At times during the past 10,000 years, cottontails and hares reproduced like rabbits and their numbers surged when the El Niño weather pattern drenched the Pacific Coast with rain, according to a University of Utah analysis of 3,463 bunny bones. The study of ancient rabbit populations at a Baja California site may help scientists better understand how mammals that range from the coast to the interior will respond to climate change, says anthropology doctoral student Isaac Hart. He is first author of the study to be published in the July issue of the journal Quaternary Research.
At times during the past 10,000 years, cottontails and hares reproduced like rabbits and their numbers surged when the El Niño weather pattern drenched the Pacific Coast with rain, according to a University of Utah analysis of 3,463 bunny bones.
The study of ancient rabbit populations at a Baja California site may help scientists better understand how mammals that range from the coast to the interior will respond to climate change, says anthropology doctoral student Isaac Hart. He is first author of the study to be published in the July issue of the journal Quaternary Research.
During the past 10,000 years, the number of El Niños per century “correlates very strongly with the total rabbit population in Baja California, as well as relative abundance of the moisture-loving species of rabbits,” Hart says.
“There weren’t many El Niños from 10,000 to 5,000 years ago,” perhaps zero to two per century, says the study’s senior author, anthropology professor Jack Broughton. “After 5,000 years ago, there was a relatively dramatic increase in frequency of El Niños in Baja, and the rabbits go through the roof.”
Broughton says the new study “is the first long-term – in thousands of years – record of vertebrates responding to El Niño or any other climate system” and the resulting rainfall-caused increase in plants the rabbits ate. “Our study contributes to the growing understanding of variables that enable threatened species to persist despite the myriad threats they face in an uncertain climatic future. The longer record we’ve provided here should ultimately allow us to better predict how El Niño will vary in the future, and how animal populations will vary as a result.”
Compared with earlier studies of lagomorphs – rabbits, hares and pikas – in Utah and elsewhere in the Great Basin during the last 10,000 years, the new study shows lagomorphs “are harmed less by temperature changes on the coast than in the interior,” Broughton says. “Threatened species will be more vulnerable as distance increases from both the temperature-ameliorating effect of the Pacific Ocean and the reach of El Niño-based precipitation.”
The study involved analysis of 3,463 cottontail rabbit and hare bones separated from more than 1 million small bird and animal bones deposited over the past 10,000 years at Abrigo de los Escorpiones – Shelter of the Scorpions – a rock cliff shelter near the ocean 95 miles south of Tijuana, Mexico.
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Rabbit image via Shutterstock.
