Captivity, Inbreeding, Cross-Lineage Matings, and

Body Size in Mexican Wolves

Richard Fredrickson

Department of Biology, Arizona State University, Tempe, AZ 85287-1501; Richard.Fredrickson@asu.edu

Philip Hedrick

Department of Biology, Arizona State University, Tempe, AZ 85287-1501; Philip.Hedrick@asu.edu

Abstract

The Mexican gray wolf (Canis lupus baileyi) appears to be extinct in the wild and exists now only

in captivity and in a single, small, reintroduced population. A recent study of captive animals

found no evidence for inbreeding depression in juvenile viability or litter size. We examined the

relationship between inbreeding and body weight in captive wolves. We found that captive wolves

with little or no known inbreeding had lower body size than wild caught wolves. In addition,

captive wolves with higher inbreeding had lower body size than captive wolves with little or no

inbreeding. The captive population was descended from three founders until two other lineages,

each descended from two founders, were recently added to the population. Consequently we

examined the potential statistical power associated with future comparisons of body weights

between inbred wolves and the offspring of cross-lineage matings. In this case it appears likely

that in the next few years there will be an adequate sample size to statistically evaluate differences

in body size between these groups.