No abstract

Domestic cats (Felis catus) are one of the world's most damaging invasive species. Freeranging cats kill billions of wild animals every year, spread parasites and diseases to both wildlife and humans, and are responsible for the extinction or extirpation of at least 63 species. While the ecology and conservation implications of free-ranging cats have well studied in some locations, relatively little is known about cats inhabiting urban nature preserves in the United States. To address this knowledge gap, we used camera traps to study the occupancy and activity patterns of free-ranging cats in 55 suburban nature preserves in the Chicago, IL metropolitan area. From 2010-2018 (4,440 trap days), we recorded 355 photos of free-ranging cats across 26 preserves ( naïve = 0.45) and 41 randomly distributed monitoring points ( naïve = 0.18). Cats were detected every year, but rarely at the same point or preserve, and cats were largely crepuscular/diurnal. Using single-season occupancy models and a "stacked" design, we found that cat occupancy increased with .

Assessments of novel capture techniques are important to wildlife research. We used Comstock traps, a new live-capture technique, to capture North American river otters Lontra canadensis. We measured Comstock trap functionality in terms of river otter capture efficiency, furbearer capture efficiency, nonfurbearer capture efficiency, and malfunction rate. During 2014–2016, we captured 36 river otters (19 male, 17 female) in Comstock traps during 2,533 trap nights (1 capture/63 trap nights) at Crab Orchard National Wildlife Refuge in southern Illinois, USA. Eleven of 20 (55%) river otters assessed for capture-related injuries received an injury as a result of capture in a Comstock trap. The most common injury was claw loss (45%), followed by tooth fracture (25%) and lacerations (10%). The ease of setting Comstock traps and of releasing nontarget captures made them an appealing option for river otter live capture; however, two river otters died because of hypothermia, two died because of drowning, and one died because of traumatic injuries sustained during capture. Special care should be taken when selecting locations to set Comstock traps with regard to temperature and fluctuating water levels. Researchers attempting to live-capture river otters using this method would benefit by restricting their use to locations with predictable water levels and seasons with mild weather patterns.

River otter populations have expanded across much of their historical range, including in Illinois where they were reintroduced from 1994 to 1997. These expanding populations are recolonizing a wide range of landscapes with different levels of human modification, which could influence how river otters use space in relation to habitat characteristics and each other. Our objectives were to quantify 1) home ranges and core areas, 2) sociality, and 3) habitat selection across all available habitats and within home ranges (second- and third-order selection, respectively) of 22 radiomarked river otters (Lontra canadensis) in southern Illinois during 2014–2016. Our study area contained a diverse mix of forest, agriculture, aquatic and wetland habitats, and a range of urban development intensity. We examined sociality using the frequency at which individuals were located < 25 m from a conspecific and compared home-range overlap among individuals based on sex. Habitat selection at the second and third order was analyzed using an eigen-analysis of selection ratios based on landcover categories. Similar to other studies, male river otters had > 2-fold larger home ranges and core areas than females in southern Illinois. Several lines of evidence indicated males were more social than females. Males were located close to a conspecific more frequently than were females, and overlap of home ranges and core areas among males was greater than it was among females or between sexes. As observed in other landscapes, river otters strongly selected herbaceous and wooded wetlands at both second- and third-order scales. River otters selected terrestrial cover types with vegetative cover potentially due to shelter or prey availability. Forests were selected over crop fields at the third-order scale, which was consistent with studies using sign surveys. River otters in our study had home ranges containing 0–40% developed land cover, but we found no evidence that otters living in more developed areas used their home ranges more selectively. River otters in this landscape were plastic in regard to social behavior and habitat selection, highlighting their generalist nature and providing insight into their ability to successfully recolonize areas of the Midwest with sufficient vegetative cover and aquatic habitat, among other factors.

Live traps are commonly used to inventory, monitor, and sample populations of small mammals. Due to the variety of available trap types, understanding differences between traps is important to minimize bias and plan future studies. Sherman traps (H. B. Sherman Trap, Inc., Tallahassee, FL, USA; hereafter Sherman traps) are a popular live trap that come in a variety of sizes. However, studies comparing the relative efficacy of different‐sized Sherman traps often focus on a single species or are limited by a lack of temporal and spatial replication, leading to contradictory or ambiguous results. Therefore, to better understand the relative efficacy of two commonly‐used sizes, we used a paired design and 10 years of trapping data to compare species richness, capture numbers, and mortality rates between small Sherman traps (5.1 × 6.4 × 16.5 cm) and large Sherman traps (7.6 × 8.9 × 22.9 cm) across 55 preserves in northeastern Illinois. Despite wide annual variation, we captured more small mammals in large traps except for the smallest taxa (Sorex spp.), the proportion of captures in large traps increased with body size, and large traps significantly reduced mortality rates for Peromyscus spp., meadow voles (Microtus pennsylvanicus), and short‐tailed shrews (Blarina brevicauda). We recommend the 7.6 × 8.9 × 22.9 cm Sherman trap for monitoring surveys in the midwestern USA when research or monitoring objectives include maximizing captures and species richness while minimizing mortality. However, we note the smaller‐sized trap may be useful to minimize bycatch when smaller species are being targeted. Finally, managers and biologists conducting short‐term or pilot studies should be wary of year effects, as we found substantial annual variation in relative capture rates between trap sizes. © 2021 The Wildlife Society.