The difficulty of detecting inbreeding depression and its effect on conservation decisions

Statistical inferences about inbreeding depression are often derived from analyses with low power and a high risk of failing to detect inbreeding depression. That risk is widely appreciated by scientists familiar with the relevant statistical and genetical theory, but may be overlooked and underappreciated by decision-makers. Consequently, there is value in demonstrating this risk using a real example. We use data from the wolf population on Isle Royale to demonstrate the difficulty of making reliable statistical inferences about inbreeding depression. This wolf population is known-by other methods-to have gone effectively extinct due to deleterious genetic processes associated with inbreeding. Beyond that demonstration, we use two case-studies-wolves on Isle Royale and vaquita (porpoises) from the Gulf of California, Mexico-to show how statistical inferences about inbreeding depression can affect conservation decisions. According to most decision theory, decisions depend importantly on: 1) probabilities that certain states exist (e.g. inbreeding depression is present) and 2) the utility assigned to various outcomes (e.g. the value of acting to mitigate inbreeding when it is present). The probabilities are provided by statistical inference; whereas utilities are almost entirely determined by normative values and judgements. Our analysis suggests that decisions to mitigate inbreeding depression are often driven more by utilities (normative values) than probabilities (statistical inferences). As such, advocates for mitigating inbreeding depression will benefit from better communicating to decision-makers the value of populations persisting and the extent to which decisions should depend on normative values.

The role of governance in rewilding the United States to stem the biodiversity crisis

A critical but underattended feature of the biodiversity crisis is the contraction of geographic range experienced by most studied terrestrial vertebrates. In the United States, the primary policy tool for mitigating the biodiversity crisis is a federal law, the Endangered Species Act (ESA). For the past two decades, the federal agencies that administer the ESA have interpreted the act in a manner that precludes treating this geographic element of the crisis. Therefore, the burden of mitigating the biodiversity crisis largely falls on wildlife agencies within state government, which are obligated to operate on behalf of the interests of their constituents. We present survey research indicating that most constituents expect state agencies to prioritize species restoration over other activities, including hunting. This prioritization holds even among self-identified hunters, which is significant because state agencies often take the provisioning of hunting opportunity as their top priority. By prioritizing rewilding efforts that restore native species throughout portions of their historic range, state agencies could unify hunting and nonhunting constituents while simultaneously stemming the biodiversity crisis.

The Role of Wolves in Regulating a Chronic Non-communicable Disease, Osteoarthritis, in Prey Populations

It is widely accepted that predators disproportionately prey on individuals that are old, weak, diseased or injured. By selectively removing individuals with diseases, predators may play an important role in regulating the overall health of prey populations. However, that idea is seldom tested empirically. Here we assess the extent that wolves (Canis lupus) select adult moose (Alces alces) in Isle Royale National Park on the basis of age-class and osteoarthritis, a chronic, non-communicable disease. We also assess how temporal variation in kill rates (on moose by wolves) were associated with the subsequent incidence of osteoarthritis in the moose population over a 33-year period (1975–2007). Wolves showed strong selection for senescent moose and tended to avoid prime-aged adults. However, the presence of severe osteoarthritis, but not mild or moderate osteoarthritis, appeared to increase the vulnerability of prime-aged moose to predation. There was weak evidence to suggest that senescent moose with osteoarthritis maybe more vulnerable to wolves, compared to senescent moose without the disease. The incidence of osteoarthritis declined following years with higher kill rates–which is plausibly due to the selective removal of individuals with osteoarthritis. Together those results suggest that selective predation plays an important role in regulating the health of prey populations. Additionally, because osteoarthritis is influenced by genetic factors, these results highlight how wolf predation may act as a selective force against genes associated with developing severe osteoarthritis as a prime-aged adult. Our findings highlight one benefits of allowing predators to naturally regulate prey populations. The evidence we present for predation’s influence on the health of prey populations is also relevant for policy-related arguments about refraining from intensively hunting wolf populations.

Can Deliberative Democracy Favor a Flourishing Relationship Between Humans and Carnivores?

There is considerable interest in improving participatory governance in decision-making processes for the conservation of biodiversity and management of conflicts between humans and wildlife. Among the various modes of participatory governance, deliberative democracy has received virtually no attention for decisions focused on conserving biodiversity. This is surprising given that deliberative democracy is an important branch of democratic theory and is associated with decision-making processes that have been successfully applied to a wide range of complicated decisions across diverse cultural settings. Moreover, deliberative democracy has several distinctive properties that would seem to make it well-suited for many conservation decisions. First, deliberative democracy is better-designed than other processes to handle cases where the object of conservation appears to be insufficiently valued by those who have the most detrimental impacts on its conservation. Second, deliberative democracy engenders a rich kind of representation and impartiality that is nearly impossible to achieve with participatory governance focused on managing conflicts among hyper-engaged stakeholders. Here, we review the principles of deliberative democracy, outline procedures for its application to carnivore conservation, and consider its likelihood to favor carnivore conservation.

The Elephant in the room: What can we learn from California regarding the use of sport hunting of pumas (Puma concolor) as a management tool?

Puma (Puma concolor) management in the western United States is highly contentious, particularly with regard to the use of sport hunting as a management tool. Since the 1970s, puma in ten western states have been managed by state fish and game agencies through the use of a sport hunt. The rationale presented by wildlife managers is that sport hunting, in addition to providing recreational hunting opportunities, also reduces threats to human safety and livestock safety, and increases populations of the puma’s ungulate prey, namely deer (Odocoileus sp.) and elk (Cervus elepus). We evaluated these claims using the state of California as a control, which has prohibited sport hunting since 1972, and employing data obtained from state and federal agencies with authority and control over puma management. Specifically, we tested four hypotheses: 1) sport hunting will suppress puma populations, 2) sport hunting will reduce the number of problematic puma-human encounters; 3) sport hunting will reduce puma predation on domestic livestock, and 4) sport hunting will reduce the impact of puma predation on wild ungulate numbers, resulting in increased hunting opportunities for the sport hunt of ungulates. Our results indicated, respectively, that relative to the 10 states where puma are hunted, California had 1) similar puma densities, 2) the 3^rd lowest per capita problematic puma-human encounters, 3) similar per capita loss of cattle (P = 0.13) and a significantly lower (t = 5.7, P < 0.001) per capita loss of sheep, and 4) similar average deer densities while changes in annual deer populations correlated with changes in other states (F = 95.4, P < 0.001, R² = 0.68). In sum, our analysis of the records obtained from state and federal wildlife agencies found no evidence that sport hunting of pumas has produced the management outcomes sought by wildlife managers aside from providing a sport hunting opportunity. Consequently, and particularly because other research suggests that sport hunting actually exacerbate conflicts between pumas and humans, we recommend that state agencies re-assess the use of sport hunting as a management tool for pumas.