Search

Knowledge about the demographic and environmental factors underlying population dynamics is fundamental to designing effective conservation measures to recover depleted wildlife populations. However, sparse monitoring data or persistent knowledge gaps about threats make it difficult to identify the drivers of population dynamics. In situations where small, declining, or depleted populations show continued evidence of decline for unknown reasons, integrated population models can make efficient use of available data to improve our understanding of demography, provide fundamental insights into factors that may be limiting recovery, and support conservation decisions. We used mark‐resight and aerial survey data from 2004 to 2018 to build a Bayesian integrated population model for the Cook Inlet population of beluga whales (Delphinapterus leucas), which is listed as endangered under the U.S. Endangered Species Act. We examined the effects of prey availability and oceanographic conditions on beluga vital rates and conducted a population viability analysis to predict extinction risk across a range of hypothetical changes in beluga survival and reproduction. Our results indicated that while the survival of breeding females (0.97; 95% CI: 0.95–0.99) and young calves (0.92; 0.80–0.98) was relatively high, the survival of nonbreeders (0.94; 0.91–0.97) and fecundity (0.28; 0.22–0.36) may be depressed. Furthermore, our analysis indicates that the population will likely continue to decline, with a 17–32% probability of extinction in 150 years. Our model highlights the utility of integrated population modeling for maximizing the usefulness of available data and identifying factors contributing to the failure of protected populations to recover. This framework can be used to evaluate proposed conservation and recovery efforts for this and other endangered species. [ABSTRACT FROM AUTHOR]

Identifying conservation actions to recover threatened species can be challenging due to many ecological uncertainties. For example, major threats to a species’ conservation are commonly known or suspected, but the specific impacts on population or metapopulation dynamics can be uncertain. This is frequently the case with emerging infectious diseases, including chytridiomycosis, a global driver of amphibian population declines caused by the fungal pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans. While these diseases are known to cause amphibian declines and extirpations, the mechanisms of their landscape-scale spread are still largely unknown. Such uncertainty can lead to inaction which may jeopardize timely recovery of a species. Decision analysis is a pragmatic approach to making transparent and defensible decisions while dealing with uncertainties. We investigated whether optimal actions aimed at recovering boreal toad (Anaxyrus boreas boreas) metapopulations in the southern Rocky Mountains are robust to the unknown dynamics of Bd spread using value of information and regret analyses. Value of information is a decision-analytic tool for calculating the value of new information in terms of performance on management objectives, while regret measures the cost of acting under incorrect information. We further conducted a stochastic sensitivity analysis to identify the relative effects of metapopulation parameters on system dynamics. We found optimal actions were robust to the unknown dynamics of Bd spread. While boreal toad breeding occurrence is highly sensitive to Bd distribution, the optimal decision is not. Resolving the unknown dynamics of Bd spread would lead to a minimal gain of less than one breeding toad subpopulation at the end of 50 years, given the currently available management actions. Applying a decision-analytic framework coupled with value of information and regret analyses can help frame how uncertainties affect decisions in a way that empowers decision makers. [ABSTRACT FROM AUTHOR]

Captive breeding is an increasingly used conservation strategy for species with a high risk of extinction in the wild, but managing a captive breeding programme can be challenging if there is a deficiency in knowledge about the species' breeding biology. A knowledge gap can make it difficult to evaluate different management options. For avian species, egg hatching success is a key demographic parameter, and data‐logging egg technology can provide important information on optimal species‐specific incubation conditions, which can help inform captive breeding practises and identify efficient captive management options. In the context of a captive breeding programme for endangered Whooping Cranes Grus americana, we investigated associations between hatching success and incubation conditions, including environmental parameters (temperature, relative humidity and egg turning rate), and incubation type (artificial incubation; foster incubation by Sandhill Cranes, Grus canadensis; and Whooping Crane incubation). Finally, we considered both cost and breeding output in an analysis of incubation practises. We found that daily mean temperatures were negatively associated with hatching success, and that hatching success was highest with incubation under Sandhill Cranes. However, incubation by artificial incubators, rather than Sandhill Cranes, provided a trade‐off between cost and breeding output that is likely to be acceptable to many captive programme managers. We encourage other captive breeding programmes to use innovations that help to increase potential release numbers for conservation translocations by considering biological and financial constraints. [ABSTRACT FROM AUTHOR]

Evaluation of alternative management strategies enables informed decisions to accelerate species recovery. For reintroductions, post‐release survival to reproductive age is a key parameter influencing population growth. Here, we trial a 'stepping‐stone' method to maximize the success of captive‐bred animals when the availability of more suitable wild‐born release candidates is limited. Our approach makes use of relatively safe and established wild populations to prepare captive‐bred individuals for eventual translocation to a final release destination, thus building resilience through establishment of multiple populations over time. We developed a novel multievent model integrating encounter history and biotelemetry data to evaluate reintroduction strategies for the critically endangered Vancouver Island marmot Marmota vancouverensis. We compared post‐release survival of 176 individuals (52 wild‐born, 47 captive‐bred marmots released directly to destinations, and 77 captive‐bred marmots released with a stepping‐stone approach). Survival estimates to prime breeding‐age (PBA), were then used to quantify expected success of potential release strategies. Our analysis indicates that post‐release survival varies by source population and release method, as well as age, season, year, and years since release. Conditional on an objective of maximizing survival to PBA, our results suggest that using wild‐born marmots for translocations as often as possible, and stepping‐stone captive‐bred marmots prior to final release, will result in the best outcomes. There was a 0.86 probability that survival to PBA was greater for captive‐bred marmots released as yearlings using a stepping‐stone approach (survival to PBA mode = 0.13, 95% CRI = 0.05–0.30) than for captive‐bred animals that were directly released to destination sites as one‐year‐olds (survival to PBA mode = 0.04, 95% CRI = 0.01–0.24). Consequently, the stepping‐stone approach yields much higher population establishment or growth potential than previous release strategies that used captive‐bred marmots. Optimizing the combination of release candidates, sites and timing can thereby increase the effectiveness of reintroductions. Evaluation of alternative management strategies enables informed decisions to accelerate species recovery. For reintroductions, post‐release survival to reproductive age influences population growth but captive‐bred animals frequently have compromised survival. Here we explore a novel 'stepping‐stone' approach to improve the contribution of captive‐bred animals by optimizing release strategies across multiple sites for the critically endangered Vancouver Island marmot (Marmota vancouverensis), and by using an innovative multievent model integrating encounter history and biotelemetry data, we evaluated different reintroduction strategies. The stepping‐stone approach yielded higher population establishment or growth potential than other release strategies for captive‐bred marmots. Optimizing the combination of release candidates, sites, and timing can thereby increase the effectiveness of reintroductions. Photo credit: Stock Photo. [ABSTRACT FROM AUTHOR]

All living whooping cranes (Grus americana) are descended from 16 or fewer birds that remained alive in the early 1940s, a bottleneck that puts the species at potential risk for inbreeding depression. Although AI is commonly used in the management of the captive population of this species, little is known about seminal traits or factors affecting sperm quality in the whooping crane. In the present study, semen samples were collected from 29 adult males (age 3-27 years) during the early (March), mid (April) and late (May) breeding season over 2 consecutive years. The effects of donor age, time within reproductive season and level of inbreeding on seminal characteristics were analysed using regression and information-theoretic model selection. Only time within reproductive season significantly affected seminal traits, with total numbers of spermatozoa and proportions of pleiomorphisms increasing across the season. We conclude that, even with a highly restricted number of founders, there is no discernible influence of inbreeding (at the levels described) on sperm output or quality. Furthermore, although there is variance in seminal quality, the whooping crane produces significant numbers of motile spermatozoa throughout the breeding season, similar to values reported for the greater sandhill crane (Grus canadensis tabida). [ABSTRACT FROM AUTHOR]