Developmental changes in tonic immobility in young chicks (Gallus gallus)

Abstract

Tonic immobility (TI) was induced by means of ventral restraint in White Leghorn chicks within 12-hr posthatch (Day 0) and, in independent groups, on succeeding days through Day 10. Durations of immobility and eye closure increased and incidence of immobility termination and vocalization decreased significantly with age. Marked qualitative changes in immobility reactions were also apparent over the finst few posthatch days.

Development of the immobility response (animal hypnosis) in two species of deermice (Peromyscus)

“…The continuing increase in incidence in bairdi is much like the pattern observed in chickens (Ratner & Thompson, 1960) and bobwhite quail (Borchelt & Ratner, 1973). Later authors found that chickens would exhibit the response very early and had no increase in incidence, but other parameters of the response did show a pattern of developmental change (Rovee & Kleinman, 1974). In birds, Ratner and Thompson (1960) hypothesized that increasing incidence of immobility is correlated with development of physical independence.…”

“…In the latter studies, response incidence was complete or high from the beginning but other response parameters changed with age. Response duration and eye closure increased while vocalizations decreased (Rovee & Kleinman, 1974). Bobwhite quail under lateral restraint also exhibit an increase in incidence and duration of immobility with age, but the first strong occurrence is between 9 and 15 days of age (Borchelt & Ratner, 1973).…”

“…On the basis of earlier literature, the increasing incidence of the response with age was hypothesized by Ratner and Thompson (1960) to be correlated with developmental change associated with becoming independent of the parents. This explanation in chicks appears negated by the presence of the response in l Z-h-old chicks (Rovee & Kleinman, 1974). Salzen (1963) attributed the increase to an increase in fear responses along with maturation of the neural mechanisms releasing the response.…”

“…Salzen (1963) corroborated the dramatic increase in immobility-response incidence in chickens during the second week through use of dorsal restraint. However, immobility responses have been elicited in chickens as early as 12h posthatch (Rovee & Kleinman, 1974) by the use of ventral restraint at one day of age (Braud & Ginsburg, 1973b) through use of dorsal restraint in a cloth "trough." In the latter studies, response incidence was complete or high from the beginning but other response parameters changed with age.…”

Selective habituation of defensive behavior: Evidence for predator-prey synchrony

“…Because growing chicks exhibit progressively lengthier durations over this period (Rovee & Kleinman, 1974), either no change or a decrease in response durations could be taken as evidence of habituation. The question of selective habituation was addressed by testing chicks either during the day or at night, at times when the difference in the duration of response was greatest and the variability in duration was least (Rovee et al, 1976).…”