Mammalogy I

Contributed Oral

Differential Colonization Responses of Mammals to Long-Duration Floods
Lacy Dolan, Jennifer Nelson, William McKinley, Kristine Evans, Bronson Strickland, Dana Morin

Increasing the frequency and severity of disturbance regimes can have large and cascading effects on ecosystems. The South Delta region of Mississippi experienced an unusually severe long-duration flood in 2019 that excluded terrestrial wildlife from >2,000 km2 of habitat on private, public, and agricultural areas for 8 months. A camera trap survey was conducted one month after the floodwaters receded in a joint effort between private and public land stakeholders. To assess site use and activity of mammals in the former flood zone we fit occupancy models to data from the camera trap survey.  From the model results, we made predictions about return and recovery of white-tailed deer (Odocoileus virginianus), coyote (Canis latrans), rabbit (Sylvilagus sp.), armadillo (Dasypus novemcinctus), and squirrel (Sciurus sp.) populations to the habitats that were inaccessible during the catastrophic floods. We expected recovery would occur first in the northern and eastern regions of the impacted areas as animals returned from refugia at higher elevations, and small-bodied species would be slower to return and less likely to use areas that experienced greater flooding in the months preceding. Deer occurred throughout the study area at greater encounter rates, while other species appeared slower to return. Latitude and longitude showed the strongest effects on species occupancy. Coyotes and squirrels used areas to the north where flood water receded first, and rabbits used sites to the south, suggesting rabbits may be better adapted to post-flood habitat. Rabbits also occurred farther east suggesting use of the hills as refugia, whereas armadillos used only sites to the west, suggesting use of the levee system along the Mississippi River during the flood. Simulations of recolonization based on early site use patterns indicate increased frequency of these severe events, as predicted, could substantially change the mammal community in this region.

Anthropogenic Effects on Ocelot Density in the Maya Biosphere Reserve in Guatemala
Gabriela Palomo, Chris Sutherland, Rony Garcia-Anleu, Andrew Tyre

Human activities reduce or limit space for some carnivores, and in turn affect their demographic structure. Some carnivores have shown an increase in their densities in small forest fragments but this response may be exclusive to species that benefit from highly disturbed habitat matrix. The majority of estimates of carnivore populations have been conducted in protected areas, potentially limiting the effects of anthropogenic influences. As such, relatively little is known about how human disturbances affect carnivore ecology and demography, especially for neotropical carnivores. Ocelots (Leopardus pardalis) are medium-sized carnivores present in modified landscapes such as agricultural patches, although remaining strongly associated with dense habitat cover near those areas. Here we investigate the spatial variation in ocelot density due to human activities and ecological factors such as top carnivore presence and prey biomass availability. We used camera trap data collected in five protected areas in Guatemala in 2007, 2008, 2013, 2017, and 2019 and identified individuals by differentiating their unique spot pattern from both flanks. We obtained 18,633 camera trap nights and 748 independent ocelot records across all areas. We integrated spatial and ecological covariates to estimate variation in ocelot density in all areas by using spatially explicit capture recapture models. Here we provide the first density estimation of ocelots in Guatemala that are critical for improving conservation practices in the region.

Using Occupancy Modeling to Estimate American Marten Distribution in Michigan’s Lower Peninsula
Maria Weston, Paul Keenlance, Angela Kujawa, Robert Sanders

American marten (Martes americana) were extirpated from Michigan’s Lower Peninsula in the early-20th century due to habitat loss, habitat degradation, and overharvesting. In the 1980s, eighty-five marten were reintroduced in total between two areas of their historical range in Michigan: the Manistee National Forest and the Pigeon River County State Forest. However, a lack of monitoring post-release has led to considerable uncertanty about their current distribution. Determining marten occurrence is a crucial first step when attempting to implement active management techniques for this imperiled species that has both ecological and cultural significance within the state of Michigan. To assess current marten distribution throughout the northern Lower Peninsula (NLP), the main objectives for this project were to (1) Use occupancy modeling to estimate American marten occurrence in the NLP using species detections from a large-scale camera trap study, (2) Determine the detection probability of American marten in the NLP, and (3) Determine if habitat covariates or the presence/absence of predators and conspecifics can be used to estimate marten occurrence. We used detection-nondetection data from a large-scale camera trap study encompassing 27,371km2 of state and federal lands to estimate marten occurrence across Michigan’s northern Lower Peninsula. We modeled marten occupancy as a function of our series of covariates which indicate that marten occupy 19% of sites surveyed from 2019-2020 with a detection probability of 22%. Model predictions indicate high occupancy probabilities (>0.90) when canopy cover is high (>0.84), and when predators were not detected at the site. In this study, we demonstrate the use of occupancy modeling as an aid to determining species distribution and improving management decisions when abundance data is otherwise unavailable.

Terrestrial Habitat Use Is Risky for American Mink in a Highly Modified Landscape
Adam Ahlers, Robert Schooley, Edward Heske, Mark Mitchell

Changes to terrestrial landscapes, such as from intensive agriculture and wetland drainage, may generate a novel set of mortality risks for species. Semiaquatic species must move through terrestrial areas to find supplementary resources or to increase mating opportunities. However, movements in terrestrial areas may expose individuals to increased predation risk or negative human interactions. We used radiotelemetry and known-fate models of survival to evaluate risks associated with terrestrial habitat use for American mink (Neovison vison) in Illinois, USA (2009-2013). This region has experienced widespread landscape changes and is now an agroecosystem devoid of nearly all natural wetlands and riparian habitats. Male mink were more likely to use terrestrial habitat, and had lower survival probabilities, than females. Survival rates were lower during mating season (February-April) than during non-mating season, and adult mink had higher survival probabilities than subadults. Mink using terrestrial habitat had greater mortality risks than those that remained closer to the stream edge in this human-dominated landscape. Our study assessed the relative mortality risk for a semiaquatic mammal when using riparian versus terrestrial habitats in a human-modified landscape. Future studies should evaluate whether increased risk for semiaquatic mammals in terrestrial habitats occurs in other more natural and heterogeneous landscapes, or only in human-dominated landscapes.

Can a Mesocarnivore Fill the Functional Role of an Apex Predator?
Alexandra Avrin, Christopher Wilmers, Charles Pekins, Jinelle Sperry, Maximilian Allen
As keystone species, apex predators play a role in structuring most ecosystems on Earth through competition and facilitation, thereby affecting community structure, prey abundance and behavior, vegetation, and abiotic processes. Apex predators are also highly threatened and have been extirpated from much of North America leading to mesocarnivores, such as coyotes (Canis latrans), becoming de facto apex predators in many ecosystems. However, it is unknown if these mesocarnivores can fill the same functional keystone role as true apex predators. We compared the spatial and temporal habitat use of mesocarnivores in two similar study systems, one with pumas, and one without to determine how the role of coyotes in structuring the carnivore community changes in the absence of pumas. We used multispecies occupancy modeling and relative abundance to examine the spatial avoidance of pumas and coyotes by the smaller mesocarnivores. We also used temporal overlap based on kernel density and avoidance-attraction ratios to examine temporal avoidance by the same species. We found that coyotes partially fill the functional role of apex predators but with weaker effects than pumas. Where pumas were absent, site use intensity and relative abundance increased for coyotes (180% and 1,081%) and racoons (308% and 3,077%) and decreased for bobcats (41% and 68%) gray foxes (13% and 42%) and striped skunk (3% and 15%). Coyotes and racoons shifted their temporal activity away from pumas in their presence while gray foxes shifted theirs closer. All species were less likely to pass after a puma or coyote in both sites but avoided pumas more strongly than coyotes when pumas were present. Interactions between carnivores are complex and best understood with multiple measures and in the context of the full community. While coyotes do suppress smaller mesocarnivores by some measures, they do not by others (e.g., spatial avoidance) and have overall weaker effects than pumas. Further, coyotes do not regulate prey or provide carrion to scavengers as effectively and may cause more conflict with humans. Our results suggest that coyotes are not a substitute for apex predators and protecting true apex predators is imperative for maintaining ecosystem health.
Understanding the Role of the Western Spotted Skunk in Forests of the Pacific Northwest
Marie Tosa, Damon Lesmeister, Taal Levi

Increased knowledge of the natural history and spatial ecology of organisms can help us understand how they interact with other species and the role that these species play in their ecosystems. In the Pacific Northwest, the western spotted skunk (Spilogale gracilis) is one of the most abundant forest-adapted carnivores, but little is known about their ecology partly due to their nocturnal nature and cryptic behavior. Using individual location data and scats collected with scat-detection dogs, we describe the spatial ecology and diet of western spotted skunks in the Willamette National Forest, Oregon USA. During October 2017 – August 2019, we deployed radio-collars on 25 western spotted skunks (9 females, 16 males), relocated western spotted skunks 1222 times, and collected 107 western spotted skunk scats from summer (n=45) and fall (n=62). Mean spotted skunk home range was 859 ha (95% minimum convex polygon) and mean core home range was 192 ha (50% minimum convex polygon). Spotted skunks used both even-aged plantation areas and old-growth forests. Scat analysis through DNA metabarcoding revealed that spotted skunk have omnivorous diets that consisted of vertebrates (41.7%), vegetation (14.8%), and arthropods (47.2%). Common vertebrate prey species included the pacific tree frog (Pseudacris regilla), shrew-mole (Neurotrichus gibbsii), Townsend’s chipmunk (Tamias townsendii), Swainson’s thrush (Catharus ustulatus), and Humboldt’s flying squirrel (Glaucomys oregonensis), and Hymenopteran wasps. Spotted skunks consumed more songbirds during the summer and more amphibians and small mammals in the fall. Together, our findings suggest that the western spotted skunk plays an important role in the Pacific Northwest Forests by providing linkages between the aquatic, terrestrial, and arboreal ecosystems.

Migration Strategies of Mule Deer on Navajo Nation Lands
Hannah Manninen, Clayton Nielsen, Jessica Fort, Guillaume Bastille-Rousseau, Jeffrey Cole

Mule deer (Odocoileus hemionus) populations have declined throughout their range in the western United States since the 1980s. Habitat loss, overgrazing, disease, and predation contribute to the decline of mule deer populations. Navajo Nation, the largest sovereign tribe in the United States, encompassing 71,000 km2 in New Mexico, Arizona, and Utah, has experienced a 49% decline in mule deer over the past decade.  We studied migration of mule deer on Navajo Nation lands to determine core areas used during migration and in seasonal ranges. We placed GPS collars on 99 mule deer (79 F, 20 M) during 2018-2020. Movements were analyzed using net-squared displacement for individuals with >6 mo of data.  Movement trajectories (n = 108) from 66 unique mule deer were analyzed to determine whether mule deer were long-distance migrants, short-distance migrants, or non-migrants; we additionally quantified distances traveled and duration of migrations. Seventy-four percent (n=49) of mule deer were long-distance migrants, 20% (n=13) were short-distance migrants, and 6% (n=4) were non-migrants. Minimum distance traveled during migration was 4.5 km, the maximum distance was 69 km, and mean distance traveled for migrants was 18.9 ± 9.6 km.  Mean duration of spring and fall migrations were 12 days each. Spring migration occurred during 19 April – 2 May, while fall migration occurred during 26 October – 9 November.  Migration behavior of mule deer on Navajo Nation lands were generally similar to other populations in the southwest, but were dissimilar to northern populations, as the Navajo Nation migrations were shorter in both distance and duration. Our project will deliver information that can be used to protect high-use areas by mitigating wildlife-vehicle collisions, restore habitat in winter ranges, reassess game management units, and manage for overgrazing by feral horses.

Analysis of Red Bat Echolocation Behavior in the Presence of An Ultrasonic Acoustic Deterrent
Emma Guest, Brittany Stamps, Sara Weaver, Amanda Hale, Brogan Morton, Janine Crane, Mark Chaffee, John Ugland, Cris Hein, Sarah Fritts

Wind energy provides potential to combat global climate change by lowering carbon emissions and reducing water consumption. However, an unintended consequence of wind energy development is bat fatalities caused by turbine blade strikes. Ultrasonic acoustic deterrents (UADs), produced to “jam” bat echolocation and cause airspace surrounding turbines to be undesirable, have resulted in lower overall bat fatalities in some preliminary studies. However, effectiveness at the species level is variable, potentially due to some species altering their echolocation frequency to resist UAD jamming. Our objective was to maximize effectiveness of an UAD (NRG Systems) by filling knowledge gaps regarding bat behavior during UAD emissions. Herein we examined the influence of various UAD emissions on bat echolocation with a 60 m- x 10 m- x 4.5 m (l x w x h) flight cage located in San Marcos, Texas, USA. We released 26 wild-captured eastern red bats (Lasiurus borealis), a species commonly killed by wind turbines, into the flight cage from July–October 2020 and monitored echolocation frequencies with six ultrasonic microphones dispersed throughout the flight cage. Each trial consisted of three randomly ordered treatment periods in which a UAD broadcasted frequency ranges of 20–50 kHz, 20–32 kHz, or 38–50 kHz interspersed with control periods of no UAD emissions. All treatments and controls lasted four minutes. Results comparing shifts in maximum, minimum, and characteristic frequencies using Kolmogorov–Smirnov tests and empirical cumulative distribution functions suggest eastern red bats are shifting their maximum frequency during the 20–50 kHz treatment (P = 0.04) potentially to broaden their frequency range to navigate the sound-cluttered airspace caused by the UAD. Our results will guide improvement of UAD effectiveness to reduce turbine related bat fatalities.

Small Mammal Dynamics in Snow-Covered Forests
Allison Scott, Jonathan Gilbert, Jonathan Pauli

In seasonal environments, the winter months can drive the structure and dynamics of vertebrate communities. Most ecological studies have focused on species above the snow, overlooking those within the subnivium. The Great Lakes region of North America is characterized by seasonal snow cover and a diverse assemblage of small mammals, both of which are changing rapidly. To study the seasonal dynamics of small mammals, we sampled communities in three forest types (hardwood, hemlock-cedar, and spruce bog) in summer and winter over two years. We hypothesized that seasonal differences in communities would be moderated by forest structure in summer and snow in winter. We assessed community dominance via species diversity and the abundances of deer mice (Peromyscus maniculatus), white-footed mice (P. leucopus), and southern red-backed voles (Myodes gapperi). We estimated a community temperature index (CTI; a metric of the balance between warm- and cold-adapted species in a community) and tested seasonal drivers of CTI. Species diversity was highest in spruce bogs in winter due to increased species evenness, but diversity was consistent year-round in hardwood and hemlock-cedar forests due to unchanging species dominance. Spruce bogs supported the coldest CTI in summer, but CTIs converged across forest types in winter. In summer, forest structure drove CTI; in winter, colder CTI was associated with deeper snow and a warmer subnivium. Our work reveals that snow is a critical habitat and filter for cold-adapted species that ultimately structures small mammal communities. Given rapid changes in snow conditions due to climate change, we predict continued range contractions for subnivium-adapted species.

Influences of Landscape Patterns and Intraguild Interactions on the Spatial and Temporal Ecology of Bobcats and Coyotes
Marlin Dart, Lora Perkins, Jonathan Jenks, Chad Lehman, Robert Lonsinger

Carnivore conservation requires an understanding of how landscape patterns and intraguild interactions influence the spatial and temporal dynamics of species. In the Northern Great Plains, habitat loss and fragmentation driven by conversion of grasslands to agriculture may influence carnivores by reducing opportunities for spatial partitioning. Still, co-existence may be facilitated through temporal partitioning. In South Dakota, bobcats (Lynx rufus) are a species of management interest that are potentially vulnerable to habitat alterations and may be influenced by interspecific interactions with coyotes (Canis latrans). During the summers of 2019 and 2020, we used motion-activated cameras to generate detection data for bobcats and coyotes, evaluated the influence of habitat characteristics on space use of each species with occupancy modeling, and used activity curves to quantify overlap in temporal activity between species. Coyote space use was high (2019: 0.95, 95% CI = 0.72–0.99; 2020: 0.74, CI = 0.63–0.82) and limited our ability to formally test patterns of co-occurrence. Instead, we used a measure of relative coyote activity to evaluate the influence of coyotes on bobcat space use. Bobcat space use was low (2019: 0.08, CI = 0.03–0.19; 2020: 0.14, CI = 0.05–0.34) and positively associated with coyote activity in both years, and distance to roads and large-scale percent woodland/shrubland in 2020. Bobcat use was negatively related to mean patch size in both years, potentially a consequence of large patches of agriculture. Coyote space use was positively related to slope, large-scale percent woodland/shrubland, and small-scale percent agriculture in 2019, and positively related to the amount of edge in 2020. We found no evidence of temporal partitioning. Our results indicate that bobcats are using smaller, less-disturbed patches of woodland/shrubland, which are also associated with higher levels of coyote activity.

Contributed Oral
Location: Virtual Date: November 2, 2021 Time: 4:00 pm - 5:00 pm