Abstract
The use of space by laying hens in free-range systems is often very uneven, with
birds displaying an apparent reluctance to leave (and move away from) the house.
Using mainly small groups as models for the larger flocks normally housed in
commercial free-range systems, the role of various social and environmental factors
concerning hens' movement and use of space were investigated in this thesis.
Hens displayed a greater readiness to emerge from a familiar covered box into
an unfamiliar outdoor area when the outdoor area contained familiar feeders, even
though the birds had free access to food in their home pens. Emergence latencies
decreased with repeated testing. Birds also spent more time in the outdoor area when
feeders were present, though they tended not to move past the feeder which was
nearest the box. Birds which had been exposed to an enriching stimulus (traffic cones)
in their home pens tended to leave the box earlier than those which had not, though
this was not dependent on the actual presence of cones in the outdoor area. This
suggests that a more complex home environment can influence birds' responses to
novel environments. Furthermore, the order of emergence into the paddock was not
significantly influenced by social rank. Birds which had been regularly exposed to the
outside environment during the rearing process displayed little or no fear of the
outdoor area as adults. In contrast, regular handling had little effect on birds' readiness
to enter the outdoor area. Regular exposure to the outside environment also reduced
birds' underlying fearfulness (measured by tonic immobility), both in small
experimental groups and in a larger free-range flock. Individual birds from small
groups or from single cages took longer to move past unfamiliar birds than they did to
move past familiar birds (even those of higher rank), and took longer to move past an
increasing number of unfamiliar birds. However, birds in a free-range house
displayed a wide range of movements, and very little aggression, suggesting that any
inhibition of movement within the house was not due to "pecking pressure" from other
birds. Birds displayed greater readiness to enter into and disperse in the outdoor area
when other birds were already present in the area. This was not dependent on the
familiarity of birds in the outdoor area. A larger number of birds in the outdoor area
increased the attractiveness of the outdoor area to other birds. The introduction of
cover into an outside area had a limited effect on increasing the attractiveness of the
outdoor area to domestic fowl, though this was not reflected in the birds' vigilance
behaviour. It was concluded that birds find the outside environment aversive due to its
fear-evoking properties (such as the fear of predation), and to the large discrepancy
between the inside and outside environments. Possible implications of the present
findings for free-range systems are discussed.