Sunday, July 17, 2011

But... aren't you an archaeologist?

Why are an archaeologist and a paleontologist doing research in a modern game reserve?

We’re not digging up fossils and artifacts, but we’re looking for modern animal bones. Let me back up for a minute and explain… 

As paleontologists and archaeologists, our work often goes something like this: Dig up animal fossils. Identify what animals those fossils came from. Use “uniformitarianism” (the idea that the present is the key to the past, or that ancient animals generally had the same behaviors and habitat preferences as their modern descendants) to infer what habitats were present in the past – for instance, if we find an extinct zebra, we assume that means that somewhere near this prehistoric site was the kind of habitat that modern zebra like (open grasslands  - check out Nick's photo of a common/plains and grevy's zebra below... in open grasslands). Put the information from all the fossil animals together, and voila, we have a habitat reconstruction for our fossil site!

But hang on – we’re making a few assumptions.

One is that the overall modern bone “community” reflects the overall living animal community. In other words, we should find the same proportions (or relative abundances) of animal species when we count bones on the ground as we do when we count living animal species. For instance, if there are more living zebra than warthogs than baboons in an ecosystem, we should find the same relationship (zebra>warthogs>baboons) in the bone community. But is this the case? This is one big research question we’re trying to answer here.  Since collecting data on relative abundances of living animals takes a lot of time, we are grateful that the Earthwatch project is collecting that data year after year – and willing to share it with us. We also want to see if the living-bone community relationship holds up within different habitats (vegetation types) – and again, the Earthwatch project has created an excellent GIS-based vegetation map of the entire conservancy that they have shared with us.

Another research question we’re trying to answer is whether we can use bones to track changes in animal communities predation pressure on the conservancy. The conservancy used to be made up of two parts: a smaller game reserve, with wild animals, and a larger cattle ranch, which also had wild animals but not nearly as many. In 2007, the fence between the two was taken down and both areas were made into a single wildlife conservancy, where cattle and wildlife coexist.  We’d expect to find changes in the bones on the ground that reflect changes in the animal community, and we expect to find changes in how much damage predators are doing to bones of animals when they eat them. For instance, there were a lot of lions on the old game reserve, and now the lions have spread out so they are also living on the old ranch. So we’d expect to see less lion damage on bones on the old reserve now than we did Since I did much of my PhD research in the old game reserve, studying how carnivores damage bones when they eat their prey, it’s a great opportunity for me to apply those skills. And importantly, the conservancy management is very interested in long-term changes in predator pressure – something our research can hopefully shed light on.

So far, one other study has addressed these two research questions – a long-term study in Amboseli National Park in southern Kenya. The answers are “yes” to both. That’s a good sign! As a big part of science is replicability, we want to replicate this study in another ecosystem (with a few modifications) to see if we get the same results.

Our research methodology is fairly straightforward: we walk 1 kilometer transects within specific habitats, looking for bones. When we find bones, we try to identify what animal they are from, how fresh they are (how many years old they are, based on how weathered they are), and whether they have carnivore damage on them – and what carnivore may have done that damage. It’s actually a lot of fun, walking around the African bush, seeing animals, and looking for bones! We always have an armed guard with us – conservancy management policy, and just good sense – in case we encounter dangerous animals like lions, hyenas, elephant, buffalo, and rhino. We have had to abort transects because of encountering these animals, and occasionally because of rain.

That’s the basic gist of what we’re doing here!