Tuesday, November 2, 2010

Clues to climate change



Ancient owl vomit and hyrax urine. Yep, that's what scientists Dr. Rebecca Terry of Stanford University (1st image) and Dr. Brian Chase of the Institut des Sciences de l'Evolution de Montpellier (2nd image) have taken great pains to collect.

A team at the University of Leicester
is studying ancient environmental patterns in southern Africa. Since there are few bogs and lakes from which to collect preserved organic material, scientists are searching the dry and dusty desert for the fossilized urine of the rock hyrax and other small mammals. Because the animals deposit their urine in the same place over many generations spanning thousands of years, these "middens" provide perfect test samples. But to collect the crystallized urine requires abseiling down a cliff and using an angle grinder to cut it from the rock. Once collected, it can be analyzed down to the molecule, indicating the food that passed through the hyraxes’ digestive system, and therefore what plants were growing at the time. The results show how the region’s climate has altered over the past 30,000 years. "Palaeoenvironmental records in this area were fragmentary. The middens are providing unique terrestrial records to compare against nearby deep ocean-core records, allowing us to think in much more detail about what drives African climate change," said team member Dr. Andrew Carr.

Piles of regurgitated owl pellets have been excavated from Homestead Cave in Utah’s Lakeside Mountains and are being used to reconstruct ancient Great Basin environments. Three years of meticulous excavation by scientists Dave Madsen, Don Grayson, and Jack Broughton recovered 20 layers of undisturbed bones 2 meters deep, representing the owls’ diet for the past 13,000 years. Grayson examined and identified 186,000 tiny bones from 22 species of small mammals, but more of the material, including lizard and bird bones, has yet to be analyzed. The radiocarbon-dated layers reveal changes in each species’ relative abundance. Dr. Terry has now charted how the numbers of pack rats, mice, voles, rabbits, and shrews fluctuated in close association with climate changes documented in core samples taken from a nearby lake. “It’s an amazing record. It’s still giving us so much information and the whole strata have not been studied yet,” said Dr. Terry, whose research will be illustrated in an exhibit at the Utah Museum of Natural History. Her findings will help biologists predict how rapid warming expected in the coming decades will affect Great Basin animal communities and develop appropriate conservation strategies.

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