Conservation and Ecology of Mammals II

Contributed Paper
ROOM: CC, Room 16

8:10AM Ephemeral Temporal Partitioning May Facilitate Coexistence in Competing Species
Adia R. Sovie; Robert McCleery; Daniel Greene; Alex Potash; Catherine Frock
Understanding how species interact to partition time, space and resource across a variable environment is critical for developing conservation and management strategies. Animals change their daily rhythms in response to season, food availability, and the presence of competitors. Competition may be a particularly important driver of daily activity as animals manage conflict by partitioning the day. We evaluated how habitat structure and the presence of competitors changed the daily habits of rare Sherman’s fox (Sciurus niger) and the more common gray (S. carolinensis) squirrels. We monitored squirrel activity in North-Central Florida using passive game cameras at two spatial scales (point and patch). To understand how seasonal food scarcity and competition interact to dive behavior we compared squirrel activity during the leaf-off (January 1 – March 15) and leaf-on season (March 15 – July 1). We tested for a relationship between squirrel activity and canopy cover by fitting a Von Mises kernel distribution. To test how season and competition affect squirrel behavior we compared activity curves by computing a kernel density overlap function [ranging from 0 (no overlap – the squirrels are never active at the same time), to 1 (complete overlap- the squirrels have identical activity patterns]. We found that fox and grey squirrels display different daily patterns (overlap=0.58), Fox squirrels have a single activity peak occurring around mid-day. In contrast grey squirrels have a bi-modal activity pattern with peaks shortly after sunrise and before sunset. The intensity of this partitioning changes depended upon season and the presence of competitors. Fox and grey squirrel daily patterns overlapped the most when they were allopatric in the leaf-on season (overlap = 0.70) and the least (0.45) when the sympatric during the leaf-on season. These behavioral shifts indicate the need to consider competition in the management and conservation of rare species.
8:30AM Nest Tree Use By Southern Flying Squirrels in Fragmented Midwestern Landscapes
Chris Jacques; James Zweep; Sean Jenkins; Robert Klaver; Shelli Dubay
Southern flying squirrels (Glaucomys volans; SFS) nest in naturally-formed cavities in snags and hardwoods found in mature, oak-hickory forests. Intensive forest fragmentation of the Midwest United States limits the number of available nesting trees. We studied annual nest site selection patterns of southern flying squirrels across fragmented landscapes of west-central Illinois. We used radio telemetry to examine nest tree use by 55 SFS (30 males, 25 females) captured during 2014-2016. Of 105 nest trees used by SFS, live trees and snags comprised 75% and 25%, respectively. Probability of diurnal nest tree use increased 1.08/1 cm increase in DBH and by 1.50/1 unit increase in the number of overstory mast trees between random and nest tree habitat areas (i.e., 300 m2 circular plots). Similarly, probability of diurnal nest tree use increased 1.29/1 unit increase in the number of snags between random and nest tree habitat areas. Our results revealed no intersexual differences in patterns of nest site selection, which may reflect the tendency for SFS to compensate for reduced availability of key structural attributes (i.e., snags, overstory trees) across fragmented forests by exhibiting similar intersexual patterns of nest tree use. Use of natural cavities for denning is encouraging, but also underscores the importance of unharvested oak-hickory forests in contributing essential habitat to SFS populations in fragmented Midwestern landscapes.
8:50AM Evaluating Small Mammal Community Composition, Stress, and Health Across an Urban to Exurban Gradient in the Chicago Metropolitan Area
Matthew P. Mulligan; Mason Fidino; Michael J. Yabsley; Maureen Murray; Seth B. Magle; Rachel M. Santymire
Although small mammals are key prey species and have top-down effects on vegetation, their ecology and health are often underexplored in urban environments. Our study aims to understand small mammal population dynamics along an urban to exurban gradient in the Chicago metropolitan area and evaluate stress levels and disease prevalence to determine how surrounding landscapes can influence small mammal health. Our research objectives were to determine changes in small mammal: 1) species abundance, 2) community composition, 3) survival probability, 4) physiological stress levels, and 5) prevalence of Lyme disease (Borrelia burgdorferi) along an urban to exurban gradient. Live-trapping occurred using mark-recapture techniques from May-August 2017-2018 at urban, suburban and exurban sites. Stress hormones (glucocorticoid metabolites) have successfully been extracted from meadow vole (Microtus pennsylvanicus) and deer mouse (Peromyscus maniculatus) hair samples to characterize chronic (long-term) stress levels at varying habitats. Meadow voles and deer mice represented over 80% of individuals captured with meadow voles being the most abundant species in suburban sites (68.9%). However, meadow vole and deer mouse abundance were quite similar in more urban regions, albeit at lower overall numbers. Species richness did not significantly vary between regions, but was typically driven by one or two species-rich sites. Furthermore, estimated median survival probability for deer mice was significantly lower in exurban sites compared to more urban sites while meadow vole survival remained relatively constant. Tick dragging and collecting ticks from small mammals resulted in 54 ticks in 2017 with 19% of the Ixodes scapularis gathered (n=36) testing positive for B. burgdorferi (deer mice=30%; meadow voles=17%) in all regions across the gradient. Long-term wildlife camera data will be paired with trapping data to consider relationships with urban mesocarnivores. Understanding small mammal composition, stress, and disease across urban landscapes can lead to more resilient wildlife communities while influencing human health.
9:10AM Modeling Small Mammal Community Response to Environmental Variation in an Isolated Rangeland Site
Katelyn R. Vedolich; Kerry L. Griffis-Kyle
In the semi-arid conditions of the Southern High Plains, seasonal irregularity of rainfall drives transformations in the structure and composition of the vegetation community, affecting the abundance and diversity of species which use those resources. As rainfall patterns are expected to increase in variability, it is imperative to investigate the long-term effects of environmental predictors on shaping biological communities. We use a long term small mammal capture recapture data set to investigate the relationship among habitat structure, weather patterns, and species occurrence, abundance, and detection probability to better understand population dynamics across time. Small mammal data was annually collected from 2010 to 2017 throughout the Texas Tech University native rangeland site. Using Program MARK, we estimated annual population sizes of each species. We then evaluated soil temperature, aspects of rainfall, nighttime illumination, and percent cover of vegetation functional groups in relation to population size and detectability. Using Akaike’s Information Criterion, we evaluated biologically determined models and used model averaging to determine the relative importance of these predictors to small mammal population dynamics. Models indicate that the rainfall of the previous year’s growing season exhibits the strongest relationship with capture success while the density of mesquite (genus Prosopis) in the rangeland notably influences species detection and diversity. We were therefore able to identify the importance of abiotic and biotic predictors on community diversity, providing a basis for designing targeted survey methods which may provide insight on the effect of specific environmental predictors on small mammal community responses.
9:30AM Maximizing the Biological Value of Post Harvest Structural Retention in the Pacific Northwest: an Experimental Study of Small Mammals.
Sean M. Sultaire; Andrew J. Kroll; Jake Verschuyl; Gary J. Roloff
Retaining green trees in clearcut areas generally increases stand-level diversity of wildlife compared to clearcuts without retention, and is a requirement of State Forest Practice Rules in Oregon and Washington. However, effects of spatial pattern (dispersed vs. aggregated) and placement (upslope vs. riparian) of green tree retention are not known for many wildlife species. Small mammals are useful indicators to measure the effects of forest management because they are relatively diverse, have varied habitat requirements, and tend to function at local scales. We manipulated slope position and aggregation of retained trees within clearcuts in a randomized complete design, with 10 blocks in western Oregon and Washington. This design included 5 retention treatments that ranged from complete aggregation along riparian buffers (the control) to small upland patches dispersed throughout the harvest area. We deployed live-trap grids of consistent size within retention patches and in adjacent clearcut areas to quantify variation in small mammal density in response to retention treatment using spatial capture-recapture analysis. We observed a variety of species-specific responses to retention and retention pattern. Deer mice (Peromyscus maniculatus), habitat generalists, existed at higher densities outside retention patches and showed no density response to treatment. Creeping voles (Microtus oregoni), an open habitat species, were at higher estimated densities in clearcuts, but also showed a negative response to dispersed retention at the stand level. Townsend’s chipmunk (Neotamias townsendii) densities were higher within retention patches compared to clearcuts (β=2.27, 95%CI=1.68-2.85) and densities peaked in dispersed-upland retention treatments (β=0.35, 95% CI=0.02-0.74). Bushy-tailed woodrats (Neotoma cinerea) had significantly higher densities in retained patches than clearcuts (β=1.91, 95%CI=0.65-3.17), but low sample size prohibited estimating treatment effects for this species. Our results provide insights into small mammal responses to structural retention patterns, indicating that retention patches for forest dependent species serve as useable habitats in clearcuts.


Contributed Paper
Location: Cleveland CC Date: October 9, 2018 Time: 8:10 am - 9:50 am