Conservation and Ecology of Mammals IV

Contributed Paper
ROOM: HCCC, Room 16

12:50PM Does Harvest Influence the Size and Growth of Horns in Mountain Sheep?
Tayler LaSharr; Ryan Long; James Heffelfinger; R. Terry Bowyer; Vernon Bleich; Paul Krausman; Justin Shannon; Robert Klaver; Kevin Monteith
The influence of human harvest on the evolution of secondary sexual characteristics in wildlife is hotly debated, in part because of the implications of such effects for the sustainable management of wildlife populations. Population-level responses to harvest can include reduced size of horns or antlers, early sexual maturation, and reduced growth rates. In ungulate species in particular, assessing effects of harvest is challenging, because both age and phenotypic measurements are necessary to assess mechanisms of change through time. Harvest can affect patterns of change in horn and antler size of ungulates in 2 distinct ways. First, harvest can affect age structure, which can influence size of horns and antlers, because size of horns and antlers are affected strongly by age. Alternatively, changes to horn growth can occur through either changes in environmental conditions or selection by hunters for males with fast-growing horns. We evaluated how age, environment, and harvest influenced horn size of mountain sheep in 193 hunt areas over 35 years (1981 to 2016) in North America. Changes in mean horn size of harvested sheep in 60% of hunt areas were explained by age, indicating that those changes were related to shifts in demography rather than evolution. After accounting for both age and the environment, <8% of hunt areas showed signs of a potential evolutionary effect of harvest (i.e., change in horn growth through time). Even in hunt areas with declines in horn growth, however, levels of hunter selectivity and intensity were not consistent with observed changes of horn growth, which may indicate that selective harvest does not necessarily result in evolutionary change. Our results indicate that current harvest practices for most mountain sheep in North America likely are not resulting in evolutionary changes in horn size.
1:10PM Spatio-Temporal Dynamics of American Marten and Fisher in Michigan’s Upper Peninsula
Lizzie Croose; Florent Bled; Nicholas L. Fowler; Dean E. Beyer; Jerrold L. Belant
Understanding the mechanisms of coexistence of ecologically similar competing species is an important issue in ecology. Co-occurrence of small and medium carnivores sharing similar ecological niches and geographical areas has been seldom studied and corresponds to a dynamic process occurring over both spatial and temporal dimensions. American martens Martes americana and fishers Pekania pennanti are medium-sized mustelids occurring sympatrically in much of North America. Despite their widespread mutual distribution across the northern forests of North America, coexistence and co-dynamics of these two species are poorly understood. We examined spatio-temporal dynamics in martens and fishers in the Upper Peninsula of Michigan, USA, using data collected from remote cameras during winters 2013-2015. Using dynamic occupancy models, we assessed the impact of martens and fishers’ occurrence on their reciprocal yearly persistence and colonization probabilities. We also considered the effect of vegetation cover, hydrology and road network density. This study provides the first look at both temporal and spatial dynamics in martens and fishers in Michigan in relation to their ecology and mutual presence.
1:30PM Horn Size and Nutrition in Mountain Sheep: Can Ewe Handle the Truth?
Kevin L. Monteith; Ryan Long; Thomas Stephenson; Vernon Bleich; R. Terry Bowyer; Tayler LaSharr
Horns, antlers, and other horn-like structures are products of sexual selection, confer reproductive advantages, and are heritable and honest indicators of individual quality. Intensive harvest of large, fast-growing males, however, may have deleterious effects on the very trait being sought. Mountain sheep, possibly the only large ungulate in North America managed almost exclusively as a trophy species, embody this controversy because of the emphasis on managing for large males. Our goal herein was to discuss the relative contributions of ecological and intrinsic factors that influence horn growth, how those factors might interact with harvest strategies, and identify what determinants of horn size are most amenable to management and most effective in achieving desired outcomes. Based on data of horn size and age of males, and nutritional condition and size of females from animals captured during 2002-2016 across 6 populations in the Sierra Nevada, we evaluated associations between seasonal condition of females and age-specific horn size of males. As predicted, variation in age-specific size of horns across 6 populations, represented by predicted horn size of 7-year-old males, was correlated strongly with body mass (r2 = 0.93, P = 0.002) and IFBFat (r2 = 0.80, P = 0.016) of adult females in spring, and IFBFat of lactating females in autumn (r2 = 0.86, P = 0.007). Females play a critically important role, not just as the reproductive segment of the population responsible for producing young, but because maternal condition can produce life-long effects on size and growth of males (via maternal effects); and additionally, abundance of females, in turn, affects nutritional limitation within populations through density-dependent feedbacks. Ultimately, we call for greater recognition of the pervasive role of the ewe—and other female ungulates—in the production of trophy males and in contributions to population performance.
2:30PM Refreshment Break
3:20PM Environmental Correlates of American Marten Trapping Success in the Eastern Upper Peninsula, Michigan
Talesha J. Dokes; Gary J. Roloff; Dwayne Etter
American marten (Martes americana) were extirpated from Michigan in the 1930s, but reintroduction efforts and careful management have resulted in a population that supports a limited trapping season in the Upper Peninsula. Successful trappers must present harvested martens for a state or tribal seal, and at the time of sealing the approximate harvest location is recorded (to the nearest 2.6 km2). Little is known about the environmental correlates related to marten trapper success in Michigan. We obtained Michigan Department of Natural Resources (MDNR) marten harvest locations from 2006-2016 and examined the spatial pattern of capture likelihood relative to a suite of environmental variables deemed important to marten. From 2006-2016 trappers registered 2,471 (~225/year) marten. Given the approximate locations of harvest, we used a fixed kernel density estimator to portray a continuous surface of marten capture probability by year for the Upper Peninsula. We subsequently extracted the East Unit of the Hiawatha National Forest (~207,973.60 ha; East HNF) from this surface, and evaluated the spatial consistency of marten harvest from year to year. We found no significant difference in the locations of marten harvest likelihood over the 11 years we evaluated, indicating that marten were consistently captured from focal areas in the East HNF. We subsequently used generalized linear models to predict likelihood of marten harvest based on environmental factors, and report those results. Our study provides insights into focal tendencies of marten harvest (clumped distribution), and environmental variables that help explain those clumping tendencies.
3:40PM Climate Change Impacts on Deer and Moose in the Midwest
Sarah R. Weiskopf; Olivia LeDee; Laura Thompson
Climate change is an increasing concern for wildlife managers across the United States and Canada. Because climate change may alter populations and harvest dynamics of key species in the region, the Midwest Association of Fish and Wildlife Agencies (MAFWA) identified the impacts of climate change on ungulates as a priority research area. In this study, we conducted a literature review of projected climate change impacts in the Midwest and the potential impacts to white-tailed deer (Odocoileus virginianus) and moose (Alces americanus). Warmer temperatures and decreasing snowpack in the region are likely to favor survival of white-tailed deer. In contrast, moose are likely to become physiologically stressed in response to warming, and increasing deer populations spreading disease will likely exacerbate the problem. Although there is some uncertainty about exactly how the climate will change and to what degree, fairly robust projections make it very likely that deer will benefit from climate change and moose will be harmed. Managers should begin preparing for these changes by proactively creating management plans that take this into account.
4:00PM Assessing the Genetic Consequences of Snowshoe Hare Decline in Michigan
Genelle Uhrig; Eric Clark; Emily Latch
As Earth’s climate continues to change, species are becoming more vulnerable to population declines and extinction. Species whose survival is closely linked to the climatic environment and who inhabit the southern edges of their range are most vulnerable. It is expected that these populations would be the first to decline resulting in a loss of genetic variation that reduces the probability of adapting to their changing environment. Snowshoe hare (Lepus americanus) are closely linked to their environment through pelage changes that provide crypsis in winter and summer, and there is evidence of population declines along the southern edge of their range including in Michigan. However, no studies have examined the demography of this population and whether genetic consequences are occurring. Our study aims to characterize snowshoe hare density and abundance as well as genetic diversity and gene flow in the Hiawatha National Forest (Eastern portion) located in the Upper Peninsula of Michigan. We utilized non-invasive genetic tagging within a spatially explicit capture-recapture approach in which fecal pellets (n=850) were collected across 18 sites and genotyped at 10 microsatellite markers to identify individuals and estimate population and genetic characteristics. We present abundance and density across sites, measures of genetic diversity, patterns of genetic structure, gene flow and connectivity between sites. This information is vital for the management and conservation of snowshoe hare populations in decline along the species’ southern range as well as for understanding the genetic consequences of population declines resulting from climate change.
4:20PM Interacting Effects of Predation, Density-Dynamics, and Resource Availability on Southern Snowshoe Hare Populations
Alexej P.K. Siren
Snowshoe hare (Lepus americanus) populations along the southern extent of their range experience shallow snowpack and fragmented habitat, which increases susceptibility to predation and potentially reduces cyclicity compared to boreal populations. However, according to evolutionary trajectories, population stability is the opposite expectation for a population experiencing high predation pressure. Indeed, recent studies indicate that populations experiencing higher predation pressure may develop r-selected traits, including increased reproduction, smaller body size, and fluctuating populations; the opposite pattern is expected for populations living in resource-poor environments. We compared several demographic parameters between a lowland and a montane population in the northeastern US from 2015-2018 to evaluate the hypothesis that predation pressure influences the extent at which hare populations exhibit r– and K-selected traits. We used a combination of methods, including live-trapping, radio-telemetry, and fecal-pellet surveys, to evaluate research hypotheses. The montane population had significantly lower population density (0.09 hares/ha) due to the paucity of early-regenerating boreal forest. Predation was the primary source of mortality for both populations. However, survival for both winters was considerably higher for the montane population (82%) compared to lowland hares (47%). The ratio of adult to leveret captures was higher for the montane population (1.6:1) than the lowland population (0.9:1), indicating lower reproduction. Although body mass was 40 g larger on average for hares living in the montane region, this difference was not significant. Finally, montane populations exhibited lower annual variation (0.168 ± 0.003 hares/ha) than those living in lowland forests (0.34 ± 0.014 hares/ha), suggesting stable populations. Although our results are preliminary, and our study is limited by temporal replication, we suggest that southern hare populations exhibit more K-selected traits due to low predation pressure and this may explain dampened cyclicity compared to boreal populations.


Contributed Paper
Location: Huntington Convention Center of Cleveland Date: October 10, 2018 Time: 12:50 pm - 5:00 pm