A device for monitoring radio-marked animals
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
Assessment of telemetric motion sensors for studies of activity
Radio transmitters containing motion-sensitive devices that changed the pulse rate (mode) in response to movement were evaluated as a means for studying activity of black bears (Ursus americanus). Two types of motion sensors were used: tip switches gave immediate indications of activity, whereas reset motion sensors extended the active mode signal for 5 min. Locational accuracy was less affected by reset sensors than tip switches, and reset sensors facilitated activity monitoring of weak or fading radio signals. Tip switches were more useful in making continuous judgements of activity, and may be used to differentiate types and degrees of activity. For both sensors true activity could be distinguished from comfort movements. Also, both motion-sensitive transmitters gave indications of activity that compared well with hourly movements of bears; these transmitters were more sensitive to localized movements than measurements between radio locations determined by triangulation and were more practical because ...
A RADIO-TRACKING SYSTEM FOR WILD ANIMALS
This system of radio location has been used on rabbits (Sylvilagus floridanus), striped skunks (Mephitis mephitis), and raccoons (Procyon lotor). Size, weight, life, physical and electrical stability, and radiated power are important parameters of the transmitter. Mercury cells provide about 115 milli- watt hours per gram and were chosen as the transmitter power source. The transmitter is a transistor, crystal-controlled oscillator with the tank coil for the oscillator acting also as a magnetic dipole trans- mitting antenna. Antenna efficiencies of the order of 0.1 percent are obtained, yielding radiated power in the sub-microwatt region. The antenna is constructed of copper or aluminum and has a figure eight directional pattern. The complete transmitter without batteries weighs approximately 10 grams and costs approximately $8.00 for parts. Instructions for building transmitters are given. Transmitters were fastened to rabbits and skunks by means of harnesses and to rabbits, skunks, and raccoons by collars. The harnesses did not prove satisfactory for long-term attachment. The receiver is a portable, battery-powered unit weighing 10 lbs including the batteries. It is crystal controlled on 44 switched channels with a 4 db noise figure and a 30 CPS bandwidth. A re- ceiving system was assembled with commercially available units and used successfully for tracking skunks. The components of this system are a military surplus receiver (BC-453), a radio range filter (FL-13), and two transistorized radio frequency converters. The portable receiver is well adapted for tracking on foot using the null of its attached loop antenna for obtaining bearings on the animals carrying transmitters. The transmitters operate on different frequencies to avoid interference in taking bearings and to provide for individual identification.