Franz Schober, Susanne Reimoser
Research Institute of Wildlife Ecology, Vienna Veterinary University,
Savoyenstrasse 1, A-1160 Vienna, Austria

INTRODUCTION As a part of investigations on time and energy budgets of roe deer (Capreolus capreolus) and red deer (Cervus elaphus) biotelemetric long-term studies of heart rate (which is highly correlated to relative changes in energy expenditure) and activity in both species were carried out.

METHODS Animals were equipped with implanted heart rate and activity transmitters and held in a fence close to natural conditions. On roe deer a direct transmission (150 MHz) from the implant to the receiving station was applied, using pulse-interval modulation (for QRS detection) and pulse-duration modulation (for activity detection). On red deer a repeater system consisting of an implantable heart rate transmitter (100 kHz) and an extracorporal repeater collar (150 MHz) was used. In the receiving stations data were preprocessed on a minute basis. For detection of animal's activity the mean heart rate, the number of head-up/down changes and the number of rf signal strength variations have proven to be sufficient. An algorithm for activity detection was established experimentally and verified by simultaneous video observations. Special efforts were made to check the non-reactivity of the biotelemetric method on the behaviour of the animals.

RESULTS No difference in behaviour could be detected after day 13 post operationem compared to the behaviour before the surgical procedure. The correlation coefficient of measured and observed activity was 0.90. The mean portion of time, classified wrong (active/inactive or vice versa) during 10 days of observation was 7.6%. Detailed daily and seasonal activity and heart rate patterns are presented using the data of 16 roe deer and 12 red deer. Roe deer shows various sex-specific seasonal fluctuations of heart rate (energy expenditure) related to their biological rhythm. Red deer shows a very strong decrease in heart rate during the winter (about 60 to 50 % of the summer values).

DISCUSSION This paper gives an example for the versatility of biotelemetric studies on wildlife animals. Since "inactivity" (lying) was detectable very reliable with this method, all heart rate values related to inactivity delivered patterns of "resting heart rate" which are very important for the investigation of seasonal changes in energy expenditure.