TRACKING WILDLIFE BY SATELLITE 



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Fig. 5. Location performance indices for 

 four PTT's deployed on caribou dur- 

 ing October 1987. 



J A S 



Sea. However, these patterns were not consistent, even 

 among polar bears. Figure 7B shows the pattern of perfor- 

 mance from four PTT's deployed on polar bears in the 

 Beaufort Sea in 1987. 



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 1.2 



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 O U 



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0.8 

 0.4 



Message 

 Index 



Location 

 Index 



30 40 50 60 70 80 90 

 Mean Latitude of Study Area () 



Fig. 6. Relation between latitude and PTT performance. See text 

 for explanation of indices. 



Our data, as well as studies by others, suggested that 

 topography affected efficiency. Specifically, efficiency 

 was lower when animals were in valley bottoms, espe- 

 cially in areas of high topographic relief. In one experi- 

 ment, a PTT was placed in a north-facing talus-slope gully 

 within the Brooks Range Dall sheep study area (68 north 

 latitude). The surrounding rock walls were about 200 m 

 high, and the gully was approximately 50 m across. Dur- 

 ing > 17 h of transmission time, no messages were re- 

 ceived from the PTT. On Kodiak Island, only two loca- 

 tions for a bear were calculated during the entire month of 

 August 1987. This bear was primarily using the stream 

 bottom of a deep canyon from which radio signals might 

 have had difficulty reaching the satellite (V. Barnes, 

 AFWRC, personal communication). Keating (un- 

 published report, on file at Glacier National Park, West 

 Glacier, Montana) tested a Telonics PTT at 23 moun- 

 tainous locations in Glacier National Park. Locations were 

 classified as being valley, midslope, or mountain peak. 

 Keating defined the index R 5 as the proportion of over- 

 passes yielding locations, and reported that R 5 was signifi- 

 cantly higher (P < 0.00 1 ) for mountain peak locations than 

 for midslope locations, and significantly lower (P < 0.00 1 ) 

 for valley locations. Craighead and Craighead (1987) also 

 reported lower efficiency from PTT's on caribou in moun- 

 tain valleys than in open terrain. Because efficiency is 

 related to terrain, investigators may be misled if they 

 interpret the number of location estimates as representa- 

 tive of the time spent by the animal in different topograph- 

 ic types. 



Efficiencies summarized in Table 6 are from PTT's 

 deployed in the field. Efficiencies achieved by PTT's dur- 

 ing experiments before deployment were much higher 



