A guinea-pig-like mammal's prehistoric urine may be one of the best tools for understanding climate change in arid regions, scientists announced Tuesday. Already, analysis of crystallized rock hyrax pee appears to contradict some results of current climate models.
Looking like a rodent but more closely related to elephants and manatees, the roughly rabbit-size rock hyrax has, for tens of thousands of years, lived in colonies of up to about 50 individuals in sub-Saharan Africa and the Middle East (regional map).
The animals use communal "toilets" called middens, where rock hyrax waste slowly crystallizes into a layered, amber-esque, smelly substance.
Like amber, the middens can contain valuable evidence—in this case, traces of how much grass the animals were eating and isotopes indicating how dry that grass was. (Related: "Spider's Blood Found in Amber May Hold Prehistoric Secrets.")
As a result, some middens are essentially unbroken, 28,000-year-old records of changes in regional vegetation, said study leader Brian Chase of the Institute of Science and Evolution at the University of Montpellier 2 in France.
The ancient waste is especially prized because evidence of ancient climate change is hard to come by in arid regions—including southern Africa, where the team's recent research took place.
Clues to prehistoric climate often come from sediment layers in lakes or peat bogs, noted team member Mike Meadows. But in dry regions, "we don't have many lakes, we don't have many boggy areas," added Meadows, a physical geographer at the University of Cape Town in South Africa.
Ancient Urine Suggests Old Climate Model All Wet?
The hyrax pee is important for understanding the climate of not just southern Africa but perhaps the world, the study team says.
For example, current climate models suggest that, as the Northern Hemisphere became drier about 5,500 years ago, the Southern Hemisphere got wetter. But traces in the hyrax-urine samples suggest that the southern part of Africa also dried out during this period, according to a paper by the team published in the July 2010 issue of Quaternary Research.
"If the model can't simulate the past. ... how much trust do we have in its ability to predict the future?" study leader Chase said.
To help answer that question, Chase, also an accomplished rock climber, has been collecting hyrax urine since 2006 and is in the middle of a five-year project to collect more—not an easy process. The urine-rich middens, which need to be chipped off with power tools, are in caves and under rock ledges.
And then there's the smell: "It's not too unpleasant, but it's not all that nice," the University of Cape Town's Meadows said. "It does smell like pee. ... You kind of get used to it."