Small Mammal Ecology & Management

Contributed Oral Presentations

SESSION NUMBER: 67

Contributed paper sessions will be available on-demand for the duration of the conference, then again at the conclusion of the conference.

 

Habitat Associations of Small Mammals in Riparian Ecosystems in the Blue Mountains, Eastern Oregon
Lindsay Millward; Todd Wilson; Matt Weldy; Adam Duarte; William Ripple
There is a growing interest and investment in restoring riparian ecosystems in the Pacific Northwest (PNW) to help conserve declining salmonid populations. Common restoration practices include tree and shrub planting, ungulate exclusion, and augmenting streams with coarse woody debris. The abundance and diversity of small mammals can be a useful index for measuring management effects on the broader ecosystem. Collectively, small mammals use almost all of the biophysical components of ecosystems, from subterranean dens to food resources in the canopies of trees. However, the microhabitat associations of small mammals in some regions of the PNW have been largely understudied. Our primary objective was to better understand habitat associations of small mammals within riparian ecosystems of the Blue Mountains in northeast Oregon, in order to better predict how management activities will change the distribution, abundance, and diversity of small mammal populations associated with riparian areas over time. We estimated abundances and spatial associations for 10 small mammal species and 5 vegetation life forms (grasses, forbs, sedges and rushes, shrubs, and conifers) using a multispecies binomial N-mixture model and live-trapping mark-recapture data recorded at 36 sites from 2014-2017 in the Upper Grande Ronde Basin, near La Grande, Oregon. Coverage of shrubs was positively associated with yellow-pine chipmunks (Tamias amoenus), deer mice (Peromyscus maniculatus), bushy-tailed woodrats (Neotoma cinerea), and golden-mantled ground squirrels (Callospermophilus lateralis), and negatively associated with montane voles (Microtus montanus) and western jumping mice (Zapus trinotatus). Coverage of sedges and forbs was positively associated with montane voles and vagrant shrews (Sorex vagrans). Coverage of conifers was positively associated with yellow-pine chipmunks and bushy-tailed woodrats, and negatively associated with montane voles and Columbian ground squirrel (Urocitellus columbianus). This study may lead to new strategies for restoring riparian and grassland systems throughout the western US.
Mammal Responses to a Gradient of Forest Harvesting Treatments Across Interior British Columbia
Alexia Constantinou
Forest harvesting is part of the economic backbone of British Columbia, but the widespread use of clearcutting and the resulting homogenized landscape can be problematic for mammal species that depend on forest cover and structural diversity in uneven-aged stands. Partial harvest methods have been used to mitigate the effects of clearcuts on biodiversity while maintaining structural and functional diversity. Since winter 2018, we have been operating camera traps across a climate gradient in the interior of BC in forest harvesting treatments: clearcuts, seed tree retention, 30% and 60% partial harvests and uncut control forest. Concurrently, we live-trapped small mammals at the most northern site to determine the effects of the forest harvesting treatments on the entire terrestrial mammal community, and also incorporated a camera trap system specifically set up to analyze small mammals. We expect that partial harvesting treatments create conditions that allow usage by species that are forest-dependents or prefer closed canopy forest can use these harvest plots, as well as more generalist species that can thrive in open-canopy areas. By using non-invasive camera traps on small scale harvests, we are able to evaluate the frequency of usage of these harvesting techniques by all species, as well as their behaviour. We used generalized linear mixed effect models to determine usage of each of these treatments by all species, and spatially explicit capture-recapture models to determine density of small mammals in each treatment. Thus far, results indicate that partial harvesting sites have similar small mammal diversity to control forests, which are both greater than diversity in clearcuts. In British Columbia, forest industry influences are combining with environmental and climate change, creating compounding effects on wildlife habitats. Our results will improve understanding of wildlife responses to alternative forest harvest strategies across a climate gradient.
Habitat Associations of Small Mammal Communities in Restored Prairie Patches of Southern Illinois
Alex Glass; Michael W. Eichholz
Extensive habitat loss and degradation has transformed the grasslands of North America into one of the continent’s most vulnerable ecosystems and has greatly imperiled the plants and animals that depend on them. Small mammal communities play a pivotal role in maintaining the health and function of grassland and managing small mammal populations is an important, though overlooked, part of grassland restoration and management. Here, we identify habitat variables in restored tallgrass prairie patches that are most strongly associated with variation in small mammal abundance, with the goal of aiding management efforts to manipulate small mammal populations. We found that at the local vegetation scale, small mammal abundance was negatively related to both litter depth and plant diversity. At the landscape scale, small mammal abundance was positively associated with the amount of water surrounding a patch, and negatively associated with the amount of grassland surrounding a patch. Differences in small mammal community composition were largely governed by structural differences at the landscape level, instead of differences in vegetation structure at the local scale. We suggest that managers interested in influencing small mammal abundance in grasslands employ tools such as prescribed fire to decrease litter depth, or sow a high diversity of seed mixes to increase plant diversity.
Estimating Abundance of Southern Flying Squirrels Fragmented Midwestern Landscapes Using Spatial Capture-Recapture Models
Katherine A. Rexroad; Dr. Christopher Jacques; Dr. Robert Klaver; Seán Jenkins
Spatial capture-recapture (SCR) models are rigorous analytical tools that extend traditional closed population models by incorporating spatial information from mark-recapture data and distance between traps (i.e., Sherman trap) and animal activity centers to model spatially explicit encounter probabilities. Our objective is to evaluate the efficacy of SCR models for estimating density of a presumed low‐density southern flying squirrel population in fragmented Midwestern landscapes along the western edge of their geographic range. We integrated telemetry and capture location data from previously trapped (2015-2018) SFS into SCR models using the OSCR package in Program R. During winter 2015 and 2016, we estimated 1.64 squirrels per ha (95% CI = 1.06-2.51) and 3.10 individuals per ha (95% CI = 1.11-9.16), respectively. In addition, SFS density estimates ranged from 0.18 individuals per ha (95% CI = 0.10-0.34) to 0.25 squirrels per ha (95% CI = 0.16-0.39) during summer 2016 and 2017, respectively. Our SCR-derived estimates of SFS density are among the lowest reported in the literature, though may reflect structural differences in previously reported density estimators. Nevertheless, our ability to estimate density of SFS with relatively high precision is encouraging and should increase the confidence and flexibility of using live-trapping concurrent with SCR modeling for future conservation of SFS across a range of habitat types and animal densities. In addition, live-trapping combined with SCR modeling could provide a standardized analytical framework for comparing range-wide density data for SFS from multiple studies, and establishment of ecological benchmarks for understanding potential effects of habitat fragmentation on future assessments of SFS density across Midwestern landscapes.
Can Fluvial Geomorphology Predict New Mexico Meadow Jumping Mouse Occupancy
Charlotte A. Rozanski; Carol Chambers; Stu Tuttle; Marcus Miller; W. Barry Southerland
The New Mexico meadow jumping mouse (Zapus hudsonius luteus) is a federally endangered small mammal. This riparian obligate requires dense, structurally diverse riparian vegetation and perennial flowing water. Alterations to the natural fluvial conditions of a watershed can directly affect the quality of riparian habitat available. Stream geomorphic data is used to describe the condition of fluvial processes, riparian habitat, and floodplain creation and maintenance. The purpose of this study is to determine and quantify the effects of local fluvial geomorphology on jumping mouse occupancy. The Natural Resource Conservation Service conducted a pilot study at 20 stream locations between the Jemez Mountains, New Mexico and White Mountains, Arizona (2015-18). They successfully identified a geomorphic reference site (current stable analog), which indicates the most desirable physical condition for a natural stable system with excellent floodplain connectivity. Preliminary results indicated strong correlations with several stream metrics; entrenchment ratio, bank height ratio, flood prone width, channel slope, and channel evolution phase. A full-scale study (n=40) will be conducted summers of 2020 and 2021 to further investigate these findings. A greater understanding of the fluvial conditions at sites with and without jumping mice could assist in identifying suitable habitat, selecting potential survey sites, and developing appropriate restoration actions for degraded watersheds.
Southeastern Pocket Gopher Tunnels Provide Thermal Refugia
J. T. Pynne; Andy Whelan; L. Mike Conner; Steven B. Castleberry
Animals living underground must deal with multiple physiological challenges, including hypoxia and hypercarbia, but may have reduced thermoregulation demands because of the more stable underground microclimate. Southeastern pocket gophers (Geomys pinetis Rafinesque) occur in the fire-adapted, open-pine forests of the southeastern Coastal Plain where prescribed fire is commonly used to manage understory vegetation. Southeastern pocket gophers are almost exclusively fossorial, and their tunnels provide many ecological services, including providing thermal protection for themselves and a suite of commensal vertebrates and invertebrates. We compared temperatures in southeastern pocket gopher tunnels (n = 31) to aboveground temperatures during winter (December 2018 – February 2019) and to aboveground temperatures during spring (March – May 2019) prescribed fires (n=16). In winter, tunnels offered a more stable thermal environment relative to aboveground; temperature ranges aboveground (-3.42-24.0 °C) were greater (F1,52 = 218, p <0.0001) than within tunnels (range = 7.02-19.7 °C. Similarly, tunnel temperatures were more stable (range = 12.9-27.4 °C) during prescribed fires (aboveground temperature range = 32.2 - 815 °C; F1,60 = 47.5, p < 0.001). Tunnels provide a stable thermal environment for pocket gophers and several species of vertebrates and invertebrates that use their tunnel systems. Additionally, their fossorial existence allows pocket gophers to exist in this fire-adapted system where frequent fires maintain a diverse understory used as food.
A Multi-Omic Approach Reveals Thevenom Composition of the Northern Short- Tailed Shrew
Andreas S. Chavez; ZACHERY R. HANF
Animals that use venom to feed on a wide diversity of prey may evolve a complex mixture of toxins to target a variety of physiological processes and prey-defense mechanisms. Blarina brevicauda, the northern-short tailed shrew, is one of few venomous mammals, and is also known to eat evolutionarily divergent prey. Despite their complex diet, earlier proteomic and transcriptomic studies of this shrew’s venom have only identified two venom proteins. Here, we investigated with comprehensive molecular approaches whether B. brevicauda venom is more complex than previously understood. We generated de novo assemblies of a B. brevicauda genome and submaxillary-gland transcriptome, as well as sequenced the salivary proteome. Our findings show that B. brevicauda’s venom composition is simple relative to their broad diet and is likely limited to seven proteins from six gene families. Additionally, we explored expression levels and rate of evolution of these venom genes and the origins of key duplications that led to toxin neofunctionalization. We also found three proteins that may be involved in endogenous self-defense. The possible synergism of the toxins suggests that vertebrate prey may be the main target of the venom. Further functional assays for all venom proteins on both vertebrate and invertebrate prey would provide further insight into the ecological relevance of venom in this species.
Local Adaptation Within a Panmictic Population of Tree Squirrels Across An Ecological Gradient
Rachael M. Giglio; Andreas S. Chavez
As global environmental change intensifies, the ability of a species to adapt to a changing environment will be vital to its long-term viability. However, the goal of many genetic management strategies is to encourage gene flow in order to increase standing genetic variation. This increase in gene flow can diminish local adaptation. Our study examined the conditions in which local adaptation can occur in the presence of high gene flow. Douglas squirrels (Tamiasciurus douglasii) occupy wet, coastal forests in North America. In our study, we examined the pattern of local adaptation along an ecological gradient where the habitat shifts from wet, coastal forest to dry, inland forest. This shift includes a change in tree species composition. We documented phenotypic changes including fur color and body size along this ecological gradient. However, genetic analyses show that individuals along the ecological gradient make up a single genetic population characterized by high rates of gene flow. To identify patterns of local adaptation, we used whole exome and ecological data to conduct a genotype-environment association (GEA) analysis. We found genes associated with several environmental variables, suggesting that through natural selection, local adaptation can be maintained despite high gene flow across a heterogenous habitat.
Impacts of Management Strategies for the Allegheny Woodrat in Southern Indiana
Bradford J. Westrich
Many factors have negatively affected Allegheny woodrat (Neotoma magister) populations across their range, but notably so at the edge. These edge effects have led to reduced occupied habitat, increased susceptibility to starvation and disease, and reduced gene flow. In Indiana the limitation of available habitat coupled with mortality associated with raccoon roundworm (Baylisascaris procyonis) are likely the two main factors limiting this species success. Management of the species has included translocations (2006-09) and release of captive-bred individuals (2011-13) to increase genetic diversity, and localized treatment of raccoons to decrease the prevalence of raccoon roundworm. In the years following these efforts woodrat populations within Indiana increased for the following 2-4 years before returning to pre-management population levels. However, continued monitoring has revealed that a few post-management sites now have (2019) increasing population sizes. This suggests that although management efforts were suspended and population declines were subsequently observed, the long-term effects of management may only now be observable. Of note, Allegheny woodrats have been recently captured in a karst feature from which they had been historically extirpated; this karst feature is between two active woodrat sites and a few kilometers inland from currently occupied habitat. Indiana DNR is planning to resume management efforts at active woodrat sites to help aide future dispersal events, to increase genetic diversity, and to reduce the prevalence of raccoon roundworm eggs in the environment.
Assessing Mexican Woodrat Movement Over Patches of Different Burn Severity Using Fluorescent Powder Tracking
Sandy Slovikosky; John Koprowski; Melissa Merrick; Marina Morandini
The use of small mammals as indicators of disturbance and effects on wildlife has become popular in the field of ecology. Population densities, distributions, and behavior may change as a result of stochastic environmental events. We examined how Mexican woodrats (Neotoma mexicana), a common but understudied species, respond to fire as measured by changes in path tortuosity when translocated over patches of different burn severity. The study was conducted on Mt. Graham, site of the 2017 Frye Fire that burned over 19,400 hectares. Woodrats were captured, covered in fluorescent powder, and released 50 meters away from their middens across areas of low or high burn severity. The resulting powder trail was marked with pin flags, and bearing and vegetation were noted for each step of the trail. Tortuosity was assessed by dividing the straight-line distance into the total trail length, as well as calculating average step lengths and turning angles. Vegetation proportions were compared to proportions from randomized vegetation transects for both burn severities using Fisher’s exact test. Analyses indicated lower tortuosity over areas of higher burn severity as demonstrated by smaller turning angles. Previous research has shown that such directional movement is common in areas of low resource availability, equating to higher burned areas in this study. Logs were heavily selected in both areas, whereas grasses were avoided. This may be attributed to a preference for auditory concealment and avoidance of dense vegetation, especially because of the woodrat’s large size. Adult woodrats also demonstrated longer step lengths than juveniles, which could be explained by higher site familiarity. Lower vegetative cover in burned areas could cause higher predation risk. With the potential for increased wildfires in the future due to climate change, this work presents an understudied approach to understanding these disturbances and their effects on ecological communities.

 

Virtual
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