birth: maternal experience, season, female rearing history, and whether or not the group was on public display. We fitted all possible models to the data, but none explained more than 7.5% of the variation. Daytime delivery had few statistically significant detrimental effects, although infant survival was somewhat lower and parental rejection increased in diurnal births. Pied tamarins do not seem to fit any of the hypotheses previously put forward to explain exceptions to the typical primate circadian pattern of delivery. Zoo Biol. 35:487-494, 2016. © 2016 Wiley Periodicals, Inc.

The benefits of helpers: Effects of group and litter size on infant care in tamarins (Saguinus oedipus).

The Callitrichidae (marmosets and tamarins) typically give birth to twins, and infant care is shared by all group members. The potential benefits to callitrichids of having helpers were investigated in a study of 21 captive cotton-top tamarin (Saguinus oedipus) infants, living in groups with two to 12 older members. Time carried and suckled and amount of food received from other family members were recorded for each infant during the first 12 weeks of life. The results showed that infants in larger groups were carried more and received more food than those in smaller groups. Twin infants in larger families were less likely to be on the same carrier. Singleton infants were carried more than twins but did not receive more food. On average, individual caretakers in larger groups carried less and shared less food with infants than those in smaller groups. When parental contributions to care were analyzed, no effects of group size were found on mothers' contributions to carrying or food sharing, but fathers in larger groups both carried infants less and shared less food with them. There appear to be several benefits of a communal rearing system to cotton-top tamarins. 1) Infants may receive more care in larger families, thus increasing their chances of survival. 2) The burden of care is spread over several animals, reducing the costs to a given individual. 3) The parents, particularly fathers, may benefit most from reducing the costs of investing in the present litter and increasing their ability to invest in future litters.

The costs of infant carrying in captive cotton-top tamarins.

Marmosets and tamarins have a communal rearing system in which all group members help to care for the twin infants characteristic of this family of primates. Helpers are likely to incur time and energy costs by contributing to infant care. Predictions that cotton-top tamarin (Saguinus oedipus) helpers would change their behavior when carrying infants because of reduced mobility and/or a need for increased vigilance were tested in a captive colony. Tamarins carrying an infant spent significantly less time feeding, foraging, moving, or engaging in social activities such as grooming than they did when not carrying. Frequencies of scratching, autogrooming, and scent marking were significantly reduced in carriers, suggesting that their mobility was reduced. However, carriers were significantly less likely to be vigilant (measured by direction of gaze) than when not carrying. Further observations showed that carriers spent more time in concealed areas than they did when not carrying and were probably therefore adopting a cryptic strategy to reduce predation risks to themselves and to infants. These results demonstrate that tamarin helpers pay costs by carrying infants. Some possible compensating benefits are indicated.

Cotton-top tamarins (Saguinus (o.) oedipus) in a semi-naturalistic captive colony.

To test the prediction that the breeding success of captive cotton-top tamarins (Saguinus (o.) oedipus) could be improved by maintaining them in groups whose size and age-sex composition resembled those of wild groups, data were collated from 6.5 years of records from a breeding colony that otherwise had housing and husbandry procedures similar to those of other successful colonies. Group size and composition in the colony closely resembled those of wild groups, and infant survival was the highest yet reported for the species, with 69% of the 124 infants born reared by their parents to adulthood, and a mean surviving litter size of 1.5 infants. Abortion, stillbirth, and parental neglect of infants were rare. Parity had several effects on reproduction: mean litter size decreased, but percentage infant survival increased; interbirth intervals decreased in length; and seasonality in reproduction was more pronounced for the first four litters born to breeding females than for their subsequent litters, with a birth peak in the spring. Although a spacious and complex physical environment, retention of offspring in their natal families until experience of several sets of infant siblings had been obtained, and non-invasive husbandry and research techniques may all have contributed to the colony's success, it seems possible that the improvement over other colonies is due to the resemblance of group composition to those of wild tamarins.

Food sharing in lion tamarins: Tests of three hypotheses.

Infant marmosets and tamarins (Callitrichidae) frequently receive food from older group members. Three possible functions of food sharing in lion tamarins were examined experimentally. The first hypothesis, that food sharing ensures that infants receive sufficient food even if it is difficult for them to acquire it themselves, was tested by varying the ease with which infants could reach a food source. When access to food was restricted, infants fed themselves less, received more food from others, and had a higher success rate in begging attempts. The second hypothesis, that food sharing helps teach infants an appropriate diet, was tested by presenting fruits that were novel to infants. Although infants fed themselves less under these conditions, adults were less likely to share novel foods than familiar foods. The final experiment compared food sharing when food was abundant with behavior when food items were presented singly. Infants fed themselves less and received more food from others when food items were rare. These results suggest that food sharing in lion tamarins helps to ensure that infants receive adequate amounts of food which is difficult to locate or acquire, but that it is not involved in teaching infants which foods they should eat. © 1993 Wiley-Liss, Inc.