Thermoregulation in pronghorn antelope (Antilocapra americana,Ord) in winter

Abstract

SUMMARYConservation of energy is a prerequisite thermoregulatory strategy for survival in northern hemisphere winters. We have used thermistor/data logger assemblies to measure temperatures in the brain, carotid artery, jugular vein and abdominal cavity, in pronghorn antelope to determine their winter body temperature and to investigate whether the carotid rete has a survival role. Over the study period mean black globe and air temperature were -0.5±3.2°C and -2.0±3.4°C, respectively, and mean daytime solar radiation was ~186·W·m -2 . Brain temperature (T brain , 39.3±0.3°C) was higher than carotid blood temperature (T carotid , 38.5±0.4°C), and higher than jugular temperature (T jugular , 37.9±0.7°C). Minimum T brain (38.5±0.4°C) and T carotid (37.8±0.2°C) in winter were higher than the minimum T brain (37.7±0.5°C) and T carotid (36.4±0.8°C) in summer that we have reported previously. Compared with summer, winter body temperature patterns were characterized by an absence of selective brain cooling (SBC), a higher range of T brain , a range of T carotid that was significantly narrower (1.8°C) than in summer (3.1°C), and changes in T carotid and T brain that were more highly correlated (r=0.99 in winter vs r=0.83 in summer). These findings suggest that in winter the effects of the carotid rete are reduced, which eliminates SBC and prevents independent regulation of T brain , thus coupling T brain to T carotid . The net effect is that T carotid varies little. A possible consequence is depression of metabolism, with the survival advantage of conservation of energy. These findings also suggest that the carotid rete has wider thermoregulatory effects than its traditional SBC function.

The carotid rete and artiodactyl success

“…If a rete is absent (horse and zebra) then changes in T carotid and T brain are more tightly linked and variation in body temperatures is reduced. Our observation of the relationship between T carotid and T brain in winter in pronghorns ( Hébert et al 2008; figure 2 f ) is particularly important. It shows that in winter the effect of the rete can be suppressed and the relationship between T brain and T carotid then becomes identical to that of the non-rete animals.…”

“…We advance here the idea, based on recent evidence we have obtained (Lust et al 2007;Hébert et al 2008), that an additional factor was a difference in the ability to thermoregulate, magnified by the changing climate. Adaptation and evolution are constrained by cold and hot environments that limit food and water supplies and impose temperature stress.…”

Towards a mechanistic understanding of the responses of large terrestrial mammals to heat and aridity associated with climate change

“…Low ambient temperature itself, however, does not appear to have been the main factor responsible for the reduced body temperatures. In winters as cold as those faced by hypothermic red deer, horses and Alpine ibex, pronghorn antelope (Antilocapra americana) receiving supplementary food maintained body core temperature within a narrow 24 h range, with the 24 h minimum body core temperature higher than that in summer [142]. A reduction in body core temperature also was evident in Arabian oryx (Fig.…”

Establishment of the Black-Tailed Prairie Dog (Cynomys ludovicianus) as a Novel Animal Model for Comparing Smallpox Vaccines Administered Preexposure in both High- and Low-Dose Monkeypox Virus Challenges

“…Surgery was performed on each animal in the vaccine safety study to implant a biotelemetry transponder as described previously (36). This procedure has been shown to cause no lasting discomfort beyond a short recovery period in multiple species (11,23,24,49,66). The ER-4000 E-Mitter transponder (Mini Mitter, Respironics, Bend, OR) was programmed to record temperature and gross motor activity levels at 5-min intervals, and data were analyzed using VitalView (Mini Mitter, Respironics) software.…”