Dispersal characteristics of swift foxes

From 1997 to 2001, we monitored movements of 109 adult and 114 juvenile swift foxes, Vulpes velox (Say, 1823), at study sites in Colorado, New Mexico, and Texas to determine patterns of dispersal. Significantly more male (93%) than female (58%) juveniles dispersed, and both sexes had similar bimodal dispersal patterns with peaks in September–October and January–February. Adult dispersal occurred more evenly throughout the year, and significantly more male (32%) than female (5%) adults dispersed. Adult males tended to disperse after the death of their mate. Of dispersing foxes with known fates, settlement percentages in new territories were similar between juvenile males and females (40% overall), but they were significantly lower than for adults (89%). All other dispersing foxes with known fates died. Among juvenile females with known fates, similar percentages of philopatric and dispersing foxes reproduced as yearlings (50% overall), so the benefits of dispersal versus philopatry were not clear. Although rarely reported for other species, adult males were an important dispersal cohort in swift foxes (43% of male dispersals and 25% of all dispersals). Because of the female-biased philopatry among swift foxes, dispersal of adult males likely decreased the chances for inbreeding (e.g., father–daughter breeding)

Genetic and spatial structure within a swift fox population

1. We incorporated spatial data on swift foxes (Vulpes velox) with genetic analysis to assess the influence of relatedness between individuals on their social and spatial ecology. We recorded the space use patterns of 188 radio-collared swift foxes in southeastern Colorado from January 1997 to December 2000. One hundred and sixty-seven foxes were also genotyped at 11 microsatellite DNA loci and the degree of relatedness between individuals was estimated. 2. We described the genetic structure of the population by examining the relatedness of neighbors and the relationship between the spatial and genetic distance of all individuals. We found that close kin appeared to cluster within the population. Neighbors were significantly more related (mean R= 0.089 ± 0.01) than non-neighbors (mean R = 0.003 ± 0.01; randomization test, P \u3c 0.0002). Female clusters were more extensive than male clusters. 3. The degree of genetic relatedness among foxes was useful in explaining why foxes tolerated encroachment of their home ranges by neighbors; the more closely related neighbors were, the more home-range overlap they tolerated (Mantel test, P = 0.0004). Foxes did not appear to orientate their home ranges to avoid neighbors and home ranges overlapped by as much as 54.77% (x = 14.13% ± 0.41). Neighbors also occasionally engaged in concurrent den sharing. 4. Relatedness influenced the likelihood that an individual would inherit a newly vacated home range, with a mean relatedness of range inheritors to previous owners of 0.333 ±&#;0.074. Thus, the genetic structure of the population and interactions between kin were interrelated to space-use patterns and social ecology of the swift fox

Serologic Survey for Canine Infectious Diseases among Sympatric Swift Foxes (Vulpes velox) and Coyotes (Canis latrans) in Southeastern Colorado

Swift foxes (\\u27IL~VPGCY~ OX)a nd CoVi I otes (C~rrisl r~tr(~r~a.rse) sympatric canids distributed througllout rnany regions of tlie Great Plains of North America. ~h~ prevalence of canid diseases arnong these two species where they occur syiripatrically is presently unknown. Frorn January 1997 to January 2001, we collected blood salnples from 89 switt toxes and 122 coyotes oil the US Arlny Pifion Canyon Maneuver Site, 1,as Anilrlas County, SE lorado (USA). Seroprcvalence of ailtibodies against canine parvovirr~s (C13\i) was 71 % for adult (\u3e9 nlo old) ailcl 38% for jrlveilile (59 Ino old) swift fbxes. Adult (21 yr old) and juvenile (old) coyotes had a scroprevalence fo

Adult male emigration and a female-based social organization in swift foxes, \u3ci\u3eVulpes velox\u3c/i\u3e

Members of the family Canidae are distinguished from other carnivore families by pair bonding and male care of the young. Because of the importance of food provisioning and territorial defiance by males, social structure among canids is shared or even dominated by males. However, small, insectivorous species of canids show little male parental care, although whether social structure differs from other canids is unknown. We combined data from three independent research projects on a small canid, the swift fox, to help elucidate the social organization of this species. Based on data on movements of 35 adult mated pairs and the fate of litters, we found that adult females maintained territories and family structure, whereas adult males tended to emigrate. This is the first evidence of a female-based social organization among any canid species. This type of social organization probably resulted from the decreased importance of territorial defense and food provisioning by males, as their diet is primarily insectivorous during summer when young are weaned. Our results, along with others, indicate that variations in social structure among canid species are strongly influenced by the importance of food provisioning and territorial defense by males

Effects of Coyote Population Reduction on Swift Fox Demographics in Southeastern Colorado

The distribution and abundance of swift foxes (Vulpes velox) has declined from historic levels. Causes for the decline include habitat loss and fragmentation, incidental poisoning, changing land use practices, trapping, and predation by other carnivores. Coyotes (Canis latrans) overlap the geographical distribution of swift foxes, compete for similar resources, and are a significant source of mortality amongst many swift fox populations. Current swift fox conservation and management plans to bolster declining or recovering fox populations may include coyote population reduction to decrease predation. However, the role of coyote predation in swift fox population dynamics is not well-understood. To better understand the interactions of swift foxes and coyotes, we compared swift fox population demographics (survival rates, dispersal rates, reproduction, density) between areas with and without coyote population reduction. On the Pinon Canyon Maneuver Site, Colorado, USA, we monitored 141 swift foxes for 65,226 radio-days from 15 December 1998 to 14 December 2000 with 18,035 total telemetry locations collected. Juvenile swift fox survival rate was increased and survival was temporarily prolonged in the coyote removal area. Adult fox survival patterns were also altered by coyote removal, but only following late-summer coyote removals and, again, only temporarily. Coyote predation remained the main cause of juvenile and adult fox mortality in both areas. The increase in juvenile fox survival in the coyote removal area resulted in a compensatory increase in the juvenile dispersal rate and an earlier pulse in dispersal movements. Adult fox dispersal rate was more consistent throughout the year in the coyote removal area. Coyote removal did not influence the reproductive parameters of the swift foxes. Even though juvenile survival increased, swift fox density remained similar between the areas due to the compensatory dispersal rate among juvenile foxes. We concluded that the swift fox population in the area was saturated. Although coyote predation appeared additive in the juvenile cohort, it was compensatory with dispersal

SPATIAL ECOLOGY OF SWIFT FOX SOCIAL GROUPS: FROM GROUP FORMATION TO MATE LOSS

We examined social group formation, movements and denning relative to other group members, home-range use, and the response to social group disruption among 188 radiocollared swift foxes (Vulpes velox) in Colorado. We found that during the initial stages of pair formation mated foxes shared dens more frequently than during the remainder of their pair-bond. The average distance between mated pairs was influenced by season and time of day, with the greatest proximity in the breeding season (727.2 m 6 42.3 SE), and during diurnal hours (463.7 6 34.7 m). Female foxes spent more time in the core area of the group home range (60.71% of locations versus 54.66% for males) and males spent more time on the range boundary (19.34% of locations versus 15.61% for females). Home-range use was influenced by season, with females spending more time in the core area in the breeding and pup-rearing seasons than in the dispersal season. Males also spent the highest proportion of their time in the core area during the breeding season, but used the boundary area more frequently than the core area in the pup-rearing season. A sex difference also was found in the response of a swift fox to the death or disappearance of its mate. All females maintained their territory in the event of mate death or disappearance; however, 50% of males emigrated from their range when the female mate died or disappeared. These differences in space use between social group members provide important insights into the territorial behavior and mating system of the swift fox and indicate that the 2 sexes likely play different roles in care of young and homerange defense

Multiple breeding strategies in the swift fox, Vulpes velox

Little is known of the mating system of the swift fox or how it compares to other socially monogamous mammals. In a 4-year study of 188 swift foxes, we used microsatellite analysis at 11 loci along with spatial observations to investigate swift fox mating strategies. The mating strategies used by swift foxes were highly diverse. Previous field observations have indicated that the swift fox is socially monogamous. However, we found that extrapair mating was a common breeding strategy; 52% of offspring were sired by a male that was not the mate of their mother. There was also variation in the structure of social groups. Of 59 social groups, the most common consisted of a male and female pair (93% of social groups); however, four stable trios of both one female and two males (5%) and two females and one male (2%) were also evident. The trio groups were spatially associated, and at least one member of each trio was highly related to a member in at least one other trio. Swift foxes also engaged in mate switching, which refutes the prevailing hypothesis that they always mate for life. Thus, we found that the mating system of the swift fox is highly diverse and substantially more complex than previously believed. We discuss factors that may influence which strategies are adopted and whether they are adaptive

Adult male emigration and a female-based social organization in swift foxes, Vulpes velox

Members of the family Canidae are distinguished from other carnivore families by pair bonding and male care of the young. Because of the importance of food provisioning and territorial defence by males, social structure among canids is shared or even dominated by males. However, small, insectivorous species of canids show little male parental care, although whether social structure differs from other canids is unknown. We combined data from three independent research projects on a small canid, the swift fox, to help elucidate the social organization of this species. Based on data on movements of 35 adult mated pairs and the fate of litters, we found that adult females maintained territories and family structure, whereas adult males tended to emigrate. This is the first evidence of a female-based social organization among any canid species. This type of social organization probably resulted from the decreased importance of territorial defence and food provisioning by males, as their diet is primarily insectivorous during summer when young are weaned. Our results, along with others, indicate that variations in social structure among canid species are strongly influenced by the importance of food provisioning and territorial defence by males