Singing strategies are linked to perch use on foraging territories in heart-nosed bats

Acoustic communication allows animals to coordinate and optimize resource utilization in space. Cardioderma cor, the heart-nosed bat, is one of the few species of bats known to sing during nighttime foraging. Previous research found that heart-nosed bats react aggressively to song playback, supporting the territorial defense hypothesis of singing in this species. By tracking 14 individuals nightly during the dry seasons in Tanzania we further investigated the territorial defense hypothesis from an ecological standpoint, which predicts singing should be associated with exclusive areas containing a resource. We quantified the singing behavior of individuals at all perches used throughout the night. Using home range analysis tools, we quantified overall use night ranges and singing ranges, as well as areas used in early and later time periods at night. Males engaged in antiphonal singing from small (x̄ = 3.48 ± 2.71 ha), largely exclusive areas that overlapped with overall night ranges used for gleaning prey. Individuals varied in singing effort; however, all sang significantly more as night progressed. Subsequently, areas used earlier at night and overall use areas were both larger than singing areas. Individuals varied in singing strategies. Some males sang for long periods in particular trees and had smaller core areas, while others moved frequently among singing trees. The most prolific singers used more perches overall. The results support the hypothesis that acoustic communication repertoires evolved in support of stable foraging territory advertisement and defense in some bats.

A Camera-Trap Home-Range Analysis of the Indian Leopard (Panthera pardus fusca) in Jaipur, India

The suitability of the camera trap–retrap method was explored for identifying territories and studying the spatial distribution of leopards (Panthera pardus fusca) in the Jhalana Reserve Forest, Jaipur, India. Data from two years (November 2017 to November 2019, N = 23,208 trap-hours) were used to provide estimates of minimum home-range size and overlap. We conducted home-range analysis and estimation, using the minimum convex polygon (MCP) method with geographic information system (GIS) tools. We are aware of the limitations and advantages of camera trapping for long-term monitoring. However, the limitations of the research permit allowed only the use of camera traps to estimate the home ranges. A total of 25 leopards were identified (male = 8, female = 17). No territorial exclusivity was observed in either of the sexes. However, for seven females, we observed familial home-range overlaps wherein daughters established home ranges adjacent to or overlapping their natal areas. The median home range, as calculated from the MCP, was 305.9 ha for males and 170.3 ha for females. The median percentage overlap between males was 10.33%, while that between females was 3.97%. We concluded that camera trapping is an effective technique to map the territories of leopards, to document inter- and intraspecific behaviors, and to elucidate how familial relationships affect dispersal.

Testing cellular phone-enhanced GPS tracking technology for urban carnivores

Background We present a cellular phone-enhanced GPS tracking system (GPS mobile with CTG-001G receiver triangulation) suitable for urban carnivores, in tandem with appropriate home range analysis, as an additional tracking technology option in metropolitan settings. We conduct this proof-of-concept study working with the management of introduced invasive raccoons in Japan (and conditions implicit to this control program). Results Each tracking period averaged 17 days, and a tracking accuracy of < 50 m error was achieved in over 30% of the fixes. Variogram analysis demonstrates that these data were of sufficient quality to support home range analysis. Home range areas estimated from these data revealed that raccoons in urban Japan likely range over a much greater area than has previously been reported. Conclusions As a proof of concept, these prototype collars were successful in tracking raccoons in the difficult suburban environment, where this system (CTG) made fixes against FOMA antennae-augmented GPS and yielded data that could support home range analysis. We advocate further research and development to refine this system, with broad application as a tool to diversify wildlife tracking technology options in urbanized environments, where synanthropic and/or invasive species can cause a nuisance warranting effective management.