Comparison of foraging strategies of incubating king penguins Aptenodytes patagonicus from Macquarie and Heard islands

The foraging strategies of king penguins from Heard and Macquarie islands were compared using satellite telemetry, time-depth recorders and diet samples. Trip durations were 16.8±3.6 days and 14.8±4.1 days at Macquarie and Heard islands, respectively. At Macquarie Island, total distances travelled were 1281±203 km compared to 1425±516 km at Heard Island. The total time the penguins spent at sea was 393±66 h at Macquarie Island and 369±108 h at Heard Island. The penguins from Macquarie Island performed more deep dives than those from Heard Island. King penguins from Macquarie Island travelled 1.5±0.2 km h⁻¹ day⁻¹ compared to 1.3±0.1 km h⁻¹ day⁻¹. At Macquarie Island, 19% of dives were upto 70–90 m depth compared to 35% at Heard Island. The main dietary prey species were the fish Krefftychthis anderssoni and the squid Moroteuthis ingens in both groups. The differences in the at-sea distribution and the foraging behaviour of the two groups of penguins were possibly related to differences in oceanography and bathymetric conditions around the two islands. Dietary differences may be due to interannual variability in prey availability since the two colonies were studied during incubation but in different years.     

Seasonal diving behaviour in lactating subantarctic fur seals on Amsterdam Island

Diving behaviour was investigated in female subantarctic fur seals (Arctocephalus tropicalis) breeding on Amsterdam Island, Indian Ocean. Data were collected using electronic Time Depth Recorders on 19 seals during their first foraging trip after parturition in December, foraging trips later in summer, and during winter. Subantarctic fur seals at Amsterdam Island are nocturnal, shallow divers. Ninety-nine percent of recorded dives occurred at night. The diel dive pattern and changes in dive parameters throughout the night suggest that fur seals follow the nycthemeral migrations of their main prey. Seasonal changes in diving behaviour amounted to the fur seals performing progressively deeper and longer dives from their first foraging trip through winter. Dive depth and dive duration increased from the first trip after parturition (16.6 ± 0.5 m and 62.1 ± 1.6 s respectively, n=1000) to summer (19.0 ± 0.4 m and 65 ± 1 s, respectively, n=2000) through winter (29.0 ± 1.0 m and 91.2 ± 2.2 s, respectively, n=800). In summer, subantarctic fur seals increased the proportion of time spent at the bottom during dives of between 10 and 20 m, apparently searching for prey when descending to these depths, which corresponded to the oceanic mixed layer. In winter, fur seals behaved similarly when diving between 20 and 50 m, suggesting that the most profitable depths for feeding moved down during the study period. Most of the dives did not exceed the physiological limits of individuals. Although dive frequency did not vary (10 dives/h of night), the vertical travel distance and the time spent diving increased throughout the study period, while the post-dive interval decreased, indicating that subantarctic fur seals showed a greater diving effort in winter, compared to earlier seasons. Accepted: 1 August 1999     

Maximum diving depths of northern rockhopper penguins (Eudyptes chrysocome moseleyi) at Amsterdam Island

 The mean maximum dive depth from 49 foraging bouts by northern rockhopper penguins, measured using capillary-tube depth gauges, was 66±4 m (12–168 m). There were no differences in the maximum dive depths between male and female penguins. Northern rockhopper penguins dived deeper in early than in late creche stages (83±7 vs 57±4 m), and this was associated with probable dietary changes, squid dominating the diet by mass (44%) in November, and fish (64%) in December 1994 at Amsterdam Island. Received: 10 January 1996/Accepted: 31 March 1996     

Food requirements of breeding king penguins at Heard Island and potential overlap with commercial fisheries

The diet composition of king penguins (Aptenodytes patagonicus) at Heard Island (53°05′S; 73°30′E) was determined from stomach contents of 98 adults captured as they returned to the island throughout 1992. During the two growth seasons, the diet was dominated by the myctophid fish Krefftichthys anderssoni (94% by number, 48% by mass). The paralepidid fish Magnisudis prionosa contributed <1% by numbers but 17% by mass. Mackerel icefish (Champsocephalus gunnari) accounted for 17% by mass of chick diet in late winter, when chicks were malnourished and prone to starvation, although its annual contribution to the penguins' diet was only 3%. Squid was consumed only between April and August; Martialia hyadesi was the commonest squid taken, comprising 40–48% of the winter diet. The remainder of the diet consisted of the squid Moroteuthis ingens and fish other than K. anderssoni. The energy content of the diet mix fed to the chicks varied seasonally being highest during the growth seasons (7.83 ± 0.25 kJ g⁻¹) and lowest in winter (6.58 ± 0.19 kJ g⁻¹). From energetic experiments we estimated that an adult penguin consumed 300 kg of food each, of which its chick received 55 kg during the 1992 season. The chicks received large meals at the beginning of winter (1.2 ± 0.3 kg) and during the middle of the second growth season (1.2 ± 0.3 kg), and their smallest meals in late winter (0.4 ± 0.1 kg). The gross energy required to rear a king penguin chick was estimated to be 724 MJ. The potential impact of commercial fisheries on the breeding activities of king penguins is discussed. Received: 20 October 1997 / Accepted: 27 April 1998     

Post-breeding dispersal of Ad��lie penguins (Pygoscelis adeliae) nesting at Signy Island, South Orkney Islands

ARGOS satellite telemetry and Global Location Sensors (geolocators) were used to identify the moult locations and the winter foraging dispersal of Adélie penguins after they left their breeding colonies on Signy Island in the South Orkney Islands. Animals were tracked during the period December 2004 to October 2005. All birds displayed a similar pattern of migratory behaviour, remaining away from colonies for approximately 9 months, at distances of up to 2,235 km. Moult locations were within the pack ice. Mean daily travel speeds to the moult locations were significantly faster when moving through open water than through pack ice. Moult occurred during February/March within a narrow latitudinal range (65–71°S), at a mean distance of 126 km from the ice edge; the mean duration of individual moult was c. 18.6 days. After moult, penguins spent the subsequent winter months moving north or north-eastward within the expanding winter pack ice, at a mean distance of 216 km from the ice edge, and in areas with ice cover >80%. The penguins returned to the vicinity of their colony between September 26 and October 22, 2005. This dependence of Adélie penguins on sea ice habitat suggests that any further reductions in sea ice extent in the Weddell Sea region would potentially have important impacts on the population processes of this pagophilic species.     

Diving and foraging behaviour of Adélie penguins in areas with and without fast sea-ice

The diving and foraging behaviours of Adélie penguins, Pygoscelis adeliae, rearing chiks at Hukuro Cove, Lützow-Holm Bay, where the fast sea-ice remained throughout summer, were compared to those of penguins at Magnetic Island, Prydz Bay, where the fast sea-ice disappeared in early January. Parent penguins at Hukuro Cove made shallower (7.1–11.3 m) but longer (90–111 s) dives than those at Magnetic Island (22.9 m and 62 s). Dive duration correlated with dive depth at both colonies (r ² = 0.001 ∼ 0.90), but the penguins atg Hukuro Cove made longer dives for a given depth. Parents at Hukuro Cove made shorter foraging trips (8.1–14.4 h) with proportionally longer walking/swimming (diving < 1 m) travel time (27–40% of trip duration) and returned with smaller meals (253–293 g) than those at Magnetic Island, which foraged on average for 57.2 h, spent 2% of time walking/swimming ( < 1 m) travel, and with meals averaging 525 g. Trip duration at both colonies correlated to the total time spent diving. Trip duration at Hukuro Cove, but not at Magnetic Island, increased as walking/swimming ( < 1 m) travel time increased. These differences in foraging behaviour between colonies probably reflected differences in sea-ice cover and the availability of foraging sites. Received: 3 November 1995/Accepted: 29 May 1996     

Sex differences in Adélie penguin foraging strategies

Consistent sex differences in foraging trip duration, feeding locality and diet of breeding Adélie penguins (Pygoscelis adeliae) were demonstrated at two widely separated locations over several breeding seasons. Differences in foraging behaviour were most pronounced during the guard stage of chick rearing. Female penguins made on average longer foraging trips than males, ranged greater distances more frequently and consumed larger quantities of krill. In contrast, males made shorter journeys to closer foraging grounds during the guard period and fed more extensively on fish throughout chick rearing. Mean guard stage foraging trip durations over four seasons at Béchervaise Island, Eastern Antarctica and over two seasons at Edmonson Point, Ross Sea ranged between 31 and 73 h for females and 25 and 36 h for males. Ninety percent of males tracked from Béchervaise Island by satellite during the first 3 weeks post-hatch foraged within 20 km of the colony, while the majority (60%) of females travelled to the edge of the continental shelf (80–120 km from the colony) to feed during this period. Received: 10 December 1997 / Accepted: 10 April 1998     

Diving patterns of breeding female rockhopper penguins (<Emphasis Type="Italic">Eudyptes chrysocome)</Emphasis>: Noir Island,Chile

The diving behaviour of female southern rockhopper penguins (Eudyptes chrysocome) was studied at Noir Island (54°30′S–73°00′W), Chile, in the southeast Pacific Ocean. This isolated island is located at the edge of the continental shelf in an area where the Humboldt Current originates, and holds a population of more than 150,000 breeding pairs. On 13 December 2005, four TDRs were successfully attached to females at the end of the brooding period and recorded diving activity at intervals of 2 s over the next 4 weeks. In total, 40 complete foraging trips were recorded. Trip duration was on average 42.4 ± 40.1 h and the proportion of overnight trips (60%) was the highest value found so far for this species. Mean dive depth and dive duration was 20.6 ± 19.4 m and 63.7 ± 36.4 s, respectively. The diving effort was higher than that of brooding females from the Indian Ocean and comparable with that of conspecifics from colonies in the southwest Atlantic in terms of diving rate (38 ± 14.2 dives h⁻¹), but slightly lower as regards the proportion of time spent underwater (61 ± 10.5%). This study confirms that the diving behaviour of rockhopper penguins varies as a function of the physical and biological characteristics of the foraging areas and of the particular stage of the breeding season.     

Diving patterns of female macaroni penguins breeding on Marion Island, South Africa

Despite the large biomass of macaroni penguins Eudyptes chrysolophus in the Southern Ocean, their feeding ecology is poorly known at some important breeding localities. We investigated the diving behaviour and diet of female macaroni penguins feeding small chicks on Marion Island (46o52′S, 37o5′E), South Africa, one of the species’ most northerly breeding sites, supporting 4% of their global population. We then compared our results with similar studies from other localities. In December 2008, we collected information on 12 foraging trips from 6 individuals using time-depth recorders, as well as diet from 42 individuals. Median trip duration was 22.8 h (5.6–80.8 h). Penguins performed 42.8 ± 15.9 dives per hour at sea, with dive depths averaging 24.6 ± 8.6 m and lasting 40.8 ± 12.1 s, although 74.3% of dives were <10 m. Euphasids dominated their diet (86% by mass), mainly Thysanoessa vicina. A second peak in dive depths at 55–80 m might reflect the 12% of fish in their diet. The substantial proportion of shallow night dives (30% of total dives) suggests some foraging occurs at night. Differences in diving patterns of individual macaroni penguins in this study confirmed the behavioural flexibility of these birds reported from other breeding localities. However, most other studies assumed that dives <3–5 m were commuting dives whereas our study suggests that at least some prey are caught during shallow dives. We highlight how different analytical methods can change the outcome of studies. Despite macaroni penguins’ apparent flexibility in foraging behaviour during the breeding season, their numbers are decreasing globally. Further investigations of their foraging behaviour are needed to assess potential competition with other predators and krill fisheries.     

The movements of gentoo penguins Pygoscelis papua from Ardley Island, Antarctica

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 May 1996 with position-determining devices. Information on area usage was derived from 20 of these devices and covered the incubation period (N = 3 birds), the chick-rearing period (N = 14 birds) and the over-wintering period (N = 3 birds). During incubation birds only ventured further than 50 km from the colony 20% of the time and no individual ranged further than 200 km from the colony. In contrast, no individuals attending chicks ranged further than 16 km from the colony. During winter the maximum distance ranged from the colony was 268 km. Mean distances between the birds and the colony were 80, 81 and 127 km. Individual birds tended to associate with one spot, making short (10 day) forays away before returning to nodal areas. The ranging capacity of gentoo penguins appears considerably less than that of sympatric congeners and may reflect the ability of gentoo penguins to dive deeper and thus exploit prey not accessible to congeners. Received: 1 October 1997 / Accepted: 3 February 1998     

Southern rockhopper penguin Eudyptes chrysocome chrysocome foraging at Possession Island

The foraging ecology of rockhopper penguins was studied at Possession Island, southern Indian Ocean, by counting the number of birds departing from and arriving at colonies over the course of the day and by equipping three birds with time/depth loggers, one of which was recovered having recorded a total of 12 days foraging activity. Both the counts and the results from the diving behaviour showed that the birds foraged exclusively diurnally. Maximum dive depth was 66 m although most time was spent between 10 and 25 m, depths that did not accord with the published distribution of their principal prey as detected by nets and acoustics. Received: 29 March 1996/Accepted: 10 June 1996     

Vegetation of the McDonald Islands, sub-Antarctic

The McDonald Islands (53°03^′S, 72°36^′E) are situated in the southern Indian Ocean, approximately 43 km west of Heard Island. These sub-Antarctic islands comprise McDonald Island itself, measuring ca.1 × 2 km, and two much smaller rocky outcrops, Flat Island and Meyer Rock. Five species of vascular plant occur on the islands. Only four species of moss were found, no hepatics, and eight species of lichen, together with algal and fungal species. Phanerogamic vegetation, comprising grassland and cushion-carpet herbfield, covers about one-third of the main island. Elsewhere, vegetation is absent or restricted to cryptogamic species. The distribution and occurrence of vegetation are strongly influenced by salt deposition, exposure to wind, substrate stability and biotic influences, particularly the very large assemblages of sea birds. The species-depauperate McDonald Islands are unique and have suffered negligible human impact. A management plan has been prepared; its implementation will be assisted by the information in this paper. The islands' protection will be further enhanced by an affirmative final decision on the current proposal for World Heritage Listing of Heard and the McDonald Islands. Received: 15 November 1996 / Accepted: 24 March 1997     

Vertical movement of dolphinfish <Emphasis Type="Italic">Coryphaena hippurus</Emphasis> as recorded by acceleration data-loggers in the northern East China Sea

Environmental changes influence foraging behavior for most animals. Dolphinfish, Coryphaena hippurus, are epipelagic predators and have a cosmopolitan tropical to warm-temperate (>20°C) distribution. We simultaneously obtained the ambient temperature and the foraging behavior (i.e., swimming speed, depth and tailbeat acceleration) of dolphinfish, using an acceleration data-logger in May, September, October, November 2007, June 2008, May and July 2010 for 8 individuals. Although the dolphinfish spent a mean ± standard deviation of 43.4 ± 27.7% of their time at the surface (0–5 m), dive excursions from the surface (DES) were observed in all individuals and maximum DES depths ranged from 50.1 to 95.4 m. DES events resulted dives below the thermocline for these dolphinfish, and there was a significantly positive relationship between the isothermal layer depth (ILD) and DES depth. Our results demonstrate that dolphinfish avoided the rapid thermal change beyond the thermocline, and their prey is most likely found in the upper layers of the thermocline. Gliding behavior during the DES phase was also observed and dolphinfish gradually descended to deeper waters with gliding. The gliding time was longer when the ILD was deeper, and fish tended to dive deeper. We suggest that dolphinfish adopt gliding behavior to search a broader range of depths for prey, while minimizing energy use.     

Variation in Spatial Cohesiveness in a Group of Japanese Macaques (<Emphasis Type="Italic">Macaca fuscata</Emphasis>)

The spatial cohesiveness of a group is an important element that characterizes the social structure of group-living species. Moreover, remaining cohesive is crucial if individuals are to coordinate their activities and reach collective decisions. We measured interindividual spacing in a group of wild Japanese macaques (Macaca fuscata) to assess the spatial cohesiveness of a social group quantitatively. We used simultaneous focal animal sampling, with 2 observers recording individuals’ locations with a global positioning system (GPS) during 3 seasons. Interindividual distances differed among seasons; they were short in autumn (mean ± SD: 25.6 ± 20.1 m), intermediate in winter (mean ± SD: 46.3 ± 35.7 m), and long in summer (mean ± SD: 62.3 ± 47.1 m). Measurements taken in summer revealed extremely wide spacing (maximum: 1225 m), suggesting subgrouping. Distances also varied with activity during each season; they were short during resting and grooming, intermediate during foraging, and long during moving. Group cohesion was also influenced by food distribution. More group members were ≤20 m of the focal individual during foraging on clumped food than foraging on scattered food in each season, and the group foraged on clumped food most frequently in autumn. Individuals were also likely to aggregate at resting/grooming sites and clumped food patches and to disperse when moving within a day. These results demonstrate that Japanese macaques show considerable variation in spatial cohesiveness both within short time periods, e.g., 1 d, and among seasons, and that they adjust group cohesiveness flexibly depending on the food conditions and foraging tactics.     

Foraging behaviour of Razorbills Alca torda during chick-rearing at the largest colony in the Baltic Sea

Capsule: Foraging behaviour in the Razorbill Alca torda during breeding was similar to that found elsewhere, aside from dive shape.

Aims: To investigate the foraging behaviour of Razorbills during the breeding season at the largest colony in the central Baltic Sea.

Methods: A combination of global positioning system (GPS) and time-depth recorder (TDR) devices were used on Razorbills breeding on the island of Stora Karlsö, Baltic Sea, during the chick-rearing period.

Results: Five GPS tracks and nine TDR logs were retrieved from 12 Razorbills, and 7399 dives were analysed. Razorbills foraged south and southwest of the colony. Maximum and mean (±sd) foraging range from the colony was 72.7?km and 13.1?±?13.5?km, respectively. Mean dive depth (15.3?±?2.4?m) and duration (53.1?±?8.5?s) were similar to those of a more southern Baltic Sea Razorbill colony. Dive depth had a bimodal distribution, with 70% of dives deeper than 10?m and 30% shallower than 10?m. There was a clear diel foraging pattern with 89% of dives occurring during daytime and a higher proportion of shallow dives at night. Unexpectedly, dives were primarily U-shaped. The Razorbills spent 31% of their overall time activity budget flying or diving.

Conclusion: Aside from dive shape, foraging behaviour was consistent with that reported at other colonies of Razorbills. Inconsistency in dive shape may be due to a bimodal foraging strategy, local prey behaviour or competition with the Common Guillemot Uria aalge.     

Krill-feeding behaviour of gentoo penguins as shown by animal-borne camera loggers

Animal-borne camera loggers were used to examine the patterns of prey encounter and feeding behaviour of gentoo penguins at King George Island, Antarctica. The still images from the camera loggers showed that the penguins encountered the swarms of krill for 25.5% (range: 8–38%) of their dives (>5 m) on average, during their foraging trips (mean duration of 5.4 h, n = 7 trips). They encountered krill swarms during the dives to 10–70 m depth, in pelagic as well as benthic habitats. In the benthic habitat, the penguins swam just above the sea floor and headed downward over a krill swarm, probably using the sea floor to assist them to feed on mobile swarms. The shallow coastal waters would be the important foraging habitat of gentoo penguins breeding in King George Island.     

Distribution and diving of harbour seals (Phoca vitulina) in Svalbard

The distribution, movements and diving of high-arctic harbour seals (Phoca vitulina) were studied in Svalbard, Norway, from 1992 to 1995. A total of 14 seals were equipped with satellite transmitters at Prins Karls Forland (ca. 78°30′N 12°E). These gave data on position, but ten also gave information on dive depths (N ∼ 160,000) and dive durations (N ∼ 162,000). Dive-depth frequencies show that ∼50% of the diving is shallower than 40 m, and that 95% of the diving is shallower than 250 m. Based on dive-duration frequencies, ∼50% of the dives lasted 2–4 min, 90% of the dives lasted less than 7 min, and 97% were shorter than 10 min. All but three seals stayed in the tagging area. Accepted: 6 October 2000     

Foraging ecology of Gentoo Penguins Pygoscelis papua at Macquarie Island during the period of chick care

The diet, diving behaviour, swimming velocity and foraging range of Gentoo Penguins Pygoscelis papua were studied at Macquarie Island during the breeding season in the 1993–1994 austral summer. Gentoo Penguins are considered to be inshore feeders, and at Macquarie Island the diet and estimated foraging ranges supported this. The diet consisted of 91.6% fish and 8.3% squid, by mass. The dominant prey taxa were the fish Gymnoscopelus sp. and Paranotothenia magellanica. A mixture of pelagic and benthic prey was consumed, with a greater proportion of benthic species occurring later in the season. The penguins exhibited a strong diurnal pattern in their diving behaviour. Deep diving (≥30 m) began near sunrise (03.00 h) and finished close to sunset (21.00 h). Diving at night was less common and very shallow (<10 m). Early in the breeding season, dive profiles indicated that birds were probably following vertically migrating pelagic prey through the water column and were foraging in waters over 100 m deep. Later in the season, more uniform, shallower depths were used, suggesting an increase in benthic foraging activity. These changes in dive pattern and depth were consistent with the habitat preferences of prey species found in the diet. Gentoo Penguins swam at 1.04 m per s and had a maximum potential foraging range of about 26 km for single-day trips. They tended to forage within 14 km of the colony, with a mean range of 5.4 km. This range encompassed the deep ocean habitat to the west and east of the island and a shallow area to the north.     

Winter migration of rockhopper penguins (Eudyptes c. chrysocome) breeding in the Southwest Atlantic: is utilisation of different foraging areas reflected in opposing population trends?

Rockhopper penguins (Eudyptes chrysocome) breeding on Staten Island, Argentina, were satellite tracked in 2002 and 2003 during the onset of their winter migration. After their moult, the dispersal of 24 birds was monitored for a mean period of 50.0±40.3 days. Birds travelled at a mean velocity of 3.1±1.1 km/h. The mean minimum distance travelled was 1,640±1,425 km; the maximum distance to the colony was generally less than 1,000 km, although one bird travelled more than 2,000 km from the colony. The penguins dispersed over an area totalling about 1.3 million km2, ranging from 50 to 62°S and from 49°W in the Atlantic to 92°W in the Pacific, and covering polar, sub-polar and temperate waters in oceanic regions as well as shelf waters. Despite the very wide dispersal, both temporally and spatially, two important wintering grounds for rockhopper penguins from Staten Island could be identified, both located over shelf regions: one extended from Staten Island to the north along the coast of Tierra del Fuego up to the Magellan Strait; the other was located over the Burdwood Bank, an isolated extension of the Patagonian Shelf to the south of the Falkland Islands. The Drake Passage also appeared to be an important area for wintering penguins, although dispersal was far more widely spread. Comparison with data obtained during winter from rockhopper penguins originating from the Falkland Islands showed that the area off the coast of Tierra del Fuego was used more or less exclusively by birds from Staten Island, whereas the Burdwood Bank was shared with penguins coming from southern colonies in the Falkland Islands. The implications of these findings are discussed with regard to (a) opposing population trends of rockhopper penguins in the Southwest Atlantic, and (b) the urgent need to establish adequate conservation measures for species and habitat protection.     

Partitioning of foraging effort in Adélie penguins provisioning chicks at Béchervaise Island, Antarctica

Analyses of the body masses of Adélie penguins (Pygoscelis adeliae) departing on foraging trips of long and short duration (> and<40 h, respectively) during chick rearing showed that the departure weights of birds prior to long trips were significantly lighter than were those prior to short trips. Penguins, particularly males, were significantly heavier at the start of the guard stage than at the end and both sexes gained similar amounts of body mass during the crèche period. Results support the hypothesis that the foraging effort of Adélie penguins at Béchervaise Island is partitioned between the sexes, with males accepting a net rate of negative energy gain to provide regular meals for their offspring during the guard stage. Adélie penguin foraging behaviour may be driven by a trade-off between the allocation of food to chicks and the storage of parental body reserves, similar to that previously postulated for some species of flying seabirds. The relevance of such a foraging strategy to the breeding success of penguins in the Mawson region of eastern Antarctica is discussed in relation to micronekton distribution in the area. Accepted: 3 June 2000