North American pronghorn antelope (Antilocapra americana) endure hot summers and cold winters, and have a high aerobic exercise capacity. How they thermoregulate under these conditions is unknown. Our study was aimed at measuring their brain and blood temperatures, investigating whether these temperatures are affected by environmental temperatures and whether males and females have different body temperatures. Using isoflurane anesthesia and aseptic techniques in two male and three female pronghorns we implanted small bead thermistors (GE Thermometrics) into the carotid artery, jugular vein, near the hypothalamus, and in the abdominal cavity. Temperature was measured with an accuracy of 0.04°C, recorded every 5 min, and stored on data loggers. After recovery from anesthesia the animals were released into a 100-hectare enclosure at the Sybille Research Station, Wyoming. They were free ranging for 40 to 87 days from November 2004 to February 2005. A 15-channel weather station (Onset HOBO) was used to record black globe temperature and other weather data at the study site. Over the 3 month recording period, mean ambient temperature was -0.5 ± 8.2°C (mean ± S.D.; range -22 to +9°C). The coldest day (23/12/04) had a mean ambient temperature of -12.4 ± 8.1°C (range -22 to +2°C). Mean brain temperature over the period for all 5 animals was 38.9±0.4°C, mean carotid artery blood temperature was 38.6±0.4°C, and mean jugular vein blood temperature was 38.2±0.5°C. On the coldest day highest ambient temperature occurred at 1200h, and highest body temperatures at 0100h and 1700h. Lowest body temperatures coincided with the lowest globe temperature at 0800h. In one female and one male mean brain temperature on this day was 38.9±0.2°C, mean carotid blood temperature was 38.4±0.3°C, and mean jugular blood temperature was 38.0±0.3°C, which were the same as mean temperatures for all days. The mean brain carotid temperature difference was 0.6±0.3°C. The most frequently recorded arterial blood temperature in the female was 38.2°C and 38.7°C in the male. Our results show that body temperature of pronghorns is maintained in the winter, and has a nycthemeral rhythm with amplitude less than 1°C. The female had a lower mean body temperature than the male, narrower frequency distribution, and a higher brain-carotid difference. The mean brain temperature in both animals was similar. The male’s lower brain-blood difference could have been a consequence of its higher body temperature, or a higher cerebral blood flow combined with cooling of post-carotid rete arterial blood. The data imply that in the winter pronghorn brain temperature is regulated within a narrower range than core temperature.
University of Bristol (2005) J Physiol 567P, PC104
Poster Communications: Winter brain and body temperature in free-living pronghorn antelope
Hebert, Jennifer Elizabeth; Lust, Amanda; Fuller, Andrea; Maloney, Shane; Mitchell, Duncan; Mitchell, Graham;
1. Zoology/Physiology, University of Wyoming, Laramie, WY, USA. 2. Physiology, University of Western Australia, Perth, WA, Australia. 3. Physiology, University of the Witwatersrand, Johannesburg, South Africa.
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