UF study questions existence of rule relating animal size and temperature

GAINESVILLE, Fla. – A University of Florida Institute of Food and Agricultural Sciences doctoral student’s study turns a long-accepted scientific rule on its head. The study found that animals are unlikely to change in size as the climate gets warmer.

Scientists have previously suggested that individual animals of the same species tend to be smaller in hotter environments and larger in cooler ones, said Kristina Riemer, a Ph.D. student in the UF/IFAS wildlife ecology and conservation department. This pattern is called “Bergmann’s Rule” and describes 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, she said.

“Knowing how many species follow this rule is important because it has been proposed that globally rising temperatures could cause lots of species to become smaller,” Riemer said. “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 applies to many species, Riemer and her team assessed the relationship between temperature and body mass for 952 bird and mammal species. To examine those 952 species, Riemer leveraged one of the largest body mass datasets currently available, drawn from dozens of museum collections containing over one hundred thousand digitized specimens.

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 15 percent of species were smaller in hotter environments, and about 7 percent of species were larger in hotter environments. This suggests that Bergmann’s Rule does not apply to most species as expected,” Riemer said.

While most species may not change in size due to the climate warming, other important changes in climate could cause shifts in the size of species, Reimer said. Future research will need to investigate these other factors to understand size and the many ways it affects animals, she said.

Study co-author Rob Guralnick, Florida Museum associate curator of biodiversity informatics, said the study “shows the power of natural history collections to enable new kinds of data-intensive science. Specimens don’t just sit on shelves — they inform, and in this case, they help shed light on how climate change could impact animal life.”

Click here to read the paper, “No general relationship between mass and temperature in endothermic species,” published in the journal eLife.


The mission of the University of Florida Institute of Food and Agricultural Sciences is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS works to bring science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents. Visit the UF/IFAS web site at ifas.ufl.edu and follow us on social media at @UF_IFAS.


Posted: January 10, 2018

Category: Agriculture, NATURAL RESOURCES, Pests & Disease, UF/IFAS, UF/IFAS Research, Wildlife
Tags: Animals, Climate Change, News, Size, Species, UF/IFAS

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