The Pathological Responses of Red Foxes to Capture in
Foothold Traps and Box Traps
P. J. WHITE, TERRY 1. KREEGER, ULYSSES S. SEAL,
AND JOHN R. TESTER
Department of Fisheries and Wildlife, University of Minnesota, St.
Paul,
MN 55108; Department of Ecology and Behavioral Biology, University of
Minnesota, Minneapolis, MN 55455; Veterans Administration Medical
Center, Minneapolis, MN 55417; Department of Ecology and Behavioral
Biology, University of Minnesota, Minneapolis, MN 55455
We documented the physiological responses of red foxes (Vulpes vulpes) to capture in foothold traps and box (i.e., live) traps. Captive-raised foxes were caught and held for an 8-hour restraint period in either No. 1½ padded-jaw traps, No. 1½ unpadded-jaw traps, or Model 109 Tomahawk box traps. Free-ranging foxes were also caught in foothold traps for variable periods. Nontrapped, free-ranging foxes were used as controls. The behavior of trapped, captive foxes was video recorded and heart rate was monitored via radio telemetry. Endocrine, biochemical, hematological, and pathological samples were collected. Foxes caught in unpadded traps had higher physical injury scores to the trapped limbs than foxes caught in padded traps (P<0.05). Heart rate increased rapidly after foxes were caught, but returned to mean pretrapped levels after 80 minutes. Mean time spent physically active during the restraint period was 13.3% (SE=0.3), 17.8% (SE=6.7), and 35.7% (SE=8.8) for foxes caught in padded and unpadded foothold traps and box traps, respectively (P= 0. 17).
Foxes caught in foothold traps spent the majority of their active periods digging and pulling against the trap, whereas foxes caught in box traps generally paced in the trap. Compared to control foxes, foxes caught in foothold traps had elevated levels of the stress-indicative hormones adrenocorticotropin and cortisol (P<0.05). These hormones were not increased in foxes caught in box traps (P>0.05). Trapped foxes had higher levels of bilirubin, alkaline phosphatase (ALP), and aspartate aminotransferase (AST) than nontrapped foxes (P<0.05). Foxes caught in unpadded traps had higher values for ALP, AST, and gamma-glutamyl transpeptidase than foxes caught in padded traps (P<0.05). Foxes caught in box traps had lower ALP, AST, lactate dehydrogenase, and creatine kinase levels than foxes caught in foothold traps (P<0.05). Since foxes caught in box and padded traps had no limb damage, the endocrine and biochemical differences between these trap-type groups were likely due to psychogenic factors associated with limb restraint and differences in the intensity of exertion (i.e., pacing versus digging). Trapped foxes had higher leukocyte counts and significant neutrophilia and leukopenia compared to control foxes (P<0.05). Additionally, trapped foxes had higher incidence of adrenal and renal congestion and lung hemorrhage than did nontrapped foxes (P<0.05). Most of the pathological changes in trapped foxes were consistent with the physical exertion of resisting the trap, and none appeared life-threatening.
Overall, box traps caused less trauma to red foxes than foothold traps. However, padded-jaw foothold traps caused less trauma to red foxes than unpadded-jaw foothold traps.
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