The Academy's Department of Ornithology and Mammalogy recently traveled to the Namibian desert in Africa. It conducted five weeks of field research in one of the world's oldest and largest deserts.
The Namibian desert is 100,000 square miles of vast, open, arid plain. From here you can see the curve of the earth as the landscape spreads out unbroken before you. It is a land of superlatives: one of the largest deserts in Africa, among the oldest deserts in the world, contains the tallest sand dune in the world, and is the most arid and barren. We left San Francisco on May 29, 2007 and returned home on July 5, 2007.
Within this immensity lives a surprising number of animal species. It is home to giraffe and gerbil, bat-eared fox and oryx, and very few people. For our purposes, the Namibia desert offers scientists the chance to study one of the smaller and lesser-known species, the elephant shrew. It is also known as the round-eared sengi or by its scientific designation, Macroscelides proboscideus.
The elephant shrew can teach us a great deal about evolutionary forces. This tiny animal, resembling a gerbil, has lived relatively undisturbed by man for millions of years in a vast remote desert where it feeds entirely on ants. The expedition to Namibia offers a rare opportunity to study a species that has lived in isolation for millions of years. Specifically, the Academy scientists are trying to determine whether the reddish elephant shrew found on the desert plains and the darker elephant shrew found in the mountains are different species.
Long thought to be related to the hedgehog, new research based on DNA evidence and molecular studies reveals that the elephant shrew is more closely related to the elephant than the shrew. (Although in absolute terms, it is not genetically similar to either.) Instead the elephant shrew (or sengi) is now recognized as an ancient, solitary offshoot of the African mammal evolutionary tree, Afrotheria.
Understanding the genetics of small animals like the elephant shrew can be used as a proxy to understanding evolution in Africa. Are genes passing from one population to another? Are the species interbreeding? Or are they two genetically different species?
These are just some of the questions Dr. Galen Rathbun and Dr. Jack Dumbacher hoped to answer on the California Academy of Sciences expedition to Namibia. Together the pair of scientists left San Francisco on May 29, 2007. For the next five weeks, they traveled the Namibian desert searching for sengis, setting traps in the desert, capturing the creatures, taking DNA samples, and preserving specimens for the Academy collection.
Dumbacher and Rathbun focused on the taxonomy and systematics of Namibian elephant shrews, or sengis. By collecting DNA samples and museum specimens of Macroscelides, the two scientists will use genetics to assess how distinct each form is from the other and look for the genetic signature of genetic mixing of the two forms.
Back in the lab, Dumbacher is using the results to look for gene flow between populations, trying to better understand what the species boundaries are.