The movements of gentoo penguins pygoscelis papua from ardley island, antarctica
ORIGINAL PAPER R.P. Wilson · B. Alvarrez · L.Latorre · D. Adelung B. Culik · R. Bannasch The movements of gentoo penguins Pygoscelis papua from Ardley Island, Antarctica
Received: 1 October 1997 /Accepted: 3 February 1998
Abstract The movements of gentoo penguins (Pygoscelis papua) in Antarctica were studied by equipping a total of 37 birds captured at Ardley Island, South Shetlands between December 1991 and
factors. Birds are most limited during breed when brood
May 1996 with position-determining devices. Information on area
constraints necessitate parents to repeatedly associate with
usage was derived from 20 of' these devices and covered the
the nest site to incubate the eggs or to feed young. Two
incubation period (N = 3 birds), the chick-rearing period (N = 14
primary determinants of the marine areas birds can potentially
birds) and the over-wintering period (N = 3 birds). During
exploit are the length of time that birds can be absent from the
incubation birds only ventured further than 50 km from the colony
breeding site and their travelling speed (e.g. Williams and
20% of the time and no individual ranged further than 200 km from
the colony. In contrast, no individuals attending chicks ranged
Although penguins are the most aquatic of all birds, they are
further than 16 km from the colony. During winter the maximum
particularly restricted in the areas they can exploit compared to
distance ranged from the colony was 268 km. Mean distances
volant species because the only travel slowly (Costa 1991;
between the birds and the colony were 80, 81 and 127 km.
Wilson 1995). Penguins can be broadly divided into two groups
Individual birds tended to associate with one spot, making short (10
depending on their capacity for movement. Some species,
day) forays away before returning to nodal areas. The ranging
such as the macaroni penguin Eudyptes chrysolophus, are
capacity of gentoo penguins appears considerably less than that of
migratory during the non-breeding season, while others, such
sympatric congeners and may reflect the ability of gentoo penguins
as the African penguin Spheniscus demersus, are considered
to dive deeper and thus exploit prey not accessible to congeners.
sedentary (Croxall and Davis, in press). Migratory species
have a tendency to forage further of shore than sedentary
species during the breeding season (Croxall and Davis, in
press) and by so doing reduce inter-specific competition for
Introduction
prey with species foraging inshore (e.g. Cooper et al. 1990;
Hindell et al. 1995 ). Why gentoo penguins (Pvgoscelis papua)
The extent to which seabirds can exploit various areas of the
are generally thought to be sedentary during the non-breeding
marine environment is dependent on a number of
season (for summary see Williams 1995) while congeneric
Adélie (Pygoscelis adéliae) and chinstrap (Pygoscelis antarctica) penguins are migratory is unclear (Davis et al.
1996; Wilson et. al. 1998), as is why, even during the breeding
)·D. Adelung ·B. Culik
season, gentoo penguins forage much closer inshore than
Institut für Meereskunde, Düsternbrooker Weg 20,
either congener (cf. Lishman 1985; Trivelpiece et al. 1987;
Wilson 1995). In areas of breeding simpatry the diets of the
e-mail ifm@ifm.uni.kiel.de; Fax 0431-555876
three species are very similar (Trivelpiece et al. 1987 and
Despite the general conclusion that gentoo penguins are
Instituto Antártico Uruguayo, 8 de Octubre,
sedentary for the whole year, the published data considering
the movements of these birds are equivocal (see Bost and
Jouventin 1990 and references therein) because, to our
knowledge, no study has documented in detail distribution at
Technische Universität Berlin, FG Bionik
sea in birds from known breeding sites (as has been done, for
und Evolutionstechnik, Ackerstraße 71-76,
(see e.g. Sadleir and Lay 1990; Davis and Miller 1992; Davis et
respect to sun angle. These factors are discussed in detail by
al. 1996). To achieve this, foraging individuals must be fitted with
Wilson et al. (1995) as well as techniques used to minimise such
some sort of position-determining equipment (see e.g. Trivelpiece
errors. Generally, such errors are non-systematic so that they
et al. 1986). Rather, gentoo penguin area exploitation has been
result in a non-biased scatter around the true position.
deduced during the breeding season by consideration of foraging
All positional information derived from the global location
trip length and swim speeds (e.g. Adams and Wilson 1987;
sensors was so treated that data derived from all birds from the
Trivelpiece et al. 1987; Wilson et al. 1989) or been based on
incubation period were lumped together as were data derived
records of the presence or absence of the birds at breeding sites
from over-wintering birds. A frequency matrix was then produced
over winter (Bost and Jouventin 1990; Williams 1995).
for each time period. The matrix resolution 0.25º (latitude by longitude) squared and all were converted to a percentage time
We determined the movements of gentoo penguins from the
per 0.25° square for graphic representation. In ord er to examine
South Shetland Islands during three main phases of the year:
ice-cover conditions in areas where the penguins were
incubation, chick-rearing and overwintering using dead reckoning
determined to have been, a search was conducted for satellite
techniques (Wilson et al. 1993) and global location sensors
data on the worldwide web with emphasis being placed on
(Wilson et al. 1992, in press; Hill 1994) The aim of the study was
to determine the space utilisation by gentoo penguins during different stages of their life-cycle and, where possible, to
compare the areas used by gentoo penguins with those used by congeneric Adélie and chinstrap penguins.
The vectorial loggers were based on the DK101 logger series (Driesen and Kern, Bad Bramsted, Germany) which recorded
swim speed (via a paddle wheel), swim heading (using a compass whose orientation was measured using two Hall
sensors) and dive depth (8 bit resolution for the range0-200 m) at
intervals of 10 or 15 s. The unit had a memory of 64 bytes and was powered by two DL1/3 N lithium batteries. The electronics
were potted in water-proof resin so that the whole unit was hydrodynamically styled (cf. Bannasch et al. 1994; Culik et al.
Materials and methods
1994), weighed 200 g (in air) and had maximum dimensions of
Field work was conducted at Ardley Island (62.22°S. 58.87°W),
140 (length) X 58 (width) X 28 mm (height). More details of this
South Shetlands, Antarctica between December 1991 and
system are given in Wilson et al. (1993).
November 1996. Adult gentoo penguins were caught and
Devices were programmed and recorded data accessed by a
equipped with automatic position-determining devices to
laptop computer linked to the loggers by an interface.
elucidate the area utilisation of these birds during incubation,
Downloaded data were treated by the programme ROUTE
chick rearing and overwintering. Two types of positioning device
(Jensen Software Systems, Kiel, Germany), which integrates all
were used: global location sensors and vectorial (dead-
speed, swim direction and depth data together in vectorial
calculations so as to reconstruct the swim routes of the equipped birds (Wilson et al. 1993). Errors in vectorial calculations may
vary according to drift induced by currents. Overall error in foraging tracks could be assessed by exampling the difference in
calculated end point with respect to the known start point (since
the point of entry into and exit from the water of the birds is known). Maximum differences were never more than 600 m so
The global location sensors were based on the pillbox logger
positional error from vectorial estimates is unlikely ever to have
(Driesen and Kern, Bad Bramsted, Germany) and consisted of a
exceeded this value. All derived foraging tracks were combined in
light sensor covered by a blue filter (see Wilson et al. in press)
a single matrix to derive the percentage total time spent by the
set to record light intensity in a 128 kbyte memory once every
birds per square kilometer within the foraging area.
128 s. Resolution was a 8 bit and the dynamic range to which the unit responded was between approximately 0.1 and 25 Ix. The
global location sensors were powered by two 3 V lithium cells
and all electronics were encased in transparent resin. The fully encapsulated unit was streamlined according to suggestions
made by Bannasch et al. (1994), weighed 42 g and had maximum dimensions of 125 X 38 X25 mm. Recovered data
Between 20 and 21 October 1995, ten gentoo penguins engaged
were treated using the programme LOCATE (version 2.0 -
in nest building and courtship activities were equipped with global
Jensen Software Systems, Kiel, Germany), which determines the
location sensors. These units were attached to the centre line of
timing of dawn and dusk (considered to occur when the sun is
the lower back, as recommended by Bannasch et al. (1994), so
4.9° below the horizon) as a function of Greenwich Mean Time
as to minimise drag, using Tesa tape and two-component rubber
and Julian date so that daylength and the timing of local midnight
glue (Deutsche Schlauchbootfabrik, Eschershausen, Germany)
and midday can be used to calculate geographic position (for
(for details method 4 in Wilson et al.1997) The total time from bird
details see Wilson et al. in press). Dawn and dusk are recognised
capture to release took between 10 and 20 min. The birds were
when the units record that the light intensity has passed a certain
then released at their nest sites. Between 11 and 20 December
threshold, this threshold corresponding to a particular sun angle
1995, a search was made for the equipped birds. When located,
(nominally -4.9°). The thresholds corresponding to our specified
the global location sensors were removed by cutting the ends of
sun elevation angles were determined during calibrations made
the feathers. At this time bird body mass was measured and the
in Antarctica, Germany and Uruguay. Accuracy of these units is
status of the nests of the equipped birds noted.
estimated to be better than 40 km for class 1 fixes if no snow
covers the sensor (Wilson et al. 1995). Snow can theoretically cover the sensor for short periods though birds tend to shake it
off and, where this occurs over dawn or dusk, it can compromise the quality of fixes so that accuracy may be ± 80km. Numerous
other factors compromise the quality of fixes obtained by global
Between 29 December 1991 and 19 January 1992, 14 gentoo
location sensors; among these are cloud cover, extensive diving
penguins tending small chicks were equipped with vectorial
behaviour around dawn and dusk and sensor orientation with
in the case of incubating birds, the units were attached to the centre line of the lower back, but this time were held in place solely by Tesa tape (for details, see method 1 in Wilson et al. 1997). After return to the nest, birds were left to undertake a minimum of one foraging trip before the units were removed. Over-wintering Between 6 and 7 May 1996, 13 post-moult adult gentoo penguins were caught and restrained according to methods described in Wilson et al. (1998) while they were equipped with global location sensors. These units were attached in the same way as the devices used to determine the position of birds at sea during the incubation period. Here, however, the total time from bird capture to release took between 20 and 65 min. the longer times being mainly due to dry at the low temperatures experienced at that time. The birds were then released to allow them to go to the sea. During October and November 1996, searches were conducted to recover device-equipped birds that had returned to Ardley Island to breed. Recovered penguins were restrained in the same way as before and the device removed by cutting the ends of the feathers. Devices were then transported to Kiel, Germany, pending analysis. Results Incubation All ten device-equipped birds were recovered, the mean mass of recovered birds being 5.69kg (SD 0.43). All birds appeared in
good condition and were breeding successfully: eight nests
contained two chicks, one nest contained one chic and one nest
Fig. 1a-c Frequency of occurrence of the direct distance between monitored gentoo
one chick with one egg. Chick ages were determined to be
penguins and their breeding colony during: a the incubation period (derived from 3
between 1 and 5 days. Only three of the ten global location
birds were fixes were derived twice per 24 h for each individual giving a total of 317 fixes evenly distributed among individuals); b the chick rearing period (derived from 14
sensors produced high quality data that could be used for
birds where fixes were derived once every 15 s that they were at sea); c the over-
determination of bird position. This was due, in three cases, to
wintering period (derived from 3 birds were fixes were derived twice per 24 h for each
data corruption caused by failing batteries or, in four cases, water
individual giving a total of 618 fixes evenly distributed among individuals)
entering the devices. A total of 622 positional fixes was obtained.
Between October and December, during the courtship and
incubation period, the monitored gentoo penguins spent most
5 km (Fig. 2b). This means that no bird even ranged far enough
time within 50 km of the colony (Fig. 1a). Only about 20% of time
to move out of Maxwell Bay, either into the Bransfield Strait or
were birds at distances in excess of 50 km and no individual ever
ventured further than 200 km. Excepting the area close to the
colony, the sea areas most used by the birds were the Bransfield
Strait, between King George Island and the Antarctic Peninsula
and the Drake Passage, immediately adjacent to King George
Of the 13 gentoo penguins equipped, 6 were recovered during
October and November 1996. All recovered birds appeared in
good condition and were engaged in nesting behaviour. Three of
the global location sensors had logged data, the other units
having suffered unacceptable voltage drops so that the data were
All 14 birds equipped with vectorial loggers foraged successfully
corrupt. The three viable global location sensors had all logged
and continued feeding their chicks. Units were covered after a
data until 17 August 1996 when the memories were full. Between
mean of 2.7 days (SD 1.7) and all data could be used for the
May and August all three gentoo penguins had occupied an area
calculation of bird position. During December and January, no
west of (Fig. 2c) and ranged up to a maximum distance of 268
equipped individual foraged further than 16 km from the island
km from Ardley Island (Fig 1c). Mean distances from Ardley
(Fig. 1b), with the vast majority of the time being spent within
Fig. 2a-c Topographic plot (from Surfer) of the positions of the tracked gentoo penguins: a during the incubation period (the contour lines refer to the percentage time spent per 05º2 (lat. X long) summed over the whole of the incubation period; b during chick rearing (the contour lines refer to the percentage time spent per km2 summed over the whole of the chick-rearing period where the min. contour is 1 and increments are 1%); c during wintering period (the contour lines refer to the percentage time spent per 05º2 (lat. X long) summed over the whole of the winter period over which the birds were tracked)
et al. 1996) Device-induced detrimental effects are most likely to make themselves apparent over long intervals so that the
equipment of our gentoo penguins for the winter period for 7
months must be regarded as a severe test of the acceptability of
the devices by the birds. That we recovered 6 of the total of 13
equipped birds, all in apparently good condition, and all engaged in nesting behaviour, indicates that our devices are apparently
well tolerated by the birds. No equipped bird was sighted in poor
(SD 47, N = 206) 81 km (SD40, N = 206) and 127 km (SD53, N =
condition. The failure to sight the' other eight equipped individuals
206). Each bird tended to spend most time within a particular
is most likeky due to the fact that we equipped some moulting
area, apparently engaging in forays away from this area lasting
gentoo penguins at Ardley Island that originated from one of the
Discussion The attachment of external devices to penguins has been shown to affect aspects of their behaviour and energetics (see e.g. Wilson and Culik 1992; Culik et al. 1994; Croll
numerous colonies round King George Island and that
distances of up to 125 km away from the breeding sites, although
consequently returned to these colonies at the onset of the
the variance was high. Gentoo penguins, almost wherever they
breeding season. (In support of this, we received reports that at
occur, are considered to have relatively restricted foraging areas.
least two gentoo penguins carrying devices had been sighted at
Using distance meters, Adams and Wilson (1987) calculated a
the Jubany colony, some 18 km away from Ardley, in November
maximum foraging range of 35 km for gentoo penguins tending
chicks at Marion Island (46º54'S, 37º45'E). These data were
subsequently re-worked by Wilson et al. (1989), to correct for
vertical distance acquired due to diving, to derive a foraging
Area exploitation during the breeding season
Why should gentoo penguins, in areas of sympatry with Adélie
and chinstrap penguins, consistently be able to forage closer
inshore than congeners and, in so doing, avoid incurring
Earlier calculations of gentoo penguin foraging range based on
travelling costs while at the same time exploiting similar prey?
swim speeds and time absent from the colony ranged between 3
Trivelpiece et al. (1987) suggested that gentoo penguins might
and35 km (Adams and Wilson 1987; Trivelpiece et al. 1987;
habitually dive deeper than either Adélie penguins or chinstrap
Wilson et al. 1989). Studies where birds were equipped with radio
penguins and thus be able to exploit prey closer to their colonies
transmitters showed that gentoo penguins breeding in colonies
that is not available to either congener. There is a positive
bordering Admiralty Bay (62.2º S, 58.8º W) rarely moved outside
correlation between maximum dive depth and body mass in
this area during chick rearing. Our work confirms that gentoo
penguins (Wilson 1995). However, the capacity to exploit deeper
penguins from King George Island during chick rearing do indeed
prey not only depends on the ability of birds to reach the relevant
seem to forage almost exclusively close inshore at this time.
depths, but also to be able to do this consistently and to remain
During incubation, these birds have a more extended foraging
for extended periods at those depths in order to feed. Gentoo
range, but, even so, apparently spend around 80% of their time
penguins do indeed have greater diving capacities than either
within 50 km of the colony. This situation contrasts with that
conspecific (cf. e.g. Lishman and Croxall 1983; Whitehead 1989;
found in the Adélie penguins where males take the first shift at
Naito et al. 1990; Williams et al. 1991; Wilson et al. 1991A,b;
incubation, which lasts some 14-17 days (Sladen 1958; Davis
Bengston et al. 1993). Wilson (1995) suggested that there was
and Miller, 1982), during which time the females may range up to
little inter-specific difference in the frequency of maximum dive
186 km from the colony (cf Davis et al 1988; Sadleir and Lay
depth of pygoscelids breeding at Ardley Island. Re-evaluation of
1990; Kerry et al. 1995). Incubation shifts by chinstrap penguins
these data suggests, however, that at depths in excess of 10 m,
are markedly shorter, generally varying between 6 an d10 days
gentoo penguins dived more often to specific depths than either
(Williams 1995) so the foraging range is likely less than that of
congener in seven out of nine case, supporting Trivelpiece et al.'s
Adélie penguins although to our knowledge no telemetric studies
(1987) hypothesis. This does not mean, however, that the birds
necessarily travel overall less far. We analysed the distributions
Trivelpiece et al. (1987) calculated that gentoo penguins
of maximum depth data presented by Wilson (1995) to determine
tending for chicks at King George Island would have a likely
the distance travelled vertically during diving (see Wilson et al.
foraging range of 17 km (max. 24 km), considerably less than
1989) and found that, over 100 typical dives, Adélie penguins
either sympatric Adélie penguins (likely range 43 km, max. 50
foraging from Ardley cover a vertical distance of 4.1 km, chinstrap
km) or chinstrap penguins (likely range 27 km, max. 33 km).
penguins 3.3 km while gentoo penguins travel 5.2 km. Thus, in
Trivelpiece's values for chinstraps are somewhat higher than
diving deeper, gentoo penguins travel vertically 27% more than
those calculated by Bengtson et al. (1993) of 3-20 km for Seal
Adélie penguins and 58% more than chinstrap penguins, which at
Island. Nonetheless, Trivelpiece et al.'s (1987) contention that
least partially compensates for the apparent benefits of the
gentoo penguins at King George Island forage closer inshore
than do either Adélies or chinstraps is supported by our results
and those presented by Wilson (1995). Sympatrically brooding
Adélies and chinstraps from Ardley Island may forage over 30 km
away from the colony; this is something that the gentoo penguins
Area exploitation during the non-breeding season
The foraging ranges of pygoscelid penguins in other areas of
Antarctica may vary substantially from those determined for King
Absences at sea of gentoo penguins during the non-breeding
George Island. For example, Lishman (1985) calculated that
season become longer in the more southerly regions of the
Adélie and chinstrap penguins during the chick-rearing period
range, with birds from the Antarctic Peninsula being absent from
from Signy Island (60º43'S, 45º36'W) have foraging ranges of 83-
colonies for periods in excess of 2 months (cf. Bagshawe 1938;
119 km and 66-132 km, respectively. Kerry et al. (1995)
determined, using satellite telemetry that Adélie penguins tending
Our study demonstrates that gentoo penguins from King
George Island apparently do not fit into the classic
scheme as either truly migratory or sedentary birds. The
during the austral winter of 1996 (July/August 1996; data from
maximum distance between any bird and the breeding site of 268
http:llmullara.met.unimelb.edu.au). Our few results would indicate
km is a fraction of that determined for chinstrap penguins from
that gentoo penguins from Ardley Island during winter exploit an
Ardley Island, which may move in excess of 1000 km away from
environment that is, with respect to ice coverage at least,
their breeding colonies during the non-breeding season (Wilson
somewhat intermediate to that exploited by Adélie and chinstrap
et al. 1998). Although there are no data on over-winter
penguins. Should this prove to be a general phenomenon, the
movements of Adélie penguins from Ardley Island, birds from
exact degree to which the different ice-cover conditions
other areas may move similar long distances (Davis et al. 1996).
selectively favour each of the three pygoscelid penguins will be
Despite this, the mean bird-island distance of around 100 km for
an exciting, and difficult, topic for future research.
gentoo penguins is substantial for a flightless sea bird and is
certainly well outside the normal foraging radius for breeding
Acknowledgements supported Deutsche
birds (see above). The literature on gentoo penguins sightings at
Forschungsgemeinschaft with a grant to Dieter Adelung, as well as by the Instituto Antártico Uruguayo. We are grateful to Mandy Kierspel for help with the
sea (cf. Watson et al. 1971; Enticott 1986) indicates that birds are
analysis, as well as to Doris Abele for her constant, behind the lines, chivying
rarely sighted far from breeding point (cf. Voisin 1979; Enticott
when things seemed intractable.
1986), demonstrating that they are capable of long-distance
movements in the same way as their congeners. We conclude
from this study that there are grounds for believing that gentoo
penguins may undertake appreciable migrations in certain areas
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Journal of Ethnopharmacology 75 (2001) 141 – 164Should we be concerned about herbal remedies Department of Biology , Washington Uni 6 ersity , Box 1137, St . Louis , MO 63130-4899, USA Received 24 November 2000; received in revised form 5 December 2000; accepted 5 December 2000 Abstract During the latter part of this century the practice of herbalism has become mainstream throughou
Como en un experimento pavloviano, basta que alguien diga “despenalización” para que los actores interesados se lancen al ruedo a decir sus argumentos. Los actos reflejo tienen eso: son siempre iguales. ¿Y qué decir que no sea un déjà vu repetido hasta el hartazgo? La semana que termina lo hace con médicos sospechosos de maltrato a mujeres sospechosas de practicarse abortos y con otro m