Lj. Keeling, INTER-BIRD DISTANCES AND BEHAVIORAL PRIORITIES IN LAYING HENS - THE EFFECT OF SPATIAL RESTRICTION, Applied animal behaviour science, 39(2), 1994, pp. 131-140
The aim of this experiment was to study the effects of spatial restric
tion on the frequency with which different behaviour patterns were per
formed. Hens (Gallus domesticus) were kept in groups of three in four
different sized litter pens giving space allowances of 5630, 3000, 120
0 or 600 cm2 per bird. Using overhead time-lapse photography, the mean
distance between the birds in the group when all birds were performin
g the same activity and the mean frequency of that activity in the tim
e budget, were determined. In the largest pen, the birds were furthest
apart when they were walking (310 +/- 64 mm), closer together when th
ey were standing (234 +/- 75 mm) or ground pecking (237 +/- 13 mm) and
closest together when they were preening ( 154 +/- 98 mm). As pen siz
e decreased, the frequency of walking and ground pecking decreased sig
nificantly, the frequency of preening remained unchanged and the frequ
ency of standing increased. A comparison of time-budget changes with t
he average distances between birds while performing these different ac
tivities indicated that the behaviour patterns which were performed at
the largest inter-bird distances decreased in frequency as pen size g
ot smaller. This suggested that the distance between birds when they w
ere walking or ground pecking was sufficiently important so that when
the available space decreased, the birds performed these activities le
ss often rather than performing them at inappropriate inter-bird dista
nces. Preening was performed when birds were close to each other and t
he frequency of this behaviour was unaffected by the space restriction
s used in the experiment. As the frequency of some behaviour patterns
decreases, there must be a corresponding increase in the frequency of
others. Standing appeared to be one such 'time-filler' behaviour patte
rn. The results also suggest that the technique of reducing the space
available to birds may be useful in experimentally assessing the resil
ience of particular behaviour patterns and thus the importance birds a
ttribute to performing them.