Incorporating drivers of reproductive success improves population viability analysis

Addressing the impact of canine distemper spreading on an isolated tiger population in northeast Asia

The continuation of the isolated Amur tiger (Panthera tigris altaica) population living along the China-Russia border is facing serious challenges due to factors such as its small size (including 38 individuals) and canine distemper virus (CDV). We use a population viability analysis metamodel, which consists of a traditional individual-based demographic model linked to an epidemiological model, to assess options for controlling the impact of negative factors through domestic dog management in protected areas, increasing connectivity to the neighboring large population (including more than 400 individuals), and habitat expansion. Without intervention, under inbreeding depression of 3.14, 6.29, and 12.26 lethal equivalents, our metamodel predicted the extinction within 100 years is 64.4%, 90.6%, and 99.8%, respectively. In addition, the simulation results showed that dog management or habitat expansion independently will not ensure tiger population viability for the next 100 years, and connectivity to the neighboring population would only keep the population size from rapidly declining. However, when the above three conservation scenarios are combined, even at the highest level of 12.26 lethal equivalents inbreeding depression, population size will not decline and the probability of extinction will be <5.8%. Our findings highlight that protecting the Amur tiger necessitates a multifaceted synergistic effort. Our key management recommendations for this population underline the importance of reducing CDV threats and expanding tiger occupancy to its former range in China, but re-establishing habitat connectivity to the neighboring population is an important long-term objective.

Ex situ breeding programs benefit from science-based cooperative management

Science-based management confers a variety of benefits to wildlife populations that are cooperatively managed by zoos and aquariums, including those managed through the Association of Zoos and Aquariums. Briefly, when management strategies are successful, they result in reproductively robust populations that better retain genetic diversity and limit inbreeding than unmanaged populations. Although the benefits of demographic and genetic management have been well documented throughout both the scientific and popular literature, it has also been established that the majority of managed populations in zoos and aquariums are not meeting the minimum criteria believed to convey long-term biological viability. For most of these populations, an inability to meet viability criteria is not an inherent failure of how cooperative management is implemented. Furthermore, in recent years, we have perceived that the need to meet specific viability goals sometimes has obscured the benefits that these populations receive from rigorous, science-based management. To better clarify the conversation surrounding population viability in zoos and aquariums, we seek to decouple viability measures and how they predict population persistence from the benefits conferred to populations through science-based management. A primary goal of population management is to facilitate the persistence of priority species for longer than would be expected if no such management were implemented. Although current viability measures and future projections of viability are important tools for assessing the likelihood of population persistence, they are not indicators of which populations may most benefit from science-based management. Here, we review the history and purpose of applying science-based management to zoo and aquarium populations, describe measures of population viability and caution against confusing those measures of viability with population management goals or long-term population sustainability, and clearly articulate the benefits conferred to zoo and aquarium populations by science-based management.

Contributions of distemper control and habitat expansion to the Amur leopard viability

The Amur leopard (Panthera pardus orientalis) is a critically endangered top predator that struggles on the brink of extinction due to threats such as canine distemper virus (CDV), habitat loss, and inbreeding depression. Here we develop a viability analysis metamodel that combines a traditional individual-based demographic model with an epidemiological model to assess the benefits of alternative population management actions in response to multiple distinct threats. Our results showed an extinction risk of 10.3%-99.9% if no management actions were taken over 100 years under different levels of inbreeding depression. Reducing the risk of CDV infection in Amur leopards through the low-coverage vaccination of leopards and the management of sympatric domestic dogs could effectively improve the survival probability of the leopard population, and with habitat expansion added to these management measures, the population expanded further. Our findings highlight that protecting the Amur leopard necessitates a multifaceted synergistic effort, and controlling multiple threats together may significantly escalate overall viability of a species, especially for small-isolated threatened population. More broadly, our modeling framework could offer critical perspectives and scientific support for conservation planning, as well as specific adaptive management actions for endangered species around the world.

In the absence of management strategies, canine distemper virus threatens the future existence of the endangered Amur leopard.