They are distributed throughout the Horn of Africa which encompasses Ethiopia, Eritrea, Somalia and Kenya (Jarvis 1981). Naked mole-rats have a complex social structure and in fact are the only known mammalian example of eusociality.

There have been a few recorded sightings of naked mole-rats dispersing above ground since the 1970’s. In 1996 a disperser morph (O’Riain) with corresponding higher levels of testosterone, progesterone and LH were found in lab colonies. My focus is on the hormone level distributions in wild colonies of naked mole-rats in Meru National Park in Kenya. The population I work with has been the subject of a mark recapture study conducted by Dr. S. H. Braude for the last 14 years. Therefore demographic data are available in abundance.

Evidence for above ground dispersal can also be found using pitfall traps that we just recently installed in our study site. During our two months field season in the Park this year we caught six above ground dispersers in those traps that cover less than 50m of fencing. In addition we found various nascent colonies throughout the study site that consist of animals whose origin is in colonies more than 2km away.

Another hypothesis concerning the evolution of eusociality is the aridity food distribution hypothesis (Jarvis, 1991). This model assumes that food in arid regions is distributed very patchily and the cost of randomly digging in the hard soil in order to find those few spots is much too high for one animal alone. Using a t-maze experiment we tested if naked mole-rats in fact are digging randomly. The animals were given a choice to either dig into soil that was sterile or soil that had grown sweet potatoes and carrots in it. In over 80% of the cases they preferred burrowing in the tuber growing soil. (Details and data will be in Heth et al, in review). This shows that naked mole-rats can orient their digging towards food before actually encountering it.

Besides dispersal I’m also interested in the effect that vegetation and soil type may have on the size of naked mole-rat colonies as well as the size of their respective members and the ultimate production of dispersers by different colonies. By catching and measuring complete colonies on different geographical scales and then overlaying GIS data of vegetation, aridity and soil structure I’m hopefully going to be able to find which ecological parameters best explain differential success of colonies of naked mole-rats.

In order to win further insight in the physiological structure of wild colonies of naked mole-rats I want to gather data on the cortisol levels. Cortisol can be used as a measure of stress an individual is exposed to (method by Moestl et. al., not published yet). Stress induced by the bellicose behavior of the queen seems to be the main reason for the workers inability to breed.

Finally I would like to address a question in the field of sensory physiology: Burda et. al. have worked on magnetic compass orientation in subterranean mole-rats. So far no such work has been done on Heterocephalus. It would be quite interesting to see if they share a magnetic sense with their fellow mole-rats using an experimental set as suggested by Burda (personal communication). A circular, completely dark arena with at least four exits positioned in the four compass directions. This set could be used north as well as south of the equator in Kenya which would give additional significance to the obtained data.