Isolation-induced aggression in newly hatched ducklings.

Abstract

Newly hatched Khaki Campbell ducklings (Anas platyrhynchos domesticus) were initially housed in pairs and subsequently transferred to isolated housing conditions. Subjects living with another bird displayed filial behavior and little aggression upon encountering another duckling in a test arena. In contrast, ducklings housed in isolation exhibited aggressive pecking in addition to filial behavior when another duckling was subsequently encountered. In Experiment 2, ducklings were housed with an imprinting object (i.e., an object that elicits attachment behavior), but they were otherwise isolated from other birds. These subjects displayed little aggression when they were subsequently reunited with a conspecific, indicating that the aggression-precluding effects of social housing are not limited to the particular social stimulus with which the ducklings are housed. In Experiment 3, ducklings were again housed with an imprinting object, but this time the object was behind glass, thereby precluding tactile contact with it. Since these birds also exhibited little aggression when reunited with a conspecific, it is apparent that visual stimulation from an imprinting object is sufficient in itself to preclude subsequent aggression. These findings suggest that stimulation that elicits attachment behavior is the critical factor mediating isolation-induced aggression.Numerous species show increased aggressive tendencies toward conspecifics following a period of social isolation. The effect has been observed with chicks (Beach &

Stimulus factors in the isolation-induced aggression of Bobwhite quail and Khaki Campbell ducklings

“…To investigate this issue we housed one group of paired subjects in a completely darkened room, thereby permitting tactile stimulation from conspecifics but not visual stimulation. housed in a single unit (128 X 36 X 65 cm) for a period of four days, under normal daylight illumination (previous work has indicated that with ducklings, aggression induced by prior isolation is reduced to a low level after four days of living with a conspecific; Hoffman et al, 1975). On the fifth day, the quail were randomly divided into three groups.…”

“…Rather than the lack of opportunity to dissipate an aggressive drive through social signals, the critical factor in isolation-induced aggression might instead be the lack of stimulation that would otherwise elicit attachment behavior (Hoffman et al, 1975). Visual stimulation is well known to have powerful effects in the attachment behavior of young precocial birds (Hoffman and Ratner, 1973), and recent evidence is beginning to suggest tactile stimulation as an important factor as well (Clements and Lien, 1975).…”

“…More specifically, such aggression has been found to occur in chicks (Beach and Jaynes, 1954), quail (Kuo, 1960), and ducklings (Hoffman, Boskoff, Eiserer, and Klein, 1975). In the work with ducklings, it was found that subjects otherwise isolated did not become very aggressive towards conspecifics if an imprinting object was present in their housing unit, even when a glass barrier prevented physical contact with that object.…”

“…In the study by Hoffman et al (1975), the imprinting object was a rather artificial sort of stimulus, a white rectangular object that in no way physically resembled a conspecific. It seemed desirable to replicate the basic aggression-reducing effect under conditions in w h c h the visual stimulation derived from a more natural social stimulus.…”

“…In order to equate the amount of space available to the partial and total isolates in their housing units, a Plexiglas divider was also placed in the units of the total isolates, thereby restricting the quail to one-half the area of the unit. The two remaining birds, from whom little aggression was anticipated (Hoffman et al, 1975), were housed together without a barrier; these nonisolated birds were used as "targets" for both of the above experimental groups during the testing sessions.…”