EPOW - Ecology Picture of the Week

Explanation:   Seldom seen above ground, this is a Silky Molerat quickly trying to make its way across a dirt road in northern Malawi, Africa.  Also called Blesmols, Molerats are the evolutionary equivalents of moles.  Like moles, they have reduced eyes and ears, and are superbly adapted to burrowing with powerful front claws.  However, moles belong to a different taxonomic order (Insectivora) than molerats (Rodentia).  

Some 11 species of molerats occur in Africa, including the bizarre Sand-puppy or Naked Molerat.  The Silky Molerat (also called Silvery Molerat), pictured here, is found in south-central and eastern Africa within the range of Miombo (Brachystegia) woodlands at lower altitudes in drier climates than other molerats. It prefers well-drained, sandy soils on rocky hillsides, open plains, and woodlands with friable soils in which to tunnel.  

A recent study by Sumera and others (2002) found that Silky Molerats have a long pregnancy cycle and slow postnatal development.  These are characteristics thought to belong to social or colonial species, but the Silky Molerat seems to live a mostly solitary life underground.  These findings suggest that we need to reevaluate our interpretation of how reproductive biology shapes social (or solitary) life.  

Taxonomy of this species is still being explored, and there may be subspecies or species yet to be described (Scharff and others 2001).  Bathyergid molerats have an ancient origin, and Silky Molerats may have diverged evolutionarily long ago from its cousin species because of physical barriers created by the formation of the Kenya and Western Rift in eastern Africa along with associated changes in climate and vegetation (Faulkes and others 2004).  

Below ground, Silky Molerats navigate without reference to the sun or other visible landmarks.  How do they do this?  Recent studies by Kimchi and others (2004) suggest that they use internal signals and, amazingly, they orient their headings in relation to Earth's geomagnetic field, as do some other animals.   They need such special cues because other studies (Sumbera and others 2003) have found that they change their burrow architecture each season, possibly as an anti-predator adaptation.

Silky Molerats are not endangered.  They feed on tubers and roots ... and sometimes local people feed on them.  This individual was quickly spotted by a local boy who clubbed it to death with a stick and brought it home for the stew pot.  Lest we judge others' eating habits, we might first want to live in a land of economic strife, with the highest population density in all of Africa, and with severe food shortages.  

Information:  
     Faulkes, C. G., E. Verheyen, W. Verheyen, J. U. Jarvis, and N. C. Bennett.  2004.  Phylogeographical patterns of genetic divergence and speciation in African mole-rats (Family: Bathyergidae).  Molecular Ecology 13(3):613-629.
     Kimchi, T., A. S. Etienne, and J. Terkel.  2004.  A subterranean mammal uses the magnetic compass for path integration.  Proceedings of the National Academy of Science 101(4):1105-1109.
     Scharff, A., Macholan, M., Zima, J., Burda, H. (2001): A new karyotype of Heliophobius argenteocinereus (Bathyergidae, Rodentia) from Zambia with field notes on the species. Mammalian Biology 66(6):376-378.
     Sumbera, R., H. Burda, and W. N. Chitaukali.  2002.  Reproductive biology of a solitary subterranean Bathyergid rodent, the silvery mole-rat (Heliophobius argenteocinereus).  Journal of Mammalogy 84(1):278-287.
     Sumbera, R., H. Burda, W. N. Chitaukali, and J. Kubova.  2003.  Silvery mole-rats (Heliophobius argenteocinereus, Bathyergidae) change their burrow architecture seasonally.  Naturwissenschaften 90(8):370-373.