Was Bergman wrong?
Climate does not appear to affect the body size of most birds and mammals.
Scientists have found that individual animals of the same species tend to be smaller in hotter environments and larger in cooler ones. They named this pattern ‘Bergmann’s Rule’ to describe how temperature can influence the size of an animal. However, most studies of Bergmann’s Rule have only looked at one or a few species at a time.
Knowing how many species follow this rule is important because globally rising temperatures could cause lots of species to become smaller. Since the size of organisms affects how much food and space they need, this could disrupt natural systems around the world.
To test if Bergmann’s rule can be extended to many species, Riemer, Guralnick, and White assessed the relationship between temperature and body mass for 952 bird and mammal species. Contrary to Bergmann’s Rule, the results showed that most of the species had similar sizes regardless of the temperature of their environment. Only about 140 species were smaller in hotter environments, and about 70 species were larger in hotter environments. This suggest that Bergmann’s Rule does not apply to most species as expected.
While most birds and mammals may not get bigger or smaller due to warming global temperatures, the few species that do change in size — and the species that interact with them — may be more likely to become endangered or extinct. If we can determine which animals are at risk, we can prioritize their conservation and design better plans for doing so. Losing even a single species disrupts our ecosystems, on which we rely for critical resources like food, building materials, and clean air.
To find out more
Read the eLife research paper on which this eLife digest is based:
