Mammalogy II

Contributed Oral

Assessing Translocation Effects on the Spatial Ecology and Survival of Muskrats
Benjamin Matykiewicz, Steve Windels, Bryce Olson, Reid Plumb, Tiffany Wolf, Adam Ahlers

Muskrats (Ondatra zibethicus) are semiaquatic herbivores experiencing long-term and widespread population declines across North America. Translocation may be a viable tool to bolster or reestablish local populations; however, subsequent effects of translocation on muskrats are unknown. We live-trapped and translocated radiomarked muskrats (n = 65) during the summers of 20182019 in Voyageurs National Park, MN, USA and assessed post-translocation effects on weekly survival probabilities and space-use patterns. We did not observe homing behavior, though individuals moved an average of 2.2 km (SE = 0.30 km) from release sites and established home ranges within ~8 days (SE = 1.16 days) post-translocation. Weekly post-translocation survival probabilities (0.95, SE = 0.001) and average home-range sizes (2.52 ha, SE = 0.44 ha) were similar to other studies of non-translocated muskrats. Our most-supported known-fate survival model revealed muskrats using beaver (Castor canadensis) lodges had greater weekly survival probabilities. Additionally, weekly muskrat survival varied between years suggesting a positive response to a novel soft-release technique applied in 2019. Our study provides the first empirical assessment of translocation effects on muskrats and suggests translocation may be effective for establishing or enhancing local muskrat populations. Additionally, our study suggests beaver lodges may confer fitness benefits to sympatric muskrats particularly during dispersal.

Predation and Disease Limit Population Recovery of a Cryptic Small Carnivore, the Appalachian Spotted Skunk
Andrew Butler, Andrew Edelman, Robin Eng, Stephen Harris, Colleen Olfenbuttel, CWB, OiTF Organizer, Emily Thorne, Mark Ford, David Jachowski

The eastern spotted skunk (Spilogale putorius) is a small, secretive carnivore that has substantially declined throughout the eastern United States since the mid-1900s. To better understand the current status of eastern spotted skunks, we investigated survival and reproduction of the Appalachian subspecies (S. p. putorius) across 4 states in the central and southern Appalachian Mountains from 2014–2020. Using encounter histories from 99 radio-collared Appalachian Spotted Skunks in a Kaplan-Meier known-fate survival analysis, we calculated a mean annual adult survival rate of 0.58. The largest causes of mortality were avian and mammalian predation (57%), and canine distemper virus (17%). We did not find support for this survival rate varying by sex, predator cover (canopy cover and topographic roughness), or weather. Compared to estimates of survival from previous research on other subspecies, our data suggest that Appalachian spotted skunk survival is intermediate to the plains (S. p. interrupt) and Florida (S. p. ambarvalis) subspecies of eastern spotted skunk. We located 11 Appalachian spotted skunk natal dens and estimated mean litter size to be 2.8 juveniles per female. We used a Lefkovitch matrix to identify the most elastic demographic rates and found that adult survivorship had the largest impact on the population growth rate. We estimated that Appalachian spotted skunks within the core of their range in the central and southern Appalachian Mountains are declining at rate of 0.3% per year, indicating that the population has limited potential to recolonize its former distribution. To inform future conservation actions, we suggest that future studies of this subspecies be conducted 1) at the edge of the range where there is a wider land use gradient, and 2) before and after habitat management or disease mitigation.

Novel DNA Collection Method for Identification of Roosting Bat Species
Rob Schell, Katie Smtih, Cheryl Dean

Identification of North American microchiropteran bat species at roost sites, especially in urban or suburban environs is challenging.  Capture and acoustic detection methods are effective, but only when bats are present, and it can result in disturbance to the bats.  Analysis of guano or other physical cues can be effective, but only when present.  In this paper we investigate the efficacy of genetic analysis of residues left directly on roosting surfaces. At two sites in Northern California roosts were identified based on the presence of residues on surfaces with guano beneath them, and were swabbed for trace DNA. Samples were then sequenced and identified to clade or species. This method was then challenged against genetic analysis of guano and tissues present at the sample location to determine accuracy of the technique.  We found that swabbing and sequencing trace DNA from the surfaces of bat roosts was sufficient to identify all species speculated to have recently used the roost based on guano and tissues, and others that were not indicated by any physical cues.  This new technique has the potential to greatly improve the ability to identify which species of bats have recently utilized roost, even when no animals or physical cues are present, which will improve our ability to protect bats when roost sites must be disturbed, and will allow managers to accurately identify suitable habitat for conservation.  Further, it is cost effective and low risk to both animals and biologists. We encourage environmental professionals to consider utilizing this technique and contributing to evaluating its utility for various bat species in different habitat types.

The Influence of Patch Type and Structure on the Foraging Preferences of White-Tailed Deer
Matthew Wuensch, David Ward

Across much of the range of white-tailed deer (Odocoileus virginianus), many populations persist at high densities that have deleterious effects on forest ecosystems. Factors that contribute to high deer densities are an abundance of high-quality forage and a lack of predation upon adult deer. The objective of our research was to quantify the ecological characteristics of the patches that white-tailed deer prefer to forage in while at high densities. To assess preference, we collected giving-up densities (GUD) in forest and grassland patches, and at the edge between the two patches, at three sites in northeast Ohio. The GUD indicates the amount of food that an animal will consume in a given habitat before it forages elsewhere. A GUD incorporates the cost of foraging, predation risk, and the missed-opportunity cost of not foraging elsewhere. We measured the effects of seasonality, plant community composition and predatory chemical cues (coyote urine) on GUDs.

We found that deer patch preference varied depending on the season. During summer and fall, GUDs were high (=low preference) and little evidence of patch preference was shown. However, winter and spring sampling displayed lower GUDs (=high preference) in the grassland and ecotone than in the forest. Redundancy analysis (RDA) revealed that plant communities at two of our three sites were similar, and so too were the GUDs at these two sites. The plant community at our third site was less diverse, and GUDs were consistently higher, suggesting plant community may have affected preference. GUDs initially increased in response to the introduction of coyote urine. However, the effect was short lived without the physical threat of a predator present. This information enables us to discern patches that are highly preferred by deer and can be used in models that discern the nutritional carrying capacities of habitats with high deer densities.

Mammal Communities and Human Disturbance: Our Experience in Myanmar
Giacomo Cremonesi, Francesco Bisi, Lorenzo Gaffi, Thet Zaw, Maria Vittoria Mazzamuto, Alessandra Gagliardi, Lucas Armand Wauters, Damiano Giovanni Preatoni, Adriano Martinoli

Anthropogenic disturbance is one of the major threats for wildlife populations, especially in tropical forest environments. This is particularly true in Southeast Asia, where rates of habitat loss and wildlife depletion have increased dramatically in the last decades. We focused on two different regions in Myanmar (Rakhine and Sagaing), characterized by similar habitat types but with different levels of human pressure and habitat degradation. We used camera traps in a three-year structured monitoring scheme to study the medium-large mammal community and to investigate the effects of human presence on wildlife distribution, using hierarchical occupancy analysis with Bayesian formulation. We evaluated species richness and ecosystem functionality (as per body mass and trophic niche) and used occupancy values as proxy for population density. Occupancies were evaluated considering both environmental covariates (e.g., evergreen forest presence and elevation) and anthropogenic covariates (as the number of humans detected in the forest and the distance from settlements). We found that the more disturbed area hosts a lower mammal diversity, especially for carnivore and herbivore species, and that two species showed significantly lower occupancy values. Surprisingly, community composition was not significantly different between the two areas, except for the absence of large predators. Dealing with human activities, we found that occupancies of threatened species, target of the illegal wildlife trade, were positively linked to forest habitats (i.e., well-preserved evergreen forest), while for some common species, target of hunting for bushmeat consumption, occupancies were negatively linked to the human presence. Our findings suggest that the use of camera traps combined with hierarchical modeling can be a useful tool to study mammal communities and to assess species responses to human disturbances.

Historic Population Estimates for Bottlenose Dolphins in Aragua, Venezuela Indicate Monitoring Need
Sergio Cobarrubia-Russo, Shannon Barber-Meyer, Guillermo Barreto, Alimar Molero-Lizarraga

This study reports historic, capture-mark-recapture survival and abundance estimates of common bottlenose dolphins (Tursiops truncatus) based on photo-identification surveys of coastal Venezuela (along the Aragua coast between Turiamo Bay and Puerto Colombia). We used the most recent data available: dolphins identified by unique dorsal fin marks during wet and dry season surveys conducted from 2004-2008. Dolphin encounter histories were analyzed in the Closed Capture Robust Design framework, with the top model including random movement, constant survival, and capture / recapture probabilities that varied by secondary periods. Survival of marked adults was estimated at 0.99 (95% CI = 0.97-1.00). Population estimates for all adults (marked and unmarked) averaged 31 animals (SD = 13.8), and for all dolphins (all adults and calves), 41 (SD = 17.2). Coastal bottlenose dolphins face numerous threats including ship strikes, oil spills, conflict with recreational and industrial fisheries, other negative human interactions, biotoxins, chemicals, noise, freshwater discharge, and coastal development. Further, small populations are, in general, at increased risk due to reduced resiliency and recovery potential when exposed to such threats and to expected environmental and demographic stochasticity. These historic estimates of abundance and survival are critical for establishing a reference state and indicate a need for ongoing monitoring of the small dolphin population while the Aragua coast is still, as-of-yet relatively little-impacted by humans. Should coastal development increase (as is the global trend) and / or environmental catastrophes occur (e.g., harmful algal blooms, hurricanes, oil spills), these historic estimates will be essential for assessing impacts and guiding management and conservation interventions. Our results show year-round dolphin presence and highlight the Venezuelan coastal-oceanic landscape as an area of both future research and conservation importance.

Contributed Oral
Location: Virtual Date: November 3, 2021 Time: 12:00 pm - 1:00 pm