Reproductive Ecology of American Black Bears in the Alleghany Mountains of Virginia,USA

We studied reproduction of American black bears (Ursus americanus) in western Virginia from 1994 to 2003. We handled 326 ≥2-year-old female black bears 672 times during summer trapping and followed 176 of these individuals through 424 winter den seasons. We examined 183 litters consisting of 455 cubs. Primiparity occurred at mean and modal ages of 3.8 and 3 years, respectively. Composite mean litter size was 2.49 (SE = 0.06) cubs/litter; 3- and 4-year-olds had smaller litters than older bears. We tracked reproductive synchrony using 5 indices and documented a resetting of this synchrony, likely in response to hard-mast failure. The amplitude of oscillations in synchrony indices dampened through time after the synchronizing events. Documentation and quantification of relationships between nutrient availability, reproduction and population dynamics can be used to inform population modeling efforts and more accurately forecast harvest. © 2011 The Wildlife Society.     

Maternal parity affects neonatal survival rate in a colony of captive bred baboons (Papio hamadryas)

Background Non‐human primates, particularly baboons, are valuable as animal models for reproductive research, because of their similarity to humans. Knowledge of colony‐specific pregnancy and neonatal outcomes is essential for interpretation of such research. Methods A retrospective review of the reproductive records of the Australian National Baboon Colony (ANBC) from 1994 to 2006 was performed. Results The overall live birth rate was over 70% of recognized pregnancies. Pregnancy loss was due to equal proportions of spontaneous abortion and stillbirth, and was not affected by maternal age or parity. Stillbirth rates were increased by the use of animals in novel late pregnancy experimental protocols. Neonatal mortality rates were low overall, but significantly higher in primiparous compared with multiparous mothers (P < 0.05). There were no cases of maternal mortality. Conclusions The success of the ANBC breeding programme is demonstrated by the low rate of pregnancy loss, high neonatal survival rate and lack of maternal mortality.     

Primigravidity,body weight,and costs of rearing first offspring in rhesus macaques

Body size is associated with menarche and ovarian function, but the relationship to first conception is rarely examined. We conducted a longitudinal investigation of rhesus macaques, Macaca mulatta, to determine the effect of differences in body weight on both the age at first conception and survivorship of first progeny. Young females who became pregnant weighed significantly more than peers who remained barren, with weight changes for females who successfully raised offspring no different than those for females who did not produce offspring. Infant mortality among primiparae was not significantly greater than that among multiparae, although nearly twice as high. First-born males tended to have lower survivorship than first-born female offspring. We suggest that reproductive costs encountered by primiparous females are more likely to be modulated by immature neuroendocrine function than by inexperience, small body size, or infant suckling patterns. We conclude that body size influences probability of first conception, socioendocrine factors mediate the likelihood of infant survival, and primiparous production of male progeny seems to exert a greater reproductive cost than does production of female progeny. Am. J. Primatol. 46:135–144, 1998. © 1998 Wiley-Liss, Inc.     

Age-specific cost of first reproduction in female southern elephant seals

When to commence breeding is a crucial life-history decision that may be the most important determinant of an individual''s lifetime reproductive output and can have major consequences on population dynamics. The age at which individuals first reproduce is an important factor influencing the intensity of potential costs (e.g. reduced survival) involved in the first breeding event. However, quantifying age-related variation in the cost of first reproduction in wild animals remains challenging because of the difficulty in reliably recording the first breeding event. Here, using a multi-event capture–recapture model that accounts for both imperfect detection and uncertainty in the breeding status on an 18-year dataset involving 6637 individuals, we estimated age and state-specific survival of female elephant seals (Mirounga leonina) in the declining Macquarie Island population. We detected a clear cost of first reproduction on survival. This cost was higher for both younger first-time breeders and older first-time breeders compared with females recruiting at age four, the overall mean age at first reproduction. Neither earlier primiparity nor delaying primiparity appear to confer any evolutionary advantage, rather the optimal strategy seems to be to start breeding at a single age, 4 years.     

Known unknowns in an imperfect world: incorporating uncertainty in recruitment estimates using multi‐event capture–recapture models

Studying the demography of wild animals remains challenging as several of the critical parts of their life history may be difficult to observe in the field. In particular, determining with certainty when an individual breeds for the first time is not always obvious. This can be problematic because uncertainty about the transition from a prebreeder to a breeder state – recruitment – leads to uncertainty in vital rate estimates and in turn in population projection models. To avoid this issue, the common practice is to discard imperfect data from the analyses. However, this practice can generate a bias in vital rate estimates if uncertainty is related to a specific component of the population and reduces the sample size of the dataset and consequently the statistical power to detect effects of biological interest. Here, we compared the demographic parameters assessed from a standard multistate capture–recapture approach to the estimates obtained from the newly developed multi‐event framework that specifically accounts for uncertainty in state assessment. Using a comprehensive longitudinal dataset on southern elephant seals, we demonstrated that the multi‐event model enabled us to use all the data collected (6639 capture–recapture histories vs. 4179 with the multistate model) by accounting for uncertainty in breeding states, thereby increasing the precision and accuracy of the demographic parameter estimates. The multi‐event model allowed us to incorporate imperfect data into demographic analyses. The gain in precision obtained has important implications in the conservation and management of species because limiting uncertainty around vital rates will permit predicting population viability with greater accuracy.     

Milk intake and development in a newborn captive African elephant (Loxodonta africana)

In August 2003 the San Diego Zoo's Wild Animal Park (WAP) and the Lowry Park Zoo, under the auspices of the AZA's Elephant SSP and a USFWS permit, imported 3.8 African elephants (Loxodonta africana) from the Kingdom of Swaziland. When they were captured, transrectal ultrasound examinations revealed that one nulliparous cow was approximately 10 months pregnant. At the time of their arrival (August 2003), all of the animals were estimated to be approximately 13 years old and were thought to be nulliparous. Based on the ultrasound examination results and the average African elephant gestation period, parturition was predicted to be 20 February 2004. In this report, we provide the first detailed data about nursing activity around the clock and newborn calf development, describe maternal and neonatal nighttime activity budgets, and explore maternal weight changes during suckling and lactation. The newborn calf suckled significantly more at night than during the day, but suckled for only about 2 hr per 24‐hr period. Regression analysis revealed that through the first 3 months of life the calf gained 0.385 kg/day while it suckled on a regular basis. We compare our findings with published information on wild elephants, and conclude that although the growth rate is reduced compared to hand‐reared elephant calves, the suckling patterns are almost identical to those reported for wild calves. Zoo Biol 0:1–7, 2005. © 2005 Wiley‐Liss, Inc.     

Father's death does not affect growth and maturation but hinders reproduction: evidence from adolescent girls in post-war Estonia

The popular concept of predictive–adaptive responses poses that girls growing up without a father present in the family mature and start reproduction earlier because the father''s absence is a cue for environmental harshness and uncertainty that favours switching to a precocious life-history strategy. Most studies supporting this concept have been performed in situations where the father''s absence is caused by divorce or abandonment. Using a dataset of Estonian adolescent girls who had lost their fathers over the period of World War II, we show that father''s death did not affect the rate of pubertal maturation (assessed on the basis of development of breasts and axillary hair) or growth. Father''s death did not affect the age of first birth but, contrary to predictions, reduced lifetime reproductive success. Our findings thus do not support the concept of predictive–adaptive responses and suggest that alternative explanations for covariation between fatherlessness and early maturation are required.