Biotelemetry as a Technique in Disease Ecology Studies

Abstract

Disease ecology studies frequently demand a detailed knowledge of movements and activity patterns of infected animals, base-line data from apparently healthy individuals and/or inter-action rates between hosts. Additionally, some investigations require periodic examinations of hosts and the recovery of dead animals for necropsy. Until quite recently these data have been obtained primarily by live trapping and marking animals, systematic collections of specimens, or, as in the case of rabies, reports of state public health or veterinary diagnostic laboratories. All of these approaches present difficulties which may limit the quality or quantity of the information gained. For example, the technique of live trapping requires the assump- tion that movement and activity parameters are not affected by the experimental procedures. Balph ( 1968 ) , however, has shown that ground squirrels may become trap happy in response to a ready source of food or trap shy as a result of the noxious experience of being captured and handled. Similarly information obtained from systematic collections of specimens and from laboratory diagnostic reports frequentlyprove to be of limitedvalue in unravelingthe ecologicalrelationships of disease complexes. The technique of attaching miniature radio transmitters to free ranging wild animals, or biotelemetry, may prove to be quite useful in disease investigations by reducing or eliminating the above limitations and by providing more data per unit effort than are provided by current techniques. A properly designed biotelemetry system enables the investigator to determine, with minimal disturbance, behavior patterns of unconfined wild animals. It also provides for determination of the time of death of radio-marked animals and thus permits immediate collection of the remains for necropsy. Houseknecht (1969) used this technique to determine the denning habits of striped skunks (Mephitis mephitis) and the resulting exposure potential for disease. By quickly retrieving carcasses of succumbed radio-marked fawns (Odocoileus virginianus), Cook et a!. (1967) determined the cause of death in 49 of 58 cases. The capability of continuously monitoring the location of radio-marked animals also permits examination of hosts or the collection of specimens at will. Montgomery (1968) attached radio collars to a white-tail deer fawn then recaptured the animal at predetermined intervals in order to investigate the rate of tick attachment. Simi- larly one could recapture radio-marked striped skunks for monthly bladder traps for an investigation into the ecology of leptospirosis. The technique of biotelemetry has been employed in animal movement studies since 1959. These first transmitter packages (Le Munyan et a!., 1959) measured 7.5 x 4.0 x 1.4 cm, weighed 122.5 gm and were designed for implantation into the