In the course of evolution, wild boars (Sus scrofa) have spread all over the world and are surpassed in this respect only by humans and their permanent companions, the mouse (Mus musculus) and the rat (Rattus norvegicus). An essential factor of the high adaptability to the most diverse environmental conditions is the distinctive ability of wild boars to regulate their body temperature. According to a study just published by the Research Institute of Wildlife Ecology at the University of Veterinary Medicine Vienna, this could mean that global climate change will have little impact on wild boars.
Evolutionarily, the wild boar originates from warm islands in Southeast Asia, but today it can be found on all continents except Antarctica. It would be logical to attribute this triumph to rising environmental temperatures.
For their study, the scientists tested the hypothesis that temperature is unimportant as a habitat factor compared to other habitat factors because wild pigs are excellent thermoregulators. 13 adult females living in an outdoor enclosure in Burgenland were studied. The wild boars were equipped with sensors for heartbeat and body temperature. According to the researchers at the Vetmeduni, temperature has only an indirect effect. More important is the abundant availability of food resources, which can fully compensate for the negative effects of cold winters.
Wild boars show high resilience to temperature differences
“We found that the thermoneutral zone in summer is about 6 to 24°C. In winter, the thermoneutral zone is 0 to 7°C. In addition, the increase in heart rate and energy expenditure is comparatively small in cold conditions,” said study first author Thomas Ruf of the Research Institute of Wildlife Ecology (FIWI) at Vetmeduni. “This relatively small increase in energy expenditure during cold exposure puts the wild boar in the ranks of Arctic animals, such as the polar bear, while tropical mammals increase their energy expenditure many times over. On the other hand, the response of the wild boars we studied to high ambient temperatures was weak at all times of the year.”
Advantage in times of global climate change
For thermoregulation, wild boars rely on daily cycles, especially rhythms of subcutaneous temperature. Says Claudia Bieber, head of the Vetmeduni's FIWI: “These allow them to build up large differences in skin and core body temperature with little energy expenditure, which in turn reduces heat loss.” According to the researchers, it is primarily this ability - together with effective behavioral strategies to compensate for heat - that has led to wild boars inhabiting the most climatically diverse areas of the world today.
Against this background, it would not be surprising if wild boars showed only minor reactions to global climate change, according to the scientists. However, the increasing drought associated with global warming could lead to reduced food availability and thus pose a different problem for wild boars.
The article “Thermoregulation in the wild boar (Sus scrofa)” by Thomas Ruf, Sebastian G. Vetter, Johanna Painer-Gigler, Gabrielle Stalder and Claudia Bieber was published in “Journal of Comparative Physiology B”.