Associate Editor: Jeff Bowman
Factors influencing reproductive success and litter size in captive island foxes†
Article first published online: 12 JAN 2013
Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
The Journal of Wildlife Management
Volume 77, Issue 2, pages 346–351, February 2013
How to Cite
Calkins, E. S., Fuller, T. K., Asa, C. S., Sievert, P. R. and Coonan, T. J. (2013), Factors influencing reproductive success and litter size in captive island foxes. The Journal of Wildlife Management, 77: 346–351. doi: 10.1002/jwmg.492
- Issue published online: 28 JAN 2013
- Article first published online: 12 JAN 2013
- Manuscript Accepted: 19 JUN 2012
- Manuscript Received: 20 JUN 2011
- captive breeding;
- island fox;
- Urocyon littoralis
A severe decline of island foxes (Urocyon littoralis) on the northern Channel Islands in the 1990s prompted the National Park Service to begin a captive breeding program to increase their numbers. Using detailed records of all the fox pairs (N = 267) that were part of the program on San Miguel, Santa Rosa, and Santa Cruz Islands from its inception in 2000 through 2007, we identified factors influencing the breeding success of pairs in captivity in the interest of formulating strategies that could increase captive productivity. We compiled a database of variables including litter size, reproductive success, distance to nearest occupied pen during the breeding season, subspecies, exposure, female age, male age, age difference, female and male origin (wild vs. captive born), same versus different origin, years paired, previous reproductive success by the pair, previous reproductive success by the female, mate aggression-related injuries, male previous involvement in a pair with mate aggression, and female previous involvement in a pair with mate aggression. We used multiple linear regression to identify factors predictive of litter size, and logistic regression to predict the probability of reproductive success. A larger inter-pen distance, older male age, less exposure, and a smaller intra-pair age difference positively affected litter size. The probabilities of reproductive success increased with fewer years paired and less exposure. Comparatively, pairs with wild born females (vs. captive born females), and previously successful pairs (vs. previously unsuccessful and new pairs) were most likely to be successful. These results indicate that the optimal situation was to pair wild-caught females with older males in sheltered pens that were as far from other pens as possible, to maintain successful pairs and repair unsuccessful ones. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.