Improving the Adaptability of Animals by Selection - Genetics and the Behavior of Domestic Animals - page 301

(b)

(a)

150

100

75

100

50

50

25

0

0

(c)

STI

200

EH
NEH
ENH
NENH

150

100

LT I

50

EH
NEH
ENH
NENH

0

FIGURE 8.13 Variation in measures of fear in response to handling and environmental enrich-
ment in lines of Japanese quail selected for long or short duration of tonic immobility over nine
generations (EH: enriched, handled; NEH: non-enriched, handled; ENH: enriched, non-handled;
NENH: non-enriched, non-handled). (a) Latency to peep, (b) number of peeps, (c) tonic
immobility.

Handling and environmental enrichment are known to reduce fear levels
in chickens ( Candland et al., 1963; Jones, 1982; Jones and Faure, 1981 ).
When these treatments were applied to chicks of the long TI and short TI
lines of quail ( Jones et al., 1991 ) they were effective in reducing fear levels
in both the lines ( Figure 8.13 ). However, there was a tendency for handling
and environmental enrichment to be more effective in the short TI lines than
in the long TI line. This effect might be explained by a reduction in informa-
tion input in the long TI quail during handling or enrichment, attributable to
greater fear-induced behavioral inhibition and fear.
The long TI and the short TI lines also had very different reactions to
capture by a person. Two hundred and fifty quail of the long TI and short TI
lines were reared together in a floor pen and were caught at three successive
ages (2, 4, and 6 weeks of age). Birds were captured at random, and the short
TI (low fear) animals were easier to catch, and were captured first at all the
ages tested ( Figure 8.14 ).
Ratner (1967) proposed that the fear (antipredator) reaction is dependent
on predator proximity. At long distances, the first reaction is freezing which