Telemetry as a Technique in the Study of Predation

Abstract

Eight snowshoe hares (Lepus americanus) and five cottontail rabbits (Sylvilagus floridanus) were radio-tagged and tracked by an automatic system. Three of the hares, injured upon capture, lived an average of 2.3 days before being killed by predators. The remaining five survived for an average of at least 28.2 days. Of two uninjured rabbits killed, one was preyed upon within an hour after being disturbed; the other evaded predators for 24 days. Red foxes (Vulpes fulva) and owls probably were the main predators. Accounts of each instance of predation are given, including one in which both predator and prey were radio-tagged. The potential of telemetry for predation studies is emphasized, and suggestions are made for setting up such studies. The use of radio transmitters attached to animals for studies of movements and behavior is now a standard procedure (Lemunyan et al. 1959, Marshall et al. 1962, Cochran and Lord 1963, Cochran et al. 1965). However, little use has been made of this technique for investigating predation and other mortality factors, although mention has been made of its potential in this regard by Marshall and Kupa (1963). These authors were able to locate four predatorkilled grouse (Bonasa umbellus) and determine the type of predation in three cases. Recently McEwen and Brown (1966) used telemetry to study reactions of sharp-tailed grouse (Pedioecetes phasianellus) to insecticides. Through this technique they learned that at least three of their treated birds succumbed to predation. This paper emphasizes the potential of telemetry for predation studies and presents predation information obtained via the technique. Data were obtained from January through March, 1964, incidental to investigations of snowshoe hares and cottontail rabbits. Information on a night's movements of a red fox were contributed by Alan B. Sargeant. Besides foxes, other predators probably involved were barred owls (Strix varia), great horned owls (Bubo virginianus), and large hawks. The study was conducted in cedar (Thuja occidentalis) and alder (Alnus rugosa) swamps on the Cedar Creek Natural History Area, 30 miles north of Minneapolis, Minnesota. A snow cover of several inches existed throughout the study. W. W. Cochran designed and built the transmitters and automatic track-