Application testing of a GPS - based
automatic location system prototype
in Przewalski Horses (Equus
przewalskii POLJAKOV, 1881)

Driemel, U. Scheibe, K.M.; Eichhorn, K.
Institute for Zoo Biology and Wildlife Research Berlin
PF 1103, 10252 Berlin

INTRODUCTION The NAVSTAR GPS system is applicable for monitoring habitat utilisation of free ranging animals now. A GPS receiver will be used on wild horses to define feeding grounds, translocations and resting places. This study shows precision and application characteristics of a prototype in a semireserve.

METHODS A GPS - receiver, and a datalogger were integrated in a collar. The weight of the collar (2 kg) is acceptable to be used in larger mammals like horses. The receiver is a six channel type and fixes are taken every five minutes. The results are saved in a 32k RAM of a data logger which is sufficient for 2047 data sets. The data logger had to be connected to the RS 232 interface of a laptop or PC for data transmission during the tests period. Telemetric readings are planned for application in the future. The instrument was applied on individuals in a herd of 12 free ranging Przewalski-horses in a semireserve north of Berlin. The semireserve is an enclosure of 36 ha, with a large meadow and some smaller plots of woodland. It is largely surrounded by wood and on one side it is flanked by a path. Three observation points allow nearly a complete overview. We compared GPS fixes to visual observations. For this purpose, the animal wearing the collar was located by optical bearings in 540 cases from two or three points simultaneously to the programmed GPS fixes. The horse's utilisation of the enclosure was measured by 2200 fixes to identify preferred feeding areas, paths and resting grounds.

RESULTS The collar was accepted by the horses without any problems. Social grooming related to the collar was observed but diminished after adapting its colour to the fur of the horses. For most of the GPS fixes errors of about 20 metres were affirmed. In the period before July 1996 larger errors were observed occasionally due to the "Selective Availability" of the system. After this date the frequency of such large scale errors diminished significantly. The horses utilised the enclosure in a specific pattern. Feeding grounds could be defined and changed in relation to season, food resources, and time of the day.

DISCUSSION The GPS system has been approved for its capabilities and application in larger mammals. Precision and location frequency make it convenient for example in studies on feeding and resting behaviour in relation to ecological conditions.