ArticlePDF Available

Abstract and Figures

Crèching behaviour in penguins is defined as the rearing of chicks by their own parents in large flocks called ‘crèches’. Although several hypotheses have been proposed to account for the behaviour, the factors inducing chicks to aggregate remain relatively poorly understood, in particular for colonial seabirds. We studied crèching behaviour in the king penguin, Aptenodytes patagonicus, by looking at the dynamics of crèche formation and possible costs and benefits associated with this strategy. Crèches increased in size but declined in number throughout the austral winter. They were located preferentially in the central parts of the colony. Lone chicks suffered the most aggression from unrelated adults, whereas chicks in a crèche suffered the least. Chicks attacked by unrelated adults preferentially joined a crèche. Adult aggression appeared to be a major factor inducing crèching behaviour. Chicks at the periphery of a crèche were more vigilant while sleeping, as measured by eye openings. Crèches seemed to occasion intense competition among chicks for access to the centre. Chicks in poor condition were attacked and pushed to the periphery of the crèche, where they were preyed on by giant petrels. During harsh weather conditions, chicks amalgamated into larger crèches, tolerated lower interindividual distances and turned their backs to the wind and rain. Our results accord with the idea that crèching behaviour in king penguins is a strategy that protects chicks from adult aggression, predation and severe weather.
Content may be subject to copyright.
The adaptive significance of cre
`ches in the king penguin
*Centre d’E
´cologie et Physiologie E
yStation Biologique de la Tour du Valat
(Received 14 January 2004; initial acceptance 6 March 2004;
final acceptance 10 November 2004; published online ---; MS. number: 7963R)
`ching behaviour in penguins is defined as the rearing of chicks by their own parents in large flocks
called ‘cre
`ches’. Although several hypotheses have been proposed to account for the behaviour, the factors
inducing chicks to aggregate remain relatively poorly understood, in particular for colonial seabirds. We
studied cre
`ching behaviour in the king penguin, Aptenodytes patagonicus, by looking at the dynamics of
`che formation and possible costs and benefits associated with this strategy. Cre
`ches increased in size but
declined in number throughout the austral winter. They were located preferentially in the central parts of
the colony. Lone chicks suffered the most aggression from unrelated adults, whereas chicks in a cre
suffered the least. Chicks attacked by unrelated adults preferentially joined a cre
`che. Adult aggression
appeared to be a major factor inducing cre
`ching behaviour. Chicks at the periphery of a cre
`che were more
vigilant while sleeping, as measured by eye openings. Cre
`ches seemed to occasion intense competition
among chicks for access to the centre. Chicks in poor condition were attacked and pushed to the periphery
of the cre
`che, where they were preyed on by giant petrels. During harsh weather conditions, chicks
amalgamated into larger cre
`ches, tolerated lower interindividual distances and turned their backs to the
wind and rain. Our results accord with the idea that cre
`ching behaviour in king penguins is a strategy that
protects chicks from adult aggression, predation and severe weather.
Ó2005 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
`ching behaviour is a rearing strategy observed in several
colonial species (Gorman & Milne 1972). Coloniality, the
aggregation of conspecific individuals on breeding territo-
ries distinct from foraging sites (Kharitonov & Siegel-
Causey 1988), appears to supply many benefits such as
optimal breeding habitat selection (Danchin & Wagner
1997) and reduction of predation (Wittenberger & Hunt
1985; Siegel-Causey & Kharitonov 1991). However, there
are several obvious disadvantages of colonial breeding, such
as having to forage away from the colony, needing a parent–
offspring recognition system and having to protect young
against conspecific adult aggression (Wittenberger & Hunt
1985; Kharitonov & Siegel-Causey 1988). Cre
`ching appears
to be a partial substitute for continuous parental protection
and care, permitting both parents to leave their young
temporarily and go to foraging areas (Evans 1984; Besnard
2001). Several adaptive advantages have been proposed for
`ching behaviour, including reduced predation (Pettingill
1960; Davis 1982; Tourenq et al. 1995), increased thermo-
regulation efficiency (Pettingill 1960; Yeates 1975; Davis
1982; Evans 1984; Carter & Hobson 1988; Tourenq et al.
1995) and improved social tolerance (Bildstein 1993). Some
authors have suggested that intraspecific aggression could
be the main proximate cause of cre
`che formation (Seddon &
van Heezik 1993; Tourenq et al. 1995; Besnard 2001).
However, there is little agreement on why chicks form
`ches, mainly because the behaviour is so variable
between species.
The term ‘cre
`che’ was first used to describe cases of chick
amalgamation in the emperor penguin, Aptenodytes forsteri
(Wilson 1907). Although this concept of cre
`che applies
specifically to birds (Brown & Root 1971; Gorman & Milne
1972), a few authors have used it to describe offspring
gatherings in mammals such as Mexican free-tailed bats,
Tadarida brasiliensis mexicana (McCracken 1984), harbour
seals, Phoca vitulina richardsi (Slater & Markowitz 1983),
giraffes, Giraffa camelopardalis (Leuthold 1979), Nubian
ibexes, Capra ibex nubiana (Levy & Bernadsky 1991) and
sable antelopes, Hippotragus niger (Thompson 1998). The
king penguin, Aptenodytes patagonicus, is a prime model for
studying cre
`ching behaviour. Its breeding cycle is unusual
for seabirds because it exceeds a year and the chick
fledging period lasts about 11 months (Barrat 1976).
During the austral winter, chicks left alone in the colony
are subject to prolonged starvation (up to 5 months)
Correspondence: Ce
´line Le Bohec, CEPE-CNRS, 23 rue Becquerel, 67087
Strasbourg Cedex 02, France (email: celine.lebohec@c-strasbourg.
fr). Michel Gauthier-Clerc is at the Station Biologique de la Tour du
Valat, Le Sambuc, 13200 Arles, France.
0003–3472/04/$30.00/0 Ó2005 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
AN IM AL BE HA V IO UR , 2005, --,----
between the infrequent feeding visits by their parents
(Cherel et al. 1987; Descamps et al. 2002). Thus, large
metabolic reserves and cre
`ching behaviour are important
for the chicks’ survival (Barrat 1976; Cherel et al. 1987).
King penguin cre
`ches are aggregations of unrelated chicks,
in which the chicks continue to be fed only by their own
parents. Cre
`ching behaviour in king penguins has been
mentioned by some authors (e.g. Barrat 1976; Descamps
et al. 2002; Le Bohec et al. 2003), but has not been
examined in detail. Our aim in this study was to describe
`ching by king penguin chicks over the annual cycle for
various habitats within a colony. Since king penguins are
very aggressive to conspecifics (Le Maho et al. 1993;
Challet et al. 1994; Co
´2000), we tested the effect of
aggression on cre
`ching. Finally, we investigated whether
`ches protect against predation and inclement weather.
Study Species
The king penguin is a subantarctic seabird that breeds in
large dense colonies. The pair incubates a single egg
directly on their feet. During incubation and brooding
periods, the birds vigorously defend a small territory
(approximately 0.5–0.8 m
) against breeding neighbours
and intruders that approach within pecking distance
´2000). The breeding cycle lasts 14–16 months.
Two peaks of laying occur: a first peak of early breeders
(at the beginning of December) that failed their previous
breeding season and a second peak of breeders (at the end
of January) that bred late because they fledged a chick
during the previous breeding season (Barrat 1976). Chick
rearing can be split into four periods: (1) brooding of
young chicks by their parents; (2) formation of small
prewintering cre
`ches while chicks wait for their parents to
return from feeding trips (Descamps et al. 2002); (3)
formation of large wintering cre
`ches when feeding visits
become infrequent (Descamps et al. 2002) and the
majority of the adults have deserted the colony; (4) at
the end of winter, progressive breaking up of cre
when adults return to the colony to moult and start
breeding again and the chicks moult before going to sea.
Data Collection
We conducted the study in the breeding colony La
Grande Manchotie
`re (around 16 000 pairs) on Possession
Island, Crozet Archipelago (46250S, 51 450E) during
a complete breeding cycle (2001–2002). For each aspect
of the study we collected data during similar time slots
and under similar weather conditions to minimize bias.
`che formation and dynamics
A cre
`che has been defined as two or more chicks in close
association (Evans 1984; Carter & Hobson 1988), where
individuals are less than two chick wing lengths apart (i.e.
less than 60 cm in king penguins). From February 2001 to
February 2002, we determined cre
`che numbers and sizes
(chicks per cre
`che) in two designated parts of the colony
(Fig. 1): Zone A (beach and river, 0.6 ha) and Zone B (side
of the valley, 0.8 ha). The high frequency of observations
conducted in Zone A (twice a week until May then once
a week when cre
`che sizes varied less) allowed us to follow
in detail the progressive formation of cre
`ches during the
annual cycle. To investigate whether chicks gather prefer-
entially in particular areas, we divided Zone B into 60
squares (each of about 10 !10 m) which we observed
once a week until May and then twice a month. We
defined four categories of habitat in Zone B: Central zone:
nonfloodable central areas; Floodable zone: areas poten-
tially floodable at the bottom of the slope; Peripheral
zone: peripheral areas at the top of the slope; Rocky zone:
rocky faced areas. The average number of chicks per cre
per square and the average number of cre
`ches per square
were determined for each category. We made these
observations for the three cre
`ching phases of the annual
cycle: prewintering (February to May), wintering (June to
October) and postwintering (November to February).
Intraspecific aggressiveness
To record aggressive behaviours, we used the focal
animal and continuous sampling method (Altmann
1974; Martin & Bateson 1993). We quantified agonistic
interactions (number of bill strokes, hits and misses)
between an individual selected randomly in the colony
and conspecifics during 10-min observation periods. A
total of 720 focal observations were conducted in Zone A
from February to November 2001.
Adult–adult aggressive interactions. From 3 to 13 February,
we counted the acts of aggression on neighbours by adults
at different breeding stages: incubating (NZ40), brood-
ing a 1-week-old chick (NZ40) and brooding a 3-week-
old chick (NZ40). We estimated chick size by the chick’s
height relative to that of its parent to define the following
two categories: (1) approximate height of 10%, 1-week-old
grey chick (with no down, hence dependent on its parent)
and (2) approximate height of 30%, 3-week-old brown
chick (covered by down).
Adult–chick aggressive interactions. From about 20 days,
when they can thermoregulate (Barre
´1984), chicks are left
alone between feeding visits. At this age chicks either
remain alone or approach other adults or chicks. From 15
February to 10 March 2001, we recorded the number of
pecks that chicks received from breeding adults and other
chicks (guarded by an adult and/or in a cre
`che; NZ120).
Chicks guarded by parents were used as a control situation
(NZ120). We used the method of all occurrence behav-
iour sampling (Altmann 1974) to record lone chicks
starting to move, (2) duration and number of pecks
received from adults during the movement, and (3) the
chicks’ destination.
Chick–chick aggressive interactions. Agonistic interactions
between chicks in good and poor condition were observed
at the beginning of cre
`che formation (March) and at the
end of the wintering cre
`ches (September). Chicks in good
condition were the tallest and heaviest individuals in the
`che: 70–80% (March, NZ20) or 90% (September,
NZ20) of an adult’s height, with an invisible breastbone
and protruding abdomen. Chicks in poor condition were
the smallest and thinnest individuals in the cre
`che: 30–
50% (March, NZ20) or 60% (September, NZ20) of an
adult’s height, with a prominent breastbone and abdomen
not protruding. We also took focal samples of chicks fed
by an adult and chicks in a cre
`che from March to
November to compare their aggressiveness (N Z260).
Body mass of chicks and position in the cre
We defined the cre
`che periphery as that part formed by
the first two rows of chicks on the outside of the group.
Chicks on the periphery (NZ25) and in the centre
(NZ25) of cre
`ches in Zone A were caught by hand and
weighed with an electronic balance (G10g) monthly from
March to October to establish a correlation between chick
position in the cre
`che and body condition.
Vigilance and sleep
We collected vigilance and sleep data using the focal
animal and continuous sampling technique (Altmann
1974; Martin & Bateson 1993). Observations lasted
2 min. Using a 40!telescope, a tape recorder and
a stopwatch, we recorded the frequency of eye openings,
the duration of consecutive eye openings and intervals
between eye openings for randomly selected individuals
(Gauthier-Clerc et al. 1998, 2000). These data were
collected for birds on the periphery (NZ30) and in the
centre (NZ30) of cre
`ches adopting the typical sleep
posture, i.e. standing up, head lying on back, with the
visible eye closed and bill tucked underneath a flipper
(Challet et al. 1994; Dewasmes et al. 1989). This part of
the study was conducted in Zone A in May (beginning of
wintering cre
`ches), at the end of June (middle of wintering
`ches) and at the end of August (end of wintering
We recorded instances of predation (NZ157) according
to the method of all occurrence behaviour sampling
(Altmann 1974). In all zones we recorded the type of
predator (giant petrels Macronectes halli and M. giganteus,
brown skua, Catharacta lonnbergi, kelp gull, Larus domi-
nicanus, or lesser sheathbill, Chionis minor), chick size
(small, medium or tall, depending on its height relative to
the adult), chick body condition (see above), and pre-
dation outcome: success or failure.
Weather conditions
We investigated cre
`ching in relation to weather in
Zone C (beach and river, 0.3 ha, Fig. 1): (1) winter,
Cold)Wind)Rain (NZ8 days, %5C, wind R28 knots,
La Baie
du Marin
Zone B
Zone A
Zone C
Camp River
30 m
Central zone
Floodable zone
Peripheral zone
Rocky zone
Figure 1. Schematic map of the breeding colony La Baie du Marin showing the various study areas. Dashes: boundary of the breeding colony
La Grande Manchotie
`re. Zone A (beach and river, blue outline), for study of cre
`che formation dynamics during the annual cycle; Zone B (side
of the valley, red outline), for study of the habitat; Zone C (beach and river, green outline), for study of the effect of weather conditions.
with rain); (2) winter, Cold)Wind)No rain (NZ12 days,
%5C, wind R28 knots, without rain); (3) winter,
Cold)No wind)No rain (NZ10 days, %5C, no wind,
no rain); and (4) summer, Warm)No wind)No rain (NZ8
days, R10C, wind 0–6 knots, without rain). Variables
recorded were number and size of cre
`ches, interindividual
distance (NZ100) estimated in units of chick flipper
length, and position of chicks in good condition
(NZ20) and poor condition (NZ20) within the cre
Data Analysis
Results are reported as means GSE. We assume that our
random samplings did not include significant replication
because there were more than 20 000 king penguin chicks
in the colony, and the same bird was unlikely to be
observed more than once. When the data were normally
distributed and homoscedasticity of data was confirmed,
we compared samples using one-way or two-way ANOVAs
followed by a parametric post hoc test adjusted by
Tukey (parametric tests, Scherrer 1984). When application
conditions for ANOVA were not satisfied (even after
transformation), we used nonparametric tests (Sheirer–
Ray–Hare test (two-way analysis of variance by ranks) or
Kruskal–Wallis test (one-way analysis of variance by
ranks), Siegel & Castellan 1988) to compare more than
two samples. These tests were followed by a nonparametric
post hoc test adjusted by Dunn (samples of different size).
To compare means of two independent groups and to
analyse frequencies we used the Mann–Whitney Utest
and the chi-square test, respectively. For correlations
between variables we used Spearman rank and Kendall
rank partial correlation coefficients. For the statistical
analyses we used SYSTAT 9.0 and Sigmastat 2.0 (SPSS
Inc., Chicago, IL, U.S.A.). All tests were two tailed with
significance level set at aZ0.05.
Ethical Note
Observations were made 10–100 m from outside the
colony. At short distances, we observed the birds from
behind a low wall or from a blind. This type of observation
did not cause any disturbance nor did it expose birds to
predators. During monthly weighings we minimized
disturbance by moving slowly towards the cre
`ches and
releasing captured chicks close to the cre
`che from where
they came. We verified that the cre
`ches reformed imme-
diately after the capture. No predation was observed
during that time. Observed and weighed birds were
selected randomly in the colony and were not marked.
The study received the consent of the Ethics Committee of
the Institut Polaire Franc¸ais – Paul-Emile Victor.
Number and Size of Cre
The first chicks abandoned temporarily were seen
during the week 9–15 February. The number of such
chicks increased progressively until the end of June (to
about 6500 chicks in Zone A). At the same time, the
number of cre
`ches with up to 20 chicks increased until 6
April, when it reached a maximum (357 in Zone A; Fig. 2).
The number of cre
`ches was highly correlated with the
number of chicks left unattended by their parents (Spear-
man rank correlation: r
Z0.90, NZ17, P!0.005).
`che size was negatively related to the number of
`ches (Kendall rank partial correlation coefficient:
Z0.25, NZ60, P!0.005) and size increased pro-
gressively from February to September (Fig. 2). The
number of cre
`ches started to decrease at the beginning
of April. This decrease resulted from the grouping of
several small cre
`ches (less than 50 chicks) into larger ones.
The minimum number of cre
`ches (8) and the maximum
size (about 500 chicks) were observed between 13 August
and 24 October. At the end of October, cre
`ches split up
and became more numerous but smaller in size.
Location in the colony and period of the year had
a significant effect on the number of chicks in cre
`ches per
square (two-way ANOVA: zone: F
Z15.66, P!0.005;
period: F
Z22.11, P!0.005; interaction:
Z3.51, PZ0.001; Fig. 3a) and the number of cre
per square (two-way ANOVA: zone: F
P!0.005; period: F
Z81.75, P!0.005; interaction:
Z4.73, P!0.005; Fig. 3b). During the prewintering
and wintering periods, the number of chicks in cre
`ches and
the number of cre
`ches were significantly higher in the
central zone than in the other three locations (Tukey tests:
P!0.005). There were no significant differences between
the four locations during the postwintering period (Tukey
tests: NS). These were significantly more prewintering than
wintering and postwintering cre
`ches in the floodable and
peripheral zones (Tukey tests: P!0.05) and more post-
wintering than wintering cre
`ches in the floodable and
rocky zones (Tukey tests: P!0.05).
Intraspecific Aggression
The level of adult aggression was on average very high
whatever their reproductive status (23 G2 agonistic in-
teractions per 10 min, NZ120). Adult aggressive behav-
iour varied significantly with reproductive status (ANOVA:
Z3.59, PZ0.031) and was highest for adults
brooding a 3-week-old chick (30 G3 interactions,
NZ40; Tukey tests: P!0.05). However, there was no
significant difference between adults incubating and
adults brooding a 1-week-old chick (19 G2 and 20 G2
interactions, respectively, NZ40 for both cases, Tukey
test: NS).
Aggression towards a chick by adults and by other chicks
(guarded by an adult and/or in a cre
`che) differed in the four
scenarios (Kruskal–Wallis tests: from adults: H
NZ240, P!0.001; from chicks: H
Z91.76, NZ240,
P!0.001; Fig. 4). A chick with one of its parents
experienced the fewest pecks in both cases (0.14 G0.06
and 0.21 G0.07, respectively; Dunn tests: P!0.05).
Attacks by adults on a lone chick (20.98 G2.99) were
about four times higher than aggression towards a chick
with an unrelated adult (4.90 G1.30; Dunn test: P!0.05)
or towards a chick in a cre
`che (3.23 G0.54; Dunn test:
P!0.05). Conversely, other chicks pecked a lone chick
less (1.30 G0.72) than a chick with an unrelated adult
(3.25 G1.43; Dunn test: P!0.05) or a chick in a cre
(3.63 G0.46; Dunn test: P!0.05).
Lone unguarded chicks mainly moved away in response
to adult aggression (72%). During the displacement
(which lasted on average 33 G5 s), a chick received on
average 1 peck/s. Chicks usually moved to cre
`ches and
stayed in them (61%).
Interindividual Relations within the Cre
Within a cre
`che, chicks in good condition were signif-
icantly more aggressive than chicks in poor condition at
the beginning of cre
`che formation in March and at the
end of winter in September (Mann–Whitney Utests:
March: UZ342, N
Z20, P!0.005; September:
UZ328, N
Z20, P!0.005; Fig. 5). Chicks in poor
condition received significantly more pecks than chicks in
good condition, in March and in September (March:
UZ73, N
Z20, PZ0.001; September:
UZ66.50, N
Z20, P!0.005). Chicks in cre
became significantly less aggressive between March and
September (Fig. 5).
The presence of a feeder adult and period of the year had
a significant effect on the agonistic interactions between
chicks (two-way Sheirer–Ray–Hare tests: effect on the
number of pecks given: adult present: F
P!0.005; period: F
Z15.234, P!0.005; interaction:
Z19.70, P!0.005; effect on the number of pecks
received: adult present: F
Z52.19, P!0.005; period:
Z17.782, P!0.005; interaction: F
PZ0.005). A chick fed by an adult was more aggressive
than a lone chick in a cre
`che (Dunn tests: P!0.05; Fig. 6)
except in November (Dunn test: P!0.05). Lone chicks in
`ches were least aggressive from May to August.
Chick body mass was significantly different according
to position within the cre
`che and month (two-way
ANOVA: position: F
Z51.13, P!0.005; month:
Z30.40, P!0.005; interaction: F
P!0.005; Fig. 7). Throughout the wintering period,
chicks situated on the periphery of cre
`ches weighed less
than chicks in a central position.
The time spent with an eye open in a typical sleep
posture corresponds to both the vigilance level and the
time spent awake. Position within the cre
`che and month
had a significant effect on the proportion of time spent
with one eye open (two-way Sheirer–Ray–Hare test: posi-
tion: F
Z368.48, P!0.001; month: F
P!0.001; interaction: F
Z11.33, PZ0.001), the
frequency of eye openings (two-way Sheirer–Ray–Hare test:
position: F
Z368.48, P!0.001; month: F
Z9.51, P!0.001; interaction: F
Z11.33, PZ
0.001) and the duration of eye closure (two-way Sheirer–
Ray–Hare test: position: F
Z372.68, P!0.001;
month: F
Z9.52, P!0.001; interaction: F
Z11.95, P!0.001). The proportion of time spent with
one eye open and frequency of eye openings were signif-
icantly higher among peripheral chicks than central chicks
whatever the month (Dunn tests: P!0.05; Table 1). The
duration of eye closure was significantly higher among
central chicks than peripheral chicks whatever the month
(Dunn tests: P!0.05). Time spent with one eye open and
frequency of eye openings increased from May to August in
the periphery, but were minimal in June in the central
position. The duration of eye closure decreased from May
0Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb
Number of crèches
Crèche size
Figure 2. Change in number (histogram) and size (curve) of cre
`ches in Zone A. Cre
`che sizes (number of chicks per cre
`che) are reported as
means CSE.
to August in the periphery, but was maximal in June in the
central position.
Out of 157 instances of predation observed on chicks,
giant petrels were the most frequent predators with 95%
of the attacks. Brown skuas, kelp gulls and lesser sheath-
bills committed only 1% of the attacks and were generally
scavengers and detritivores, feeding notably on carcasses
abandoned by giant petrels. The remaining 4% corre-
sponded to attacks by mixed groups of these four preda-
tors. Small chicks were the object of 77% of the attacks
(Table 2). Attacks on chicks in poor condition and/or
already weakened by previous injuries represented 43% of
the instances of predation and generally ended with
predator success (97%). In contrast, attacks on chicks in
(N = 20)
(N = 20)
(N = 20)
(N = 20)
March September
Received from chicks
By chicks
Aggressive behaviour per 10 min
(number of pecks)
Figure 5. Aggressive behaviour between chicks in a cre
`che according
to body condition. Values are means CSE. Mann–Whitney Utests
comparing March and September data: number of pecks received by
chicks in good condition: UZ338, N
Z20, P!0.001;
chicks in poor condition: UZ343, N
Z20, P!0.001;
number of pecks by chicks in good condition: UZ335,
Z20, P!0.001; chicks in poor condition: UZ287,
Z20, PZ0.004.
Central Floodable Peripheral
Area of Zone B
Number of chicks in crèches
per square
Number of crèches
per square
Figure 3. (a) Number of chicks in cre
`ches per square and (b) number
of cre
`ches per square by zone in the colony (Central zone:
nonfloodable central area; Floodable zone: areas potentially flood-
able at the bottom of the slope; Peripheral zone: peripheral areas at
the top of the slope; Rocky zone: rocky areas) and period
(prewintering cre
`ches: February to May; wintering cre
`ches: June to
October; postwintering cre
`ches: November to February). Values are
means CSE.
Aggressive behaviour per 10 min
log (number of pecks)
Received from adults
Received from chicks
(N = 120)
(N = 40)
(N = 40)
In crèche
(N = 40)
Figure 4. Aggressive behaviour shown by adults and by other chicks
to a chick with one of its parents, a chick with an unrelated adult,
a lone chick and a chick in a cre
`che. Values are means CSE. Values
not assigned the same letter (aggression from adult: a,b,c;
aggression from chicks: d,e,f) are significantly different (post hoc
test adjusted by Dunn: P!0.05).
(N = 60)
(N = 50)
(N = 50)
(N = 50)
(N = 50)
Chick alone in crèche
Chick fed by an adult
Aggressive behaviour per 10 min
(number of pecks)
Figure 6. Aggression shown by a chick fed by an adult or by a lone
chick in a cre
`che during the austral winter. Values are means CSE.
Values not assigned the same letter (lone chick: a,b; fed chick: c,d,e)
are significantly different (post hoc test adjusted by Dunn). Compar-
ison of lone and fed chicks: *P!0.05, post hoc test adjusted by Dunn.
good condition (57% of attacks) succeeded only 24% of
the time.
Weather Conditions
Weather conditions had a significant effect on number
of cre
`ches (ANOVA: F
Z11.85, P!0.001) and size of
`ches (ANOVA: F
Z6.33, PZ0.002; Fig. 8). The
number of cre
`ches was significantly lower in Cold)Wind)
Rain and Cold)Wind)No rain conditions than in
Warm)No wind)No rain (Tukey tests: P%0.001). There
were also fewer cre
`ches during Cold)Wind)Rain than in
Cold)No wind)No rain (Tukey test: PZ0.005). Cre
size was markedly higher in Cold)Wind)Rain than in
Warm)No wind)No rain or Cold)No wind)No rain
(Tukey tests: PZ0.009 and PZ0.003, respectively).
Weather conditions had a significant effect on distance
between chicks (ANOVAs: chicks half a flipper apart:
Z12.42, P!0.001; chicks one flipper apart: F
Z2.94, PZ0.047; chicks two flippers apart: F
PZ0.007; chicks three flippers or more apart: F
Z16.93, P!0.001). Interindividual distance was lower
during the Cold weather conditions (nearly 70% of chicks
up to half a flipper apart) than when it was Warm)No
wind)No rain (25% of chicks; Tukey tests: P!0.005). On
the other hand, cre
`ches were clearly looser when weather
conditions were better (30% of chicks three flippers or
more apart versus 6% during Cold weather conditions,
Tukey tests: P!0.001).
During harsh weather conditions (Cold)Wind)Rain
and Cold)Wind)No rain), the distribution within the
`che of chicks in good and poor condition was not
uniform (ANOVAs: good: F
Z15.84, P!0.001; poor:
Z50.07, P!0.001). Fewer chicks were in poor
condition in the central position than on the periphery
(4.68 G0.76 versus 15.32 G0.76 chicks; Tukey tests:
P!0.001) and more chicks were in good condition in
the centre (13.37 G0.51 chicks; Tukey test: P!0.001).
Fewer chicks were in good condition on the periphery
(6.63 G0.51 chicks) than in the central position (Tukey
test: P!0.005). In contrast, when it was Cold)No
wind)No rain and Warm)No wind)No rain, chicks had
a uniform distribution within the cre
`che for both body
conditions (10 G0.53 chicks for each category; ANOVAs:
good: F
Z2.35, PZ0.088; poor: F
Dynamics of Cre
`che Formation
`che size gradually increased from February to Sep-
tember, whereas the number of cre
`ches dropped from the
beginning of April as a result of small cre
`ches grouping
together into larger ones. The process of gradual amal-
gamation first into numerous small prewintering cre
can be explained as the consequence of hatching asyn-
chrony, which generates an asynchrony of temporary
chick desertions and the formation of cre
`ches constituted
of chicks of all ages. At the end of the summer, the colony
is deserted by adults, freeing space for chicks to gather into
fewer and larger cre
`ches. White ibis, Eudocimus albus, and
greater flamingo, Phoenicopterus ruber, chicks also gather
first in small then in larger groups and finally into a single
`che (Dinep 1988; Tourenq et al. 1995). Evans (1984)
considered that the temporary desertion of young by
parents is the single most important factor triggering the
onset of cre
`ching, whereas the return of parents to the
Peripheral chicks
Central chicks
Body mass (kg)
(N = 40)
(N= 50)
(N = 50)
(N = 50)
(N = 50)
(N = 50)
(N = 50)
(N = 51)
Figure 7. Chick body mass and distribution in cre
`ches (peripheral or
central position) during the austral winter. Values are means GSE.
Comparison of central and peripheral chicks: *P!0.05, post hoc
test adjusted by Tukey.
Table 1. Proportion of time spent with one eye open, frequency of eye openings and duration of eye closure by position in the cre
`che and
Periphery Centre
May June August May June August
Sample size
30 30 29 30 30 30
% Time spent with one eye open 14.7G2.9 33.5G4.9 38.6G4.3 0.7G0.3 0.5G0.2 0.8G0.3
Frequency of eye openings (per 2 min) 10.2G1.8 18.8G2.2 26.0G2.4 1.0G0.3 0.6G0.2 0.9G0.3
Duration of eye closure (s) 31.6G7.7 8.3G2.1 3.7G0.5 89.4G7.6 96.4G6.4 92.0G7.1
Values are means GSE.
colony stimulates young to leave a cre
`che. Davis (1982)
showed that cre
`ching behaviour is closely associated with
the number of adults present in the colony and suggested
that the cre
`che may serve as an alternative means of
defence against predators when too few adults are present
in the colony to deter predators effectively. This hypoth-
esis does not appear to be valid for king penguins, however,
because, first, they do not cooperate to deter predators and,
second, they are aggressive towards each other during the
breeding period. Cre
`ches are consequently more likely
to be a partial substitute for continuous parental care
(Besnard 2001) and dependent on how much space is
available for their formation.
Habitat Quality
We found that chicks congregated mostly in the central
areas of the colony, as do pelicans and flamingos (Brown
& Root 1971; Tourenq et al. 1995). In other species such as
terns and gulls, cre
`ches are set up on the edge of the
colony (Buckley & Buckley 1976). In king penguins,
central parts of the colony are initially occupied by early
breeders (Co
´2000). Individuals that lay first also leave
their chick first once it can thermoregulate efficiently.
Spaces free of adults are then created in those central areas
of the colony, allowing chicks to gather together and form
numerous small prewintering cre
`ches. As the summer
wears on, chicks born later in peripheral and potentially
floodable zones are temporarily abandoned by their
parents and the number of small cre
`ches increases in
these areas.
From June to October, the great majority of adults desert
the colony. The whole area of the colony then becomes
accessible to chicks. However, chick distribution was not
uniform on the space available, and rocky areas, periph-
eral areas at the top of the slope and potentially floodable
areas at the bottom of the slope remained unoccupied.
This suggests that wintering cre
`che locations of king
penguins depend on habitat quality. Central areas are
considered high-quality territories in colonial species
(Kharitonov & Siegel-Causey 1988; Vinuela et al. 1995).
Carter & Hobson (1988) suggested that the location of
`ches of chicks of Brandt’s cormorant, Phalacrocorax
penicillatus, depends on habitat quality. Levy & Bernadsky
(1991) noted that Nubian ibex, Capra ibex nubiana, formed
`ches on shady even terrain.
In our study, cre
`ches broke up progressively in the spring
when adults returned for moulting and courting. As for
prewintering cre
`ches, available space again became a re-
strictive factor because adults occupied most of the colony
area. Chicks were pushed towards peripheral areas of the
colony, probably of lower quality, since they had avoided
these areas before the adults returned. These peripheral
areas are known to be infested by Ixodes uriae ticks, which is
a parasite of the king penguin (Gauthier-Clerc et al. 1999;
Mangin et al. 2003). The parasitic constraint hypothesis
could explain the nonoccupation of peripheral areas by
the chicks when central areas were still available.
Adult Aggression
Breeders were aggressive to alien chicks, especially lone
unguarded chicks. Attacked chicks preferentially joined
`ches where they experienced less aggression and where
the risk of injury was lower compared with pecks and
flipper blows from adults. Other studies have also shown
a high level of aggression between breeders (Le Maho et al.
1993; Challet et al. 1994; Co
´2000). Since fights entail
high energetic costs (Ho
¨gstad 1987), the benefits of
defending a territory should therefore be high in terms
of reproductive success (Montgomerie & Weatherhead
1988). Intraspecific aggression in colonial species varies
during the reproductive cycle (Burger & Gochfeld 1990;
Lamey 1993; Challet et al. 1994). The increase in aggres-
sion between adult king penguins from incubation to
brooding may be explained by the higher fitness value of
a chick, as proposed by parental investment theory
(Williams 1966; Trivers 1972; Burger 1981; Siegel-Causey
& Hunt 1981). Adelie penguins, Pygoscelis adeliae (Spurr
1974) and chinstrap penguins, Pygoscelis antarctica
(Vinuela et al. 1995; Amat et al. 1996) similarly defend
chicks more strongly than eggs.
Table 2. Success of predation by giant petrels on chicks according to
chick height (estimated in relation to adult height) and chick
condition (estimated from breastbone and abdomen prominence)
Chick size/condition Attacks (%) Predation success (%)
Small 77
Poor 51 97
Good 49 34
Medium 17
Poor 22 100
Good 78 5
Tall 6
Poor 0 d
Good 100 10
NZ149 predation events.
Number of crèches
Crèche size
Cold * Wind
* Rain
(N = 8)
Cold * Wind
* No rain
(N = 12)
Cold * No wind
* No rain
(N = 10)
Warm * No wind
* No rain
(N = 8)
Figure 8. Number (histogram) and size (curve) of cre
`ches for four
categories of weather conditions (Zone C, see Methods for
description of categories). Values are means CSE.
Chicks temporarily abandoned by their parents experi-
enced the highest level of aggression because of the strong
territoriality of incubating and brooding adults. Intraspe-
cific aggression towards such chicks has been frequently
reported in colonial species (Wittenberger & Hunt 1985)
and attack by unrelated adults is generally recognized as
one of the major causes of chick mortality in gulls (Pierotti
1988; Brown & Morris 1995). In our study, aggression by
adults resulted in chicks leaving their natal territory in
72% of cases and joining a cre
`che in 61% of cases. Seddon
& van Heezik (1993), who obtained similar results for the
jackass penguin, Spheniscus demersus (moving towards
a cre
`che: 74%), suggested that intraspecific aggression is
the main proximate cause of cre
`che formation. In March,
up to 10% of adult king penguins guard two or three
chicks and will adopt chicks, at least temporarily. A lone
unguarded chick heads for an unrelated adult in 24% of
movements from the natal territory, tries to take the place
of the legitimate chick and attempts to chase it away by
pecking. Then the parent attacks both chicks without
distinction until its own chick vocalizes. If the parent is
unable to recognize its own chick quickly, the risk of
injuring it is high. The conflict of interest between an
adult and an alien chick may result in a forced adoption
that would then reduce the care for the legitimate chick
and would increase its risk of rejection and injury. This
may explain why a parent defends its territory against
alien chicks.
A cre
`che might then offer the most advantages to
unguarded chicks in terms of less aggression and more
safety than close proximity to an unrelated adult. Indeed,
our data show that the level of aggression between chicks
in a cre
`che is low. In contrast, when a chick is joined by
a parent, it leaves the centre of a cre
`che and becomes more
aggressive towards other chicks. This behaviour can
manifest itself as pushing away foreign chicks that might
steal meals (Boersma & Davis 1997).
Protection from Predators
The central position within a cre
`che allows a chick to
reduce its vigilance and increase time spent sleeping. One
of the functions of gregarious behaviour is to reduce
predation risk (Pulliam 1973; Powell 1974; Caraco et al.
1980). Individuals in a group can reduce the time spent in
vigilance against predators by taking advantage of vigi-
lance by other group members, without reducing the
probability of detecting the predator or increasing an
individual’s risk of capture by a predator (Elgar & Catterall
1981). A reduction in individual vigilance with an increase
in group size has been reported for numerous birds,
mammals and fish (Lendrem 1984; Martella et al. 1995;
Gauthier-Clerc et al. 1998). This group size effect has been
explained by the ‘many eyes hypothesis’, i.e. a collective
detection that increases with group size (Dimond &
Lazarus 1974). King penguin chicks should thus have
a two-fold advantage of being in large cre
`ches: an in-
creased likelihood of predator detection (detection effect)
allowing an individual to devote less time to vigilance and
hence more time to sleep, and a reduction in risk for any
given individual (dilution effect, Dehn 1990). Larger
`ches suffer less predation, probably because the pro-
portion of chicks at the periphery of the cre
`che declines
quickly as the cre
`che gets larger (Hamilton 1971). This
may be an influential factor in the tendency for cre
`che size
to increase over the wintering cre
`che period.
Sleep and vigilance are mutually exclusive. The trade-off
between these two activities may vary according to an
individual’s position in the group (Elgar 1989). Individuals
at the periphery are more vigilant than those at the centre
because they are at greater predation risk. They are the
ones that will be encountered first by an approaching
ground predator (Hamilton 1971; Jennings & Evans 1980;
Petit & Bildstein 1987). Our results corroborate this
hypothesis. When a predator approached a cre
`che, pe-
ripheral chicks extended themselves up to their full height
and bumped into central chicks which were alerted to
danger and then all the chicks gathered in a denser flock.
We also noticed changes in sleep and vigilance during the
winter. Vigilance of central chicks was slightly lower in the
middle of the winter. June corresponded to the longest
average durations of eye closure, the shortest proportion
of time spent with one eye open, and the lowest frequency
of eye openings. Conversely, sleep decreased and vigilance
increased throughout the wintering period for peripheral
chicks. In particular, chicks undergo a long period of
fasting during the austral winter (the coldest period of the
year, around 5C). One of the adaptations allowing birds
to tolerate the fasting and cold lies in their ability to
reduce energy expenditure. Several authors have suggested
that sleep is important for energy conservation because it
decreases body temperature and thermoregulatory costs
(Stahel et al. 1984; Berger & Philipps 1993; Criscuolo et al.
2001). Chicks in the centre of cre
`ches (in a safe microen-
vironment and probably thermally more stable) can drop
their vigilance in favour of sleep in midwinter unlike
those on the periphery, which are exposed to predation as
well as the cold, and sleep less. Studies on pigeons,
Columbia livia, green-winged teals, Anas crecca, and little
penguins, Eudyptula minor, also reported a decrease in the
time spent sleeping when birds were subjected to cold
(Stahel et al. 1984; Graf et al. 1987; Tamisier & Dehorter
1999). According to Pulliam et al. (1974) both group size
and vigilance behaviour are influenced by ambient tem-
We found that chicks in poor condition experienced the
most aggression and were pushed towards the periphery
of a cre
`che. These chicks suffered the highest predation by
giant petrels. Southern and northern giant petrels are
considered the main king penguin predators, in particular
for chicks during the winter (Hunter & Brooke 1992; Le
Bohec et al. 2003). Our results show that 77% of attacks
were directed towards the smallest chicks and 43%
towards chicks in poor condition and/or already weak-
ened by previous injuries, among which were 51% of
small chicks. Predation attempts on small chicks and
chicks in poor condition were generally successful (66%
and 97%, respectively), in contrast to attacks on medium-
sized and large chicks in good condition (6% success).
Thus, a better body condition increases the chances of
chick survival, not only from the standpoint of resistance
to starvation, but also considering protection from pred-
Our data reveal an effect of chick body condition on
intraspecific relation in the cre
`che. Chicks in good
condition were more aggressive than chicks in poor
condition. This dominance status seems to give them
access to the protected area of the cre
`che centre. Chicks in
poor condition, and consequently less able to defend
themselves, were pushed to the periphery. This rejection
of chicks in poor condition to the periphery of cre
`ches was
most evident during harsh weather.
Protection from Harsh Weather
During inclement weather (cold and rain and/or wind),
there were fewer cre
`ches, but these were larger and chicks
were closer together. Choosing a thermally favourable
environment is an integral part of a chick’s thermoregula-
tory ability (Whittow 1976). The cre
`che probably works as
a hygrometrical and thermally stable microenvironment
(Pettingill 1960). This environment may allow chicks to
decrease their energy expenditure and therefore to increase
survival probability. Our results corroborate this hypothe-
sis. Indeed, as winter progresses, weather conditions
become less favourable and king penguin chicks amalgam-
ated into bigger but fewer cre
`ches. In the rockhopper
penguin, Eudyptes chrysocome, variations in cre
`che size
were related to fluctuations in air temperature (Pettingill
1960). According to Yeates (1975), harsh weather may
result in cre
`che formation in Eudyptidae and Pygoscelidae
chicks. In contrast, Davis (1982) noted that cre
`ching in the
´lie penguin did not vary consistently with fluctuations
in climatic variables. Chick rearing in this species occurs
during the summer and lasts only a month. Owing to the
relatively mild conditions during the short period when
`ching occurs, Ade
´lie chicks can probably maintain
a constant body temperature. On the other hand, contact
behaviour may be most pronounced when ambient tem-
perature is lowest and wind speed and relative humidity
are highest. This contact behaviour apparently has a ther-
moregulatory function (Davis 1982; Evans 1984).
The chill factor associated with high wind speed
dramatically increases heat loss, and this effect is further
accentuated by high relative humidity (Davis 1982). Tight
elongated cre
`ches could reduce the individual convection
surfaces to a single collective surface, which would reduce
individual heat loss and thereby energy expenditure
linked to thermogenesis during extreme climatic condi-
tions (Taylor 1962; Evans 1984). This probably implies
that chicks are in competition for access to the most
sheltered areas in the group. This life in compact groups,
as illustrated by the huddles of emperor penguins, could
be essential for survival and reproductive success (Ancel
et al. 1997). At lower temperatures, dark-eyed juncos Junco
hymelis (Caraco 1979), and willow tits, Parus montanus
¨gstad 1988), form larger flocks of birds with little
aggression. The drop in aggression observed among king
penguin chicks during winter might be explained by the
need to lower energy expenditure in harsh weather and to
establish group cohesion against predation. This social
tolerance strategy, by reducing the overall intraspecific
aggression within the cre
`che, may therefore have emerged
in response to environmental constraints.
This study has allowed us to describe the genesis and
functioning of king penguin cre
`ches during the annual
cycle and to stress the preferential occupation of the
high-quality areas of the colony by cre
`ches. Parental
aggression towards unguarded alien chicks appears to be
an important factor leading to chicks joining a cre
We suggest that cre
`ching behaviour has adaptive advan-
tages such as protection against predation and severe
weather. Food dispersion and lack of protection against
predators and severe weather, induced by the open
environment characteristic of subantarctic islands, may
be selection pressures that promote the development of
this chick-rearing strategy. Further research should look
into the costs associated with this strategy, such as the
increase in risk of disease and parasite transmission by
the close contact between individuals and food theft (i.e.
kleptoparasitism). Finally, to test the hypothesis that
`ches confer important energy savings, as has already
been shown in emperor penguin huddles (Ancel et al.
1997), the energy expenditure of chicks should be
This work was supported by the Institut Polaire Franc¸ais –
Paul-Emile Victor (Programme 137) and by the project
Zones Ateliers of the Programme Environnement Vie
et Socie
´of the CNRS. We are grateful to C. Gilbert,
D. Gre
´millet, A. Lescroe
¨l, C. Salmon, S. Samtmann,
A. Schmidt and C. Villemin for constructive comments
and the anonymous referees for greatly improving the
manuscript. We thank C. Salmon for his help in preparing
software for analysis of the data sets.
Altmann, J. 1974. Observational study of behavior: sampling
methods. Behaviour,49, 227–267.
Amat, J. A., Carrascal, L. M. & Moreno, J. 1996. Nest defence by
chinstrap penguins Pygoscelis antarctica in relation to offspring
number and age. Journal of Avian Biology,27, 177–179.
Ancel, A., Visser, H., Handrich, Y., Masman, D. & Le Maho, Y.
1997. Energy saving in huddling penguins. Nature,385, 304–305.
Barrat, A. 1976. Quelques aspects de la biologie et de l’e
´cologie du
manchot royal (Aptenodytes patagonicus) des ı
ˆles Crozet. Commis-
sion Nationale Franc¸aise de Recherche Antarctique,40, 9–51.
´,H.1984. Metabolic and insulative changes in winter and
summer acclimatized king penguin chicks. Journal of Comparative
Physiology,154, 317–324.
Berger, R. J. & Philipps, N. H. 1993. Sleep and energy conservation.
Neural Information Processing Systems,8, 276–281.
Besnard, A. 2001. Evolution de l’e
´levage des poussins en cre
chez les Laride
´s. Ph.D. thesis, Universite
´de Montpellier.
Bildstein, K. L. 1993. White Ibis: Wetland Wanderer. Washington:
Smithsonian Institute Press.
Boersma, P. D. & Davis, L. S. 1997. Feeding chases and food
allocation in Ade
´lie penguins, Pygoscelis adeliae.Animal Behaviour,
54, 1047–1052.
Brown, K. M. & Morris, R. D. 1995. Investigator disturbance, chick
movement and aggressive behavior in ring-billed gulls. Wilson
Bulletin,107, 140–152.
Brown, L. H. & Root, A. 1971. The breeding behaviour of the lesser
flamingo Phoeniconaias minor.Ibis,113, 147–172.
Buckley, P. A. & Buckley, F. G. 1976. Late-blooming terns. Natural
History,84, 46–56.
Burger, J. 1981. Aggressive behaviour of black skimmers (Rynchops
niger). Behaviour,76, 207–222.
Burger, J. & Gochfeld, M. 1990. The Black Skimmer: Social Dynamics
of a Colonial Species. New York: Columbia University Press.
Caraco, T. 1979. Time budgeting and group size: a test of theory.
Ecology,60, 618–627.
Caraco, T., Martindale, S. & Pulliam, H. R. 1980. Avian flocking in
the presence of a predator. Nature,285, 400–401.
Carter, H. R. & Hobson, K. A. 1988. Creching behavior of Brandt’s
cormorant chicks. Condor,90, 395–400.
Challet, E., Bost, C.-A., Handrich, Y., Gendner, J.-P. & Le Maho, Y.
1994. Behavioural time budget of breeding king penguins
(Aptenodytes patagonicus). Journal of Zoology,233, 669–681.
Cherel, Y., Stahl, J. C. & Le Maho, Y. 1987. Ecology and physiology
of fasting king penguin chicks. Auk,104, 254–262.
´,S.D.2000. Aggressiveness in king penguins in relation to
reproductive status and territory location. Animal Behaviour,59,
Criscuolo, F., Gauthier-Clerc, M., Le Maho, Y., Zorn, T. &
Gabrielsen, G. W. 2001. Sleep changes during long-term fasting
of the incubating common eider Somateria mollissima.Ardea,89,
Danchin, E. & Wagner, R. H. 1997. The evolution of coloniality: the
emergence of new perspectives. Trends in Evolution and Ecology,
12, 342–347.
Davis, L. S. 1982. Creching behaviour of Ade
´lie penguin chicks
(Pygoscelis adeliae). New Zealand Journal of Zoology,9,
Dehn, M. M. 1990. Vigilance for predators: detection and dilution
effects. Behavioral Ecology and Sociobiology,26, 337–342.
Descamps, S., Gauthier-Clerc, M., Gendner, J.-P. & Le Maho, Y.
2002. The annual breeding cycle of unbanded king penguins
Aptenodytes patagonicus on Possession Island (Crozet). Avian
Science,2, 87–98.
Dewasmes, G., Buchet, C., Geloen, A. & Le Maho, Y. 1989. Sleep
changes in emperor penguins during fasting. American Journal of
Physiology,256, R476–R480.
Dimond, S. & Lazarus, J. 1974. The problem of vigilance in animal
life. Brain, Behavior and Evolution,9, 60–79.
Dinep, A. 1988. Social behavior, parental care, and creching:
a chronology of development in white ibis chicks. Colonial
Waterbird Society Newsletter,12, 42.
Elgar, M. A. 1989. Predator vigilance and group size in mammals
and birds: a critical review of the empirical evidence. Biology
Review,64, 13–33.
Elgar, M. A. & Catterall, C. 1981. Flocking and predator surveillance
in house sparrows: test of an hypothesis. Animal Behaviour,29,
Evans, R. M. 1984. Some causal and functional correlates of
creching in young white pelicans. Canadian Journal of Zoology,
62, 814–819.
Gauthier-Clerc, M., Tamisier, A. & Ce
´zilly, F. 1998. Sleep-vigilance
trade-off in green-winged teals (Anas crecca crecca). Canadian
Journal of Zoology,76, 2214–2218.
Gauthier-Clerc, M., Jaulhac, B., Frenot, Y., Bachelard, C., Monteil,
H., Le Maho, Y. & Handrich, Y. 1999. Prevalence of Borrelia
burgdorferi (the Lyme disease agent) antibodies in king penguin
Aptenodytes patagonicus in Crozet Archipelago. Polar Biology,22,
Gauthier-Clerc, M., Tamisier, A. & Ce
´zilly, F. 2000. Sleep-vigilance
trade-off in gadwall during winter period. Condor,102, 307–313.
Gorman, M. L. & Milne, H. 1972. Creche behaviour in the common
eider Somateria m. mollissima L. Ornis Scandinavica,3, 21–25.
Graf, R., Heller, H. C., Sakaguchi, S. & Krishna, S. 1987. Influence
of spinal and hypothalamic warming on metabolism and sleep in
pigeons. American Journal of Physiology,252, R661–R667.
Hamilton, W. J. 1971. Geometry for selfish herd. Journal of
Theoretical Biology,31, 295–311.
¨gstad, O. 1987. It is expensive to be dominant. Auk,104, 333–
¨gstad, O. 1988. Social rank and antipredator behaviour of willow
tits Parus montanus in winter flocks. Ibis,130, 45–56.
Hunter, S. & Brooke, M. D. L. 1992. The diet of giant petrels,
Macronectes spp. at Marion Island, Southern Indian Ocean.
Colonial Waterbirds,15, 56–65.
Jennings, T. & Evans, S. M. 1980. Influence of position in the flock
and flock size on vigilance in the starling, Sturnus vulgaris.Animal
Behaviour,28, 634–635.
Kharitonov, S. P. & Siegel-Causey, D. 1988. Colony formation in
seabirds. Current Ornithology,5, 223–272.
Lamey, T. C. 1993. Territorial aggression, timing of egg loss, and
egg-size differences in rockhopper penguins, Eudyptes c. chrys-
ocome, on New Island, Falkland Islands. Oikos,66, 293–297.
Le Bohec, C., Gauthier-Clerc, M., Gendner, J.-P., Chatelain, N. &
Le Maho, Y. 2003. Nocturnal predation of king penguins by giant
petrels on Crozet Islands. Polar Biology,26, 587–590.
Le Maho, Y., Gendner, J.-P., Challet, E., Bost, C.-A., Gilles, J.,
Verdon, C., Plumere
´, C., Robin, J.-P. & Handrich, Y. 1993.
Undisturbed breeding penguins as indicators of changes in marine
resources. Marine Ecology Progress Series,95, 1–6.
Lendrem, D. W. 1984. Sleeping and vigilance in birds. II. An
experimental study of the Barbary dove (Streptopelia risoria).
Animal Behaviour,32, 243–248.
Leuthold, B. M. 1979. Social organization and behaviour of giraffe
in Tsavo East National Park. African Journal of Ecology,17, 19–34.
Levy, N. & Bernadsky, G. 1991. Cre
`che behavior of nubian ibex
Capra ibex nubiana in the Negev Desert Highlands, Israe¨l. Israe¨l
Journal of Zoology,37, 125–137.
McCracken, G. F. 1984. Communal nursing in Mexican free-tailed
bat maternity colonies. Science,223, 1090–1091.
Mangin, S., Gauthier-Clerc, M., Frenot, Y., Gendner, J.-P. & Le
Maho, Y. 2003. Ticks Ixodes uriae and the breeding performance
of a colonial seabird, king penguin Aptenodytes patagonicus.
Journal of Avian Biology,34, 30–34.
Martella, M. B., Renison, D. & Navarro, J. L. 1995. Vigilance in the
greater rhea: effects of vegetation height and group size. Journal of
Field Ornithology,66, 215–220.
Martin, P. & Bateson, P. 1993. Measuring Behaviour: An Introductory
Guide. Cambridge: Cambridge University Press.
Montgomerie, R. D. & Weatherhead, P. J. 1988. Risks and rewards
of nest defence by parent birds. Quarterly Review of Biology,63,
Petit, D. R. & Bildstein, K. L. 1987. Effect of group size and location
within the group on the foraging behavior of white ibises. Condor,
89, 602–609.
Pettingill, O. S., Jr. 1960. Cre
`che behavior and individual
recognition in the colony of rockhopper penguins. Wilson Bulletin,
72, 213–221.
Pierotti, R. 1988. Intergenerational conflicts in species of birds with
precocial offspring. Proceedings of the International Ornithological
Congress,19, 1265–1274.
Powell, G. V. N. 1974. Experimental analysis of the social value of
flocking by starlings (Sturnus vulgaris) in relation to predation and
foraging. Animal Behaviour,22, 501–505.
Pulliam, H. R. 1973. On the advantages of flocking. Journal of
Theoretical Biology,38, 419–422.
Pulliam, H. R., Anderson, K. A., Misztal, A. & Moore, N. 1974.
Temperature-dependent social behaviour in juncos. Ibis,116,
Scherrer, B. 1984. Biostatistique. Que
´bec: Gae¨tan Morin Editeur.
Seddon, P. J. & van Heezik, Y. 1993. Chick cre
`ching and
intraspecific aggression in the jackass penguin. Journal of Field
Ornithology,64, 90–95.
Siegel, S. & Castellan, N. J., Jr. 1988. Nonparametric Statistics for the
Behavioral Sciences. New York: McGraw-Hill.
Siegel-Causey, D. & Hunt, G. L., Jr. 1981. Colonial defence behavior
in double-crested and pelagic cormorants. Auk,98, 522–531.
Siegel-Causey, D. & Kharitonov, S. P. 1991. The evolution of
coloniality. Current Ornithology,7, 285–330.
Slater, L. M. & Markowitz, H. 1983. Spring population trends in
Phoca vitulina richardi in two central California coastal areas.
California Fish and Game,69, 217–226.
Spurr, E. B. 1974. Individual differences in aggressiveness of Ade
penguins. Animal Behaviour,22, 611–616.
Stahel, C. D., Megirian, D. & Nicol, S. C. 1984. Sleep and
metabolic rate in the little penguin, Eudyptula minor.Journal of
Comparative Physiology,154, 487–494.
Taylor, R. H. 1962. The Ade
´lie penguin Pygoscelis adeliae at Cape
Royds. Ibis,104, 176–204.
Tamisier, A. & Dehorter, O. 1999. Camargue, Canards et Foulques.
ˆmes: Centre Ornithologique du Gard.
Thompson, K. V. 1998. Spatial integration in infant sable antelope,
Hippotragus niger.Animal Behaviour,56, 1005–1014.
Tourenq, C., Johnson, A. R. & Gallo, A. 1995. Adult aggressiveness
and cre
`ching behavior in the greater flamingo, Phoenicopterus
ruber roseus.Colonial Waterbirds,18, 216–221.
Trivers, R. L. 1972. Parental investment and sexual selection. In:
Sexual Selection and the Descent of Man 1871–1971 (Ed. by
B. Campbell), pp. 136–179. Chicago: Aldine.
Vinuela, J., Amat, J. A. & Ferrer, M. 1995. Nest defence of nesting
chinstrap penguins (Pygoscelis antarctica) against intruders.
Ethology,99, 323–331.
Whittow, G. C. 1976. Regulation of body temperature. In: Avian
Physiology (Ed. by P. D. Sturkie), pp. 146–173. Berlin: Springer-
Williams, G. C. 1966. Natural selection, costs of reproduction and
a refinement of Lack’s principle. American Naturalist,100, 687–
Wilson, E. A. 1907. Aves. British National Antarctic Expedition
1901–1904. Natural History,2, 1–121.
Wittenberger, J. F. & Hunt, G. L., Jr. 1985. The adaptive
significance of coloniality in birds. In: Avian Biology (Ed. by D. S.
Farner, J. R. King & K. C. Parkes), pp. 1–78. New York: Academic
Yeates, G. W. 1975. Microclimate, climate and breeding success in
Antarctic penguins. In: The Biology of Penguins (Ed. by B.
Stonehouse), pp. 397–409. London: University Park Press.
... Young chicks (during weeks 1 and 2) often remained motionless when disturbed by passing humans or stray dogs, whereas older chicks (from week 3) ran far away from the source of disturbance. As in our study, Le Bohec et al. (2005) found that predation attempts by Giant Petrels (Macronectes halli and Macronectes giganteus) on chicks of King Penguin Aptenodytes patagonicus were more successful on small chicks than on medium and large ones. Additionally, we observed that when a disturbance occurred, the older chicks quickly gathered in compact groups and moved away from the colony site by swimming in the water, a strategy that may help reduce predation success. ...
... This increase in group size can reduce predation risk, as many previous studies of gull species have shown (e.g. Tourenq et al. 1995, Le Bohec et al. 2005. The efficacy of the dilution effect on reducing predation is one of the traditional hypotheses for the evolution of cr eching behaviour (Munro & Bedard 1977, Davis 1982, Evans 1984. ...
... A central position within the cr eche may offer better protection against predators, as observed in other cr eching species (e.g. Le Bohec et al. 2005 in King Penguin). Our findings are consistent with the theory that cr eche formation reduces predation risk. ...
Predation is one of the key factors shaping the dynamics of animal populations. In birds, nest loss due to predation can be a significant cause of low reproductive success. Ground‐nesting birds are among the bird groups most susceptible to predation, mainly because their nests are easily accessible to a broad suite of potential predators. For these birds, anthropogenic disturbances can generate changes in nest predation risk by altering their antipredator behaviour and also by altering behaviour of the predator species – i.e. the predator becoming much more aware of predation opportunities due to frequent disturbances and/or motivated to repeat predation attempts when some are successful. To date, most previous studies investigating this have focused on a single effect, either predation or disturbance, on chick survival. It remains unknown how the risk of predation with and without disturbance varies with chick age. In this study, we used behavioural observations to assess how the interaction between predators and disturbance affects predation risk in chicks and how this interacts with chick age. Specifically, we investigated the effect of disturbance caused by humans and stray dogs on the predation of Slender‐billed Gull (Chroicocephalus genei) chicks by Yellow‐legged Gulls (Larus michahellis), and whether this depended on the age of the chicks. Our results revealed that disturbance had a significant positive effect on predation measures of Slender‐billed Gull chicks by Yellow‐legged Gulls, but that this effect was mediated both by disturbance type and the age of chicks. Stray dogs entering the colony had a stronger disturbance effect on chicks than passing humans, increasing predation risk by Yellow‐legged Gulls. Our results also showed that chick age interacts with disturbance type to determine the predation risk. This is probably mediated by chicks’ capacity to escape predation by gathering in a single large crèche that runs into the water when disturbed. To preserve Slender‐billed Gull colonies in one of its few remaining breeding sites in Tunisia, and as gulls tend to react even when the disturbance occurs relatively far from the colonies, it is crucial to (1) restrict human access to dikes and islets where large colonies breed, and (2) construct artificial islets attractive to gulls and inaccessible to stray dogs.
... Colonial species can live in groups of dozens to millions of individuals in close association to procure strong mutual benefits such as stronger defence against predators, resistance against disease or thermoregulation (Le Bohec et al., 2005;Traniello et al., 2002), In these species, avoidance of sick conspecifics is not always observed (Poirotte & Charpentier, 2020;Stockmaier et al., 2020). In fact, resistance or tolerance might even be more efficient (Fairbanks et al., 2015;Traniello et al., 2002). ...
Full-text available
Disgust is an adaptive system hypothesized to have evolved to reduce the risk of becoming sick. It is associated with behavioural, cognitive and physiological responses tuned to allow animals to avoid and/or get rid of parasites, pathogens and toxins. Little is known about the mechanisms and outcomes of disease avoidance in wild animals. Furthermore, given the escalation of negative human-wildlife interactions, the translation of such knowledge into the design of evolutionarily relevant conservation and wildlife management strategies is becoming urgent. Contemporary methods in animal ecology and related fields, using direct (sensory cues) or indirect (remote sensing technologies and machine learning) means, provide a flexible toolbox for testing and applying disgust at individual and collective levels. In this review/perspective paper, we provide an empirical framework for testing the adaptive function of disgust and its associated disease avoidance behaviours across species, from the least to the most social, in different habitats. We predict various trade-offs to be at play depending on the social system and ecology of the species. We propose five contexts in which disgust-related avoidance behaviours could be applied, including endangered species rehabilitation, invasive species, crop-raiding, urban pests and animal tourism. We highlight some of the perspectives and current challenges of testing disgust in the wild. In particular, we recommend future studies to consider together disease, predation and competition risks. We discuss the ethics associated with disgust experiments in the above contexts. Finally, we promote the creation of a database gathering disease avoidance evidence in animals and its applications.
... Through spatial associations, the analysis of the proximity networks brought interesting results: YI females were more spatially central than OI and NN females by staying more often close (contact, 5 m) to other females, even though they did not significantly differ in their connectivity role in the group. Maintaining a central spatial position within the group for YI females promotes the protection of the young from environmental hazards, as suggested in other animal populations [90,91]. ...
Full-text available
Contraception is increasingly used to control wild animal populations. However, as reproductive condition influences social interactions in primates, the absence of new offspring could influence the females’ social integration. We studied two groups of wild macaques (Macaca fascicularis) including females recently sterilized in the Ubud Monkey Forest, Indonesia. We used social network analysis to examine female grooming and proximity networks and investigated the role of infant presence on social centrality and group connectivity, while controlling for the fertility status (sterilized N = 14, intact N = 34). We compared the ego networks of females experiencing different nursing conditions (young infant (YI) vs old infant (OI) vs non-nursing (NN) females). YI females were less central in the grooming network than other females while being more central in proximity networks, suggesting they could keep proximity within the group to protect their infant from hazards, while decreasing direct grooming interactions, involving potential risks such as kidnapping. The centrality of sterilized and intact females was similar, except for the proximity network where sterilized females had more partners and a better group connectivity. These results confirm the influence of nursing condition in female macaque social networks and did not show any negative short-term effects of sterilization on social integration.
... Allofeeding could also benefit offspring by maintaining a larger crèche, or cohort, size (Eadie et al. 1988). Group size brings many benefits, for example, through predator confusion and increased vigilance (Krause et al. 2002) or by providing more opportunities for social learning (Cantor et al. 2020), which could underpin the formation of crèches (i.e., aggregations of offspring from multiple parents; e.g., Munro and Bédard 1977;Velando 2001;Le Bohec et al. 2005). Under the group augmentation hypothesis, we therefore predict that parents with moredeveloped offspring should direct allofeeding toward non-offspring that are in greatest need-those that are less developed. ...
Reproduction is costly. Despite this, evidence suggests that parents sometimes feed unrelated offspring. Several hypotheses could explain this puzzling phenomenon. Adults could feed unrelated offspring that are 1) of their close social associates to facilitate these juveniles’ integration into their social network (the social inheritance hypothesis), 2) potential extrapair offspring, 3) at a similar developmental stage as their own, 4) coercing feeding by begging, or 5) less-developed (to enhance their survival, which could benefit the adult or its offspring; the group augmentation hypothesis). Colonial breeders are ideal for investigating the relative importance of these hypotheses because offspring are often kept in crèches where adults can exhibit allofeeding. Using automated monitoring of replicated captive zebra finch (Taeniopygia guttata) colonies, we found that while parents selectively fed their own offspring, they also consistently fed unrelated offspring (32.48% of feeding events). Social relationships among adults prior to breeding did not predict allofeeding, nor was allofeeding directed toward potential genetic offspring. Instead, adults with more-developed offspring preferentially fed less-developed non-offspring over non-offspring at a similar developmental stage as their own offspring, and this tendency was not explained by differences in begging behavior. Our study suggests that allofeeding is consistent with group augmentation, potentially benefiting adults through colony maintenance or increased offspring survival.
... Remaining with parents is thought to enhance survival (Clutton-Brock, 1991), although the length of this period of post-fledging dependency is highly variable across species [between 5 and 200 days in passerines, see Russell (2000)]. During this time, parents may provide their offspring with food (Davies, 1976), may defend them from predators (Balda and Balda, 1978;Le Bohec et al., 2005) and can limit competition by preventing other animals from accessing the natal territory (Ekman et al., 2000;. Parents can also provide opportunities for independent learning (Heinsohn, 1991), or social learning (Griesser and Suzuki, 2016) through direct teaching (Thornton, 2006;Thornton and Raihani, 2008) and observing parents whilst in spatiotemporal proximity (Griesser and Suzuki, 2017). ...
Full-text available
Many young birds die soon after fledging, as they lack the skills to find food and avoid predation. Post-fledging parental care is assumed to assist acquisition of these vital skills. However, we still lack empirical examples examining the length of time fledglings spend with parents, how they associate during this critical time, or whether such variation in the fledgling dependency period has consequences for the survival and behaviour of young as they navigate their first year of independent life. Here, we make use of observations and radio frequency identity (RFID) logs of visits to supplementary feeding stations to investigate how condition of fledgling hihi (stitchbird, Notiomystis cincta), a New Zealand passerine, predicts dispersal behaviour and tendency to follow parents during their 2 week post-fledging dependence period. We find that thinner fledglings followed their parents more closely in time when visiting feeding stations, compared to fatter siblings (all following ranged from 3 s to 10 min). However, broods in poorer condition tended to disperse from the natal territory up to 6.5 days earlier than broods of fatter fledglings (all dispersed within 14 days). Our results did not find that sociality or survival during the first year of life differed depending on variation in fledgling behaviour; neither following parents closely nor dispersing later predicted each bird's number of associates (degree), or survival over winter. These results suggest that fledglings may be able to compensate for early differences in condition with behaviour, either during the post-fledging dependence period or when independent.
... An example is provided by the crèching behavior of baby penguins, who aggregate to reduce aggression from nonparental adults. [43] Positive pseudoreciprocity occurs when the investment appears to be selfless, but there is a delayed pay-off (exploitation by the investor). Ants farming fungi is a good example of this mechanism. ...
Full-text available
For decades, myxobacteria have been spotlighted as exemplars of social “wolf‐pack” predation, communally secreting antimicrobial substances into the shared public milieu. This behavior has been described as cooperative, becoming more efficient if performed by more cells. However, laboratory evidence for cooperativity is limited and of little relevance to predation in a natural setting. In contrast, there is accumulating evidence for predatory mechanisms promoting “selfish” behavior during predation, which together with conflicting definitions of cooperativity, casts doubt on whether microbial “wolf‐pack” predation really is cooperative. Here, it is hypothesized that public‐goods‐mediated predation is not cooperative, and it is argued that a holistic model of microbial predation is needed, accounting for predator and prey relatedness, social phenotypes, spatial organization, activity/specificity/transport of secreted toxins, and prey resistance mechanisms. Filling such gaps in our knowledge is vital if the evolutionary benefits of potentially costly microbial behaviors mediated by public goods are to be properly understood. Myxobacterial predation is an oft‐cited exemplar of microbial cooperation, mediated by secretion of antimicrobial public goods into the shared commons. However, evidence for cooperation is singular, while diverse mechanistic features of predation suggest evolved selfishness. Here, definitions of cooperativity are clarified and it is hypothesized that myxobacterial predation is not actually cooperative.
... Climate change may actually play a more direct role in the complex life cycle of the King Penguin by controlling the extent to which King Penguin chicks need to crèche. Studies have demonstrated that King Penguin crèching behavior increases in colder and wetter weather (LeBohec et al. 2005) presumably because large breeding aggregations allow chicks to stay warm through the austral winter. Climate change in this region is predicted to cause warmer (though wetter) winters (Summerhayes 2009;Constable et al. 2014;Gutt et al. 2015), which may reduce the required crèche size and facilitate more successful colonization of new colonies. ...
Full-text available
While dramatic increases in populations of King Penguins (Aptenodytes patagonicus) have been documented throughout their range, population changes on the island of South Georgia have not been assessed. We reconstructed time series of population size for six major colonies across South Georgia using historical data stretching back to 1883 and new population estimates derived from direct on-the-ground censuses and oblique, high-resolution digital photographs. We find evidence for a significant increase in the population of King Penguins at all colonies examined over the 124 years of available survey data. We discuss our findings in the context of four established hypotheses explaining King Penguin population growth: (1) favorable changes in the pelagic food web; (2) climate forcing; (3) greater availability of breeding habitat; and (4) the cessation of harvesting. While we do find evidence that glacial retreat may have increased suitable breeding habitat at some colonies and facilitated population expansion, glacial retreat is not associated with all of South Georgia’s growing populations. Local anomalies in sea surface temperature have increased in parallel with King Penguin population growth rate, suggesting that climate forcing may contribute to colony growth, but a complete explanation for the island’s rapidly growing King Penguin population remains unclear.
... Unlike many penguin species, they remain almost the full year in the colony (Otley et al. 2007;Bost et al. 2013). Their overwinter survival depends on several factors, including predation, adverse weather conditions and feeding frequency of their parents (Descamps et al. 2005;Le Bohec et al. 2005;Otley et al. 2007). The beginning of the fledging period is in November, and then, they leave to the sea (e.g. ...
King penguins (Aptenodytes patagonicus) have a circum-subantarctic range though recently, pairs breeding in Antarctica were reported. In a scenario of environmental variability as it is recorded in Antarctic Peninsula and adjacent islands, one ecological response registered in penguins was the shift in its distribution and breeding range probably due to the increment in the areas available to breed and/or feed. In the 2014–2015 season, the first king penguin chick was registered at Stranger Point (62 S. 25 de Mayo/King George Island), which remained alive until 5 months old. This record represents the southernmost birth of this species and the fourth consecutive breeding attempts in this site. This provides further evidence of a possible consolidation of a new breeding site at South Shetland Islands and thus the southward expansion of the bio-geographic range. Moreover, it suggests that both terrestrial and marine environmental conditions were favourable for king penguins, at least until the beginning of the créche stage. Nevertheless, an increase in the number of breeding pairs is essential to ensure the survival of chicks and enable the colonization.
Full-text available
Die Gesetze der Physik beschreiben die unbelebte Welt mit großer Genauigkeit und werden beständig verfeinert, um sie noch detaillierter zu beschreiben und zu verstehen. Die Anwendung dieser physikalischen Gesetze ist jedoch nicht auf die passive Materie beschränkt. Zum Beispiel die Methoden der statistischen Physik, die beschreiben, wie die Eigenschaften der Materie aus der Wechselwirkung von Atomen oder Molekülen entstehen, können auf biologische Systeme von Tiergruppen übertragen werden. In dieser Arbeit werden die Pinguinkolonien der beiden Vertreter der Gattung Aptenodytes untersucht — der Königs- (Aptenodytes patagonicus) und der Kaiserpinguin (Aptenodytes fosteri). Diese Vögel bilden während der Brutzeit Kolonien, die oft aus Tausenden von Individuen bestehen, und sind daher ideal für die Untersuchung von emergenten Phänomenen, die bei der Interaktion zahlreicher Individuen auftreten. Während die meisten Pinguinarten ortsfeste Nester bauen, was keine Dynamik in Brutkolonien zulässt, tragen die Aptenodytes Pinguine ihr einzelnes Ei auf ihren Füßen, und so bleiben die Kolonien auch während der Brut dynamisch. Daher wurden diese beiden Arten ausgewählt, um zu untersuchen, wie kollektive Dynamik mit physikalischen Gesetzen beschrieben werden kann. Diese Arbeit untersucht das Verhalten beider Pinguinarten anhand von Zeitrafferaufnahmen aus Observatorien in der Antarktis und den subantarktischen Inseln. Im Rahmen dieser Arbeit wurden spezielle Software-Werkzeuge entwickelt, um die aufgenommenen Bilder auszuwerten und die Struktur und Dynamik von Königs- und Kaiserpinguinkolonien zu analysieren. Interessanterweise weisen die Kolonien beider Arten ähnliche Strukturen auf wie man sie in physikalischen Systemen finden kann. Während Brutkolonien von Königspinguinen eine flüssigkeitsähnliche Ordnung aufweisen, die über längere Zeiträume stabil ist, zeigen die Kaiserpinguine beim Huddling kristalline Strukturen, die hochdynamisch sind. Diese Arbeit analysiert die Struktur der Brutkolonien von Königspinguinen anhand der Positionen von Tausenden von Königspinguinen aus Luftbildern. Die Charakterisierung dieser Struktur durch die radiale Verteilungsfunktion zeigt auffallende Ähnlichkeiten mit zweidimensionalen Flüssigkeiten, wobei jeder Brutplatz einem Atom der Flüssigkeit entspricht. Brütenden Pinguine, bei denen der Partner gerade in der Kolonie anwesend ist, besetzen in dieser zweidimensionalen Flüssigkeit nur einen Gitterpunkt, genau wie ein einziges Bruttier. Dennoch zeigt die Analyse, dass zwischen den Brütenden eine 25%ige Variation des “Pick”-Radius, d.h. der Abstoßung zwischen Pinguinen, besteht. Die Stärke der Abstoßung zwischen den Pinguinen hängt folglich stark davon ab, wie aggressiv ein brütendes Tier seinen Platz verteidigt. Die Brutplätze sind während der gesamten Brutzeit sehr stabil, was darauf hindeutet, dass die Flüssigkeitsstruktur in der Brutkolonie in einen glasartigen Zustand gekühlt wurde, was als Kompromiss zwischen hoher Dichte und Flexibilität angesehen werden kann, um auf äußere Störungen, z.B. durch die Kolonie gehende Robben, zu reagieren. Wenn die Küken der Königspinguine geschlüpft und alt genug sind, um längere Zeit allein in der Kolonie zu verbringen, bilden sie auch kollektive Strukturen. Diese Crèches, wie sie genannt werden, sind dichte Gruppen von Küken, im Gegensatz zu den weniger dichten Strukturen brütender Erwachsener. Diese Arbeit zeigt eine mögliche Erklärung dafür auf, wie sich diese Cluster bilden: Wiederkehrende Angriffe von Raubvögeln auf ungeschützte Küken, die vor dem Raubtier fliehen, induzieren Clusterbildung, auch wenn keine attraktiven Wechselwirkungen zwischen den Küken vorhanden sind. Im Gegensatz zu Königspinguinen haben Kaiserpinguine keine Territorialität und können daher dichte, kristalline Strukturen in ihren Huddles bilden. Diese Huddles sind unerlässlich, um Energie zu sparen, wenn Kaiserpinguine während des kalten und stürmischen antarktischen Winters brüten. Die Huddles sind jedoch nicht statisch wie die brütenden Königspinguine, sondern zeigen kleine periodische wellenartige Bewegungen. Die Entstehung und Verbreitung dieser Bewegungen werden in dieser Arbeit anhand eines Modells, das von Beschreibung von Verkehrsstaus abgeleitet wurde, analysiert. Die Analyse zeigt, dass diese kleinen Bewegungen im Laufe der Zeit zu einer großflächigen Translokation, Reorganisation und Verdichtung des Huddle führen und kleinere Huddle zusammenwachsen lässt. Das Modell zeigt in Übereinstimmung mit den Daten, dass jeder Pinguin im Huddle die wellenartigen Bewegungen auslösen kann. Die statistischen Schwankungen der einzelnen Auslöseereignisse solcher Wellen werden durch die große Anzahl von Tieren im Huddle vermindert, was zu regelmäßigeren Intervallen in größeren Huddels führt. Runde, rotierende Huddle-Strukturen, die auch in dieser Arbeit auch detailliert analysiert werden, bieten einen noch besseren Schutz gegen die Umwelt, da alle Pinguine nach innen zeigen und ihre empfindliche Vorderseite vor der Kälte schützen. Das vorgestellte Modell sagt voraus, dass die Geschwindigkeit der Pinguine linear mit dem Abstand von der Mitte des Huddle zunimmt, was zeigt, dass sich die Huddles wie starre Platten drehen. Die Winkelgeschwindigkeit der Huddles ist indirekt proportional zum Durchmesser der Huddles, was durch die Verfolgung von Pinguinen am Rand der Huddle in Zeitrafferaufnahmen bestätigt wird. Diese Ergebnisse vertiefen unser Verständnis wie sich diese einzigartigen Vögel in lebensfeindlichen Umgebungen fortpflanzen können. Die neuen Modellbeschreibungen können helfen vorherzusagen, wie die Kolonien auf Veränderungen dieser fragilen Ökosysteme durch globalen Wandel oder menschliche Interaktion reagieren.
The megafauna (Greek μεγα: great; Latin fauna: animal life) of Antarctica is defined by absence. Two classes of vertebrates, reptiles and amphibians, are missing from the continent and its surrounding waters, and Antarctica has lacked true land vertebrates since dinosaurs last roamed the continent in the late Cretaceous. The ocean is the foundation of all vertebrate life in Antarctica, and none of its native birds and mammals can survive permanently in the continent's frigid, white interior. Antarctic vertebrates are all classified as marine and ultimately derive their food from the sea. Unlike in much of the Arctic, the harsher climate of Antarctica does not allow for significant plant growth, and no vertebrate herbivores exist. Antarctica's long isolation from other landmasses has resulted in the absence of surface predators such as the polar fox Alopex lagopus or polar bear Ursus maritimus, an important distinction between Antarctic and Arctic habitats. Antarctica and the Southern Ocean present some of the most challenging environmental conditions on Earth, including extreme cold, wind, dryness, radical seasonal changes in photoperiod, and extensive ice cover. But Antarctica also offers tremendous opportunity because it is a continent free of terrestrial mammalian predators, and the Southern Ocean surrounding the Antarctic continent includes some of the most productive marine habitats in the world. © Springer International Publishing Switzerland 2015. All rights are reserved.
Full-text available
Captive King Penguin (Aptenodytes patagonica) chicks can fast for 5 months during the subantarctic winter with a 70% decrease in body mass. To investigate the adaptive value of this remarkable resistance to starvation, we compared captive chicks with free-ranging chicks in their colony at Possession Island, Crozet Archipelago. The chicks in the colony, from mid-April to beginning of September (i.e. all winter) were fed only every 39 days by their parents; some were not fed at all. In spring (October-December) the surviving chicks were fed every 6 days, and their growth was completed. Overall chick mortality in the colony during the winter and subsequent spring was about 50%. Mortality was highest in October, 6 months after the beginning of the winter, and may be attributed mainly to starvation. The decrease in body mass in the free-ranging chicks was remarkably similar to that for captive birds. In both groups, three periods were characterized according to the observed changes in the daily decrease in body mass per unit body mass (dm/mdt): dm/mdt dropped during the first period (I) of 5-6 days, was minimum and steady during period II, which lasted about 4 months, and increased in period III. Blood analysis of the captive chicks indicated the three periods correspond to modifications in protein breakdown. An initial decrease in uricacidemia indicates period I is a short period of transition, marked by a decrease in protein breakdown. In period II a minimum and constant uricacidemia, in parallel with a progressive increase in ketonemia, indicates efficient protein sparing while most of the energy is derived from lipids. Period III is critical because, from a rise in uricacidemia concomitant with a decreasing ketonemia, proteins are no longer spared. The extreme resistance of King Penguin chicks to starvation in winter may be explained partly by the ability to spare proteins for several months (period II). It occurs at a growth stage when the parents' feeding visits are rare. Other laboratory and field investigations of birds suggest that the means by which a wide variety of domestic and wild species adapt to fasting also may be interpreted in terms of three periods corresponding to changes in protein breakdown.
Sleep, circadian torpor, and hibernation constitute an electrophysiological continuum. When energy reserves decline, energy can be conserved by increasing the duration of sleep or by lowering sleeping body temperature proportionally to remaining reserves. Sleep in pigeons is controlled by light-dark cycles through their transduction to internal melatonin rhythms.
Sea-birds fast when breeding ashore and, therefore, breeding success largely depends upon body fuels accumulated at sea and food stored in the stomach for chicks. By weighing breeding king penguins Aptenodytes patagonicus, the authors demonstrate seasonal differences in the daily gain in body mass and duration of foraging trips of breeders at sea. It takes longer for the breeders to obtain food when marine resources are decreasing. The overall gain in body mass of the birds at sea is unchanged. However, they accumulate larger body fuel reserves, which therefore increases their energetic safety margin at predictable times of lower food availability but reduces food brought back to the chicks. Variations in the duration of sojourns into the colony, when penguins come independently to feed the chicks, can be attributed to the stages of the breeding cycle. -from Authors