body temperature and breath rate in response to handling stress

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index of the emotional and stress response [8], but are
difficult to obtain in a small songbird. Recently, breath rate
has been counted in great tits about 18 h following social
defeat (Parus major), but no effect was detected, probably
because an increased activity of the adrenergic system
occurs only in the very short term following exposure to a
stressful stimulus [12].
Individuals differ nonrandomly in the way they deal with
stressors and novelties and appear to vary along a
behavioural continuum from shy to bold [15–17]. These
differences covary with other behavioural traits, such as
aggression, exploration, risk taking, fearfulness and reactivity:
for example, bold and less fearful individuals are
more aggressive than shy and fearful individuals [18–24].
Several lines of evidence, including selection lines experiments,
suggest that these differences are aspects of a
coherent and heritable behavioural organization maintained
by natural selection [21–25]. Such individual behavioural
organizations are referred to as behavioural syndromes,
predispositions, profiles, coping styles, strategies, and axes
[26,27], comparable to human personalities [28]. In rodents,
proactive personalities (bold, bactiveQ and aggressive
animals) are associated with high neurosympathetic activity
and low HPA reactivity, whereas reactive personalities (shy,
bpassiveQ and less aggressive animals) are associated with
high cardiac parasympathetic activity and high HPA
reactivity [21,22,29,30].
In the great tit (P. major), a small passerine bird, many
individuals show extreme phenotypes within a given
population, being bfastQ (or bold) or bslowQ (or shy) in
exploration tasks, including novelty responses [15]. Recent
studies demonstrate the presence of considerable amount of
both additive genetic variation and dominance genetic
variation of such personality traits in wild great tit
populations [31] and selection lines experiments have
shown high heritability for early exploratory behaviour
based on four generations of artificial selection [23]. These
trait characteristics are relatively stable across age [23].
They correlate both phenotypically and genetically with
differences in aggression [19,24,32], foraging behaviour
[15,33], response to social stress and risk-taking behaviour
[12,34–36]. Therefore, they may indeed reflect personalities
[27,36]. The lines show resemblance to selection lines
established from wild house mice populations [18,24,27].
This resemblance includes also physiological parameters
involved in the stress response: the great tit data on breath
rate indicate a trend for higher levels in the line of slow
individuals [12], while data on the adrenocortical response
indicate higher HPA reactivity in the same line [35]. The
great tit lines also resemble two lines of leghorns originally
selected for productivity traits, the so-called high feather
pecking frequency (HP) and low feather pecking frequency
(LP) lines [27]. Hens of the LP line, that resemble shy great
tits, had higher basal and stress-induced (manual restraint)
plasma corticosterone levels than hens of the HP line, that
resemble the bold great tits [37,38]. Hens of the LP line also
showed higher parasympathetic response than birds of the
high feather pecking line [39].
This study was designed to test how great tits different
for shyness and boldness respond physiologically (body
temperature and breath rate) to an unpredictable and acute
stressful event (capture and handling). We tested two
independent groups, one during daytime (active phase)
and one during nighttime (inactive phase). The nighttime
group was tested primarily in an attempt to record minimum
resting levels. We hypothesised that shy individuals show
higher or more prolonged responses than bold individuals in
both parameters [10,12,21,30,39].
2. Methods
2.1. Subjects and housing
The great tit is a territorial, nonmigratory passerine bird
(body mass: 16–20 g) inhabiting woods and parks. The
group of birds tested during the active phase consisted
originally of 90 chicks collected from a wild population at
the age of 10 days in May–June and hand reared under
standard conditions until independence [15]. From independence
onwards (days 25–30 after hatching), birds were
housed individually in standard cages of 0.90.40.5 m
with a wooden bottom, top, sides and rear walls, a wiremesh
front and three perches. They were kept under natural
light conditions (LD 10:14 h during the period of the stress
protocol, December 1998), and had auditory and visual
contact with other individuals housed in the same room.
Food (commercial seed mixture, sunflowers and a protein
rich mixture supplemented daily with mealworms, Tenebrio
molitor) and water were provided ad libitum.
The birds tested during the inactive phase were 16 adult
male great tits (2–3 years old) originating from a program of
bidirectional artificial selection started in 1993 on the basis
of the outcome of exploration tests carried out at the age of
30–40 days [23]. Lines did not differ in body mass or tarsus
length. The birds belonged to the third and fourth
generation, 6 of the Slow (shy) and 10 of the Fast (bold)
line. They were housed and maintained as described above.
Birds were sexed with molecular markers [40]. Body
mass and other morphometric measurements were taken
about 2 weeks before the stress protocol.
2.2. Novel object tests
Two tests were carried out at the age of 35–40 days after
hatching, introducing a novel object on one of the outer
perches. A penlight battery was used on the first day and an
8-cm pink rubber toy on the second day. Birds were
characterized for shyness and boldness assessing their
latency to approach the object and the shortest distance to
it within 120 s. The results for each test were converted
linearly to a 0–5 scale. A score of 5 was given when the bird