Mother-offspring interaction and pup development in genetically deaf mice.

Abstract

The role of ultrasonic calls emitted by pups on maternal behavior has been investigated by using genetically deaf (dn/dn) and normal-hearing (+/+) mice of the GFF strain. The behavior and the sensory-motor development of unfostered and cross-fostered pups, as well as the behavior of the mothers, was analyzed. Deaf pups emitted fewer ultrasonic calls than pups with normal hearing. The cross-fostering procedure decreased the amount of vocalizations produced by normal pups, thus stressing the reinforcement effect of maternal behavior on pups' ultrasonic communication. No difference in maternal behavior emerged between deaf and normal-hearing mothers toward their pups. However, cross-fostered pups received less maternal care than pups raised by their natural mothers, this effect being more evident in deaf pups reared by mothers with normal hearing, than vice versa. Deafness, in both mothers and pups, seemed to be associated with increased locomotor activity, possibly to offset their auditory handicap in mother-offspring relationships. Furthermore, deaf pups showed a faster gain in weight than normal pups, this capability being affected by the genotype of the rearing parent. On the whole, these data could suggest that maternal behavior in deaf mice has became independent of ultrasonic stimuli emitted by the pups. Other biobehavioral characteristics of deaf mice indicate a more active role played by these pups in mother-offspring interaction in comparison with pups with normal hearing.