The Chrysochloridae: studies toward a broader perspective of adaptation in subterranean mammals

Earliest chrysochlorids (from the Miocene) resemble contemporary members of the family. Unlike talpids, chrysochlorids have eyes covered with skin; pick-like foreclaws; a blunt, padded rostrum; and no external tail. Golden moles are an ancient lineage of mammals (related to tenrecs) with many unique features; it has been suggested that the Chrysochloridae constitute a separate order, the Chrysochloridea. In contrast, a constancy of structure within the group belies the wide range in habitat of the various species (including grassland, forest, and shifting desert sands), in contrast to the aquatic desmans and shrew-like talpids. Some species of golden mole are able to disperse over large distances, being accomplished swimmers (as are talpids) and having a wide range of diet; nonetheless, populations and species are patchily distributed throughout the range of the family (Africa south of the Sahara whereas talpids occur in the northern hemisphere). Diversity of chrysochlorid species is greatest in Southern Africa, from which emigrations to the north probably occurred. Although solitary, there is little evidence for competitive exclusion between the chrysochlorids, rhizomyids, or the more social and aggressive bathyergid rodent moles to explain the high incidence of endemism. Low litter sizes are indicative of the few predators known to effectively prey on golden moles. Physical factors which might restrict species from an area (such as food shortages and temperature extremes) may be overcome by becoming torpid, an ability unknown for other subterranean mammals. Clustering of largely immobile food resources and friable soils appear to be the major factors influencing chrysochlorid distribution. There is substantial need for basic studies on all aspects of the biology of chrysochlorids for a better understanding of evolutionary processes within the family, which will in turn contribute to a broader understanding and more balanced view of evolutionary processes in all subterranean mammals.