Douglas W. Smith’s research while affiliated with National Park Service and other places

COVID-19 lockdowns in early 2020 reduced human mobility, providing an opportunity to disentangle its effects on animals from those of landscape modifications. Using GPS data, we compared movements and road avoidance of 2300 terrestrial mammals (43 species) during the lockdowns to the same period in 2019. Individual responses were variable with no change in average movements or road avoidance behavior, likely due to variable lockdown conditions. However, under strict lockdowns 10-day 95th percentile displacements increased by 73%, suggesting increased landscape permeability. Animals' 1-hour 95th percentile displacements declined by 12% and animals were 36% closer to roads in areas of high human footprint, indicating reduced avoidance during lockdowns. Overall, lockdowns rapidly altered some spatial behaviors, highlighting variable but substantial impacts of human mobility on wildlife worldwide.

Although it is well established that density dependence drives changes in organismal abundance over time, relatively little is known about how density dependence affects variation in abundance over space. We tested the hypothesis that spatial trade‐offs between food and safety can change the drivers of population distribution, caused by opposing patterns of density‐dependent habitat selection (DDHS) that are predicted by the multidimensional ideal free distribution. We addressed this using winter aerial survey data of northern Yellowstone elk (Cervus canadensis) spanning four decades. Supporting our hypothesis, we found positive DDHS for food (herbaceous biomass) and negative DDHS for safety (openness and roughness), such that the primary driver of habitat selection switched from food to safety as elk density decreased from 9.3 to 2.0 elk/km². Our results demonstrate how population density can drive landscape‐level shifts in population distribution, confounding habitat selection inference and prediction and potentially affecting community‐level interactions.

Over the past two decades, populations of Shiras moose (Alces alces shirasi) in western Wyoming have declined. Recent work on the Jackson herd in northwest Wyoming suggests that the 1988 Yellowstone fires and regional drought contributed to a considerable decline in calf recruitment, which coincided with the recovery of grizzly bears (Ursus arctos horribilis) and gray wolves (Canis lupus occidentalis) to the Greater Yellowstone Ecosystem (GYE). Predation is also presumed to have contributed to declines in calf recruitment, but the relative influence of these predators has yet to be evaluated. We analyzed a time series of vital rates to identify the spatial extent and intensity at which predator density, habitat condition, and interacting abiotic factors limit population growth. We focused on neonate and winter calf survival because calves are the most vulnerable age class and because calf recruitment been shown to be one of the most important vital rates influencing population dynamics in large herbivores. Variables affecting calf survival were calculated at the seasonal home range scale from 100 individuals in the Jackson herd, and 90 individuals in an adjacent herd directly to the south, where moose are exposed to markedly lower predator density. We detected negative effects of grizzly bear density and habitat condition on neonate survival. Wolf density negatively influenced winter calf survival, but the effect was weak. Our spatial analysis of individual fitness in these two herds suggests that Shiras moose in the GYE have struggled to cope simultaneously with the effects of sub-optimal habitat conditions and predator density, highlighting the need to prioritize efforts to conserve Shiras moose as climate change continues to progress.

Over the past two decades, populations of Shiras moose (Alces alces shirasi) in western Wyoming have declined. Recent work on the Jackson herd in northwest Wyoming suggests that the 1988 Yellowstone fires and regional drought contributed to a considerable decline in calf recruitment, which coincided with the recovery of grizzly bears (Ursus arctos horribilis) and gray wolves (Canis lupus occidentalis) to the Greater Yellowstone Ecosystem (GYE). Predation is also presumed to have contributed to declines in calf recruitment, but the relative influence of these predators has yet to be evaluated. We analyzed a time series of vital rates to identify the spatial extent and intensity at which predator density, habitat condition, and interacting abiotic factors limit population growth. We focused on neonate and winter calf survival because calves are the most vulnerable age class and because calf recruitment been shown to be one of the most important vital rates influencing population dynamics in large herbivores. Variables affecting calf survival were calculated at the seasonal home range scale from 100 individuals in the Jackson herd, and 90 individuals in an adjacent herd directly to the south, where moose are exposed to markedly lower predator density. We detected negative effects of grizzly bear density and habitat condition on neonate survival. Wolf density negatively influenced winter calf survival, but the effect was weak. Our spatial analysis of individual fitness in these two herds suggests that Shiras moose in the GYE have struggled to cope simultaneously with the effects of sub-optimal habitat conditions and predator density, highlighting the need to prioritize efforts to conserve Shiras moose as climate change continues to progress.

Wolves in road packs and the probability of wolf sightings along the Denali Park Road, Alaska, USA. Cumulative count of wolves in road packs in the eastern region of Denali National Park and Preserve (grey bars) and the probability of wolf sightings along the Denali Park Road (black triangles) from 1997 to 2012. Shading indicates years with a harvest buffer zone adjacent to the park in effect. (TIF)

Recording Wildlife Sightings in Denali National Park and Preserve. (DOCX)

Summary of wolf harvest for the Eastern Region of Denali National Park and Preserve, Alaska, USA. Population size estimates, number of collared wolves, number of collared breeding wolves, and their proportions in the population and harvest included. Population size, number of collared wolves, and number of collared breeders were pre-hunt numbers. (DOCX)

Annual probability of sighting index for Yellowstone National Park, Wyoming, USA. Sample size (in number of days within the observation period), number of days with wolf sightings, relative effort for each year (calculated as hours of effort in the given year divided by the maximum number of hours in the field from sampled years), and annual probability of sighting index for wolves in the Lamar Valley and Little America region of Yellowstone National Park from 2008 to 2013. (DOCX)

The desire to see free ranging large carnivores in their natural habitat is a driver of tourism in protected areas around the globe. However, large carnivores are wide-ranging and subject to human-caused mortality outside protected area boundaries. The impact of harvest (trapping or hunting) on wildlife viewing opportunities has been the subject of intense debate and speculation, but quantitative analyses have been lacking. We examined the effect of legal harvest of wolves (Canis lupus) along the boundaries of two North American National Parks, Denali (DNPP) and Yellowstone (YNP), on wolf viewing opportunities within the parks during peak tourist season. We used data on wolf sightings, pack sizes, den site locations, and harvest adjacent to DNPP from 1997-2013 and YNP from 2008-2013 to evaluate the relationship between harvest and wolf viewing opportunities. Although sightings were largely driven by wolf population size and proximity of den sites to roads, sightings in both parks were significantly reduced by harvest. Sightings in YNP increased by 45% following years with no harvest of a wolf from a pack, and sightings in DNPP were more than twice as likely during a period with a harvest buffer zone than in years without the buffer. These findings show that harvest of wolves adjacent to protected areas can reduce sightings within those areas despite minimal impacts on the size of protected wolf populations. Consumptive use of carnivores adjacent to protected areas may therefore reduce their potential for non-consumptive use, and these tradeoffs should be considered when developing regional wildlife management policies.

Model selection table evaluating factors potentially affecting probability of wolf sightings in Denali National Park and Preserve, Alaska, USA (including the factor RoadPop). Candidate model set includes the factor RoadPop. K is the number of parameters in the model, PNRI is the Pack Near Road Index, TotalPop is the wolf population size, RoadPop is the number of wolves in packs that overlap the Denali Park Road, Buffer is a factor indicating the presence/absence of a harvest buffer, WolfHarv is the number of wolves harvested in the prior year and BreedHarv is a binary factor describing if breeders were or were not harvested from road packs in the prior year. (DOCX)