TRACKING WILDLIFE BY SATELLITE 



43 



on ice or at traditional terrestrial sites. Because of the vast 

 expanses and unpredictable weather off Alaska's western 

 coast, quantifying patterns in diving and haul-out behav- 

 iors using traditional VHP telemetry and fixed-wing air- 

 craft would be prohibitively expensive. Satellite transmit- 

 ters were used to develop a method of quantifying these 

 behaviors, and thus of improving the reliability of subse- 

 quent aerial surveys. 



The behavior and habitats used by marine mammals 

 present special problems for satellite telemetry. Because 

 salt water does not allow transmission of radio signals, a 

 saltwater switch was used to turn the transmitter on when 

 the animal was above the water's surface. The saltwater 

 switch also functioned as a sensor, quantifying the amount 

 of time the animal spent out of the water during a sampling 

 period. 



In August 1987, a prototype FIT designed for walrus 

 was attached to a male walrus on Round Island near 

 Togiak, Alaska. The PTT functioned until December 

 1987; it provided information on animal location, tem- 

 perature, duration of the last dive recorded, average time 

 spent below the surface during the past 24 h, and number 

 of dives during the past 24 h. Movements of this walrus 

 from coastal areas into Bristol Bay and back during fall 

 1987 are shown in Fig. 40. 



PTT's subsequently deployed on walruses have had the 

 temperature sensor replaced with a pressure sensor. In 

 addition to animal location and the amount of time spent 

 out of water, these units were designed to yield the amount 

 of time spent at depths of 0-4, 4-10, and >10 m; the 



number of dives > 10 m deep; and the deepest dive during 

 the 24-h sampling period. These PTT's have generally 

 worked well for 1-2 months but have failed thereafter. 

 Reasons for the relatively short life spans are currently 

 being investigated. 



Application and Sampling 

 Considerations 



In addition to field considerations, the quantity and 

 quality of data received using satellite telemetry require 

 consideration of data processing methods and analytical 

 procedures. 



Data Processing 



For projects with few satellite collars deployed or sim- 

 ple objectives, it may be possible to analyze data without 

 computers. However, for most applications, the quantity 

 and complexity of data necessitate computer processing. 

 Computers allow for rapid storing, sorting, summarizing, 

 mapping, and analyzing of data. Some tasks are impos- 

 sible without the aid of a computer: algorithms required to 

 predict the time and location of satellite passes are too 

 complex to be formulated without a computer. Also, com- 

 puting distances between locations and areas formed by 

 polygons are tasks that cannot realistically be attempted 

 without computers. Many of our analyses used a geo- 

 graphic information system (GIS) to store, select, and map 

 locational data. 



Fig. 40. Locations of an adult male walrus 

 tracked by satellite in Bristol Bay, Alaska, 

 fall 1987. A. 14 August. B. 26 August. 

 C. 16 September. D. 18 October. E. 22 Octo- 

 ber. F. 14 November. Data courtesy of S. 

 Hills, U. S. Fish and Wildlife Service. 



