Thursday, October 14, 2010

Animal Urine: A Window into the Past

For years scientist have used droppings left behind from animals to determine past environments in the area which the droppings were found. However these droppings needed to be naturally preserved in order to study the organic matter found within. Such organic matter can be preserved in lakes and bogs (Carr et al, 2010). This poses a major problem in dry land areas such as the deserts in South Africa where it is very rare to find droppings that have been properly preserved and can provide accurate data (Carr et al, 2010). Discovering the organic contents of droppings can give scientists clues as to what types of environments were previously present in that area and in turn, what kind of climate change has occurred up until now. Fortunately a small animal called the rock hyrax has provided a way to analyze preserved droppings in the dry climates of South Africa.


The rock hyrax is looks quite similar to a large guinea pig but is actually related to the elephant. These animals, who live in the crevasses of large rocks high from ground level, tend to use the same area as communal toilets, sometimes from generations of hyrax over thousands of years (Carr et al, 2010). The hyrax’s urine seems to act as a preservative keeping the organic matter intact as the urine evaporates, precipitating salts which enclose the organic material. These large masses of preserved droppings are called middens. (Carr et al, 2010).

With funding from Leverhulme Trust, the South African National Research Foundation and the University of Cape Town Research Committee, Drs Chase, Carr and Boom have been able to lead an expedition in which they recovered multiple samples to take back to the lab in order to study. (Carr et al, 2010). All samples were drilled from the rock, freeze dried and homogenized in a ball-mill after which they could be analyzed. The preserved droppings provided insight to the changes in environment in the hyrax habitat up to tens of thousands of years in the past. (Carr et al, 2010).

(Image: University of Leicester)

As stated in the paper written by Carr et al, (2010) the scientist at the University of Leicester were able to identify certain organic compounds in the middens which could be traced back to the plants which the hyrax’s ate. Using this information, they were able to conclude what types of environments were needed in order to grow these plants and thus, the kinds of climate changes that have occurred in the South African region over the past 30, 000 years.

They were also able to conclude that the plants did in fact grow in the region where the middens were found because the hyrax does not generally go more than 500m away from its den to find food (Carr et al, 2010). Through carbon dating, the approximate ages of the droppings were also able to be deciphered in a timely fashion.

The middens from the hyrax have provided scientist with a window into the past of southern Africa which has been nearly impossible to open before now. This discovery has provided many new opportunities and questions about the dry climate of southern Africa and how it got to be the way it is today. Scientist now know that the regions climate has changed drastically since the last ice age and Carr et al, (2010) have stated that the next step is to explore why and how the climate changed as it did. The middens are also being compared with deep ocean core records, allowing scientist to think in much more detail about what drives the Africa climate (Carr et al, 2010). The middens have provided a route around the dry unforgiving climates in southern Africa and have allowed scientist to look into the past to observe the African climate change.

Carr A., Boom A. and Chase B. 2010. The potential of plant biomarker evidence derived from rock hyrax middens as an indicator of palaeoenvironmental change. Palaeogeography, Palaeoclimatology, Palaeoecology, 285 : 321-330.

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