Mima mounds in the Kenya highlands: significance for the Dalquest-Scheffer hypothesis

The Dalquest-Scheffer Hypothesis that Mima mounds in western North America are the long-term product of burrowing activities of geomyid pocket gophers was tested by examination of areas of similar topography in the highlands of Kenya. Two mound areas, located near Nyahururu at an elevation of about 2,400 m, were studied in detail. The mounds ranged from less than 25 cm to 2 m in height and from a few m to about 20 m in diameter, and were not the remains of large termite nests. Populations of the rhizomyid mole rat, Tachyoryctes splendens, a fossorial rodent similar in morphology and social behavior to geomyid pocket gophers, were associated with these mounds. Mound density and dispersion pattern were similar to North American Mima mounds, and the distribution of fresh soil heaps indicated that the activities of these animals were mound-centered. A shallow laterite hardpan underlay these mound areas, fulfilling another requirement of the Dalquest-Scheffer hypothesis. It is concluded that Mima mounds are the product of the burrowing of fossorial rodents such as pocket gophers and mole rats, and that these two groups are convergent in morphology, burrowing behavior, and impact on the landscape.