Kerry L. Nicholson

Possible Vector Dissemination by Swift Foxes following a Plague Epizootic in Black-tailed Prairie Dogs in Northwestern Texas

To determine whether swift foxes (Vulpes velox) could facilitate transmission of Yersinia pestis to uninfected black-tailed prairie dog (Cynomys ludovicianus) colonies by acquiring infected fleas, ectoparasite and sero-logic samples were collected from swift foxes living adjacent to prairie dog towns during a 2004 plague epizootic in northwestern Texas, USA. A previous study (1999–2001) indicated that these swift foxes were infested almost exclusively with the flea Pulex irritans. Black-tailed prairie dogs examined from the study area harbored only Pulex simulans and Oropsylla hirsuta. Although P. irritans was most common, P. simulans and O. hirsuta were collected from six swift foxes and a single coyote (Canis latrans) following the plague epizootic. Thus, both of these canids could act as transport hosts (at least temporarily) of prairie dog fleas following the loss of their normal hosts during a plague die-off. All six adult swift foxes tested positive for antibodies to Y. pestis. All 107 fleas from swift foxes tested negative for Y. pestis by mouse inoculation. Although swift foxes could potentially carry Y. pestis to un-infected prairie dog colonies, we believe they play only a minor role in plague epidemiology, considering that they harbored just a few uninfected prairie dog fleas (P. simulans and O. hirsuta).

Swift Fox Use of Black-Tailed Prairie Dog Towns in Northwest Texas

Abstract Biologists have suggested that prairie dog (Cynomys ludovicianus) towns provide important habitat for several prairie species including swift foxes (Vulpes velox). To examine this issue for swift foxes, we radiocollared and monitored 72 swift foxes in areas occupied by prairie dogs on the Rita Blanca National Grasslands and on fragmented private ranches in northwest Texas from January 2002 to April 2004. We overlaid swift fox locations on vegetation maps and found that swift foxes used prairie dogs towns proportionately less than expected (P < 0.001) in 5 of 6 comparisons based upon availability at both study sites. In one comparison swift foxes used prairie dog towns as expected. We also mapped swift fox den locations and found that den sites were located in prairie dog towns (2 of 106 den sites on national grasslands and 2 of 87 on private ranch for all years pooled) as expected based upon availability (P = 0.54 and P = 0.34). Previous research in these areas of Texas indicated that prairie dogs were a minor component of swift fox diet (<2%). Prairie dog towns do not appear to provide important habitat for swift foxes in northwest Texas or other similar sites because prairie dogs are not a significant source of food for swift foxes, because swift foxes generally avoid prairie dog towns during their normal activities, and because swift foxes only den in prairie dog towns in relation to their availability.

DISPERSAL AND EXTRATERRITORIAL MOVEMENTS OF SWIFT FOXES (VULPES VELOX) IN NORTHWESTERN TEXAS

Abstract Dispersal plays an important role in the population dynamics of many carnivores, yet little information exists about the dispersal and movement patterns of swift foxes (Vulpes velox). We radio-collared and monitored 68 swift foxes for dispersal at 2 study sites in northwestern Texas from January 2002 to April 2004. Dispersal distance for juveniles (13.1 ±0.3 km, s), adults (10 ±4.7 km) and transients (25.4 ±9.1 km) did not differ by age class (F = 1.49, df = 2, P = 0.24) or sex (F = 0.23, df = 1, P = 0.63) but differed by study site (F = 4.72, df = 1, P = 0.04). Mean dispersal distance from private ranches (PR) was greater than from National Grasslands (NG). Peak dispersal occurred during October–November (13 individuals) and January–February (7 individuals). Dispersal direction was influenced by land-use practices (i.e., toward rangelands and away from anthropogenic features). Direction of dispersal among foxes that occupied the NG was uniform (n = 16, P = 0.08), whereas foxes from PR dispersed in a northwesterly direction (n = 18, P ≤0.001) away from a town and croplands. Three resident adult foxes made extraterritorial movements. Distances of these movements ranged from 0.2 km to 11.4 km. Distance of extraterritorial movements did not differ by sex (F = 0.05, P = 0.83), nor by duration of movement (F = 1.11, P = 0.32). Knowledge of movement distances and patterns is important for conservation and protection of swift foxes and their habitats.

A comparison of survey techniques for swift fox pups

Swift foxes (Vulpes velox) are one of the smallest and most den-dependent and nocturnal canids in North America (Egoscue 1979, Tannerfeldt et al. 2003)Though research concerning swift fox fecundity has been conducted, it is a difficult and arduous task because pups do not emerge from natal dens until they are weaned at 5-7 weeks of age (Egoscue 1979). Previous techniques for determining fecundity of swift foxes have included excavating the den and counting pre-emergent pups (Cutter 1958, Kilgore 1969) and visual counts of post-emergent pups (Covell 1992, Olson and Lindzey 2002, Schauster et al. 2002, Harrison 2003, Sovada et al. 2003). Visual counts are the most commonly reported technique for counting post-emergent swift fox pups (Covell 1992, Olson and Lindzey 2002, Schauster et al. 2002, Harrison 2003, Sovada et al. 2003). In this technique >1 concealed observers with binoculars or spotting scopes watch a females den from a distance (usually >40 m) in the evening and morning hours during early summer, in an attempt to count the number of pups. Visual counts also have been effectively used with similar species such as the kit fox (Vulpes macrotis; Cypher et al. 2000, Koopman et al. 2000) and arctic fox (V.lagopus; Strand et al. 2000). Prior research concerning determination of preemergent pups has been highly invasive, as dens were excavated or disturbed via observer presence. As more advanced technology becomes available to researchers, less insidious means of obtaining data can be implemented. Recently, video probe systems have been used to document various cavity-nesting and burrowing animals such as red-cockaded woodpeckers (Picoides borealis; Richardson et al. 1999) and western burrowing owls (Athene cunicularia hypugea; Gervais et al. 2000). Night-vision devices have been used to enumerate migrating owls (Tyto alba,Aegolius acadicus,Asio otus, Asio flammeus, and Otus asio; Russell et al. 1991) and to observe the emergence of big brown bats (Eptesicus fuscus) from maternal colonies (Kirkwood and Cartwright 1993). Automated videography has been used to observe nests and index population abundance (York 1991, Kristan et al. 1996, Booms and Fuller 2003). Yet, none of this technology has been evaluated for use in swift fox research. Measuring fecundity is an essential component in examining demographics of any wildlife species. Information on litter sizes is necessary to understand the dynamics of swift fox populations. Yet, no pups were observed from preliminary efforts at visual counts of swift fox pups during our study. Thus, the objective of this study was to compare visual counts, night vision, a den-probe system, and an automated video monitoring system for counting swift fox pups.

CHARACTERISTICS OF SWIFT FOX DENS IN NORTHWEST TEXAS

Abstract The swift fox (Vulpes velox) was classified in 1995 as a candidate for listing under the Endangered Species Act. Since then, several studies have addressed survey methods for monitoring swift fox populations. The purpose of this paper is to assist field researchers in documenting the presence of swift foxes by identification of recently active den sites. We propose that swift foxes have unique external den characteristics that can be distinguished during aerial surveys. We collected data from 30 swift fox den complexes on both continuous rangeland and landscapes fragmented by cropland in northwest Texas. There were no differences in den characteristics between landscape types (P > 0.10). The number of openings per den ranged from 1 to 8 and had an average opening height of 20 cm. As number of openings increased, the maximum distance between openings also increased (r = 0.88, P < 0.001). One of the most distinguishing characteristics of swift fox dens was their dirt tailing. Of 74 den openings examined, all but 3 had conspicuous dirt tailings that averaged 267.0 cm long by 63.4 cm wide. We found that swift fox den openings were smaller than those of coyotes (Canis latrans) and red foxes (Vulpes vulpes), 2 species that can be sympatric with swift foxes. We suggest that aerial den searching followed by ground verification may be an effective technique for determining presence of swift foxes in areas of short-grass prairies and fragmented habitats.

MOUNTAIN LION HABITAT SELECTION IN ARIZONA

Abstract Wildlife managers in the 21st century are challenged to maintain balance for wildlife and human use of the landscape. Because mountain lion (Puma concolor) habitat is often adjacent to urbanization in Arizona, mountain lions are ideal models to examine how human alteration of habitats influences life-history characteristics. We quantified mountain lion home-range characteristics and selection of vegetative associations in central and southern Arizona. We calculated 95% and 50% fixed kernel home ranges for eight female and 21 male mountain lions radiocollared in Payson, Prescott, and Tucson, Arizona, from August 2005 through August 2008. We assessed use of vegetative associations and urban areas within the study area (second order) and within the home range (third order). At both levels of selection at all study sites, mountain lions avoided human-dominated landscapes. At second-order selection, mountain lions preferred woodland habitat in Tucson and Prescott and chaparral in Payson. At the third order, lions in Tucson and Payson selected riparian and chaparral in Prescott. Season, mountain lion mass, and ungulate density had no effect on the size of home ranges. Home-range sizes for resident males ranged from 5,286 to 83,859 ha; transient males covered up to 409,195 ha. Home ranges for females ranged from 2,860 to 21,772 ha. Intensive development and conversion of large open spaces to small properties and subdivisions has caused increased loss, fragmentation, and encroachment into mountain lion habitat. Preserving natural landscapes for access to habitat patches is important in maintaining connectivity to ensure viable populations.