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Southern elephant seals experience a “catastrophic molt”, an energetically costly physiological event characterized by the total renewal of hair and epidermis and that requires a high peripheral vascular circulation. Molting individuals are therefore constrained by high metabolic heat loss. Molting animals have an extended period of fasting and in this species the molt period was previously thought to be spent entirely on land. We therefore investigated movement-patterns and stomach temperature of female Southern elephant seals during the molting period. In contrast to previous predictions, our data demonstrated for the first time that molting females, conversely to what has been hypothesized, do travel at sea, and ingest water and/or prey items, despite the cost of cold exposure during their critical molt period. We conclude that the paradigm of exclusive fasting during the molt in this species should be reconsidered as well as the possible fitness consequences of this behavior.

Penguins face a major thermal transition when returning to land in a hypothermic state after a foraging trip. Uninsulated appendages (flippers and feet) could provide flexible heat exchange during subsequent rewarming. Here, we tested the hypothesis that peripheral vasodilation could be delayed during this recovery stage. To this end, we designed an experiment to examine patterns of surface rewarming in fully hypothermic (the cloaca and peripheral regions (here; flippers, feet and the breast)

The moult in southern elephant seals (Mirounga leonina) represents an especially energetically demanding period during which seals must maintain high skin temperature to facilitate complete replacement of body fur and upper dermis. In this study, heat flux from the body surface was measured on 18 moulting southern elephant seals to estimate metabolic heat loss in three different habitats (beach, wallow and vegetation). Temperature data loggers were also deployed on 10 southern elephant seals to monitor skin surface temperature. On average, heat loss of animals on the beach was greater than in wallows or vegetation, and greater in wallows than in vegetation. Heat loss across all habitats during the moult equated to 1.8 x resting metabolic rate (RMR). The greatest heat loss of animals was recorded in the beach habitat during the late moult, that represented 2.3 x RMR. Mass loss was 3.6 ± 0.3 kg day-1, resulting in changes in body condition as the moult progressed. As body condition declined, skin surface temperature also decreased, suggesting that as animals approached the end of the moult blood flow to the skin surface was no longer required for hair growth.

An increasing number of marine animals are equipped with biologgers, to study their physiology, behaviour and ecology, often for conservation purposes. To minimise the impacts of biologgers on the animals’ welfare, theRefinementprinciple from the Three Rs framework (Replacement,Reduction,Refinement) urges to continuously test and evaluate new and updated biologging protocols. Here, we propose alternative and promising techniques for emperor penguin (Aptenodytes forsteri) capture and on-site logger deployment that aim to mitigate the potential negative impacts of logger deployment on these birds. We equipped adult emperor penguins for short-term (GPS, Time-Depth Recorder (TDR)) and long-term (i.e. planned for one year) deployments (ARGOS platforms, TDR), as well as juvenile emperor penguins for long-term deployments (ARGOS platforms) in the Weddell Sea area where they had not yet been studied. We describe and qualitatively evaluate our protocols for the attachment of biologgers on-site at the colony, the capture of the animals and the recovery of the devices after deployment. We report unprecedented recaptures of long-term equipped adult emperor penguins (50% of equipped individuals recaptured after 290 days). Our data demonstrate that the traditional technique of long-term attachment by gluing the biologgers directly to the back feathers causes excessive feather breakage and the loss of the devices after a few months. We therefore propose an alternative method of attachment for back-mounted devices. This technique led to successful year-round deployments on 37.5% of the equipped juveniles. Finally, we also disclose the first deployments of leg-bracelet mounted TDRs on emperor penguins. Our findings highlight the importance of monitoring potential impacts of biologger deployments on the animals and the need to continue to improve methods to minimize disturbance and enhance performance and results.

An increasing number of marine animals are equipped with biologgers, to study their physiology, behaviour and ecology, often for conservation purposes. To minimise the impacts of biologgers on the animals’ welfare, the Refinement principle from the Three Rs framework (Replacement, Reduction, Refinement) urges to continuously test and evaluate new and updated biologging protocols.Here, we propose alternative and promising techniques for emperor penguin (Aptenodytes forsteri) capture and on-site logger deployment that aim to mitigate the potential negative impacts of logger deployment on these birds. We equipped adult emperor penguins for short-term (GPS, Time-Depth Recorder (TDR)) and long-term (i.e. planned for one year) deployments (ARGOS platforms, TDR), as well as juvenile emperor penguins for long-term deployments (ARGOS platforms) in the Weddell Sea area where they had not yet been studied.We describe and qualitatively evaluate our protocols for the attachment of biologgers on-site at the colony, the capture of the animals and the recovery of the devices after deployment. We report unprecedented recaptures of long-term equipped adult emperor penguins (50% of equipped individuals recaptured after 290 days). Our data demonstrate that the traditional technique of long-term attachment by gluing the biologgers directly to the back feathers is detrimental to the birds. It causes excessive feather breakage and the loss of the devices at an early stage. We therefore propose an alternative method of attachment for back-mounted devices. This technique led to successful year-round deployments on 37.5% of the equipped juveniles. Finally, we also disclose the first deployments of leg-bracelet mounted TDRs on emperor penguins.Our findings highlight the importance of monitoring potential impacts of biologger deployments on the animals and the need to remain critical towards established and new protocols.

The overall study was funded by the IPEV (Program 1037 HEnergES), doctoral fellowships of French Ministry of Higher Education and Research, the University of St Andrews, the Marine Alliance for Science and Technology for Scotland (MASTS) and the Carnegie Trust for the Universities of Scotland. While endotherms can rely on their insulation to reduce heat loss to adapt to cold environments, renewing of fur during molt impairs insulation while they have to perfuse the periphery to support epidermal tissues. The southern elephant seal Mirounga leonina undertakes an annual catastrophic molt while fasting on land in a wet, windy and cold environment. However, southern elephant seals show characteristic aggregation patterns that are predicted to reduce high metabolic costs during the molt. Between 2012 and 2016, 59 female elephant seals were tracked on land during their molt to study their aggregation behavior in relation to molt stage, habitat type and local weather conditions. Infrared thermography and stomach temperature loggers were used to observe variation in body surface and internal temperature in relation to molt stage and aggregation behavior. We found that thermal constraints varied during the molt, with a peak in surface temperature during the mid-stage of the molt. Wallows (mud pools) appear as favorable habitat to aggregate while molting. Indeed, wallows offered a warmer microclimate with greater ground temperature and lower wind speed. Moreover, there was a greater proportion of aggregated seals and larger group size in wallows. These aggregation patterns in wallows were influenced by local weather such that a greater proportion of seals were located in the center of the aggregation, and larger group size occurred during days of unfavorable meteorological conditions. We also observed a higher proportion of seals at mid-stage of molt amongst aggregated seals compared to isolated individuals. This aggregation behavior may reduce the cost of thermogenesis as surface body temperature and stomach temperature were cooler by 1.0 °C and 1.5 °C, respectively, in aggregated compared to isolated seals. As a consequence, huddling behavior may be thermally advantageous for female southern elephant seals during the molt. Postprint

International audience; We argue the need to improve climate change forecasting for ecology, and importantly, how to relate long-term projections to conservation. As an example, we discuss the need for effective management of one species, the emperor penguin, Aptenodyptes forsteri. This species is unique amongst birds in that its breeding habit is critically dependent upon seasonal fast ice. Here, we review its vulnerability to ongoing and projected climate change, given that sea ice is susceptible to changes in winds and temperatures. We consider published projections of future emperor penguin population status in response to changing environments. Furthermore, we evaluate the current IUCN Red List status for the species, and recommend that its status be changed to Vulnerable, based on different modelling projections of population decrease of ≥50% over the current century, and the specific traits of the species. We conclude that current conservation measures are inadequate to protect the species under future projected scenarios. Only a reduction in anthropogenic greenhouse gas emissions will reduce threats to the emperor penguin from altered wind regimes, rising temperatures and melting sea ice; until such time, other conservation actions are necessary, including increased spatial protection at breeding sites and foraging locations. The designation of large-scale marine spatial protection across its range would benefit the species, particularly in areas that have a high probability of becoming future climate change refugia. We also recommend that the emperor penguin is listed by the Antarctic Treaty as an Antarctic Specially Protected Species, with development of a species Action Plan.

The overall study was funded by the Institut Polaire Français Paul-Emile Victor (IPEV program 1037 HEnergES), doctoral fellowships of French Ministry of Higher Education and Research, the University of St Andrews, the Marine Alliance for Science and Technology for Scotland (MASTS), and the Carnegie Trust for the Universities of Scotland. Southern elephant seals (Mirounga leonina) are known to move and aggregate while molting, but little is known about their behavior on land during this time. In this study, 60 adult females were monitored (23 with GPS tags) during four molting seasons, between 2012 and 2016 at Kerguelen Archipelago, Indian Ocean. Population surveys were recorded each year (N = 230 daily counts), and habitat use was analyzed in relation to the stage of the molt and local weather. Based on stage of molt, habitat use, and movements on land, we classified the molt of elephant seals into three phases: (1) a “search phase” at the initial stage of molt when grass and wallow habitats were used and characterized by greater mean distances travelled on land per day compared with the two other phases; (2) a “resident phase”: during initial and mid‐stage of molt when animals were found in grass and wallow habitats but with less distance moved on land; and (3) a “termination phase” at the final stage of molt where grass and beach habitats were occupied with no change in distances. Windchill and solar radiation influenced individual distances moved per day (mean 590 ± 237.0 m) at the mid‐ and final stage of molt such that animals travelled greater distances on days of low windchill or high solar radiation. Individual variation in distance moved and relative habitat use were also linked to body mass index (BMI) at arrival on the colony, as females with higher BMI moved less and preferred beach habitat. Moreover, the individual rate of molt increased with the use of wallows. Aggregation rate tended to be negatively correlated with distances moved. We therefore suggest that individuals face an energetic trade‐off while molting, balancing energy expenditure between movement and thermoregulation. Publisher PDF

International audience; Social facilitation of reproduction occurs in humans and animals, and may represent one of the bases of reproductionin groups. However, its underlying physiological mechanisms remain largely unexplored. Here, we found ina colonial bird, the Adélie penguin (Pygoscelis adeliae), that the number of parental interactions (nest relief ceremonies)performed by breeding individuals on the colony was positively related to prolactin levels in otherbreeding individuals exposed to these interactions (i.e. focal individuals). As prolactin is typically involved inthe expression of parental behaviour in birds, this suggests that parental interactions by conspecifics representsocial cues that might increase parental motivation in focal individuals. Moreover, parental interactions werenot related to corticosterone levels in focal individuals, suggesting that these social cues were not stressful forpenguins. However, social stimulation still had a cost for focal individuals, as itwas negatively related to their antioxidantdefences (a component of self-maintenance). As social stimulationwas also positively related to prolactinlevels, this highlights the fact that social stimulation acts on the trade-off between reproduction and selfmaintenance.For the first time, the results of the current study shed light on the physiological factors potentiallyunderlying social facilitation of parental care. Importantly, they suggest that, even though social facilitation of parentalcare may increase breeding performance, it can also negatively affect other fitness components.

International audience; Unlike most phocid species (Phocidae), Miroungaleonina (southern elephant seals) experience acatastrophic moult where they not only replace their hairbut also their epidermis when ashore for approximately1 month. Few studies have investigated behavioural andphysiological adaptations of southern elephant seals duringthe moult fast, a particularly energetically costly lifecycle’s phase. Recording heart rate is a reliable techniquefor estimating energy expenditure in the field. For the firsttime, subcutaneous heart rate data loggers were successfullyimplanted during the moult in two free-rangingsouthern elephant seals over 3–6 days. No substantialpostoperative complications were encountered and consistentheart rate data were obtained. This promising surgicaltechnique opens new opportunities for monitoring heartrate in phocid seals

International audience; Detecting and predicting how populations respond to environmental variability are crucial challenges for their conservation. Knowledge about the abundance and distribution of the emperor penguin is far from complete despite recent information from satellites. When exploring the locations where emperor penguins breed, it is apparent that their distribution is circumpolar, but with a few gaps between known colonies. The purpose of this paper is therefore to identify those remaining areas where emperor penguins might possibly breed. Using the locations of emperor penguin breeding colonies, we calculated the separation distance between each pair of geographically adjacent colonies. Based on mean separation distances between colonies following a circumpolar distribution, and known foraging ranges, we suggest that there may yet be six undiscovered breeding locations with half of these in Eastern and the remainder in Western Antarctica. Productivity in these regions suggests that food resources are likely to sustain emperor penguin populations. Our analysis highlights a fundamental requirement, that in order to predict how species might respond to regional climate change, we must better understand their biogeography and the factors that lead to their occupation of particular sites. Regarding emperor penguins , remote sensing should target the identified gaps apparently devoid of penguins in order to update the total number of colonies, to re-evaluate both the regional and global population of emperor penguins, and to gain a better understanding of their biogeography.

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.

Defining reliable demographic models is essential to understand the threats of ongoing environmental change. Yet, in the most remote and threatened areas, models are often based on the survey of a single population, assuming stationarity and independence in population responses. This is the case for the Emperor penguin Aptenodytes forsteri, a flagship Antarctic species that may be at high risk continent-wide before 2100. Here, using genome-wide data from the whole Antarctic continent, we reveal that this top-predator is organized as one single global population with a shared demography since the late Quaternary. We refute the view of the local population as a relevant demographic unit, and highlight that (i) robust extinction risk estimations are only possible by including dispersal rates and (ii) colony-scaled population size is rather indicative of local stochastic events, whereas the species' response to global environmental change is likely to follow a shared evolutionary trajectory., Delimiting populations is crucial for conserving threatened species. Using genome-wide data from the whole of Antarctica, Cristofari et al. show that Emperor penguins are organised into a single global population that have shared demography since the late Quarternary.

Summary 1. Life-history theory predicts that high reproductive investment alters self-maintenance. Several mechanisms underlying the cost of reproduction have been previously suggested, but how parental effort may impact cell and organism maintenance remains largely unknown. The effects of oxidative stress – the imbalance between oxidative damage and defences – on telomere dynamics may underlie this relationship. Indeed, oxidative stress is associated with costly activities like breeding, and impacts telomere length that is known to predict survival in birds. According to life-history theory, long-lived species are expected to minimize the adverse effects of current reproduction on their body maintenance and should therefore enhance their antioxidant capacity and preserve their telomeres when breeding workload increases. 2. In this study, we tested this hypothesis by determining experimentally how the oxidative status

International audience; In biparental species, the response of parents when their mates are disadvantaged is highly variable. Moreover, experimental studies on parental effort have mainly focused on short-lived birds whose breeding constraints largely differ from those of long-lived species such as seabirds. We investigated the short- and long-term consequences of handicapping one parent within Ade´ lie penguin, Pygoscelis adeliae, pairs. We also examined whether handicapped mates and offspring could convey cues informing the other parent of the need to increase breeding effort and whether this parent adjusted its behaviour accordingly. While handicapped penguins foraged for longer and lost more mass than controls, partners, fasting for longer at the nest, did not change their behaviour or lose more mass suggesting that they compensated at least for themselves. Information exchange was increased between mates after the return of handicapped females from foraging. However, partner males did not respond to this. Handicapped- pair chicks, which were smaller than control chicks, did not increase their solicitation rate for food. In the subsequent breeding season, compared to controls, 40% of previously handicapped females laid fewer eggs, the resight rate of previously handicapped males was lower and pair instability was higher. No additional cues seemed to be detected by Ade´ lie penguins when their mates were handicapped and, for handicapped-pair offspring, the cost associated wih a higher solicitation rate was probably too high for these small chicks to support. Consequently, we found no compensatory behaviour from partners in this long-lived species: handicapped individuals and offspring both supported the whole additional cost in both the short term and the long term.

SUMMARYThis paper investigates the energy savings of male emperor penguins Aptenodytes forsteri linked to their huddling behaviour, the key factor that allows them to assume their incubating task while undergoing a long fast. Drawing on new studies by our team, this review examines the energetic benefits accrued from huddling and estimates the respective contributions of wind protection, exposure to mild ambient temperatures,reduction in cold-exposed body surfaces and body temperature adjustments in these energy savings. The metabolic rate of `loosely grouped' birds(restrained in small groups of 5–10 individuals, which are unable to huddle effectively) is reduced by 39% compared to metabolic rate of `isolated'birds, with 32% of these energetic benefits due to wind protection. In addition, metabolic rate of `free-ranging' emperors, i.e. able to move freely and to huddle, is on average 21% lower than that of `loosely grouped' birds. Exposure to mild ambient temperatures within the groups and reduction in cold-exposed body surfaces while huddling, though overestimated, would represent a 38% metabolic reduction. About two thirds of metabolic lowering is attributable to the reduction in cold-exposed body surfaces and one third to the mild microclimate created within the groups. Moreover, body temperature adjustments contribute to these energetic benefits: maintaining body temperatures 1°C lower would represent a 7–17% reduction in energy expenditure. These processes, linked together, explain how huddling emperors save energy and maintain a constant body temperature, which ensures a successful incubation in the midst of the austral winter.

International audience; Social thermoregulation is a cooperative strategy in which animals actively aggregate to benefit from thewarmth of conspecifics in response to low ambient temperatures. Emperor penguins, Aptenodytes forsteri,use this behaviour to ensure their survival and reproduction during the Antarctic winter. An emperorpenguin colony consists of a dynamic mosaic of compact zones, the so-called huddles, included in alooser network of individuals. To maximize energy savings, birds should adjust their huddling behaviouraccording to environmental conditions. Here, we examined the dynamics of emperor penguin aggregations,based on photo and video records, in relation to climatic factors. Environmental temperature,wind and solar radiation were the main factors contributing to huddle formation. The analysis of individualmovements showed that birds originating from loose aggregations continually joined huddles.Sometimes, a small number of birds induced a movement that propagated to the entire huddle, causingits breakup within 2 min and releasing birds, which then integrated into looser aggregations. Differentparts of the colony therefore appeared to continually exchange individuals in response to environmentalconditions. A likely explanation is that individuals in need of warmth join huddles, whereas individualsseeking to dissipate heat break huddles apart. The regular growth and decay of huddles operates aspulses through which birds gain, conserve or lose heat. Originally proposed to account for reducingenergy expenditure, the concept of social thermoregulation appears to cover a highly dynamic phenomenonthat fulfils a genuine regulatory function in emperor penguins.

International audience; : Evaluating the demographic trends of marine top predators is critical to understanding the processes involved in the ongoing rapid changes in Antarctic ecosystems. However, the remoteness and logistical complexity of operating in Antarctica, especially during winter, make such an assessment difficult. Satellite imaging is increasingly recognised as a valuable method for remote animal population monitoring, yet its accuracy and reliability are still to be fully evaluated. We report here the first ground visit of an emperor penguin colony first discovered by satellite, but also the discovery of a second one not indicated by satellite survey at that time. Several successive remote surveys in this coastal region of East Antarctica, both before and after sudden local changes, had indeed only identified one colony. These two colonies (with a total of ca. 7,400 breeding pairs) are located near the Mertz Glacier in an area that underwent tremendous habitat change after the glacier tongue broke off in February 2010. Our findings therefore suggest that a satellite survey, although offering a major advance since it allows a global imaging of emperor penguin colonies, may miss certain colony locations when challenged by certain features of polar ecosystems, such as snow cover, evolving ice topology, and rapidly changing habitat. Moreover our survey shows that this large seabird has considerable potential for rapid adaptation to sudden habitat loss, as the colony detected in 2009 may have moved and settled on new breeding grounds. Overall, the ability of emperor penguin colonies to relocate following habitat modification underlines the continued need for a mix of remote sensing and field surveys (aerial photography and ground counts), especially in the less-frequented parts of Antarctica, to gain reliable knowledge about the population demography and dynamics of this flagship species of the Antarctic ecosystem.

Northwestern European populations of White Storks (Ciconia ciconia) have been restored by settling young birds which, after having been maintained captive for 3 years, do not migrate when released. Since they are still supplied with food, the question we address here is how settled White Storks would cope with a fast resulting from a cold spell if food were no longer available. We therefore measured daily body mass loss, nitrogen excretion and daily energy expenditure under natural photoperiod and climatic conditions in six captive White Storks exposed to 5 days of food deprivation during winter. Daily ambient temperature ranged between -10 and 17 degrees C. After an initial decrease in both daily body mass loss and nitrogen excretion during the first day of fasting, these two parameters stabilized at low values. Lipids were the main fuel energy source (91%) and body proteins accounted for the remainder (9%). The rate of CO(2) production, measured with the doubly labeled water method, decreased significantly (P0.001) during fasting when compared to the ad libitum value. Our data show that the metabolic adjustments of White Storks facing starvation are similar to those found in birds well-adapted to long-term fasting. From the determination of lipid and protein stores and of lipid and protein depletion rates, we conclude that White Storks would be able to survive at least during 4 weeks, a period of time twice as long as the duration of cold spells usually occurring in the Alsace region.

Fresh egg mass (FEM) is an important measure as it relates to many allometric relationships. Adelie penguin (Pygoscelis adeliae) eggs, as other bird eggs, begin to lose weight as soon as they are laid but their linear dimensions remain constant. The FEM of an Adelie penguin’s egg can be estimated within 1% from the relationship FEM = 0.564 × LW 2, where L is the length and W is the width. The constant 0.564 was calculated by weighing the eggs after replacing the air cell with water. The calculated mean egg mass agrees well with that obtained by weighing eggs after replacement of the air cell with water (r 2 = 0.996). This method of estimating FEM based on linear measurements is easily applicable in the field.

International audience; The 18 penguin species are exclusively and widely distributed in the Southern hemisphere, from the Equator to the Antarctic continent, and are thus submitted to various ecological constraints in their reproductive strategy. This results in a high variability in all aspects of the breeding biology of the different species. Although penguins appear primarily adapted for a marine existence, they remain dependent on land for breeding, rearing young and moulting. Here we describe and compare the breeding cycle of all the penguin species highlighting the characteristics of each species in terms of breeding range, population status, threats induce by environmental changes, duration of the different phases of the breeding cycle, mate fidelity, body mass, body height, egg mass and duration of egg formation. We also focus on the breeding cycle of the genus Aptenodytes since it largely differs from the breeding cycle of most of the other penguin species.

Emperor penguins Aptenodytes forsteri are able to survive the harsh Antarctic climate because of specialized anatomical, physiological and behavioural adaptations for minimizing heat loss. Heat transfer theory predicts that metabolic heat loss in this species will mostly depend on radiative and convective cooling. To examine this, thermal imaging of emperor penguins was undertaken at the breeding colony of Pointe Géologie in Terre Adélie (66°40′ S 140° 01′ E), Antarctica in June 2008. During clear sky conditions, most outer surfaces of the body were colder than surrounding sub-zero air owing to radiative cooling. In these conditions, the feather surface will paradoxically gain heat by convection from surrounding air. However, owing to the low thermal conductivity of plumage any heat transfer to the skin surface will be negligible. Future thermal imaging studies are likely to yield further insights into the adaptations of this species to the Antarctic climate.

Background: Within their litter, young altricial mammals compete for energy (constraining growth and survival) but cooperate for warmth. The aim of this study was to examine the mechanisms by which huddling in altricial infants influences individual heat production and loss, while providing public warmth. Although considered as a textbook example, it is surprising to note that physiological mechanisms underlying huddling are still not fully characterised.\ud \ud Methodology/Principal Findings: The brown adipose tissue (BAT) contribution to energy output was assessed as a function of the ability of rabbit (Oryctolagus cuniculus) pups to huddle (placed in groups of 6 and 2, or isolated) and of their thermoregulatory capacities (non-insulated before 5 days old and insulated at ca. 10 days old). BAT contribution of pups exposed to cold was examined by combining techniques of infrared thermography (surface temperature), indirect calorimetry (total energy expenditure, TEE) and telemetry (body temperature). Through local heating, the huddle provided each pup whatever their age with an ambient “public warmth” in the cold, which particularly benefited non-insulated pups. Huddling allowed pups facing a progressive cold challenge to buffer the decreasing ambient temperature by delaying the activation of their thermogenic response, especially when fur-insulated. In this way, huddling permitted pups to effectively shift from a non-insulated to a pseudo-insulated thermal state while continuously allocating energy to growth. The high correlation between TEE and the difference in surface temperatures between BAT and back areas of the body reveals that energy loss for non-shivering thermogenesis is the major factor constraining the amount of energy allocated to growth in non-insulated altricial pups.\ud \ud Conclusions/Significance: By providing public warmth with minimal individual costs at a stage of life when pups are the most vulnerable, huddling buffers cold challenges and ensures a constant allocation of energy to growth by reducing BAT activation.

International audience; Infrared thermography (IRT) is a technique that determines surface temperature based on physical laws of radiative transfer. Thermal imaging cameras have been used since the 1960s to determine the surface temperature patterns of a wide range of birds and mammals and how species regulate their surface temperature in response to different environmental conditions. As a large proportion of metabolic energy is transferred from the body to the environment as heat, biophysical models have been formulated to determine metabolic heat loss. These models are based on heat transfer equations for radiation, convection, conduction and evaporation and therefore surface temperature recorded by IRT can be used to calculate heat loss from different body regions. This approach has successfully demonstrated that in birds and mammals heat loss is regulated from poorly insulated regions of the body which are seen to be thermal windows for the dissipation of body heat. Rather than absolute measurement of metabolic heat loss, IRT and biophysical models have been most useful in estimating the relative heat loss from different body regions. Further calibration studies will improve the accuracy of models but the strength of this approach is that it is a non-invasive method of measuring the relative energy cost of an animal in response to different environments, behaviours and physiological states. It is likely that the increasing availability and portability of thermal imaging systems will lead to many new insights into the thermal physiology of endotherms.

International audience; Age-related changes in breeding performance are likely to be mediated through changes in parental foraging performance. We investigated the relationship of foraging performance with age in female little penguins at Phillip Island, Australia, during the guard phase of the 2005 breeding season. Foraging parameters were recorded with accelerometers for birds grouped into three age-classes: (1) young, (2) middle age and (3) old females. We found the diving behaviour of middleaged birds differed from young and old birds. The dive duration of middle age females was shorter than that of young and old birds while their dive effort (measure for dive and post-dive duration relation) was lower than that of young ones, suggesting middle-aged birds were in better physical condition than other ones. There was no difference in prey pursuit frequency or duration between age classes, but in the hunting tactic. Females pursued more prey around and after reaching the maximum depth of dives the more experienced they were (old . middle age . young), an energy saving hunting tactic by probably taking advantage of up-thrust momentum. We suggest middle age penguins forage better than young or old ones because good physical condition and foraging experience could act simultaneously.

International audience; Bio-logging studies suffer from the lack of real controls. However, it is still possible to compare indirect parameters between control and equipped animals to assess the level of global disturbance due to instrumentation. In addition, it is also possible to compare the behaviour of free-ranging animals between individuals equipped with different techniques or instruments to determine the less deleterious approach. We instrumented Ade´lie Penguins (Pygoscelis adeliae) with internal or external time-depth recorders and monitored them in parallel with a control group during the first foraging trip following instrumentation. Foraging trip duration was significantly longer in the internally-equipped group. This difference was due to a larger number of dives, reflecting a lower foraging ability or a higher food demand, and longer periods of recovery at the surface. These longer recovery periods were likely to be due to a reduced efficiency to ventilate at the surface, probably because the implanted devices pressurised adjacent organs such as air sacs. Moreover, descent and ascent rates were slightly lower in externally-equipped penguins, presumably because external instrumentation increased the bird drag. Looking at our results, implantation appears more disadvantageous—at least for short-term deployment— than external equipment in Ade´lie Penguins, while this method has been described to induce no negative effects in long-term studies. This underlines the need to control for potential effects due to methodological aspects in any study using data loggers in free-ranging animals, to minimise disturbance and collect reliable data.

International audience; Dive duration generally decreases with dive depth in air-breathing vertebrates. In most penguin species, this occurs due to increasing transit (descent and ascent) durations. However, in U-shaped dives, this is also because the duration of the bottom phase of the dive increases with increasing depth. We considered the time-based efficiency with which birds can use different diving depths by using depth recorders on 9 foraging emperor penguins Aptenodytes forsteri, studied during the early and late chick-rearing period in Adélie Land, Antarctica. Dive and post-dive duration positively correlated with diving depth, but particularly long recovery durations were apparent for dives longer than 456 s. This inflection point (i.e. 456 s) corresponded to a theorized maximum rate of gain of prey per dive cycle. By using the number of undulations in the bottom phase of the dive as a proxy for prey capture success, we conclude that the most lucrative dive depths for the birds studied were between 50 and 225 m. Since these depths were also those most often visited, we think that foraging emperor penguins focus on depths where profitability is highest.

The use of data-loggers has permitted to explore the biology of free-ranging animals. However, this method has also been reported to reduce reproductive success while the reasons of this deleterious effect remain poorly documented. In this study, we aimed to identify critical periods of the breeding cycle of Adelie penguins (Pygoscelis adeliae) when the reproductive success may decrease because of instrumentation. For this purpose, we monitored 40 pairs, where one parent was instrumented before egg laying and 30 pairs without devices (controls). These pairs were followed at least during the incubation period but the majority was monitored during the entire breeding season. Reproductive success was affected in pairs where males were instrumented. This was not due to extra chick mortality during chick rearing but to a significantly lower hatching success. Moreover, the use of artificial eggs recording incubation temperatures and egg rotation indicated that in instrumented incubating males, eggs spent as much time at optimal incubation temperatures as control eggs but were rotated at a higher frequency. In Adelie penguins, males initiate incubation and it has been established that the early stage of incubation is one of the most critical periods for embryonic development. The low hatching rate observed in instrumented males was associated with a higher egg rotation rate, perhaps as a stress response to the presence of the instrument. Even though the causal effects remain unclear, instrumentation severely affected hatching success. For these reasons, we recommend equipping birds after the early incubation.

SUMMARY Foraging strategies play a key role in breeding effort. Little is known, however, about their connection with hormonal and nutritional states, especially when breeding constraints vary. Here, we experimentally increased foraging costs and thus breeding constraints by handicapping Adélie penguins (Pygoscelis adeliae) with dummy devices representing 3–4% of the penguins' cross-sectional area. We examined food-related stress (via plasma corticosterone concentration) and nutritional state (via metabolite levels). Concurrently, we investigated the use of ecological niches via the isotopic signature of red blood cells indicating the trophic position (δ15N) and the spatial distribution (δ13C) of penguins. Handicapped birds performed ∼70% longer foraging trips and lost ∼60% more body mass than controls and their partners. However, corticosterone levels and the nutritional state were unchanged. The isotopic signature revealed that males and females differed in their foraging behaviour: upper trophic levels contributed more in the males' diet, who foraged in more pelagic areas. Handicapped and partner birds adopted the same strategy at sea: a shift towards higher δ13C values suggested that they foraged in more coastal areas than controls. This change in foraging decisions may optimize feeding time by decreasing travelling time. This may partly compensate for the presumed lower foraging efficiency of handicapped birds and for the energetic debt of their partners who had to fast ∼70% longer on the nest. We propose that this flexible use of ecological niches may allow birds facing increased breeding constraints to avoid chronic stress and to minimize the impact on their body condition.

International audience; 1. In Polar Regions, the extent and dynamics of sea-ice are changing. This affects the ocean productivity which consecutively impacts plankton communities and polar top predators like penguins. Yet, the underlying behavioural and physiological mechanisms remain poorly understood. 2. Here we monitored the ecophysiological responses of Ade´ lie penguin (Pygoscelis adeliae) pairs during two seasons of contrasting timing of sea-ice retreat. Beside classical breeding parameters like foraging trip duration, body mass and reproductive success, we also investigated food-related stress (via plasma corticosterone concentration), nutritional state (via metabolite levels) and the use of penguins' habitat (via blood isotopic values). 3. Body mass and reproductive success remained unchanged but foraging trips were shorter when sea-ice retreated earlier. Constant plasma corticosterone concentrations indicated that none of the feeding conditions resulted in a food-related stress. However metabolite levels were lower when sea-ice retreated early, suggesting that the foraging performance and the quality ⁄ quantity of food differed. Indeed isotopic ratios indicated that coastal prey like fish contributed more to the penguins' diet when sea-ice retreated prematurely. 4. The early sea-ice retreat was related to higher chlorophyll concentrations, known to favour krill recruitment. Paradoxically, this was not associated to a higher krill contribution in the penguins' diet. We propose that a shift in the phytoplankton quality (rather than quantity), affecting krill recruitment, forced penguins to switch to more available prey like coastal fish. 5. In some Antarctic regions, sea-ice is retreating earlier and earlier. In the present study, even though the timing of sea-ice retreat and the consecutive ocean productivity differed drastically between the 2 years, Ade´ lie penguins were not severely affected because they were able to adjust their at-sea behaviour and thus maintained their body condition and reproductive success unchanged. 6. This suggests that the timing of sea-ice retreat does not represent an important threat to populations of Ade´ lie penguins at least as long as alternative resources are still available and other environmental parameters like winter sea-ice extent are not dramatically altered.

The alternation of short/coastal and long/pelagic foraging trips has been proposed as a strategy for seabirds to reconcile self-feeding and parental care. Both types of foraging trips may result in different foraging efforts and diet qualities, and consequently are likely to modify the oxidative status of seabirds. We examined the relationship between the oxidative status of Adélie penguins and (i) the duration of their foraging trips and (ii) their plasma δ 13 C values reflecting their spatial distribution. The oxidative status did not correlate with the foraging trip duration but with the δ 13 C values: high values being associated with high levels of oxidative damage. This relationship is likely to be related to the prey properties of penguins as both parameters are largely determined by the diet. Two non-exclusive hypotheses can be proposed to explain this relationship: (i) penguins foraging in coastal areas feed on a diet enriched in 13 C and depleted in antioxidant compounds; (ii) birds with low antioxidant capacity are constrained to forage in coastal areas. Our study is the first to show that the adoption of different foraging strategies is associated with different levels of oxidative stress. However, further studies are needed to investigate the underlying mechanisms of this intriguing relationship.

International audience; Antarctic fast ice is of key climatic and ecological importance, yet its distribution and variability are poorly understood. We present a detailed analysis of fast ice along the Adélie Land coast (East Antarctica) using satellite data from 1992 to 1999. Fast ice formation along this coastline is intimately linked to grounded iceberg distribution in waters of 75% success) coincided with lower-than-average fast ice extents and persistently short distances to nearest open water (foraging grounds), and corresponded to a strong positive phase of the Southern Annular Mode. Poor breeding seasons in 1992, 1994 and 1995 (success

International audience; 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.

In sexually dimorphic species, the sex of the offspring may induce different constraints for parents. At the same time, within pairs, males and females may have conflicting optimal reproductive strategies. As a result, they may adjust their level of parental investment differently according to the sex of the young. In this study, we examined whether Adelie penguin (Pygoscelis adeliae) chicks were sexually dimorphic and whether parents adjusted their parental investment accordingly. Male chicks were on average approximately 10% heavier than female chicks but not larger. Despite the presumed additional cost associated with male chick growth, no fitness cost differences were observed between parents rearing 1 chick whatever its sex: Adult body mass changes and resight rates during the subsequent breeding season were similar. However, the sex of offspring affected the duration of foraging trips during the early guard stage: At this stage, female adults rearing a female chick performed longer foraging trips than female adults rearing a male chick and males rearing either a male or a female chick. We propose that, because female adults present a lower survival rate after a breeding attempt, they are more prone to modify their level of parental investment than male adults. Moreover, the modulation of the foraging behavior by female adults according to the sex of the chick is likely to reduce intraspecific competition at a time when resource availability at sea is not optimal and when food requirement for female chicks may be lower than for male chicks. Key words: biparental care, foraging strategies, sex-related breeding effort. (Behav Ecol)

We investigated alloparental interactions and conditions which could facilitate or prevent the expression of alloparental behaviours in Adelie penguins (Pygoscelis adeliae), a long-lived seabird which nests in high-density colonies around Antarctica. Observation sessions were carried out during the creche stage on 48 identified pairs and 50 identified chicks in a 217-nest subcolony. As the season progressed, young were fed less often by their own parents because these were increasingly absent from the breeding site and less responsive to their offspring’s solicitations. As a consequence, young and particularly those with a low body mass, coming from a two-chick brood, opted for gradually soliciting more from other adults to obtain food, preferentially those nesting in their direct vicinity. Unsuccessful breeders represented a low and constant part of the adult population and were not specifically solicited by unrelated young. Despite the increasing chick demand, only 4.1% (3 out of 73) of alloparental solicitations resulted in feeding, which is negligible compared to parental feeding. To investigate factors that could trigger the appearance of alloparental care, we carried out comparisons with king (Aptenodytes patagonicus) and emperor penguins (Aptenodytes forsteri) which represent the closest species for which data on alloparental behaviour were available. Our results show different trends to those observed in these species and three factors may explain the low occurrence of alloparental behaviour in Adelie penguins: (1) the low and constant proportion of unsuccessful breeders, (2) the absence of chick selectivity towards unsuccessful breeders, and (3) the late period of chick accessibility for potential alloparents.

International audience; The foraging ability of visual hunters depends critically on light conditions. Emperor penguins Aptenodytes forsteri are reported to be visual hunters, but breed and forage at high latitudes and are thus exposed to extreme changes in light conditions in the course of the year. We examined how light influenced the foraging ability of breeding emperor penguins using loggers in winter (n = 5) and spring (n = 4) 2005 at Pointe Géologie (66° 40' S, 140° 01' E), Antarctica, as well as by using models of light availability over the year and as a function of depth. The model showed that daylight was continuous between days of the year 350 and 363 and that the sun did not rise between days of the year 166 and 180. Logger-measured light intensity decreased with water depth, and depth-specific values were higher at greater sun elevation angles. Depth–time use (given by the maximum depth reached multiplied by the number of hours at which this depth could be achieved over 24 h) of spring-foraging penguins was 8394.5 m × h, which was more than twice that of winter-foraging birds at 3845.4 m × h, showing the severe constraints imposed by winter conditions. Average catch-per-unit effort was related to mean maximum diving depth and was highest around mid-day in winter and highest during dawn and dusk in spring. This reflects availability of prey to foraging emperor penguins.

International audience; The foraging distributions of 20 breeding emperor penguins were investigated at Pointe Ge´ologie, Terre Ade´lie, Antarctica by using satellite telemetry in 2005 and 2006 during early and late winter, as well as during late spring and summer, corresponding to incubation, early chick-brooding, late chick-rearing and the adult pre-moult period, respectively. Dive depth records of three post-egg-laying females, two post-incubating males and four late chick-rearing adults were examined, as well as the horizontal space use by these birds. Foraging ranges of chick-provisioning penguins extended over the Antarctic shelf and were constricted by winter pack-ice. During spring ice break-up, the foraging ranges rarely exceeded the shelf slope, although seawater access was apparently almost unlimited. Winter females appeared constrained in their access to open water but used fissures in the sea ice and expanded their prey search effort by expanding the horizontal search component underwater. Birds in spring however, showed higher area-restricted-search than did birds in winter. Despite different seasonal foraging strategies, chick-rearing penguins exploited similar areas as indicated by both a high ‘Area-Restricted-Search Index' and high ‘Catch Per Unit Effort'. During pre-moult trips, emperor penguins ranged much farther offshore than breeding birds, which argues for particularly profitable oceanic feeding areas which can be exploited when the time constraints imposed by having to return to a central place to provision the chick no longer apply.

International audience; Huddling allows emperor penguins to conserve energy and survive their long winter fast while facing harsh climatic conditions. Here we report the Wrst investigation into the eVects of changes in wind speed and ambient temperature on diVerent 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 diVerently depending on these two parameters. Weather conditions may then aVect emperor penguins ability to save energy and survive their winter fast.

International audience; Huddling is considered as a social strategy to reduce thermal stress and promote growth in newborn altricial mammals. So far, the role of huddling on the allocation of saved energy has not been quantified nor have the related impacts on body temperature rhythms. To determine the energy partitioning of rabbit pups either raised alone or in groups of eight, four, or two individuals, when thermoregulatory inefficient (TI) and efficient (TE), we first investigated their total energy expenditure and body composition. We then monitored body temperature and activity rhythms to test whether huddling may impact these rhythms, centered on the suckling event. Pups in a group of eight utilized 40% less energy for thermogenesis when TI than did pups alone and 32% less energy when TE. Pups in groups of eight and four had significantly lower thermoregulatory costs in the TI period, whereas pups in groups of two, four, and eight had lower costs during the TE period. Huddling pups could therefore channel the energy saved into processes of growth and accrued more fat mass (on average 4.5 +/- 1.4 g) than isolated pups, which lost 0.7 g of fat. Pups in groups of four and eight had a body temperature significantly higher by 0.8 degrees C than pups in groups of two and one when TI, whereas no more differences were noted when the TE period was reached. Moreover, pups alone showed an endogenous circadian body temperature rhythm that differed when compared with that of huddling pups, with no rise before suckling. Thus huddling enables pups to invest the saved energy into growth and to regulate their body temperature to be more competitive during nursing, particularly at the early time when they are TI.

International audience; Although huddling was shown to be the key by which emperor penguins (Aptenodytes forsteri) save energy and sustain their breeding fast during the Antarctic winter, the intricacies of this social behavior have been poorly studied. We recorded abiotic variables with data loggers glued to the feathers of eight individually marked emperor penguins to investigate their thermoregulatory behavior and to estimate their "huddling time budget" throughout the breeding season (pairing and incubation period). Contrary to the classic view, huddling episodes were discontinuous and of short and variable duration, lasting 1.6+/-1.7 (S.D.) h on average. Despite heterogeneous huddling groups, birds had equal access to the warmth of the huddles. Throughout the breeding season, males huddled for 38+/-18% (S.D.) of their time, which raised the ambient temperature that birds were exposed to above 0 degrees C (at average external temperatures of -17 degrees C). As a consequence of tight huddles, ambient temperatures were above 20 degrees C during 13+/-12% (S.D.) of their huddling time. Ambient temperatures increased up to 37.5 degrees C, close to birds' body temperature. This complex social behavior therefore enables all breeders to get a regular and equal access to an environment which allows them to save energy and successfully incubate their eggs during the Antarctic winter.

International audience; Huddling is the key energy-saving mechanism for emperor penguins to endure their 4-mo incubation fast during the Antarctic winter, but the underlying physiological mechanisms of this energy saving have remained elusive. The question is whether their deep body (core) temperature may drop in association with energy sparing, taking into account that successful egg incubation requires a temperature of about 36 degrees C and that ambient temperatures of up to 37.5 degrees C may be reached within tight huddles. Using data loggers implanted into five unrestrained breeding males, we present here the first data on body temperature changes throughout the breeding cycle of emperor penguins, with particular emphasis on huddling bouts. During the pairing period, core temperature decreased progressively from 37.5 +/- 0.4 degrees C to 36.5 +/- 0.3 degrees C, associated with a significant temperature drop of 0.5 +/- 0.3 degrees C during huddling. In case of egg loss, body temperature continued to decrease to 35.5 +/- 0.4 degrees C, with a further 0.9 degrees C decrease during huddling. By contrast, a constant core temperature of 36.9 +/- 0.2 degrees C was maintained during successful incubation, even during huddling, suggesting a trade-off between the demands for successful egg incubation and energy saving. However, such a limited drop in body temperature cannot explain the observed energy savings of breeding emperor penguins. Furthermore, we never observed any signs of hyperthermia in huddling birds that were exposed to ambient temperatures as high as above 35 degrees C. We suggest that the energy savings of huddling birds is due to a metabolic depression, the extent of which depends on a reduction of body surface areas exposed to cold.

1. Foraging determines the intake of resources that are expended on fitness related activities, and allocation links foraging and life-history traits, but the extent to which individuals are able to adjust energy expenditure according to allocation decisions is still poorly studied.2. To examine this, we studied for the first time the efficiency of foraging trips (defined as the ratio of energy gained over energy spent while foraging) in a pelagic seabird provisioning its chick by measuring simultaneously the energy flow to the chick, changes in adult body mass and foraging cost using doubly labelled water. The study was performed over two seasons.3. Blue petrels (Halobaena caerulea ) alternate between short foraging trips (average 1.9 days, range 1-4 days) where they maximize food delivery to the chick but loose mass, and long foraging trips (7.3 days, 5-10 days) where they increase in mass. They expend 1.5-2.2 times more energy per unit of time during short trips (2561 kJ day(-1) kg(-1) , i.e. 3.2 times the resting metabolic rate) compared to long trips (1142-1676 kJ day(-1) kg(-1) , i.e. 1.4-2.1 the resting metabolic rate).4. The currency during long trips is therefore to maximize efficiency, whereas during short trips the currency is to maximize rate of energy delivery to the chick. Maximum efficiency peaks for 6-day trips, i.e. when adult mass gain is highest, foraging costs are lowest and efficiency was extremely low during short trips. A duration of 6 days is therefore the optimal duration of long foraging trips but trips of 7 days were more common.5. Our study shows that self-feeding during long trips is crucial for the success of short trips because most of the energy used during short trips is probably derived from the energy stored during long trips. Self-feeding during short trips is probably negligible.6. The study indicates that surprisingly long distance foraging may not always result in higher foraging costs compared to shorter movements. It highlights the predominant role of body store usage as a mechanism for this animal to adjust energy expenditure and energetic efficiency during foraging for allocation purposes.