Assessing Initial Reintroduction Success in Long-Lived Primates by Quantifying Survival, Reproduction, and Dispersal Parameters: Western Lowland Gorillas (Gorilla gorilla gorilla) in Congo and Gabon

Assessing climate niche similarity between persian fallow deer (Dama mesopotamica) areas in Iran

The Persian fallow deer or Mesopotamian fallow Deer (Dama mesopotamica, Brook 1875), a species of significant ecological importance, had faced the threat of extinction in Iran. One conservation strategy involved the translocation of Persian deer to enclosed areas across Iran, where they were afforded protection from external threats and provided with essential care by human caretakers. While human caretakers diligently attend to their needs and mitigate external threats, climate variables may now become critical factors affecting population dynamics in enclosed areas. This study aims to assess the similarity in climate niches between the original area (Dez and Karkheh) of the Persian deer species and 11 newly enclosed areas. To achieve this, we employed climate data and ecological niche modeling (ENM) techniques to assess the variations in climate among 12 areas. We utilized the environmental equivalency test to determine whether the environmental spaces of area pairs exhibit significant differences and whether these spaces are interchangeable. Extrapolation analyses were also constructed in the next steps to explore climatic conditions in original fallow deer habitats that are non-analogous to those in other parts of Iran. Our results reveal significant disparities in climate conditions between the original and all translocated areas. Based on observations of population growth in specific enclosed areas where translocated deer populations have thrived, we hypothesize that the species may demonstrate a non-equilibrium distribution in Iran. Consequently, these new areas could potentially be regarded as part of the species' potential climate niche. Extrapolation analysis showed that for a significant portion of Iran, extrapolation predictions are highly uncertain and potentially unreliable for the translocation of Persian fallow deer. However, the primary objective of translocation efforts remains the establishment of self-sustaining populations of Persian deer capable of thriving in natural areas beyond enclosed areas, thus ensuring their long-term survival and contributing to preservation efforts. Evaluating the success of newly translocated species requires additional time, with varying levels of success observed. In cases where the growth rate of the species in certain enclosed areas falls below expectations, it is prudent to consider climate variables that may contribute to population declines. Furthermore, for future translocations, we recommend selecting areas with climate similarities to regions where the species has demonstrated growth rates.

Review of hyperdispersal in wildlife translocations

Species translocation is a common tool to reverse biodiversity loss, but it has a high failure rate. One factor that contributes to failure is postrelease hyperdispersal, which we define as the long-distance movement of individuals resulting in their failure to contribute to population establishment. We reviewed reported incidences of hyperdispersal and compared rates of hyperdispersal among taxa, population demographics, release cohorts, and success of mitigation techniques. Of 151 conservation translocations (reinforcements and reintroductions) in which animals were tracked, hyperdispersal was confirmed in 52.1% of programs. The prevalence of hyperdispersal (percentage of studies) was relatively consistent across taxa (42.9-60%), but hyperdispersal rates in birds were likely underestimated because 76.9% of bird translocations showed incidences in which birds could not be located after release, but hyperdispersal was unable to be confirmed. Eutherians exhibited a higher average incidence of hyperdispersal (percentage of hyperdispersing individuals in a cohort) of 20.2% than birds, reptiles, and marsupials (10.4%, 15.7%, and 10.3%, respectively). No significant trends were observed for sex, source population, or translocation type, but there were nonsignificant trends for males to hyperdisperse more than females and for higher incidences of hyperdispersal in reinforcements relative to reintroduction programs. Mitigation techniques included temporary confinement, supplementation of resources, and releasing animals in social groups, but only half of studies examining mitigation techniques found them useful. Hyperdispersal incidence was variable within taxa, and we advise against forming translocations strategies based on results from other species. Hyperdispersal is a significant welfare, economic, and conservation issue in translocations, and we suggest definitions, reporting, and experimental strategies to address it.

Human and Non-Human Primate Coexistence in Argentina: Conflicts and Solutions

There are five different primate species inhabiting widely distinct ecoregions in Argentina. Each of them faces various threats in terms of conservation and conflicts that hamper their ability to coexist with human populations. We present here some of the drivers known to be the causes of conflicts between humans and primates in the southernmost area of distribution of Latin American primates. We focus our synthesis on two of the biggest sources of conflict: the effects of different anthropogenic disturbances, and human misconceptions concerning the role of primates in the ecosystem. In each section, we briefly characterize the conflicts worldwide and then provide specific cases and examples from Argentina. In the last part of the manuscript, we further describe some ongoing national and regional educational, research, and conservation approaches to mitigate those effects.

Successful acclimatization of mandrills (Mandrillus sphinx) translocated to Conkouati-Douli National Park, Republic of Congo, as measured by fecal glucocorticoid metabolites

Translocation and reintroduction are common tools in conservation management and can be very successful. However, translocation can be stressful for the animals involved, and stress is implicated as a major cause of failure in release programs. Conservation managers should therefore seek to understand how the stages of translocation impact stress physiology in the animals involved. We quantified fecal glucocorticoid metabolites (fGCMs) as a noninvasive measure of response to potential stressors during a translocation of 15 mandrills (Mandrillus sphinx) into Conkouati-Douli National Park, Republic of Congo. The mandrills were initially housed in a sanctuary, transferred to a pre-release enclosure in the National Park and then released into the forest. We collected repeated fecal samples (n = 1101) from known individuals and quantified fGCMs using a previously validated enzyme immunoassay. Transfer from the sanctuary to the pre-release enclosure correlated with a significant 1.93-fold increase in fGCMs, suggesting that transfer was a stressor for the mandrills. fGCM values decreased over time in the pre-release enclosure, suggesting that the mandrills recovered from the transfer and acclimatized to the enclosure. Release to the forest was not linked to a significant increase in fGCMs over the final values in the enclosure. Following release, fGCMs continued to decrease, fell below sanctuary values after just over a month and were about half the sanctuary values after 1 year. Overall, our results suggest that the translocation, although initially presenting a physiological challenge to the animals, was not detrimental to the well-being of the animals over the timescale of the study and, in fact, may have been beneficial. Our findings show the value of non-invasive physiology in monitoring, evaluating and designing wildlife translocations and, ultimately, contributing to their success.

Assessments made easier: examining the use of a rating-based questionnaire to capture behavioral data in rehabilitant orangutans (Pongo pygmaeus morio)

Rehabilitation and release are commonly used for confiscated, surrendered, and rescued primates. To improve release efficacy it is important to generate accurate behavioral profiles of release candidates. Research on primates traditionally uses observer ratings to measure individual differences. This method is easily implemented, but its validity has been questioned. We evaluated whether observer ratings reflect behavioral data indicating forest adaptation in 18 free-ranging rehabilitant orangutans (Pongo pygmaeus morio). In 2017, we used a species-specific questionnaire to measure how often orangutans engaged in behaviors linked to living successfully in the wild (e.g., nest building) and the extent to which they express personality traits that may influence forest adaptation. We collected 11 months of observational data on 17 of the orangutans concurrently to validate the questionnaire items, and collected further questionnaire data for 16 of the individuals in 2019. We used regularized exploratory factor analysis (REFA) and parallel analysis to condense the ratings and determine that two factors could be reliably extracted. We conducted another REFA using the observational data, and calculated factor congruence coefficients following procrustean rotation. The first of the two factors represented forest skills and human aversion, and was congruent with observational data. The second factor reflected boldness, sociability, and exploration, and was not congruent with observational data. Ratings correlated significantly with observations for all five questionnaire items reflecting adaptation to forest life, and for three of seven items reflecting personality traits. We conclude that ratings can be a valid approach to obtain individual-based behavioral information reflecting forest adaptation in free-ranging rehabilitant orangutans, and may be particularly useful in summarizing behaviors relevant to forest adaptation that are otherwise challenging to gather in primates.

Use of genetic tools to assess predation on reintroduced howler monkeys (Alouatta caraya) in Northeastern Argentina

Despite strong support from the media, the reintroduction of animals into natural environments does not always achieve its goal. Alouatta caraya is the primate species facing the greatest hunting pressure due to the illegal pet trade in Argentina. Confiscations of this species are common, as is the voluntary surrender of animals by owners no longer able or willing to care for them. These animals ultimately arrive at rehabilitation centers and, in many cases, are released into natural environments that may differ from the original sites where they were captured. Until recently, the lack of genetic analysis of the individuals involved led to biased relocation decisions. We followed the reintroduction of 12 A. caraya individuals in a protected area (Isla Palacio, Misiones, Argentina). The presence of potential predators such as pumas (Puma concolor) and jaguars (Panthera onca) in this area was confirmed by camera traps, footprints and feces. After the disappearance of four A. caraya at the reintroduction site, we investigated the applicability of genetic assignment tests based on genotypic data to accurately identify predated individuals. Genetic analyses allowed us to determine the predator species (P. onca) and to identify the predated individuals as two of the reintroduced animals. This procedure is promising for identifying the remains of predated individuals, and can contribute to the design of reintroduction policies based on scientific evidence.

Spatial behavior in rehabilitated orangutans in Sumatra: Where do they go?

Wildlife restoration is one of the key components of conservation strategies, and this includes the rehabilitation and release of animals confiscated from wildlife traffickers. When primates are re-introduced, most individuals need a pre-release training to acquire the skills needed to survive in the wild. Pre-release training may either negatively or positively affect primate post-release behavior and survival. Post-release behavior, however, has rarely been monitored even though it is the only means to assess the survival of released individuals. Here, we present a thorough analysis of data from a 3-year radio tracking study on 32 orangutans (Pongo abelii) released in Sumatra after their rehabilitation. We investigated whether and how the age at release, the duration of the pre-release rehabilitation and training, and the release location affected the post-release individual spatial behavior. Orangutans released at older age exhibited post-release habitat selection patterns that were more comparable to that shown by wild conspecifics, i.e., they chose areas closer to rivers and at lower elevations (150-250 meters a.s.l.) where previous research had documented greater food availability. In contrast, individuals released at younger age showed a stronger spatial dependency on the rehabilitation station and exhibited disrupted habitat selection patterns; although after several months after the release all individuals tended to decrease their spatial reliance on the rehabilitation facility. This study indicates that the rehabilitation of individuals for a longer period and their release further from the rehabilitation station have facilitated the subsequent development of more natural spatial behavior, i.e. driven by food availability rather than by the dependence on care-giving human facility. Our study provides indications on how to improve the rehabilitation and release of confiscated orangutans, highlighting the importance of the age at release, the length of the rehabilitation program, and the location of the release site.

Application of the geographic population structure (GPS) algorithm for biogeographical analyses of wild and captive gorillas

Background

The utilization of high resolution genome data has important implications for the phylogeographical evaluation of non-human species. Biogeographical analyses can yield detailed understanding of their population biology and facilitate the geo-localization of individuals to promote their efficacious management, particularly when bred in captivity. The Geographic Population Structure (GPS) algorithm is an admixture based tool for inference of biogeographical affinities and has been employed for the geo-localization of various human populations worldwide. Here, we applied the GPS tool for biogeographical analyses and localization of the ancestral origins of wild and captive gorilla genomes, of unknown geographic source, available in the Great Ape Genome Project (GAGP), employing Gorillas with known ancestral origin as the reference data.

Results

Our findings suggest that GPS was successful in recapitulating the population history and estimating the geographic origins of all gorilla genomes queried and localized the wild gorillas with unknown geographical origin < 150 km of National Parks/Wildlife Reserves within the political boundaries of countries, considered as prominent modern-day abode for gorillas in the wild. Further, the GPS localization of most captive-born gorillas was congruent with their previously presumed ancestral homes.

Conclusions

Currently there is limited knowledge of the ancestral origins of most North American captive gorillas, and our study highlights the usefulness of GPS for inferring ancestry of captive gorillas. Determination of the native geographical source of captive gorillas can provide valuable information to guide breeding programs and ensure their appropriate management at the population level. Finally, our findings shine light on the broader applicability of GPS for protecting the genetic integrity of other endangered non-human species, where controlled breeding is a vital component of their conservation.

Electronic supplementary material

The online version of this article (10.1186/s12859-018-2568-5) contains supplementary material, which is available to authorized users.

Effects of age and sex ratios on offspring recruitment rates in translocated black rhinoceros

Success of animal translocations depends on improving postrelease demographic rates toward establishment and subsequent growth of released populations. Short-term metrics for evaluating translocation success and its drivers, like postrelease survival and fecundity, are unlikely to represent longer-term outcomes. We used information theory to investigate 25 years of data on black rhinoceros (Diceros bicornis) translocations. We used the offspring recruitment rate (ORR) of translocated females-a metric integrating survival, fecundity, and offspring recruitment at sexual maturity-to detect determinants of success. Our unambiguously best model (AICω = 0.986) predicted that ORR increases with female age at release as a function of lower postrelease adult rhinoceros sex ratio (males:females). Delay of first postrelease reproduction and failure of some females to recruit any calves to sexual maturity most influenced the pattern of ORRs, and the leading causes of recruitment failure were postrelease female death (23% of all females) and failure to calve (24% of surviving females). We recommend translocating older females (≥6 years old) because they do not exhibit the reproductive delay and low ORRs of juveniles (<4 years old) or the higher rates of recruitment failure of juveniles and young adults (4-5.9 years old). Where translocation of juveniles is necessary, they should be released into female-biased populations, where they have higher ORRs. Our study offers the unique advantage of a long-term analysis across a large number of replicate populations-a science-by-management experiment as a proxy for a manipulative experiment, and a rare opportunity, particularly for a large, critically endangered taxon such as the black rhinoceros. Our findings differ from previous recommendations, reinforce the importance of long-term data sets and comprehensive metrics of translocation success, and suggest attention be shifted from ecological to social constraints on population growth and species recovery, particularly when translocating species with polygynous breeding systems.

Assessment of releases of translocated and rehabilitated Yucatán black howler monkeys (Alouatta pigra) in Belize to determine factors influencing survivorship

Rehabilitation and reintroduction have become important to the management and welfare of primates worldwide. However, the suitability and success of these practices must be evaluated to determine their effectiveness as well as to improve programs and methods, as little is known about the factors influencing survival of released individuals. Between 2011 and 2014, 28 howler monkeys, Alouatta pigra, were released at Fireburn Reserve, northern Belize by the Primate Rehabilitation Centre of Belize: Wildtracks. From March to August 2015, field trips were made to determine the number and identity of surviving individuals to assess whether differences in individual outcomes (survived or disappeared) could be associated with specific characteristics or backgrounds of the monkeys. Fourteen of the twenty rehabilitated monkeys and seven of the eight translocated monkeys were found alive. The proportion of surviving individuals was not significantly different between rehabilitants and translocated animals, males and females, former pets and wild animals, short- and long-term rehabilitants, or different ages at release or intake. As mortality was low and none of the general factors analyzed influenced survivorship, it is suggested that chance or individual traits may be important in the outcomes of releases. This study provides an example of successful population reintroduction from both rehabilitation and translocation programs, and the first analyses of characteristics impacting the success of releases of howler monkeys.

Modeling variation in early life mortality in the western lowland gorilla: Genetic, maternal and other effects

Uncovering sources of variation in gorilla infant mortality informs conservation and life history research efforts. The international studbook for the western lowland gorilla provides information on a sample of captive gorillas large enough for which to analyze genetic, maternal, and various other effects on early life mortality in this critically endangered species. We assess the importance of variables such as sex, maternal parity, paternal age, and hand rearing with regard to infant survival. We also quantify the proportions of variation in mortality influenced by heritable variation and maternal effects from these pedigree and survival data using variance component estimation. Markov chain Monte Carlo simulations of generalized linear mixed models produce variance component distributions in an animal model framework that employs all pedigree information. Two models, one with a maternal identity component and one with both additive genetic and maternal identity components, estimate variance components for different age classes during the first 2 years of life. This is informative of the extent to which mortality risk factors change over time during gorilla infancy. Our results indicate that gorilla mortality is moderately heritable with the strongest genetic influence just after birth. Maternal effects are most important during the first 6 months of life. Interestingly, hand-reared infants have lower mortality for the first 6 months of life. Aside from hand rearing, we found other predictors commonly used in studies of primate infant mortality to have little influence in these gorilla data.

Behavioural ecology and group cohesion of juvenile western lowland gorillas (Gorilla g. gorilla) during rehabilitation in the Batéké Plateaux National Park, Gabon

Rehabilitation of animals followed by reintroduction into the wild can benefit conservation by supplementing depleted wild populations or reintroducing a species in an area where it has been extirpated or become extinct. The western lowland gorilla (WLG, Gorilla g. gorilla) is persistently poached; infants are often illegally traded and used as pets. Some are confiscated and rehabilitated, then kept in sanctuaries or reintroduced into the wild. Prior to reintroduction, the ability of the orphans to survive independently in their environment needs to be assessed. Here, we performed a multivariate analysis, including diet composition, activity-budget, and pattern of strata using of a group of five juvenile WLG in the process of rehabilitation and distinguished three sub-periods of ecological significance: the high furgivory period, the Dialium fruits consumption period, and the high folivory period. The consequences of these variations on their well-being (play behaviour) and the group cohesion (spatial proximity and social interactions) were examined. Like wild WLGs, diets shifted seasonally from frugivorous to folivorous, while the same staple foods were consumed and large amounts of Dialium fruits were seasonally gathered high in trees. When succulent fruit intake was the highest, thus providing high energy from sugar, juveniles spent less time feeding, more time playing and group cohesion was the highest. Conversely, the cohesion decreased with increasing folivory, individuals spent more time feeding and less time playing together. Nonetheless, the group cohesion also decreased after the death of one highly social, wild-born orphan. This may underscore the importance of skilled individuals in the cohesion and well-being of the entire group and, ultimately, to rehabilitation success. This study evaluates the rehabilitation success with regards to the methods used and highlights the need to consider a set of individual and environmental factors for enhancing rehabilitation while preserving the local biodiversity and individual well-being.

Admixture between historically isolated mitochondrial lineages in captive Western gorillas: recommendations for future management

Although captive populations of western gorilla have been maintained in the United States for over a century, little is known about the geographic origins and genetic composition of the current zoo population. Furthermore, although previous mitochondrial analyses have shown that free-range gorilla populations exhibit substantial regional differentiation, nothing is known of the extent to which this variation has been preserved in captive populations. To address these questions, we combined 379 pedigree records with data from 52 mitochondrial sequences to infer individual haplogroup affiliations, geographical origin of wild founders and instances of inter-breeding between haplogroups in the United States captive gorilla population. We show that the current captive population contains all major mitochondrial lineages found within wild western lowland gorillas. Levels of haplotype diversity are also comparable to those found in wild populations. However, the majority of captive gorilla matings have occurred between individuals with different haplogroup affiliations. Although restricting crosses to individuals within the same haplogroup would preserve the phylogeographic structure present in the wild, careful management of captive populations is required to minimize the risk of drift and inbreeding. However, when captive animals are released back into the wild, we recommend that efforts should be made to preserve natural phylogeographic structure.

Assessing reintroduction success in long-lived primates through population viability analysis: western lowland gorillas Gorilla gorilla gorilla in Central Africa

The use of population modelling has become an increasingly common tool in reintroduction planning and assessment. Although initial reintroduction success is often measured by quantifying post-release survival and reproduction, longer-term success is best assessed through measurements of population viability. Here we develop a population model capable of providing useful results for influencing management of a reintroduction programme for a long-lived and slow-reproducing primate, the western lowland gorilla Gorilla gorilla gorilla. We used post-release monitoring data from two reintroduced populations in the Batéké Plateau region of Congo and Gabon, complemented with published data on wild and captive populations, to develop a population model using Vortex. Sensitivity testing illustrated that the model was highly sensitive to changes in the input parameters for annual birth rates, the number of lethal equivalents, and for female annual mortality rates, especially for adults. The results of the population viability analysis suggested that the reintroduced gorilla populations have a reasonable chance of persistence (> 90% over 200 years) but illustrated that reinforcement of the populations could significantly improve probabilities of population persistence and retention of genetic diversity. Equally, catastrophic events could have significant negative impacts. Continued monitoring of the populations should allow refinement of the model, improving confidence in its predictions and its relevance to decision-making.