Diving behaviour of Adélie penguins ( Pygoscelis adeliae ) at Dumont D'Urville, Antarctica: nocturnal patterns of diving and rapid adaptations to changes in sea-ice condition

We studied the foraging areas and diving depths of male emperor penguins Aptenodytes forsteri raising chicks at Pointe Géologie, Adélie Land, in relation to bathymetry and sea-ice conditions during the first foraging trip after incubation in August 1996 and 1997. Combining satellite-tracking and dive-recording devices on the same penguins allowed individual dives to be localised and related to water depth. The penguins mostly dived in zones less than 300 m deep, where they performed 50% of their dives and spent 54% of their bottom time near the sea floor, on average. Analyses including bathymetry and sea-ice cover for the 2 years suggest that after leaving the colony the penguins targeted the nearest available, fast-ice free shallow shelf waters (< 300 m). Once in these areas, the penguins foraged by diving near the sea floor during most of the remaining part of their foraging trip. Day-by-day analysis showed that during this central part of the foraging trip, 68% of the dives ended near the sea floor. The most likely function of these dives appeared to be feeding on benthic or bentho-pelagic prey. Benthic dives were rare during the first and last days of trips, when penguins were apparently in transit. Benthic-feeding is interpreted as a strategy towards predictable prey during a critical stage of the breeding cycle. Shallow areas of the Antarctic continental shelf may be important for some emperor penguin colonies around Antarctica. The importance of the benthic strata for this top predator of the Antarctic shelf ecosystem gives new insights on the trophic networks in the pack-ice during the Antarctic winter. KEY WORDS: Benthic dives · Emperor penguins · Foraging behaviour · Satellite tracking · Dive recordingResale or republication not permitted without written consent of the publisher

Section: Methodsmentioning

confidence: 99%

Benthic diving in male emperor penguins Aptenodytes forsteri foraging in winter

Rodary¹,

Bonneau²,

Maho³

et al. 2000

“…Penguins commonly show a range of responses to changes in prey type and location. For example, in response to variability in diet, location, year, season and conditions of sea-ice, Adélie penguins change not only their diving behaviour, but also the magnitude of this change (Rodary et al 2000, Kato et al 2003. Macaroni penguins at Bird Island have shown themselves to be flexible in their choice of diet.…”

Section: Seasonal Variability In Diving Characteristicsmentioning

confidence: 99%

Behavioural flexibility during year-round foraging in macaroni penguins

Green¹,

Boyd²,

Woakes³

et al. 2005

Penguins are major consumers in the marine environment. However, like many top predators, very little information exists on their foraging behaviour outside the breeding season. We investigated the foraging behaviour of the macaroni penguin Eudyptes chrysolophus continuously for 2 consecutive years, from the end of December 2001. This allowed us to investigate whether foraging behaviour varied between sexes, years or phases of the annual cycle. Male penguins tended to dive deeper and longer than female penguins, but at a lower frequency, probably as a result of their larger body size. There was little variation in foraging behaviour between the 2 years studied, although neither year included a notable period of low Antarctic krill abundance. Diving behaviour varied substantially within years and general linear models were used to investigate this variability. In summary, all penguins tended to dive deeper, longer and more efficiently during their winter migration than during the summer breeding season. The penguins dived predominantly during daylight hours at all times of the year, but appeared to be more constrained by daylight during the short winter days. Several diving variables including dive duration, dive rate and amount of time spent diving were significantly related to day length and these associations were stronger during winter than summer. The macaroni penguin shows flexibility in its foraging behaviour as it adapts to differing constraints and challenges during its annual cycle. KEY WORDS: Behavioural plasticity · Penguin · Southern Ocean · Diving behaviour · Eudyptes chrysolophus Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 296: [183][184][185][186][187][188][189][190][191][192][193][194][195][196] 2005 hence food demands are likely to be high (Green et al. 2002), but there is currently no information about the location, foraging habits or diet of macaroni penguins during this period.This paucity of information on year-round behaviour is not restricted to macaroni penguins. With the exception of some information on location (Weimerskirch & Wilson 2000, no other seabirds, or indeed any other marine predators, have had their foraging behaviour studied continuously throughout their annual (or biannual) cycle. However, several species have been studied at different times of year, or at the same time in years of differing environmental conditions, including king penguins Aptenodytes patagonicus (Charrassin & Bost 2001) and Antarctic fur seals Arctocephalus gazella . These studies frequently identified differences in foraging patterns at different times of the year. The changes are often related to differences in foraging location and therefore the underlying oceanography/topography (Charrassin & Bost 2001 and/or prey species (Kato et al. 2003). This flexibility in behaviour illustrates the importance of studying animals at all stages of their life history, in order to understand how they interact with their environment and how they might re...

“…Diving behaviour of penguins has been reported to vary according to physical parameters (Wilson et al 1993, Watanuki et al 1997, Rodary et al 2000, prey species and food availability (Croxall et al 1988, Radl & Culik 1999, sex (Bethge et al 1997, Clarke et al 1998, breeding stage and energy demands (Tremblay et al 1997, Charrassin et al 1998, and seasons and years (Kirkwood & Robertson 1997b, Moore et al 1999, Hull 2000. The ultimate factors explaining those behavioural variations are, however, difficult to pinpoint, as they are often mixed and covariate.…”

Section: Flexible Diving Parameters and Behaviourmentioning

confidence: 99%

Geographic variation in the foraging behaviour, diet and chick growth of rockhopper penguins

Tremblay¹,

Cherel²

2003

108

100

The foraging ecology of rockhopper penguins was investigated at 3 sites marked by contrasting ecological conditions. The northern subspecies was studied at Amsterdam Island (AMS) in oceanic subtropical waters, and the southern subspecies at the Kerguelen Archipelago (KER) in a subantarctic coastal habitat and at the Crozet Archipelago (CRO) in subantarctic neritic waters. During the brooding period, females from every site mainly made daily foraging trips lasting 11 to 12 h. A principal component analysis (PCA) on 22 variables of daily foraging trips reduced these variables to 3 principal components, which were related to diving mode (PC1), foraging effort (PC2) and variation in diving behaviour (PC3). Overall, PC1 indicated that birds from AMS dived shallower, had shorter dive duration and bottom time, and were less active during less efficient dives than birds from KER and CRO. On the other hand, PC3 showed that birds from KER segregated from those of AMS and CRO by performing more uniform foraging trips with less variability in dive parameters. The PCA emphasised that most of the characteristics of daily trips and all the characteristics of foraging dives varied according to the study sites, thus stressing the importance of distinct environments in shaping the foraging behaviour of seabirds. Food loads, and accordingly chick growth, were lower at AMS, medium at CRO and higher at KER, while indices of foraging effort presented little variation. Birds at AMS fed mainly on the euphausiid Thysanoessa gregaria and on larger juvenile squids, while birds from CRO and KER preyed upon the subantarctic krill Euphausia vallentini. Diving strategies together with food loads and chick growth rates suggest that prey availability was low at AMS, intermediate at CRO and high at KER, which is in agreement with previous data on chlorophyll concentrations and zooplankton biomass. The study shows the complexity of foraging behaviour of penguins. It illustrates the importance of behavioural plasticity and suggests that it is a fundamental trait of the life history of seabirds living in highly variable environments.