Validation of a biotelemetric technique, using ambulatory miniature black globe thermometers, to quantify thermoregulatory behaviour in ungulates

Abstract

Behavioural thermoregulation is an animal's primary defence against changes in the thermal environment. We aimed to validate a remote technique to quantify the thermal environment behaviourally selected by free-ranging ungulates. First, we demonstrated that the temperature of miniature, 30 mm diameter, black globes (miniglobes) could be converted to standard, 150 mm diameter, black globe temperatures. Miniglobe temperature sensors subsequently were fitted to collars on three free-ranging ungulates, namely blue wildebeest (Connochaetes taurinus), impala (Aepyceros melampus) and horse (Equus caballus). Behavioural observations were reflected in animal miniglobe temperatures which differed from those recorded by an identical miniglobe on a nearby exposed weather station. The wildebeest often selected sites protected from the wind, whereas the impala and the horse sheltered from the sun. Nested analysis of variances revealed that the impala and horse selected significantly less variable environments than those recorded at the weather station (P<0.001) over a 20-min time interval, whereas, the microclimates selected by wildebeest tended to be more variable (P=0.08). Correlation of animal miniglobe against weather station miniglobe temperature resulted in regression slopes significantly less than one (P<0.001) for all species studied, implying that, overall, the animals selected cooler microclimates at high environmental heat loads and/or warmer microclimates at low environmental heat loads. We, therefore, have developed an ambulatory device, which can be attached to free-ranging animals, to remotely quantify thermoregulatory behaviour and selected microclimates.

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

“…Through the use of biologgers to detect microclimate selection without human observers, we also have shown that Arabian oryx selected cooler microclimates with increasing environmental temperatures (Fig. 3) [91], and at times accessed microclimates with a black globe temperature (which integrates the effects of air temperature, radiation, and wind speed; [92]) as much as 12°C below that of the open environment. In dry periods in which the oryx had no access to drinking water, they selected cooler microclimates than they did at the same environmental heat load in wetter periods, when they had access to drinking water [91].…”

Does size matter? Comparison of body temperature and activity of free-living Arabian oryx (Oryx leucoryx) and the smaller Arabian sand gazelle (Gazella subgutturosa marica) in the Saudi desert

“…4.3 ± 0.2) and oryx (upper right panel, y = 0.85 ± 0.006x ? 3.5 ± 0.2), indicating the selection of cooler microclimates during this period J Comp Physiol B (2012) 182:437-449 445 were able to detect the selection of cooler microclimates without observers present, by using miniature globe thermometers attached to collars, a novel technique we developed for recording microclimate selection by freeliving animals (Hetem et al 2007). There was no difference in the pattern of microclimate selection by the two species, consistent with them being stationary and in the shade during the hottest times of the day.…”

“…In addition to a tracking radio transmitter, the collar supported a miniature black globe thermometer (''miniglobe''), to allow for the dynamic ambulatory measurement of the microclimate that each animal chose to occupy. This technique has been validated previously on other ungulate species (Hetem et al 2007). Miniglobe temperature was measured by a small temperature-sensitive data logger (see below) inserted into the centre of a matt-black hollow copper sphere (30 mm diameter, Press Spinning and Stamping Co., Cape Town, South Africa).…”

Shearing at the end of summer affects body temperature of free-living Angora goats (Capra aegagrus) more than does shearing at the end of winter

“…Each collar supported a miniature black globe thermometer ('miniglobe'), which allowed for the dynamic measurement of the microclimate that the goat chose to occupy. This technique has proven successful on other ungulate species (Hetem et al, 2007). Miniglobe temperature was measured by a small temperature-sensitive data logger (see temperature measurements) inserted into the center of a matt-black hollow brass sphere (30-mm diameter; Press Spinning & Stamping Co., Cape Town, South Africa).…”