Effects of supplementary feeding on the offspring sex ratio of kakapo: a dilemma for the conservation of a polygynous parrot

The kakapo (Strigops habroptilus) is a large, flightless, nocturnal parrot, endemic to New Zealand. It is critically endangered, with a world population of ca. 62 individuals and a male-biased adult sex ratio. The species has a polygynous “lek” mating system and adult males typically weigh 30-40% more than females. The kakapo is subject to intensive conservation efforts, including the provision of supplementary food to wild birds to encourage successful nesting. There is mounting evidence that, in polygynous species with large variance of male reproductive success, females in better condition may maximise their fitness by producing more offspring of the larger, more costly sex to be reared. We used data on the sex ratio of progeny of female kakapo that had or had not received supplementary food, to test the hypothesis that supplementary feeding might cause a male-biased offspring sex ratio. There was a significant excess of males in the clutches of females provided with supplementary food, suggesting that changes need to be made to the feeding regime to increase recruitment of females. This is an example of applying evolutionary theory to a practical conservation problem.     

Mating system in a gopher tortoise population established through multiple translocations: Apparent advantage of prior residence

Population manipulations such as translocation are becoming increasingly important tools in the management of rare and declining species. Evaluating the effectiveness of such manipulations requires comprehensive monitoring of population processes, including dispersal, survivorship, and reproduction. We investigated the mating system of a translocated population of gopher tortoises (Gopherus polyphemus) established through multiple releases, which occurred primarily during 1987–1994. During 2006–2007, we sampled and genotyped 27 candidate males (candidate sires), 34 candidate females (candidate dams), and 121 offspring from 19 clutches at five polymorphic microsatellite loci to determine the relative frequency of multiple paternity and to estimate individual reproductive success. Multiple paternity was detected in 57% of clutches genotyped, and females of single-sire clutches and females of multiple-sire clutches were of similar size. Reproductive success varied among male tortoises, and successful sires were significantly larger than males to which no offspring were attributed. Among successful sires, previously established males sired a disproportionate number of the offspring sampled, despite being significantly smaller than subsequently released males. The high variance in individual reproductive success and the apparent reproductive advantage associated with prior residence observed in this gopher tortoise population has important implications for the design of future translocation projects.     

Stress: An inevitable component of animal translocation

As the number and diversity of animal species meriting conservation intervention increases, improving the success of translocation efforts is vital and understanding the role of physiological stress in translocation failure is essential. Though the short-term acutestress response is critical for survival in the wild, chronic stress results in pathology and occurs when the physiological stress response system is pushed beyond the normal capacity and becomes dysregulated. As this review discusses, translocation may inevitably lead to a state of chronic stress; however, this translocation-induced stress does not doom an animal to post-release failure or preclude translocation as a conservation tool. Rather, because chronic stress in translocated animals may actually be the norm rather than the exception, “stress” can be considered a predictable factor to incorporate into translocation planning. In terms of translocation failure, we argue that the role of stress is an indirect one. Translocation-induced chronic stress increases the overall vulnerability of the individuals and, as a result, decreases the probability that the population will become self-sustaining. In this review, we further propose techniques to potentially decrease the total number and magnitude of stressor exposures throughout the translocation procedure in order to diminish the incidence of chronic stress-related pathology. Aspects of the translocation activities, such as capture techniques and care procedures during captivity, can be adjusted to accomplish this. Though stress may be an inevitable component of translocation, reducing the impact and time course of chronic stress on the physiology and behavior of translocated animals will increase the likelihood of translocation success as measured by the formation of a new, self-sustaining population     

Conservation of the red-winged grasshopper, Oedipoda germanica (Latr.): the influence of reproductive behaviour

Reproductive isolation can function as a mechanism to maintain locally adapted gene complexes while decreasing the heterozygosity in distinct populations. As a result, reproductive behaviour should be considered a fundamental factor influencing reproductive isolation. This is of interest to conservation biology when one desires to regulate gene flow between two populations either by creating opportunities for increased dispersal, by relocation of individuals, or by re-introduction of a species to its natural habitat. Reproductive behaviour can also influence the effective population size and the actual population size through the Allee effect. We investigated the reproductive behaviour of individuals from two isolated populations of the red winged grasshopper, Oedipoda germanica, an endangered species in Central Europe. We detail several methods to show how several aspects of the reproductive behaviour of this species interact with the conservation of this species. Foreign males were not disfavoured in mate choice and male body size was also unimportant in mating success. Heterogamic matings were as productive as homogamic matings in terms of total number of eggs per female, egg hatching rate, or nymph survival. Therefore, we suggest that cross-matings of individuals from different populations do not positively influence population size by heterosis effects nor act they negatively in the form of outbreeding depression. We found that female O. germanica were able to store viable sperm for extended periods but egg pods showed a decrease in hatching rate when these females were deprived of additional mating opportunities. Multiple mated females laid more eggs than once-mated females. Hence, females are capable of founding new populations even after only one mating but their reproductive output may be reduced. Present-day gene flow between populations of O. germanica probably does not occur. Consequently, there is an urgent need to pursue habitat management and release programmes that maintain current population sizes of this species. With regard to the reproductive behaviour of the red-winged grasshopper, we suggest that relocation programmes release males and female together and at an early adult stage. Also, because female reproductive output increases with mating activity, the initial release should involve excess females. Because males have a shorter lifespan than females a subsequent release of males at a later time may enhance the overall success of local conservation efforts by resulting in more offspring per female.     

The effect of translocation and temporary captivity on wildlife rehabilitation success: An experimental study using European hedgehogs (Erinaceus europaeus)

Translocation is frequently used to return rehabilitated animals to the wild, and is an important tool for the population management of endangered species. Whilst experimental field manipulations are important in determining optimal rehabilitation and translocation strategies, they are rarely implemented in practice. We used an experimental approach to examine the effects of translocation on post-release survival and behaviour, and the impact of introductions on the recipient wild population, using the European hedgehog (Erinaceus europaeus), the most common mammal admitted to British wildlife hospitals. The post-release survival and behaviour of five groups were compared: three different translocation treatments, one wild population at the release sites and one control wild population away from the release sites. Individuals that were held in captivity prior to translocation had a better survival rate on release than individuals that were translocated with a minimum time spent in captivity. We suggest that temporary captivity improves chances of survival by allowing the build up of fat reserves and reducing manipulation stress suffered on release. No evidence was found for intra-specific competition between introduced individuals and the recipient wild hedgehog population.     

Survival, interactions with conspecifics and reproduction in 37 chimpanzees released into the wild

We report the results of eight years of post-release monitoring of 37 wild-born, captive chimpanzees released into the Conkouati-Douli National Park, Republic of Congo. Overall survival was high, with 23 (62%) individuals remaining in the release zone, and only 5 (14%) confirmed dead. Released females regularly interacted with wild chimpanzees. Several females appeared to have integrated into wild groups for extended periods of time, and four released females gave birth to a total of five offspring. However, encounters with wild chimpanzees were a major cause of mortality in released males, and 40-50% of released males would have died without veterinary intervention. These sex differences are in accordance with knowledge of chimpanzee behavioural ecology. Our results demonstrate that wild-born, captive chimpanzees can be released into the wild successfully, under certain specific conditions. Most importantly, careful planning and preparation is critical at all stages; a suitable release area must be identified; potential risks to existing wild populations, including the possibility of disease transmission, must be minimised; and post-release monitoring is essential. Adolescent females are the most suitable candidates for release, as they appear to be able to integrate successfully into wild communities. However, males should not be released where wild chimpanzees occur, as they are likely to be attacked and killed. Release into the wild addresses the welfare of certain individual animals, although it clearly cannot address the fate of all captive, wild-born chimpanzees. Knowledge of how to successfully release chimpanzees into the wild also has both current and potential future benefits for the conservation of wild chimpanzee populations.     

Return to the wild: Translocation as a tool in conservation of the Desert Tortoise (Gopherus agassizii)

Translocation could be used as a tool in conservation of the threatened Mojave Desert Tortoise (Gopherus agassizii) by moving individuals from harm’s way and into areas where they could contribute to conservation of the species. Numerous factors may affect the success of translocations, including the conditions experienced by tortoises in holding facilities while awaiting translocation. The tortoises available for our translocation study had been provided supplemental water during their years spent in a captive holding facility, potentially inducing carelessness in water conservation. In addition to generally investigating the efficacy of translocation, we compared the effects of continuing with the effects of ceasing the holding facility’s water supplementation regimen. After exposure to one of the two water regimens, all tortoises were given the opportunity to hydrate immediately prior to release. We examined behavior, body mass, carapace length, movement, and mortality of tortoises for two activity seasons following release to the wild. Water supplementation was correlated with high rates of carapace growth and distant movements by males after release. Lengthy movements following translocation may be problematic for conservation planning, but this should be evaluated in light of the goals and circumstances of each translocation project. Although the mortality rate was 21.4% in 1997, data suggest that drought conditions at the site rather than the translocation itself negatively affected the tortoises. None of the tortoises died during their second season at the site. Our results indicate that translocation should be considered a useful tool in conservation of the Desert Tortoise.     

Assessing translocation outcome: Comparing behavioral and physiological aspects of translocated and resident African elephants (Loxodonta africana)

Evaluating translocation outcomes is important for improving wildlife management and conservation actions. Often, when quick decisions need to be made and long-lived animals with slow reproduction rates are translocated, traditional assessment methods such as long-term survival and reproductive success cannot be used for assessing translocation outcomes. Thus, alternative, seldom used, measures such as comparing the behavior and physiology of translocated animals to those of local residents should be employed to assess the translocated animals’ acclimation to their new home. Here we monitored the survival, physiology, and behavior of translocated African elephants (Loxodonta africana) and compared these measures to the local resident population at the release site. Adult male and female translocated elephants’ death rates were higher than those of the local population. Furthermore, the mortality rate of translocated adult males and calves was greater than expected based on their proportion in the translocated elephant population. No difference was found in stress hormone levels between the two populations, but the body condition of the translocated elephants was significantly poorer than that of the local population throughout the study period. The behavioral time budgets of the translocated elephants converged with those of the local population over time. Finally, translocated elephants utilized habitat that was similar to their source site (hills and permanent rivers) more than did the local population. Based on these findings we recommend careful consideration of timing, release location, and individuals targeted in future elephant translocations. More broadly, we introduce and explore seldom used translocation assessment techniques.     

Translocation of captive-bred dibblers Parantechinus apicalis (Marsupialia: Dasyuridae) to Escape Island, Western Australia

The introduction of threatened marsupials to islands affords a high degree of translocation success due to the lack of exotic species on islands, or the feasibility of eradicating them. The dibbler Parantechinus apicalis is a small marsupial endemic to the southwest of Australia. It is listed under international and national legislation as Endangered, and has been the focus of a successful conservation strategy to introduce captive-bred individuals to an island as a security measure, and as part of a formal Interim Recovery Plan. A total of 88 individuals were released in four groups on Escape Island from 1998 to 2000. The population was monitored using radiotelemetry and trapping techniques from 1998 to 2001. Breeding and dispersal of young occurred within the first year of release. Three years after the initial release, the third generation of wild-born dibblers had entered into the population. The total cost of this translocation exercise approximated $AUS 0.6 million. The conservation effort to give additional security to dibblers has been successful, at least in the short term, due to the collaboration between four organisations and a commitment to support a monitoring program of the released population over time.     

Wild rabbit restocking for predator conservation in Spain

The decline of rabbit (Oryctolagus cuniculus) populations in Mediterranean Spain has been shown to be one of the main threats to rabbit-specialist predators such as the Iberian lynx (Lynx pardina) and the Spanish imperial eagle (Aquila adalberti), two species which are in serious danger of extinction. Consequently, corrective measures such as increasing rabbit populations by restocking have been carried out to help the recovery of predator populations. In order to determine the general applicability of rabbit restocking for predator conservation, we performed three experimental restockings and evaluated their success in relation to season, habitat quality and the number of animals introduced. Rabbits were released either in large or small numbers in all four seasons of the year, and in habitat types defined as `poor' or `rich' according to the food availability for rabbits. For each restocking we evaluated rabbit survival, degree of residency and expected population increase. As a rule, the highest restocking success occurred whenever smaller number of rabbits were released in the richest quality habitat. Restocking during the breeding season was less successful than in other seasons. Problems concerning intraspecific competition, reproductive failure and diseases are discussed.     

Polygyny and female breeding failure reduce effective population size in the lekking Gunnison sage-grouse

Populations with small effective sizes are at risk for inbreeding depression and loss of adaptive potential. Variance in reproductive success is one of several factors reducing effective population size (N_e) below the actual population size (N). Here, we investigate the effects of polygynous (skewed) mating and variation in female breeding success on the effective size of a small population of the Gunnison sage-grouse (Centrocercus minimus), a ground nesting bird with a lek mating system. During a two-year field study, we recorded attendance of marked birds at leks, male mating success, the reproductive success of radio-tagged females, and annual survival. We developed simulations to estimate the distribution of male reproductive success. Using these data, we estimated population size () and effective population size N_e for the study population. We also simulated the effects of population size, skewed vs. random mating, and female breeding failure on N_e. In our study population, the standardized variance in seasonal reproductive success was almost as high in females as in males, primarily due to a high rate of nest failure (73%). Estimated N_e (42) was 19% of in our population, below the level at which inbreeding depression is observed in captive breeding studies. A high hatching failure rate (28%) was also consistent with ongoing inbreeding depression. In the simulations, N_e was reduced by skewed male mating success, especially at larger population sizes, and by female breeding failure. Extrapolation of our results suggests that six of the seven extant populations of this species may have effective sizes low enough to induce inbreeding depression and hence that translocations may be needed to supplement genetic diversity.     

Generations in captivity increases behavioral variance: considerations for captive breeding and reintroduction programs

Long-term maintenance of captive populations followed by release of captive animals into the wild is one of many approaches to endangered species conservation. To assess captivity's effects on behavior, a simulated predator was presented and response behaviors measured in oldfield mice, Peromyscus polionotus subgriseus. The animals tested were from four populations collected from Ocala National Forest, Florida, and held in captivity for varying numbers of generations: 35, 14, 2, and 0 (wild caught). Results show (1) that the more generations a population has been in captivity, the less likely an individual is to take cover after seeing a predator and (2) variance in predator-response behaviors increases with generations in captivity. These results point to two ways in which captivity can compromise animal behavior and, in turn, the success of reintroduction programs. First, because individuals from populations that have been in captivity for multiple generations seek refuge less often than their wild counterparts, they might experience increased mortality in the wild due to predation. Second, increased behavioral variance could translate into decreased survivorship upon reintroduction. Therefore, more individuals will need to be released to reach the targeted wild population size.     

Can small, isolated primate populations be effectively reinforced through the release of individuals from a captive population?

Since November 1997 the Madagascar Fauna Group (MFG) has released 13 captive-bred black and white ruffed lemurs (Varecia variegata variegata) into the Betampona reserve in eastern Madagascar. Five of the thirteen are currently surviving, including one male who has integrated into a wild group. Five of the released lemurs fell victim to predation by fossa (Cryptoprocta ferox), one died of malnutrition, one disappeared from the reserve and one was withdrawn from the release programme. Ten of the released lemurs survived for more than one year post release, although all required varying levels of supplementary feeding. One pair bred twice—the first time the infants did not survive, but on the second occasion triplets were successfully raised beyond weaning. One of the triplets (male) is still surviving. One male has integrated into a wild group and sired a single infant in 2002 and a female released in 2001 gave birth to twins sired by a wild male also in 2002. The release programme has thus achieved a major objective of reinforcing the existing wild population. To date there is no significant difference in survival rates between animals born and raised in free-ranging environments and those raised in cages, between animals greater than or less than 5 years old at time of release, or between males and females.     

Risks of a late start to captive management for conservation: Phenotypic differences between wild and captive individuals of a viviparous endangered skink (Oligosoma otagense)

Maintenance of demographically and genetically self-sustaining populations in captivity can assist conservation of threatened species. Captivity can, however, lead to changes in phenotype, though to date this issue has received little attention in reptiles. We compared phenotypic differences in the now critically-endangered Otago skink (Oligosoma otagense) between wild specimens (Otago, southern New Zealand) and in captivity (North Island). Individuals of this long-lived, viviparous species have been maintained up to three generations in captivity, primarily by private herpetoculturists, but increasingly there is interest in integrating management of captive stocks with conservation in situ. For the same snout-vent length, captive skinks pooled across three colonies had a significantly heavier body mass, wider tail base, longer tail (juveniles only), faster growth rate and much slower sprint speed than in the wild. Captive skinks also lacked ectoparasitic mites and haemogregarine parasites, and experienced warmer temperatures with probably greater access to food. Our study demonstrates the importance of not treating captive management for conservation as a tool of last resort. Important questions, if captive-raised animals are to be released to the wild, are is it better for released skinks to run swiftly or to be heavy-bodied, and what role does reinfestation with native parasites have in determining this balance? We also recommend genetic analysis and studbook management of captive stocks, research to determine implications of heavy body mass for reproduction in captivity, and production of at least some offspring for release inside larger enclosures within the local climate.     

Modeling the reintroduction of lynx to the southern portion of its range

We modeled populations of lynx (Lynx canadensis) and snowshoe hares (Lepus americanus) to determine prey densities required for persistence of lynx translocated to the southern portion of the species' range. The models suggested that a density of 1.1-1.8 hares/h is required for lynx persistence; these densities are higher than those reported for most hare populations across the USA. We found that lynx dispersal and density-independent mortality substantially increased the hare density required for lynx persistence. Reintroduction success was associated with number of release events, total number of animals released, and timing of release relative to the phase of the hare population cycle. However, no release protocol could override the negative effects of low prey density or high population losses. We conclude that successful lynx reintroduction requires high hare densities and minimal anthropogenic disturbance; few areas in the contiguous USA currently posses such qualities.     

Population management of threatened taxa in captivity within their natural ranges: Lessons from Andean bears (Tremarctos ornatus) in Venezuela

Populations of threatened taxa in captivity within their natural ranges can make important contributions to conservation, but these may be compromised by the inappropriate application of population management goals developed in other contexts. We conducted demographic, genetic, and population viability analyses on the captive population of Andean bears (Tremarctos ornatus) in Venezuela to investigate the management of within-range captive populations in general, and to better integrate this population into the conservation of Andean bears in particular. We found that although the present population is very small and not internally self-sustaining, incorporation of confiscated wild individuals has resulted in a low average number of generations in captivity and low inbreeding, with moderate gene diversity and a high probability of future population persistence. However, past imports from extra-range populations have been from over-represented lineages of unknown origin, which have mixed with under-represented Venezuelan ones, reducing the future value of the Venezuelan population as a source for founder stock. Our analyses indicate that the rate of incorporation of wild recruits is a major factor influencing proxy measures of conservation value, and distinguishing within- from extra-range populations. This implies that, contrary to conventional wisdom, internal self-sustainability can be a misguided goal in within-range populations, which furthermore may not be suitable destinations for surplus animals from captive populations elsewhere.     

Pragmatic management increases a flagship species, the Himalayan brown bears, in Pakistan’s Deosai National Park

Deosai Plateau in Northern Pakistan was designated a national park to protect the largest remnant population of brown bears in Pakistan. The natural resources of this high elevation (3500-5000 m) park make a significant contribution to the livelihood of local and nomad communities. The present legislation excludes people from a park, which increases conflicts between management and local people. However, a pragmatic approach was adopted to involve people in conservation in Deosai. Community participation, achieved by recognizing rights and introducing incentives, reduced resistance against the conservation efforts, reduced grazing pressure in bear habitat and helped reduce poaching. The size of the brown bear population was set as an indicator of park success, and was monitored annually from 1993 through 2006. We observed a 5% annual growth of the brown bear population, suggesting that the conservation program has been successful due to a successful cooperation between an NGO, people, and the park management.The increase of the bear population is significant, because we observed an extremely low reproductive rate, due to late age of first reproduction (8.25 years), a long reproductive interval (5.7 years), and a small litter size (1.33). The reproductive rate of the Deosai population is the lowest yet documented for brown bear populations. Poor habitat quality, low quality food, high seasonality, and extreme weather conditions in the Himalaya probably explain the poor reproductive performance. Considering such low reproduction and known exchange of individuals with neighboring populations, we believe that the observed growth was a sum of reproduction and immigration. Brown bears are declining throughout South Asia and often have low-productive rates. Therefore, conservation efforts for brown bears in this region must target reducing human-caused mortalities, particularly of adult females. Involvement of people can increase efficiency in conservation, in addition to reducing cost and conflicts.     

Habitat fragmentation reduces plant fitness by disturbing pollination and modifying response to herbivory

In fragmented landscapes plant species are often confined to remnants of formerly more widespread habitats, with many of their populations being small and isolated. This study experimentally examined the effects of population size and isolation on pollination, herbivory and reproductive success in the forest herb Phyteuma spicatum (Campanulaceae). In an experiment in which population size and isolation were manipulated using plants from the same origin, population size positively affected pollinator visitation, but did not alter the generally high levels of herbivory. As a result, seed production was higher in large populations. Conversely, plants originating from 14 natural populations of varying size and degree of isolation did not differ in reproductive success when grown in the same environment, suggesting similar attractiveness to pollinators and reproductive potential. The intensity of herbivory, however, was higher in progeny of small populations, at least in terms of the proportion of biomass removed. In both experiments, there were no effects of population isolation. The results suggest (1) that small population size decreases reproductive success via direct negative effects on plant-pollinator interactions, (2) that this pattern is not offset by herbivory, but (3) that herbivory enforces fragmentation effects on pollination by further reducing the number of flowering individuals and (4) that habitat fragmentation may influence plant fitness by affecting plant response to herbivory. The effects of habitat fragmentation on plant populations in present-day landscapes are thus complex, illustrating the need for more integrated studies in conservation biology that take into account both mutualistic and antagonistic plant-animal interactions.     

How much is enough? Landscape-scale conservation for the Florida panther

The Florida panther (Puma concolor coryi) is an endangered, wide-ranging predator whose habitat needs conflict with a rapidly growing human population. Our goal was to identify specific regions of the south Florida landscape that are of high conservation value to support a self-sustaining panther population. We used compositional and Euclidean distance analyses to determine relative importance of various land cover types as panther habitat and to investigate the role of forest patch size in habitat selection. A model of landscape components important to Florida panther habitat conservation was created. The model was used in combination with radio telemetry records, home range overlaps, land use/land cover data, and satellite imagery to delineate Primary and Secondary zones that would comprise a landscape mosaic of cover types sufficient to support a self-sustaining population. The Primary Zone generally supports the present population and is of highest conservation value, while the Secondary Zone is of lesser value but could accommodate expansion of the population given sufficient habitat restoration. Least-cost path models identified important landscape linkages, and model results were used to delineate a Dispersal Zone to accommodate future panther dispersal outside of south Florida. We determined that the three habitat zones could support 80-94 panthers, a population likely to persist and remain stable for 100 years, but that would be subject to continued genetic problems. The Primary, Dispersal and Secondary zones comprise essential components of a landscape-scale conservation plan for the protection of a viable Florida panther population in south Florida. Assessments of potential impacts of developments should strive to achieve no net loss of landscape function or carrying capacity for panthers within the Primary Zone or throughout the present range of the Florida panther.     

An assessment of the contribution of captive breeding to the conservation of rare mammals

There have been few attempts to examine the success of zoos in the establishment and maintenance of captive populations of rare animals. Annual census data for population size and births of species in zoos are now available for a 15-year period. Sixty-one of 274 rare mammal species were considered to have bred frequently enough in captivity to warrant investigation. By comparing these species with each other and with a theoretical model it proved possible to identify five consecutive stages in the development of a successful population in captivity. Species were then assigned to each stage to determine the success of breeding programmes in zoos. Twenty-six species can be considered self-sustaining. With some idea of their contribution to date, the role of zoos in conservation is discussed. It is concluded that captive-breeding for reintroduction is a much less significant role for zoos than the maintenance and development of captive populations of all species for educational and research purposes, and as insurance for the future.