model of stress in animals

McBride (1980) proposed a model that suggested
how animals adapt to stress at an individual level. There
are three levels where adaptation of the animals to
stress could occur:
1. Behavioural level
If an animal can avoid an unpleasant stimulus it has
removed itself from the stress. In many intensive situations this may be difficult for all animals in a group to do
and possibly the dominant animals will be the only ones
able to adapt.
2. Psychological level
Those unsuccessful animals must try to adapt by the
psychological process of habituation. If they do not
habituate to the aversive conditions they may enter a
state of learned helplessness or apathy in which they
remain distressed but no longer attempt to make appropriate responses to improve their plight.
3. Physiological level
In the animals that still have not adapted, continued
arousal generates the General Adaptation Syndrome
(GAS) of Selye (1976). There is a general pattern of
alarm (alarm reaction) leading to homeostatic resistance to change (stage of resistance) and the stage of
exhaustion follows if the stressor is severe enough and
is applied for a sufficient length of time. It is at this stage
that strain develops and may be characterised by a susceptibility to a variety of infectious or other environmental stressors. In other words, the a