Effects of Radiocollars on San Joaquin Kit Foxes

Effects of radiocollars on San Joaquin kit foxes (Vulpes macrotis mutica; Mecure et al. 1993) at the Naval Petroleum Reserves, California were assessed by comparing survival, body mass changes, and reproductive indices between uncollared and collared foxes, and between foxes wearing 100-110 and 50-60-g collars. Among adults, higher survival for foxes surviving the first 30 days post-collaring (P = 0.07) and higher mass loss among newly collared foxes (P = 0.02) may have been attributable to a post-collaring acclimation period. The increased survival after 30 days only was evident among foxes with 100-110-g collars. Lower survival and higher mass loss among newly collared juvenile foxes also provided evidence of an acclimation period. Effects among juveniles were particularly evident after parental care presumably had ceased and when many juveniles may have been dispersing. Tests of collar:body mass ratios indicated that juvenile survival was lower at ratios ≥6%. Finally, analyses revealed little evidence of sex-specific collar effects and no evidence of reduced reproductive success among collared adult females. The potential for a post-collaring acclimation period should be considered in investigations of kit fox survival and body mass dynamics, and collaring should be avoided during periods of increased vulnerability or stress.