Pathological Responses of Red Foxes to Capture in Box Traps

We documented the physiological responses of captive-raised red foxes (Vulpes vulpes) to capture in box (i.e., live) traps. The behavior of captured foxes was video recorded, and heart rate and body temperature were monitored via radio telemetry throughout an 8-hour restraint period. Endocrine, biochemical, hematological, and pathological samples were collected. Responses of foxes caught in box traps were compared to the responses reported by Kreeger et al. (1990c) for untrapped (i.e., control) foxes and foxes caught in padded-and unpadded-jaw foothold traps. Heart rate and body temperature increased after foxes were caught in box traps, but never significantly exceeded mean pretrapped levels. Foxes caught in box traps were physically active for 35.7 ± 8.8 (SE)% of the restraint period. The majority of this activity consisted of pacing in the trap. Foxes caught in box traps had higher (P < 0.03) adrenocorticotropin and cortisol values than untrapped foxes, and lower (P < 0.001) β-endorphin and cortisol levels than foxes caught in foothold traps. Bilirubin, alkaline phosphatase, lactate dehydrogenase, and aspartate aminotransferase levels for foxes caught in box traps were elevated (P < 0.01) above levels of untrapped foxes. Foxes caught in box traps had lower (P < 0.004) alkaline phosphatase, lactate dehydrogenase, creatine kinase, and aspartate aminotransferase levels than foxes caught in foothold traps. Because foxes caught in box and padded-jaw foothold traps had no limb damage, the observed biochemical differences between animals caught in these traps were likely due to psychogenic factors associated with limb restraint and differences in the intensity of exertion (i.e., pacing vs. digging). Hematological profiles of foxes caught in box traps or foothold traps were similar, but trapped foxes had higher (P < 0.01) leukocyte counts and significant neutrophilia and lymphopenia compared to untrapped foxes. The gross and histopathological findings for foxes caught in box and foothold traps were generally similar. Foxes caught in box traps had higher (P < 0.05) incidences of adrenal and renal congestion and lung hemmorhage than did untrapped foxes. We conclude that factors associated with limb restraint directly contribute to the trauma experienced by trapped red foxes and, therefore, foxes caught in box traps undergo less trauma than foxes that are restrained by a limb in a padded- or unpadded-jaw foothold trap.