International Journal of Comparative Psychology

The

present study examined the effects of two treatments on the approach / avoidance responses of pair-housed female domestic chicks of a Ross broiler and two laying strains (one docile ISA Brown medium hybrid, one flighty White Leghorn light hybrid) to a visible experimenter. Chicks in the visual contact (VC)group were  allowed to see the experimenter for 30 s twice a day from 1 day of age until testing at 10 or 11 days whereas controls (CON) received minimal human exposure throughout the study. Apart from the visible presence of the experimenter, treatment procedures were similar for the two groups. All chicks were tested individually but pair means were used as data points. Chicks of all three strains which had received the VC treatment showed considerably lower avoidance of humans than did their CON counterparts. The present results demonstrate that fear of humans was markedlyreduced by a simple regime of close visual contact with the experimenter presumably through habituation, and that this effect was common to chicks of flighty as well as docile strains. These findings are discussed in terms of their imphcations for resource management in the laboratory and on the farm.

 

Our

aim was to determine whether the characteristics of an olfactorycue influenced the experience-dependent approach behavior observed in domestic chicks and to look at the effects of these odors on behavior in the home-cage. Chicks were reared individually with tubes containing an odor suspended in the home-cage. At day 4 post-hatching they were tested in a runway with visually identical test stimuli suspended at either end; one of these contained the familiar odor and the other was unscented. Chicks reared with the odor of nesting-litter approached the familiar stimulus in preference to the unscented stimulus. Chicks reared with a garlic odor did not demonstrate a preference for either stimulus. A specific preference for the odor f nesting-litter was demonstrated by altering the visual, but not olfactory, cues of the stimuli. Thus, exposure to nesting-litter establishes a preference for this odor, but exposure to garlic odor has no such effect. The same chicks were given a  choice test between nesting-litter and garlic on day 9 post-hatching. Only those chicks reared with garlic-scented stimuli demonstrated a preference; they approached the nesting-litter-scented stimulus. The response of chicks to the presentation of olfactory stimuli within the familiar rearing environment was also assessed. When odors were presented, chicks reared with an unscented stimulus demonstrated a decrease in pecking frequency and increased attention to the testing stimulus, indicated by pecks directed at the testing stimulus and circling activity. Thus, young chicks can detect odors (nesting-litter and garlic odor) and form an association with certain odors (nesting-litter and not garlic odor). The odor of nesting-litter may serve to keep the chick in the proximity of the nest during early post-hatching life. 

 

by

Lesley J. Rogers. CAB International, Wallingford, U.K., 1995, 288 pp.£45 (US$77.50)*.