Effects of rearing environment on adrenal weights, sexual development, and behavior in gerbils: an examination of Richter's domestication hypothesis.

Mongolian gerbils (Meriones unguiculatus) reared and maintained in standard laboratory cages exhibited accelerated eye opening, more rapid growth, earlier sexual maturity, and marked reduction in adrenal gland size in comparison with gerbils reared in more natural cages providing access to shelter. Gerbils reared in standard laboratory cages were also easier to handle and less responsive to sudden stimulation than those reared in sheltered cages. Changes in phenotype resulting from rearing in environments lacking shelter parallel changes in phenotype resulting from the domestication process. The implications of the data for genetically oriented hypotheses of domestication are discussed.