Modeling Huddling Penguins

We present a systematic and quantitative model of huddling penguins. In this mathematical model, each individual penguin in the huddle seeks only to reduce its own heat loss. Consequently, penguins on the boundary of the huddle that are most exposed to the wind move downwind to more sheltered locations along the boundary. In contrast, penguins in the interior of the huddle neither have the space to move nor experience a significant heat loss, and they therefore remain stationary. Through these individual movements, the entire huddle experiences a robust cumulative effect that we identify, describe, and quantify. This mathematical model requires a calculation of the wind flowing around the huddle and of the resulting temperature distribution. Both of these must be recomputed each time an individual penguin moves since the huddle shape changes. Using our simulation results, we find that the key parameters affecting the huddle dynamics are the number of penguins in the huddle, the wind strength, and the amount of uncertainty in the movement of the penguins. Moreover, we find that the lone assumption of individual penguins minimizing their own heat loss results in all penguins having approximately equal access to the warmth of the huddle.     

How do weather conditions affect the huddling behaviour of emperor penguins?

Huddling allows emperor penguins to conserve energy and survive their long winter fast while facing harsh climatic conditions. Here we report the first investigation into the effects of changes in wind speed and ambient temperature on different components of penguin huddling behaviour. We attached light and temperature recorders to male emperor penguins at the Pointe Géologie colony, Antarctica, which recorded huddling events. We then compared the frequency, duration, occurrence and intensity of huddling bouts, with ambient air temperatures and wind speeds. Huddling occurrence increased with lower ambient temperatures and higher wind speeds, whereas huddling intensity was mainly enhanced by lower ambient temperatures. Moreover, huddling group movements were linked to wind direction and its global density to lower ambient temperatures. Hence, emperor penguins complex huddling behaviour was modulated differently depending on these two parameters. Weather conditions may then affect emperor penguins ability to save energy and survive their winter fast.     

Emperor penguin mates: keeping together in the crowd

As emperor penguins have no breeding territories, a key issue for both members of a pair is not to be separated until the egg is laid and transferred to the male. Both birds remain silent after mating and thereby reduce the risk of having the pair bond broken by unpaired birds. However, silence prevents finding each other if the pair is separated. Huddles—the key to saving energy in the cold and the long breeding fast—continuously form and break up, but not all birds are involved simultaneously. We studied the behaviour of four pairs before laying. Temperature and light intensity measurements allowed us to precisely detect the occurrence of huddling episodes and to determine the surrounding temperature. The four pairs huddled simultaneously for only 6 per cent of the time when weather conditions were harshest. Despite this asynchrony, the huddling behaviour and the resulting benefits were similar between pairs. By contrast, the huddling behaviour of mates was synchronized for 84 per cent of events. By coordinating their huddling behaviour during courtship despite the apparent confusion within a huddle and its ever-changing structure, both individuals save energy while securing their partnership.     

Hidden keys to survival: the type,density, pattern and functional role of emperor penguin body feathers

Antarctic penguins survive some of the harshest conditions on the planet. Emperor penguins breed on the sea ice where temperatures drop below −40°C and forage in −1.8°C waters. Their ability to maintain 38°C body temperature in these conditions is due in large part to their feathered coat. Penguins have been reported to have the highest contour feather density of any bird, and both filoplumes and plumules (downy feathers) are reported absent in penguins. In studies modelling the heat transfer properties and the potential biomimetic applications of penguin plumage design, the insulative properties of penguin plumage have been attributed to the single afterfeather attached to contour feathers. This attribution of the afterfeather as the sole insulation component has been repeated in subsequent studies. Our results demonstrate the presence of both plumules and filoplumes in the penguin body plumage. The downy plumules are four times denser than afterfeathers and play a key, previously overlooked role in penguin survival. Our study also does not support the report that emperor penguins have the highest contour feather density.     

The winter migration of Adelie penguins breeding in the Ross Sea sector of Antarctica

Satellite telemetry was used to monitor the migratory movements of a single Adelie penguin (Pygoscelis adeliae) from Cape Hallett (72.31°S, 170.21°E) following the 1997/1998 breeding season. Locations were obtained using the ARGOS satellite system and compared with the migratory paths taken by two penguins from the Northern Colony at Cape Bird, Ross Island (77.22°S, 166.48°E) following the 1990/1991 breeding season. Although the sample sizes are small, if representative they would indicate that: (1) Adelie penguins breeding in the Ross Sea follow a common migratory path, (2) Adelie penguins breeding in the Ross Sea may travel to a common over-winter feeding ground west and north of the Balleny Islands, and (3) Adelie penguins breeding at 77°S on Ross Island travel nearly twice the distance during their over-winter migration as do those penguins breeding at Cape Hallett and colonies further north. While the Cape Hallett penguin was tracked successfully for 172 days, a record for Adelie penguins, the problem of long-term attachment of transmitters to penguins remains.     

Responses of Emperor Penguins (Aptenodytes forsteri) to encounters with ecotourists while commuting to and from their breeding colony

Emperor penguins (Aptenodytes forsteri) were studied at the Snow Hill breeding colony in November 2006 to determine the effect of people on penguins traveling between the colony and the sea to forage. We tested the null hypothesis that the presence and number of people had no effect on the trajectory of movement or the number and duration of pauses. The distances at which penguins noticed people (mean 35.6 m), changed direction (mean 22.8 m), and the number and duration of pauses increased significantly with increases in the number of tourists in their path, which explained more than 50% of the variance. Undisturbed penguins usually tobogganed on their ventral surface over the ice. When penguins noticed people, they usually stood up and often called. In 10 min observation periods, penguins traveling more than 200 m from people paused an average of <1 min vs. 3.8 min for those passing near people, increasing the energetic cost of commuting. After passing people, penguins rarely stopped. Penguins response to people varied by time of day; later in the day they responded less quickly, changed directions when closer to people, stopped for less time, and passed by people closer than they did earlier in the day. We suggest that the effect of ecotourists on traveling penguins can be partly mitigated by having people walk in small, tight-knit groups, by having people stop moving whenever traveling penguins are within about 25 m to allow the penguins to choose the direction of their passage, and by keeping the visitor pathway separate from the penguin paths insofar as possible.     

The long engagement of the emperor penguin

In birds, courtship is generally short relative to the whole breeding cycle. Emperor penguins (Aptenodytes forsteri), however, are an exception as their courtship period is much longer (ca. 6 weeks) than the courtship of other penguin species. This strategy may appear surprising, as it is especially costly to fast and endure drastic climatic conditions for long periods at the colony (1.5 and up to 4 months for females and males, respectively). We examined here the reasons of this extended courtship period and found that emperor penguins returned earlier to the colony when primary oceanic production before breeding was high. This suggests that emperor penguins return to the colony as soon as primary oceanic production in summer allows them to replenish their body reserves. The extended period of time spent at the colony during courtship may therefore result from an evolutionary process that confers advantages to emperor penguins that arrive earlier at the colony by reducing predation risks and offering better chances of securing a partner.     

Diurnal sleep depth changes in the king penguin (<Emphasis Type="Italic">Aptenodytes patagonicus</Emphasis>)

Avian sleep quality depends on its depth (deeper sleep being of better quality). In king penguins (Aptenodytes patagonica), sleep may be disturbed by congeners passing in the sleeper's vicinity. As king penguin activity is increased in the morning, sleep disturbances are more likely to occur during this time period. One might therefore assume that afternoon sleepers (AS) sleep more profoundly than morning sleepers (MS). To test this hypothesis, we examined the diurnal variations in sleep depth of king penguins sleeping in resting sites adjacent to the colony of 'La Baie du Marin' (Crozet Archipelago). We measured the bodily tactile arousal threshold at the upper back level. The arousal threshold in AS was twice as high as in MS. This study demonstrates for the first time that sleep depth changes according to time of day in a diurnal wild bird. We postulate that diurnal sleep depth is increased due to decreased congener movements close to the sleeping penguin.     

Foraging behaviour of the little penguin, Eudyptula minor: initial results and assessment of instrument effect

We investigated the foraging behaviour of little penguins using a new archival electronic activity recorder which simultaneously measures speed and depth against time. We present the first integrated data of foraging behaviour of two little penguins, from which we were able to distinguish between several types of travelling and foraging behaviours. The little penguins foraged mainly within 15 m of the surface and travelled at speeds between 8 and 9 km h^-1. Using attachments ranging between 1.4 and 11.8% penguin cross-sectional area (0.1 and 6% penguin mass), and isotopic water, we also assessed the effects of carrying devices while foraging. Both water influx and metabolic rates were significantly lower in penguins carrying devices, compared to penguins foraging without devices attached. Even the relatively small attachments resulted in a decreased foraging efficiency and we suggest that there is no simple or fixed relationship between size of device and the effect on the bearer.     

Genetic evidence for three species of rockhopper penguins, Eudyptes chrysocome

The taxonomy of rockhopper penguins, Eudyptes chrysocome (Forster 1781), is contentious. Some authorities recognise three subspecies based on morphological differences and geographical separation of breeding populations while others suggest that morphological differences support classifying rockhopper penguins as two distinct species. The taxonomy of rockhopper penguins is of more than academic interest as breeding colonies worldwide have declined markedly in size since the 1930s and rockhopper penguins are currently listed as vulnerable by the IUCN. We compared the genetic distances between three mitochondrial gene regions from the three putative rockhopper penguin subspecies with the distances between various penguin sister species to clarify the taxonomy and systematics of rockhopper penguins. Genetic distances between the rockhopper penguin taxa, relative to other closely related penguin species, support reclassifying the three rockhopper penguin subspecies as species. Reclassification of rockhopper penguins as three species could result in their conservation status being upgraded from vulnerable to endangered.     

Morphological aspects of the heart of the northern rockhopper penguin (Eudyptes chrysocome moseleyi ): possible implication in diving behavior and ecology?

We compared the heart morphology of the small, deep-diving northern rockhopper penguin to the hearts of small, shallow-diving and large, deep-diving penguin species. The rockhopper penguin had a heart larger than expected for its body mass, and its heart weight/body weight was significantly greater than in the larger Adélie penguin. We found the rockhopper's right ventricle weight/heart weight to be significantly greater than this relationship in both the larger chinstrap and Adélie penguins. The relationship of the right to left ventricular weights in the rockhopper heart is not different to that of the large, deepest-diving emperor penguin. A larger heart in the rockhopper penguin might be related to its diving behavior and ecology if it contributes to diving efficiency during foraging by increasing lung perfusion during surface recovery. This would lead to decreased surface time. Accepted: 20 May 2000     

Dominance and huddling behaviour in Bronze Mannikin Lonchura cucullata flocks

Bronze Mannikins Lonchura cucullata form flocks of up to 30 birds at the end of the breeding season and huddle in communal nests during winter. Assuming there are thermoregulatory benefits associated with huddling for these small endotherms, particularly during winter, we predicted that dominant individuals in flocks would obtain the central locations within the huddles. We tested this prediction by determining the dominance hierarchies of six captive flocks of five individuals by examining interactions at a feeder. Mannikins were observed to huddle when cold-stressed. Although mannikins do not naturally form linear huddles, for ease of observation we recorded the positions of individually marked birds in linear huddles at 5 °C before and after disturbances every half hour for 3 h. Captive flocks of mannikins established linear dominance hierarchies and dominant individuals obtained the central location within the huddle. The central position in the huddle may be beneficial in thermodynamically challenging environments through reduced energy expenditure.     

Where do penguins go during the inter-breeding period? Using geolocation to track the winter dispersion of the macaroni penguin

Although penguins are key marine predators from the Southern Ocean, their migratory behaviour during the inter-nesting period remains widely unknown. Here, we report for the first time, to our knowledge, the winter foraging movements and feeding habits of a penguin species by using geolocation sensors fitted on penguins with a new attachment method. We focused on the macaroni penguin Eudyptes chrysolophus at Kerguelen, the single largest consumer of marine prey among all seabirds. Overall, macaroni penguins performed very long winter trips, remaining at sea during approximately six months within the limits of the Southern Ocean. They departed from Kerguelen in an eastward direction and distributed widely, over more than 3.10⁶ km². The penguins spent most of their time in a previously unrecognized foraging area, i.e. a narrow latitudinal band (47–49° S) within the central Indian Ocean (70–110° E), corresponding oceanographically to the Polar Frontal Zone. There, their blood isotopic niche indicated that macaroni penguins preyed mainly upon crustaceans, but not on Antarctic krill Euphausia superba, which does not occur at these northern latitudes. Such winter information is a crucial step for a better integrative approach for the conservation of this species whose world population is known to be declining.     

Hormonal correlates of parental behavior in yellow-eyed penguins (Megadyptes antipodes)

Penguins show varying degrees of brood reduction behavior, from obligate brood reducers to brood maximizers, and we hypothesize that this is associated with differences in prolactin secretion. To address this hypothesis, we determined the breeding season prolactin profile of the yellow-eyed penguin (Megadyptes antipodes) for comparison with those of other penguin species found in the literature. We also measured sex steroid plasma concentrations to better characterize the reproductive cycle of the species. Plasma concentrations of prolactin increased from early in the season, reaching a peak during late incubation, and remained elevated up to the guard period. This general pattern was similar to that of other penguins for which we have corresponding data. However, we found that throughout the laying period, prolactin titers in yellow-eyed penguins remained elevated while they fell to basal levels after the laying of the first egg in macaroni penguins, which corresponds to differences in incubation behavior during this time. We conclude, therefore, that differences in the brood reduction behavior in penguins, may be reflected in the pattern of PRL concentrations around the time of egg laying.     

The challenges of detecting subtle population structure and its importance for the conservation of emperor penguins

Understanding the boundaries of breeding populations is of great importance for conservation efforts and estimates of extinction risk for threatened species. However, determining these boundaries can be difficult when population structure is subtle. Emperor penguins are highly reliant on sea ice, and some populations may be in jeopardy as climate change alters sea‐ice extent and quality. An understanding of emperor penguin population structure is therefore urgently needed. Two previous studies have differed in their conclusions, particularly whether the Ross Sea, a major stronghold for the species, is isolated or not. We assessed emperor penguin population structure using 4,596 genome‐wide single nucleotide polymorphisms (SNPs), characterized in 110 individuals (10–16 per colony) from eight colonies around Antarctica. In contrast to a previous conclusion that emperor penguins are panmictic around the entire continent, we find that emperor penguins comprise at least four metapopulations, and that the Ross Sea is clearly a distinct metapopulation. Using larger sample sizes and a thorough assessment of the limitations of different analytical methods, we have shown that population structure within emperor penguins does exist and argue that its recognition is vital for the effective conservation of the species. We discuss the many difficulties that molecular ecologists and managers face in the detection and interpretation of subtle population structure using large SNP data sets, and argue that subtle structure should be taken into account when determining management strategies for threatened species, until accurate estimates of demographic connectivity among populations can be made.     

A new automated logging gateway to study the demographics of macaroni penguins (Eudyptes chrysolophus) at Bird Island, South Georgia: testing the reliability of the system using radio telemetry

The use of automated systems to record the identity of individual penguins and their movements in and out of a colony can provide an effective means of studying penguin biology remotely. A new gateway installed at the macaroni penguin colony at Fairy Point (513 breeding pairs in 2003) on Bird Island, South Georgia in February 2003 and the implantation of passive integrated transponders for identifying individuals is described. The reliability of the system in recording penguin arrival and departure during the end of the 2002/2003 breeding season and over the complete 2003/2004 breeding season was tested using an independent method of radio telemetry. Results from two seasons of trials indicated that there was only a 3.7% probability of the gateway missing a penguin in 2002/2003 (185 total logged crossings) and 3.9% in 2003/2004 (1,309 total logged crossings); this compared with probabilities of 16.2 and 7.9% using radio telemetry, both differences being highly significant. This automatic logging gateway is therefore shown to be a more reliable means of recording the transit of penguins between the colony and sea and, over the longer term, elucidating colony attendance and survival rates of this species at South Georgia.     

南极Gerlache海峡海鸟的取食集群及食性

1997年12月至1998年2月,我们对南极半岛席尔瓦角善于飞翔海鸟与企鹅的取食关联性进行了研究,同时调查了取食集团中主要鸟种的食性.发现每个取食集团中有35.6-37.0只善于飞翔的海鸟,其中几乎都有纹颊企鹅群 (Pygoscelis antarctica),黑背鸥(Larus dominicanus)、灰贼鸥(Catharacta maccormicki)、花斑鹱(Daption capensis)和巨鹱(Macronectes giganteus)是各集团中最常见的鸟类.各取样单元内有相关性的种数随季节变化而减少,一些种类的减少与特定的物候期有关.南极磷虾(Euphausia superba)是绝大部分飞翔海鸟的主要食物,研究发现黑背鸥与纹颊企鹅所捕食的南极磷虾的大小最为接近.飞翔海鸟的觅食行为表明:在海面上短时停留的飞翔海鸟也能够成功捕捉到磷虾,这可能与磷虾躲避企鹅的捕食有关[动物学报 53(3):425-430,2007].     

Penguins and vegetations on Ardley Island,Antarctica: evolution in the past 2,400 years

The impact of penguins on vegetation cover is a frequently documented but not fully explained phenomenon, especially over geological time scales. To address this we collected two ornithogenic sediment cores from Ardley Island, Antarctica, and reconstructed historic variations of penguin population and different vegetations by using biomarkers fecal sterols and n-alkanols in the cores. The three major types of vegetations in the colony, namely coprophilic algae, moss and lichen, exhibited quite different trends, in concert with fluctuations in the penguin populations: a moderate penguin population is favorable for coprophilic algae and mosses, while lichen abundances decreased whenever penguin population increased, and vice versa. Cholestanol and alkanols biomarkers, in combination with bioelements, provided integrated information about the 2,400-year evolution of the penguin colony: historical penguins and vegetation populations, their fluctuations, and their interactions.