Fever is an effective defence against disease, but new research suggests that not all animals use it when exposed to infection.
The study, published online in the British Ecological Society's journal Functional Ecology, found large differences in fever responses among closely related species of mice and suggests that an animal's reproductive strategy could explain some of this intriguing variation.
Although often treated in the medical world as part of disease, fever is an essential way for many organisms to prevent or eradicate infections. But even though fever is an effective strategy for animals to protect themselves against pathogens, fever varies a great deal within and between species, and scientists are unsure why immune defences vary so much when evolution should strongly favour animals with the strongest immune systems.
Part of the reason for this variation seems to lie in the fact that fever is expensive and therefore involves trade-offs with other physiological processes. According to the lead author Professor Lynn Martin of the University of South Florida: “Fever is very costly energetically. A 1oC rise in body temperature in a warm-blooded animal requires around a 10% increase in metabolic rate.”
Martin's hypothesis is that an animal's reproductive strategy could hold important clues as to why some species favour fever more than others. In particular, he wondered whether animals that “live fast, die young” might invest fewer resources in mounting fevers to combat infections because their life history involves putting their resources into breeding quickly rather than living to a ripe old age.