Ancient mammals shifted diets as climate changed

June 3rd, 2009 - 1:33 pm ICT by ANI  

Washington, June 3 (ANI): A new study has shown that mammals change their dietary niches based on climate-driven environmental changes, contradicting a common assumption that species maintain their niches despite global warming.

Led by Florida Museum of Natural History vertebrate paleontologist Larisa DeSantis, researchers examined fossil teeth from mammals at two sites representing different climates in Florida: a glacial period about 1.9 million years ago and a warmer, interglacial period about 1.3 million years ago.

The researchers found that interglacial warming resulted in dramatic changes to the diets of animal groups at both sites.

“When people are modeling future mammal distributions, they’re assuming that the niches of mammals today are going to be the same in the future,” DeSantis said. “That’s a huge assumption,” she added.

According to study co-author Robert Feranec, curator of vertebrate paleontology at the New York State Museum, “The study definitively shows that climate change has an effect on ecosystems and mammals, and that the responses are much more complex than we might think.”

The two sites in the study, both on Florida’s Gulf Coast, have been excavated quite extensively, according to DeSantis.

During glacial periods, lower sea levels nearly doubled Florida’s width, compared with interglacial periods.

But because of Florida’s low latitude, no ice sheets were present during the glacial period. Despite the lack of glaciers in Florida, the two sites show dramatic ecological changes occurred between the two periods.

Both sites include some of the same animal groups, allowing the scientists to clarify how mammals and their environments responded to interglacial warming.

The research examined carbon and oxygen isotopes within tooth enamel to understand the diets of medium to large mammals, including pronghorn, deer, llamas, peccaries, tapirs, horses, mastodons, mammoths and gomphotheres, a group of extinct elephant-like animals.

Differences in how plants photosynthesize give them distinct carbon isotope ratios. These differences are incorporated in mammalian tooth enamel, allowing scientists to determine the diets of fossil mammals.

Animals at the glacial site were predominantly browsing on trees and shrubs, while some of those same animals at the warmer interglacial site became mixed feeders that also grazed on grasses.

Increased consumption of grasses by mixed feeders and elephant-like mammals indicates Florida’s grasslands likely expanded during interglacial periods.

“This study emphasizes the importance of using the fossil record to look at how mammals and other animals responded to climate change in the past, also helping us gain a better understanding of how they might respond in the future,” said DeSantis. (ANI)

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