Successful Use of Pup Fostering to Increase Survival of Endangered Channel Island Foxes (Urocyon littoralis)
Four subspecies of the Channel Island fox (Urocyon littoralis) were listed as endangered under the Federal Endangered Species Act on March 5, 2004 due to serious declines in populations over the last decade.1 One of the four listed subspecies, U. littoralis catalinae, is present on Santa Catalina Island where the population declined by approximately 90% in 1999. This decline was believed to be the result of an outbreak of canine distemper.2 One aspect of population recovery efforts on Santa Catalina Island was a captive breeding program which incorporated monitoring of dens with a closed-circuit video system. During 2001 and 2002 we observed certain mothers in the facility demonstrating negligent, rejection, or aggressive behavior that resulted in pup deaths. In 2002, these behaviors resulted in the deaths of 6 neonates (43% of total pups born that year). Because of the very small population size of foxes on Santa Catalina Island, and our desire to maximize productivity at the captive breeding facility, we instituted a program to intervene in circumstances where the female demonstrated inappropriate parental behavior. Though fostering of pups into new litters had never been utilized in this species, we believed that previous pup losses justified attempting this intervention technique.
Based on our behavioral observations in 2001 and 2002, we developed specific protocols for making the decision to intervene, nursing pups till fostering occurred, choosing an appropriate foster litter, and introducing pups to new litters. In the combined 2003 and 2004 breeding seasons, intervention was undertaken to assist eleven fox pups in four litters. We successfully fostered eight pups from three females into the litters of five other females. All foster females accepted the new pups immediately and did not show any rejection or aggressive behaviors toward them. For the other three pups, intervention was undertaken due to the female spending inadequate time with the pups but otherwise exhibiting normal behavior toward them. Though we believe fostering would have been a successful option, we chose to first closely confine this female to the immediate vicinity of the den and to temporarily remove her mate. After these steps were taken, this female spent adequate time with her pups. All eleven pups that received additional care were successfully raised to weaning. We believe these results suggest that fostering and other interventions can increase survival of young in captive breeding programs for this species if close observation and rapid response to abnormal parental behavior are employed.
1. Coonan, T. J. 2001. Draft recovery plan for island foxes (Urocyon littoralis) on the Northern Channel Islands. Prepared for the National Park Service.
2. Timm, S.F., J.M. Stokely, T.B. Gehr, R.L. Peebles, and D.K. Garcelon. 2000. Investigation into the decline of island foxes on Santa Catalina Island. Institute for Wildlife Studies.