Environmental influence on development, behavior, and endocrine morphology of gerbils

Gerbils reared under standard laboratory conditions grow and develop more rapidly, achieve sexual maturity when younger, and are less reactive to stimulation than gerbils reared in environments providing access to a tunnel-like shelter. Gerbils reared in open cages have lighter adrenal glands, heavier pituitary glands, and heavier reproductive organs than gerbils raised with access to shelter. Comparison of gerbils reared in cages providing access either to opaque or transparent shelter with animals maintained in open cages either on a 12-hr light-dark cycle or in constant darkness revealed that different aspects of environments providing shelter affected different characteristics. Opportunity to move from an open area to a sheltered one increased behavioral reactivity. Reduced exposure to illumination affected developmental rates, reproductive organ and pituitary gland weights. Both reduced exposure to illumination and access to a shelter affected adrenal gland and body weights. These data suggest that expression of the phenotype typical of domesticated gerbils requires deprivation of a variety of stimuli normally experienced by burrow-dwellers during ontogeny.