Field Evaluation of Radiotransmitters for Northern Pocket Gophers

A field study was conducted in northern Idaho from June to November 1995 to evaluate the design and functional aspects of four types of Radio-transmitters for use on northern pocket gophers (Thomomys talpoides) as well as the effects of the transmitters on behavior of the animals. Twenty-five of 46 northern pocket gophers were fitted in the field with one of three models of radio-collars (AVM, NWRC, and Holohil), nine received Wildlife Materials abdominal implant transmitters (surgery conducted off-site), and 12 without transmitters served as controls. Study animals were relocated every second to fourth day until the end of the study. Individuals not retrieved by the end of the study were captured with live traps or kill traps. Recovery of marked animals (82.6%) and transmitters (82.4%) was high. Radio-collar shedding (35.3%) was a common phenomenon, but all implants remained intact. Transmitter malfunctions were infrequent. Physical side effects of the collars were uncommon (8.8%). No adverse effects of the implants were evident. Negative behavioral effects of transmitters included reduced spatial use and extreme length of claws on the front feet. No significant differences (P = 0.23) in body mass between the control and radio-marked northern pocket gophers were noted at the end of the study. Effective life of transmitters varied significantly (P = 0.01), with the Holohil collars having the greatest longevity (mean = 87.6, S. E. = 11.72 days). Though no single transmitter emerged as a superior choice for extended field studies, the Holohil model performed the best. It had the longest effective life, and ranked a consistent second place in size (small), mass (low), ease of attachment, and signal strength