Analysis of Radiotracking Data Using Digitized Habitat Maps

A method is described that provides a rapid and accurate analysis of habitat used by radioequipped animals. The digitizer (basically an X-Y plotter in reverse) converts maps into digital form by describing each habitat unit as a polygon that closely approximates the actual shape of the unit. The coordinates of each polygon are then stored on magnetic tape. Habitat classification data and other information are coded and combined with the proper polygon coordinates. This results in one file containing all habitat data. A computer program with inputs of tracking data and habitat data provides a listing of the habitat used by the animals studied. Analysis of habitat used by radio-equipped ucks is demonstrated using this method. J. WILDL. MANAGE. 37(3):404-409 Tracking radio-equipped animals often results in the accumulation of large numbers of fixes (animal locations) which are analyzed to determine information such as home range, movement patterns, and habitat use. Determining the habitat used by an animal in its daily and seasonal movements is of particular interest in ecological studies. Several methods have been used to analyze animal locations in relation to habitat. Most tracking studies involving fewer than several hundred fixes are efficiently handled by overlaying hand or computer drawn maps on habitat maps and visually determining the habitat for each fix. Another method is to record the habitat each time a location is obtained. In studies involving thousands of fixes, a more rapid and flexible method of data analysis is required. Siniff (1966:5) described a computer program which partitioned a study area into 0.65-hectare squares and determined the number of fixes in each square. An X-Y plotter produced a graphic display of this information which could be overlaid on a habitat map. Nicholls and Warner (1972) used 0.65-hectare squares, each with an assigned code based on the dominant habitat in that square, to study habitat used by radio-equipped barred owls (Strix varia). The number and percentage of fixes occurring in each habitat type were then calculated by a computer. The method described in the present paper used a digitizer to convert habitat maps into digital form on magnetic tape. A computer program with inputs of converted map data and animal fixes determined the habitat type of each fix and provided a listing of the number and percentage of fixes occurring in each habitat type. This method is similar to that used by Gilmer (1971: 23). Tomlinson (1968) described the use of a digitizer as a component of a system for storing and analyzing map information relating to rural development. Funds for the development of this method were provided by the Northern Prairie Wildlife Research Center, Jamestown, North Dakota; by NIH Training Grant 5 TO1 GM01779 from the National Institute of General Medical Sciences; and 1 Present address: U.S. Bureau of Sport Fisheries and Wildlife, Northern Prairie Wildlife Research Center, Jamestown, North Dakota 58401. 404 J. Wildl. Manage. 37 (3):1973 ANALYSIS OF RADIOTRACKING DATA * Gilmer et al. 405 by the U.S. Atomic Energy Commission (COO-1332-80). We acknowledge the assistance of D. H. Johnson, A. B. Sargeant, and D. B. Siniff in reviewing the manuscript. We also wish to thank personnel of the Hybrid Computer Laboratory of the University of Minnesota for their assistance in operating computer