DEVELOPMENTAL AND EXPERIENTIAL INFLUENCES ON ONTOGENY - THE GERBIL (MERIONES-UNGUICULATUS) AS A MODEL

A quantitative methodology is presented for comparison of behavioral and biological ontogeny for use either within one species or comparatively. Two studies were conducted: A longitudinal study in which ontogenetic behavioral and biological measures were recorded from 62 male and female gerbils at nine ages from birth to 5 months of age, and a cross-sectional study in which the same measures, and weights of body organs, were recorded from 5 male and 5 female gerbils of each of the same nine ages. Developmental change was inferred from quantitative data incorporated with qualitative descriptions of developing behaviors. Because ages of change differed from different behaviors, simple stages of development are insufficient to characterize ontogeny. Comparison of the two studies provided information on the effect of experiential factors in behavioral ontogeny. After 2 months of age, gerbils without prior testing had more locomotor activity, more rearing on the hindlegs, less marking with the ventral gland, and were slower to descend than gerbils given repeated tests - all effects that may be related to higher levels of stress. In addition, parallels between behavioral and physical development, sex differences, and stability of intraindividual behavior over time are discussed.