The following may be of interest - it
was on the Science Daily website last Sunday, 28
October.
Bruce
Scientists have shown that birds with higher
stress levels adopt bolder behaviour than their normally more relaxed peers in
stressful situations. A University of Exeter research team studied zebra
finches, which had been selectively bred to produce three distinct types --
'laid-back', 'normal' and 'stressed' -- based on their levels of stress hormone.
The group was surprised to find that the 'stressed' birds were bolder and took
more risks in a new environment than the group that was usually more laid-back.
Like other animals including humans, birds respond to
stress, created by the appearance of a predator or a change in their environment
for example, by producing a hormone. In birds, this hormone is called
'corticosterone' and some individuals have higher levels of the hormone than
others.
The zebra finches in this experiment were bred to
have three different corticosterone levels, with the 'laid-back' birds having
lower levels than the 'stressed' birds. The researchers put the birds into a new
environment, which housed several unfamiliar objects, including new feeders. The
'stressed' birds were the first to visit the new feeders, which they also
returned to more quickly than the other birds after being startled. Overall,
they approached more objects than their normally more relaxed peers, showing
greater risk-taking behaviour and arguably handling the situation better.
Dr Thais Martins of the University of Exeter said:
"It initially seems counter-intuitive that birds with higher levels of the
stress hormone showed bolder behaviour, normally associated with confidence.
However, corticosterone is released to help tackle stress by encouraging the
animal to adopt key survival behaviours like seeking food. So on reflection,
perhaps it is not surprising that these birds are more likely to explore the
environment and look for food."
Previous research has indicated that animals show
consistent individual differences in their behaviour when faced with certain
challenges. Traditionally in this field of research, birds have been separated
into two groups: 'bold' and 'shy', or 'active' and 'passive'. These definitions
are based on observations of their behavioural strategies, and the birds are
then studied for physiological differences.
This research took the opposite approach and
separated the birds into groups by physiology, based on corticosterone
production levels, and then looked for behavioural differences.
These findings are published October 26 in the
journal Hormones and Behaviour.
Adapted from materials provided by University of Exeter.
