Kathy Traylor-Holzer

Distribution and conservation status of the orang-utan ( Pongo spp.) on Borneo and Sumatra: how many remain?

In recognition of the fact that orang-utans (Pongo spp.) are severely threatened, a meeting of orang-utan experts and conservationists, representatives of national and regional governmental and non-governmental organizations, and other stakeholders, was convened in Jakarta, Indonesia, in January 2004. Prior to this meeting we surveyed all large areas for which orang-utan population status was unknown. Compilation of all survey data produced a comprehensive picture of orang-utan distribution on both Borneo and Sumatra. These results indicate that in 2004 there were c. 6,500 P. abelii remaining on Sumatra and at least 54,000 P. pygmaeus on Borneo. Extrapolating to 2008 on the basis of forest loss on both islands suggests the estimate for Borneo could be 10% too high but that for Sumatra is probably still relatively accurate because forest loss in orang-utan habitat has been low during the conflict in Aceh, where most P. abelii occur. When those population sizes are compared to known historical sizes it is clear that the Sumatran orang-utan is in rapid decline, and unless extraordinary efforts are made soon, it could become the first great ape species to go extinct. In contrast, our results indicate there are more and larger populations of Bornean orang-utans than previously known. Although these revised estimates for Borneo are encouraging, forest loss and associated loss of orang-utans are occurring at an alarming rate, and suggest that recent reductions of Bornean orang-utan populations have been far more severe than previously supposed. Nevertheless, although orang-utans on both islands are under threat, we highlight some reasons for cautious optimism for their long-term conservation.

Subspecies Genetic Assignments of Worldwide Captive Tigers Increase Conservation Value of Captive Populations

Tigers (Panthera tigris) are disappearing rapidly from the wild, from over 100,000 in the 1900s to as few as 3000. Javan (P.t. sondaica), Bali (P.t. balica), and Caspian (P.t. virgata) subspecies are extinct, whereas the South China tiger (P.t. amoyensis) persists only in zoos. By contrast, captive tigers are flourishing, with 15,000-20,000 individuals worldwide, outnumbering their wild relatives five to seven times. We assessed subspecies genetic ancestry of 105 captive tigers from 14 countries and regions by using Bayesian analysis and diagnostic genetic markers defined by a prior analysis of 134 voucher tigers of significant genetic distinctiveness. We assigned 49 tigers to one of five subspecies (Bengal P.t. tigris, Sumatran P.t. sumatrae, Indochinese P.t. corbetti, Amur P.t. altaica, and Malayan P.t. jacksoni tigers) and determined 52 had admixed subspecies origins. The tested captive tigers retain appreciable genomic diversity unobserved in their wild counterparts, perhaps a consequence of large population size, century-long introduction of new founders, and managed-breeding strategies to retain genetic variability. Assessment of verified subspecies ancestry offers a powerful tool that, if applied to tigers of uncertain background, may considerably increase the number of purebred tigers suitable for conservation management.

Use it or lose it: Characterization, implications, and mitigation of female infertility in captive wildlife

Zoos and other ex situ wildlife institutions can play an important role in species conservation by maintaining populations for education and research, as sources for potential re-introduction or reinforcement, and as ambassadors for financial support of in situ conservation. However, many regional zoo associations are realizing that current captive populations are unsustainable, with many programs failing to meet demographic and genetic goals to ensure long-term viability. Constraints on population size due to limited space often mandate delayed and/or less frequent breeding, but for females of many species this can have profound effects on fertility. A retrospective analysis combined with published literature and reliable anecdotal reports reveals that, when females are housed in a non-breeding situation for extended periods of time, reproductive changes that negatively impact fertility have occurred in multiple species, including canids, elephants, white rhinoceros, Sebas bats, wildebeest, stingrays, and some felid species. Competing space needs and changing interest in taxa for exhibits over time compound the problem. Counter strategies to breed early and often have their own demographic and genetic consequences as well as logistical and political implications. Strategies to mitigate the sustainability crisis in these taxa might include a mixed strategy in which young, genetically valuable females are bred earlier and at more regular intervals to ensure reproductive success, in combination with the judicious use of available tools to manage the number of offspring produced, including contraception and culling. An understanding of the issues at stake is the first step towards developing management strategies for sustainable populations.

Simulation model for contraceptive management of the Assateague Island feral horse population using individual-based data

The National Park Service (NPS) manages a culturally significant population of feral horses (Equus caballus) inhabiting the Maryland portion of Assateague Island, a barrier island in the eastern United States. Rapid growth of this population over the past few decades from 28 to 166 horses negatively impacts native species and ecological processes on the island. Since 1994, contraception via porcine zona pellucida vaccine has been used to control horse numbers, although herd reduction has been slower than initially expected, leading NPS to consider other management options. An individual-based stochastic simulation model was developed using the Vortex software program to examine the effects of different management strategies on the population. Data from the managed population were used to populate the model parameters. Model projections over the next 50 years using current management practices show an average rate of population decline of 13% per year, suggesting that the population will reach the management target of 80–100 horses in 5–8 years. The effectiveness of contraception to reduce the herd and maintain it at various target sizes of 20–100 horses was also assessed. The accumulation of inbreeding at each target population size was also modelled.

Factors influencing breeding success, ovarian cyclicity, and cub survival in zoo-managed tigers (Panthera tigris)

Understanding factors that influence reproduction and offspring survival in zoo populations is critical for management of threatened and endangered species. Examination of long-term data (1989-2011) compiled from the Association of Zoos and Aquariums zoo-managed tiger breeding program provides the basis for a more thorough understanding of reproduction and scientifically based decisions for effective population management in this endangered felid. Biological and management-related factors that could influence tiger breeding success and cub survival were evaluated using logistic mixed models. Breeding success improved with female age until approximately age five, then declined thereafter. Experienced female breeders had greater breeding success than inexperienced females. Litter size was most predictive of cub survival, with average-sized litters (3-4 cubs) experiencing the highest proportional survival. Management-related factors, such as whether the breeding institution had a recent tiger litter and whether both animals were already located at the same institution, also influenced breeding success and cub survival. These results highlight the importance of institutional husbandry experience and the need to retain knowledge through staff turnovers to achieve optimal reproductive success. Using fecal estrogen data, frequency of ovarian cyclicity and mean cycle length did not differ by female age or parity; thus, lack of cyclicity and/or increased cycle duration are not likely explanations for declining breeding success with age. These results provide valuable reproductive information that should improve scientific management of zoo-based tiger populations.

Restoration of Reproductive Potential After Expiration or Removal of Melengestrol Acetate Contraceptive Implants in Tigers (Panthera tigris)

The need for contraception in the successful management of captive wild animals is becoming increasingly apparent. Because concerns exist regarding the reversibility of the contraceptive implant melengestrol acetate (MGA), reproductive data for 94 female Amur (Panthera tigris altaica) and Sumatran tigers (Panthera tigris sumatrae) were analyzed using survival analyses to evaluate return to reproductive status after implant removal or assumed expiration. Females placed in potential breeding situations after MGA implants were surgically removed showed a 62% return to reproduction by 5.25 years, whereas females with implants that were assumed to have expired showed only a 30% return to reproduction by 6 years. Implanted females did not reproduce as successfully as non-implanted control females, which showed an 85% probability of reproducing after placement in a new breeding situation by 2.66 years. Parturition increased the probability of reproducing in non-implanted females, but not in implanted females. Litter size, stillbirths, and offspring survival were not significantly different between non-implanted, implant-removed and implant-expired female tigers. Ten female tigers reproduced both before and after implant placement, and the differences in litter size, stillbirths, and offspring survival were not significant, nor were they significantly different from non-implanted females. Prior parturition, age when implant was removed, and duration of implantation did not affect the probability of reproducing for females after implant removal. These results show substantial reversibility of MGA implants, leading to 62% successful reproduction after implant removal. The reasons for lower successful reproduction in animals previously treated with the contraceptive compared to non-implanted females are not known, but a greater delay in reversibility was seen when implants were left in place and only presumed expired. Zoo Biol 26:275-288, 2007. (c) 2007 Wiley-Liss, Inc.

The Science and Art of Managing Tigers in Captivity

Publisher Summary Threats to todays fragmented wild tiger populations include not only the obvious but also the added extinction risks associated with small populations—increased vulnerability to demographic stochasticity, environmental variation, catastrophic events such as disease or fire, and genetic issues such as loss of variation and inbreeding depression. The smaller the population, the greater potential influence these stochastic events are likely to have on population persistence. Tiger populations in captivity are also small and therefore are vulnerable to these same risks. Population management gives zoo biologists the ability to improve the viability of captive populations through well-planned demographic and genetic management. Population biologists can use this rich database to analyze the current status of populations, examine past trends, and project what the future might hold given different management strategies. Demographic and genetic analyses guide a committee of zoo tiger managers and experts in assessing the long-term viability of the population, setting realistic population goals, and making breeding and transfer recommendations to work toward these goals. Tiger management must also consider all the other factors such as costs and risks of moving tigers to form good genetic breeding pairs; factors affecting the likelihood of success, such as age, behavior, health, and prior reproduction; and the requests of participating zoos.

Conserving the world's rarest ape: action planning for the Hainan gibbon

The Critically Endangered Hainan gibbon Nomascus hainanus is the world’s rarest ape and possibly rarest mammal species, comprising a single population of c. 25 individuals in Bawangling National Nature Reserve, Hainan, China. The species occurred historically across Hainan, with an estimated population of c. 2000 in the 1950s, but experienced a precipitous decline during the 20th century driven by hunting and extensive habitat loss. Periodic surveys since 2003 have failed to locate any individuals outside the Reserve, and there are no captive populations.

The Struggle to Save the Last South China Tigers

Publisher Summary The South China tiger holds a place of honor in China—as a cultural icon in art, literature, and philosophy, as a symbol of wilderness to promote a new conservation ethic amid an expanding human population, and as a source of national pride as the only uniquely Chinese tiger subspecies. Early in its history, the captive South China tiger population flourished. By 1990, the pedigree represented several generations in captivity, gene diversity begin to decline, and inbreeding levels averaged over 20%. Tiger experts became increasingly alarmed about the critical status of this subspecies both in the wild and captivity. In the face of a plummeting wild population, the need for effective captive management drew national and international attention. The greatest challenges to the viability of the captive population are low reproductive success and low level of genetic variation. Population growth is paramount to slow genetic loss and stabilize the population. The South China tiger has yet to cross over the threshold of viability in captivity. A healthy, self-sustaining captive population is critical to the preservation of what remains of this subspecific genetic line; this milestone must be achieved before this population has the ability to provide tigers to repopulate the mountains and forests of south-central China.

A Review of Population Viability Analysis and its use in Cheetah Conservation

Cheetah ( Acinonyx jubatus ) populations are subjected to a variety of complex, interacting anthropogenic and natural pressures. Understanding the causes of population decline is essential for being able to develop management strategies aimed at arresting the decline or reversing negative trends. Population viability analysis (PVA) uses computer modeling to infer population trajectories, allowing estimation of extinction probabilities, identification of factors contributing to declines, and exploration of relative impacts of different management strategies. We present core parameters used in previous PVAs (using Vortex software) for cheetah populations. The accuracy and value of population projections will benefit from further empirical investigation of parameter values that characterize the current status and threats. However, our succinct review of PVA applications to cheetah conservation identifies that adult female survival and connectivity are some of the most important factors for population persistence and highlights the urgency of conservation action, particularly fostering cheetah–human coexistence.