Fossil Vomit, Well Aged
Effective, but maybe a little icky by human standards. When faced with an intruder, snow petrels — which breed only in Antarctica — spit up their stomach oil. The rich oil solidifies in Antarctica’s cold, dry climate, forming a waxy, yellow-brown deposit called “mumiyo.” Now, researchers have used mumiyo to reveal a 37,000-year old petrel colony. The find is helping fill in some gaps in the history of bird breeding on the coldest continent, and could help researchers understand past and future climate change.
An estimated 4 million snow petrels (Pagodroma nivea) live in Antarctica, and the birds flock to numerous breeding colonies late each year to lay eggs. The birds nest only on ice-free areas—and that’s made the colonies of growing interest to scientists studying climate and the advance and retreat of Antarctica’s glaciers. By radiocarbon dating mumiyo deposits, for instance, they can get a better idea of how long an area has been ice-free.
The new study – which appears in Polar Biology – began in 1991, when Goran Thor of the Swedish University of Agricultural Science in Uppsala visited Antarctica’s mountainous Dronning Maud Land. While surveying a petrel colony with particularly thick mumiyo at a spot called Heimfrontfjella, Thor used a hammer and chisel to chip some 6- to 11-centimeter-thick (2- to 4-inch-thick) samples off exposed rocks. The samples then sat, for decades, in cold storage at his university.
Eventually, however, Thor and his colleague, Matthew Low, sent the samples in for dating. It turned out the base layer on one sample was 37,400 years old (plus or minus 1,500 years). That means the snow petrel colonies were ice-free “during the last glacial period,” the authors write. And the dating “pushes back the estimated timing of establishment… by several thousand years” for that part of the continent. It also means you can’t judge a colony’s age by the thickness of its fossilized vomit: local climate conditions may alter how much builds up over time.
By dating more mumiyo, the authors say researchers can piece together “historical bird population distributions in continental Antarctica,” and aid efforts to understand how the continent’s glaciers have shifted. The aged throw-up might even help predict how the petrels will respond to future climate shifts. – David Malakoff | March 21, 2011
Source: Thor, G., & Low, M. (2010). The persistence of the snow petrel (Pagodroma nivea) in Dronning Maud Land (Antarctica) for over 37,000 years. Polar Biology, 34 (4), 609-613 DOI: 10.1007/s00300-010-0912-y
Image courtesy Matt Low