A Device for Monitoring Radio-Marked Animals

Abstract

A simplen portable, and economical recording system consisting of a receiver, signal conditioner, recorder, and power source is described. The system was designed to monitor the signal strength from a radio-marked animal at a particular location. Information is stored on recorder chart paper. Radio-marked ucks have been successfully monitored at nest sites, potholes, and other locations. Within the last 10 years, radiotelemetry as a technique to study wild animals has developed rapidly. Because most field telemetry projects are not designed to obtain data on a continuous basis, as described by Cochran et al. ( 19&5 ) and Cochran ( 1967), a large proportion of ffie available information is not collected. Our recording system was developed to monitor radiomarked animals at particular locations in field studies when ruggedness, portability, and cost of the recording system were of primary concern. Williams and Williams ( 1970) briefly described a recording system for monitoring ie presence and relative adivity of radio-marked bats. A recording device for monitoring the presence of radiomarked seals on ffie surface of sea ioe was mentioned by Siniff et al. ( 1969). Funds for development of the system were provided by the Northem Prairie Wildlife Research Center, Jamestown, North Dakota; by NIH Training Grant No. 5 TQ1 GMO177W04 from the National Institute of General Medical Sciences; and by the U.S. Atomic Energy Commission, COO-133b63. We acknowledge J. R. Tezster, L. M. Cowardin, and H. W. Miller for reviewing the manuscript and R. A. Reichle for preparing the drags MATERIALS AND METHODS The recording system, block-diagrammed in Fig. 1, consists of a receiver, signal conditioner, recorder, and power source. The receiver produees an audio output from an incoming signal. A signal conditioner converts the receiver output into a d-c current activating the recorder stylus. Stylus movement of a single channel d-c recorder (Model No. 288, recorder paper Style A, Rustrak Instrument Division, Gulton Industties Inc. Manchester7 New Hampshire ) is recorded on pressure-sensitive paper. The receiver is tuned aurally by using headphones to select the desired frequency and by obselrving the rearder to obtain the desired deflections of the stylus. Range of the system can be varied by adjusting the rf gain of the receiver or antenna gain. Selection of the type of antenna will depend on the relative positions of the antenna and the animal to be monitolred. If the antenna can be placed near ffie center of the area to be monitored, a nondirectional ntenna is the best choice. When the antenna must be 829 BRIEFER ARTICLES 830 Jot4rnal of Wildlife Manugement, Vol. 35i, No. 4, October 1971 | t v +12 VDC SUPPLY C l g 1 < GROUND 50 MFD 712K_ i < F TERMINAL ON