[Show abstract][Hide abstract] ABSTRACT: Investigating wild animals while minimizing human disturbance remains an important methodological challenge. When approached by a remote-operated vehicle (rover) which can be equipped to make radio-frequency identifications, wild penguins had significantly lower and shorter stress responses (determined by heart rate and behavior) than when approached by humans. Upon immobilization, the rover-unlike humans-did not disorganize colony structure, and stress rapidly ceased. Thus, rovers can reduce human disturbance of wild animals and the resulting scientific bias.
[Show abstract][Hide abstract] ABSTRACT: Because glucocorticoid (stress) hormones fundamentally affect various aspects of the behaviour, life history and fitness of free-living vertebrates, there is a need to understand the environmental factors shaping their variation in natural populations. Here, we examined whether spatial heterogeneity in breeding territory quality affected the stress of colonial king penguin (Aptenodytes patagonicus). We assessed the effects of local climate (wind, sun and ambient temperature) and social conditions (number of neighbours, distance to neighbours) on the baseline levels of plasma total corticosterone (CORT) in 77 incubating and 42 chick-brooding birds, breeding on territories of central or peripheral colony location. We also assessed the oxidative stress status of a sub-sample of central vs. peripheral chick-brooders to determine whether chronic stress arose from breeding on specific territories. On average, we found that brooders had 55 % higher CORT levels than incubators. Regardless of breeding status, central birds experienced greater social density (higher number of neighbours, shorter distance between territories) and had higher CORT levels than peripheral birds. Increasing social density positively explained 40 % of the variation in CORT levels of both incubators and brooders, but the effect was more pronounced in brooders. In contrast, climate was similar among breeding territories and did not significantly affect the CORT levels of breeding birds. In brooders, oxidative stress status was not affected by local density or weather conditions. These results highlight that local heterogeneity in breeding (including social) conditions may strongly affect the stress levels of breeding seabirds. The fitness consequences of such variation remain to be investigated.
[Show abstract][Hide abstract] ABSTRACT: For seabirds that forage at sea but breed fasting on land, successful reproduction depends on the effective management of energy stores. Additionally, breeding often means aggregating in dense colonies where social stress may affect energy budgets.King penguin (Aptenodytes patagonicus) males fast for remarkably long periods (up to 1.5 months) while courting and incubating ashore. Although their fasting capacities have been well investigated in captivity, we still known very little on the energetics of freely breeding birds.We monitored the heart rate (HR; a proxy to energy expenditure), body temperature, and physical activity of male king penguins during their courtship and first incubation shift in a colony of some 24,000 freely breeding pairs. Males were either breeding under low but increasing colony density (early breeders), or at high and stable density (late breeders).In early breeders, daily mean and resting HR decreased during courtship but increased again 3 days before egg-laying and during incubation. In late breeders, HR remained stable throughout this same breeding period. Interestingly, the daily increase in resting HR we observed in early breeders was strongly associated with a marked increase in colony density over time. This finding remained significant even after controlling for climate effects.In both early and late breeders, courtship and incubation were associated with a progressive decrease in physical activity, whereas core body temperature remained unchanged.We discuss the roles of decreased physical activity and thermoregulatory strategies in sustaining the long courtship-incubation fast of male king penguins. We also draw attention to a potential role for conspecific density in affecting the energetics of breeding fasting seabirds, i.e. a potential energy cost to coloniality This article is protected by copyright. All rights reserved.
Full-text · Article · Nov 2013 · Functional Ecology
[Show abstract][Hide abstract] ABSTRACT: Despite the enormous amount of data available on the importance of the gastrointestinal (GI) microbiota in vertebrate (especially mammals), information on the GI microbiota of seabirds remains incomplete. As with many seabirds, penguins have a unique digestive physiology that enables them to store large reserves of adipose tissue, protein, and lipids. This study used quantitative real-time polymerase chain reaction (qPCR) and 16S rRNA gene pyrosequencing to characterize the interspecific variations of the GI microbiota of four penguin species: the king, gentoo, macaroni, and little penguin. The qPCR results indicated that there were significant differences in the abundance of the major phyla Firmicutes, Bacteroides, Actinobacteria, and Proteobacteria. A total of 132,340, 18,336, 6324, and 4826 near full-length 16S rRNA gene sequences were amplified from fecal samples collected from king, gentoo, macaroni, and little penguins, respectively. A total of 13 phyla were identified with Firmicutes, Bacteroidetes, Proteobacteria, and Fusobacteria dominating the composition; however, there were major differences in the relative abundance of the phyla. In addition, this study documented the presence of known human pathogens, such as Campylobacter, Helicobacter, Prevotella, Veillonella, Erysipelotrichaceae, Neisseria, and Mycoplasma. However, their role in disease in penguins remains unknown. To our knowledge, this is the first study to provide an in-depth investigation of the GI microbiota of penguins.
[Show abstract][Hide abstract] ABSTRACT: In colonial breeders, agonistic interactions between conspecifics are frequent and may have significant physiological implications. Physiological responses (e.g., increased heart rate) to such social stressors may be determined by the potential costs of agonistic interactions, such as personal injury or risk of breeding failure, and by the motivation of the individuals concerned. The latter may vary according to individuals' reproductive status or willingness to engage in agonistic interactions. In this study, we investigated heart rate responses to aggressive interactions in a breeding colony of king penguins Aptenodytes patagonicus. From heart rate (HR) and behavior recorded in 20 adults at various stages of the breeding season, we investigated how king penguins reacted to aggressive neighbors. A total of 589 agonistic interactions, 223 in which birds were actors and 366 in which birds remained bystanders (i.e., witnesses that were not involved in interactions), were characterized. We found that HR increased during agonistic interactions, both in actors and bystanders. The intensity (threat displays or physical attacks), duration, and rate of aggressive events (number of threats/blows per unit time) of an interaction significantly influenced the HR response in actors. For bystanders, however, only the duration of interactions seemed to matter. Our results also suggest a role for individual motivation, as initiators of agonistic interactions displayed higher HR increases than responders, and as increases were not constant throughout the reproductive season. We conclude that individual risk assessment and motivation modulate physiological responses to social stressors in group-living animals.
Full-text · Article · Nov 2012 · Behavioral Ecology
[Show abstract][Hide abstract] ABSTRACT: Body mass and body condition are often tightly linked to animal health and fitness in the wild and thus are key measures for ecophysiologists and behavioral ecologists. In some animals, such as large seabird species, obtaining indexes of structural size is relatively easy, whereas measuring body mass under specific field circumstances may be more of a challenge. Here, we suggest an alternative, easily measurable, and reliable surrogate of body mass in field studies, that is, body girth. Using 234 free-living king penguins (Aptenodytes patagonicus) at various stages of molt and breeding, we measured body girth under the flippers, body mass, and bill and flipper length. We found that body girth was strongly and positively related to body mass in both molting ( ) and breeding ( ) birds, with the mean error around our predictions being 6.4%. Body girth appeared to be a reliable proxy measure of body mass because the relationship did not vary according to year and experimenter, bird sex, or stage within breeding groups. Body girth was, however, a weak proxy of body mass in birds at the end of molt, probably because most of those birds had reached a critical depletion of energy stores. Body condition indexes established from ordinary least squares regressions of either body girth or body mass on structural size were highly correlated ( ), suggesting that body girth was as good as body mass in establishing body condition indexes in king penguins. Body girth may prove a useful proxy to body mass for estimating body condition in field investigations and could likely provide similar information in other penguins and large animals that may be complicated to weigh in the wild.
[Show abstract][Hide abstract] ABSTRACT: Body mass and body condition are often tightly linked to animal health and fitness in the wild and thus are key measures for ecophysiologists and behavioral ecologists. In some animals, such as large seabird species, obtaining indexes of structural size is relatively easy, whereas measuring body mass under specific field circumstances may be more of a challenge. Here, we suggest an alternative, easily measurable, and reliable surrogate of body mass in field studies, that is, body girth. Using 234 free-living king penguins (Aptenodytes patagonicus) at various stages of molt and breeding, we measured body girth under the flippers, body mass, and bill and flipper length. We found that body girth was strongly and positively related to body mass in both molting (R(2) = 0.91) and breeding (R(2) = 0.73) birds, with the mean error around our predictions being 6.4%. Body girth appeared to be a reliable proxy measure of body mass because the relationship did not vary according to year and experimenter, bird sex, or stage within breeding groups. Body girth was, however, a weak proxy of body mass in birds at the end of molt, probably because most of those birds had reached a critical depletion of energy stores. Body condition indexes established from ordinary least squares regressions of either body girth or body mass on structural size were highly correlated (r(s) = 0.91), suggesting that body girth was as good as body mass in establishing body condition indexes in king penguins. Body girth may prove a useful proxy to body mass for estimating body condition in field investigations and could likely provide similar information in other penguins and large animals that may be complicated to weigh in the wild.
[Show abstract][Hide abstract] ABSTRACT: Background
A central question for ecologists is the extent to which anthropogenic disturbances (e.g. tourism) might impact wildlife and affect the systems under study. From a research perspective, identifying the effects of human disturbance caused by research-related activities is crucial in order to understand and account for potential biases and derive appropriate conclusions from the data.
Here, we document a case of biological adjustment to chronic human disturbance in a colonial seabird, the king penguin (Aptenodytes patagonicus), breeding on remote and protected islands of the Southern ocean. Using heart rate (HR) as a measure of the stress response, we show that, in a colony with areas exposed to the continuous presence of humans (including scientists) for over 50 years, penguins have adjusted to human disturbance and habituated to certain, but not all, types of stressors. When compared to birds breeding in relatively undisturbed areas, birds in areas of high chronic human disturbance were found to exhibit attenuated HR responses to acute anthropogenic stressors of low-intensity (i.e. sounds or human approaches) to which they had been subjected intensely over the years. However, such attenuation was not apparent for high-intensity stressors (i.e. captures for scientific research) which only a few individuals experience each year.
Habituation to anthropogenic sounds/approaches could be an adaptation to deal with chronic innocuous stressors, and beneficial from a research perspective. Alternately, whether penguins have actually habituated to anthropogenic disturbances over time or whether human presence has driven the directional selection of human-tolerant phenotypes, remains an open question with profound ecological and conservation implications, and emphasizes the need for more knowledge on the effects of human disturbance on long-term studied populations.
[Show abstract][Hide abstract] ABSTRACT: Phospholipid (PL) compositions and fatty acid (FA) patterns of PL were determined in the erythrocytes and blood thrombocytes
of a seabird, the king penguin, living in the subantarctic area and feeding on prey rich in n−3 polyunsaturated FA. Results
were compared between birds in three different physiological states (breeding and molting adults, chicks) to those reported
for other birds. In erythrocytes, the ratios of cholesterol to PL and of sphingomyelin to phosphatidylcholine (PC) were lower
than in other birds. The PL distribution was similar to those previously reported in the hen and pigeon. In contrast to other
birds, cardiolipin levels were unexpectedly high (4%). Very long chain n−3 FA were abundant (13–27%) in phosphatidylethanolamine
(PE), phosphatidylserine and PC, probably in relation to the natural diet of these birds. Among n−3 FA, 22∶6n−3 was the most
abundant in all PL (2−20%), whereas the highest levels of arachidonic acid were observed in PE (14%). In thrombocytes, the
PL distribution and FA composition of the main PL (PC, PE) differed from those of erythrocytes, and in particular, levels
of n−3 FA (9–12%) were 1.5–2 times lower. The highest levels of arachidonic acid were found in phosphatidylinositol (24%).
The lipid profile of penguin erythrocytes could contribute to the efficiency of blood circulation and oxygen delivery in microvascular
beds, thus favoring diving capacity of these animals. Our observations do not support the hypothesis of a common origin of
avian thrombocytes and erythrocytes.
[Show abstract][Hide abstract] ABSTRACT: Surviving prolonged fasting implies closely regulated alterations in fuel provisioning to meet metabolic requirements, while preserving homeostasis. Little is known, however, of the endocrine regulations governing such metabolic adaptations in naturally fasting free-ranging animals. The hormonal responses to natural prolonged fasting and how they correlate to the metabolic adaptations observed, were investigated in subantarctic fur seal (Arctocephalus tropicalis) pups, which, because of the intermittent pattern of maternal attendance, repeatedly endure exceptionally long fasting episodes throughout their development (1-3 mo). Phase I fasting was characterized by a dramatic decrease in plasma insulin, glucagon, leptin, and total l-thyroxine (T(4)) associated with reductions in mass-specific resting metabolic rate (RMR), plasma triglycerides, glycerol, and urea-to-creatine ratio, while nonesterified fatty acids (NEFA) and β-OHB increased. In contrast, the metabolic steady-state of phase II fasting reached within 6 days was associated with minimal concentrations of insulin, glucagon, and leptin; unchanged cortisol and triiodothyronine (T(3)); and moderately increased T(4). The early fall in insulin and leptin may mediate the shift to the strategy of energy conservation, protein sparing, and primary reliance on body lipids observed in response to the cessation of feeding. In contrast to the typical mammalian starvation response, nonelevated cortisol and minimal glucagon levels may contribute to body protein preservation and downregulation of catabolic pathways, in general. Furthermore, thyroid hormones may be involved in a process of energy conservation, independent of pups' nutritional state. These original hormonal settings might reflect an adaptation to the otariid repeated fasting pattern and emphasize the crucial importance of a tight physiological control over metabolism to survive extreme energetic constraints.
Full-text · Article · Feb 2012 · AJP Regulatory Integrative and Comparative Physiology
[Show abstract][Hide abstract] ABSTRACT: A drop in body temperature allows significant energy savings in endotherms, but facultative heterothermy is usually restricted to small animals. Here we report that king penguin chicks (Aptenodytes patagonicus), which are able to fast for up to 5 months in winter, undergo marked seasonal heterothermy during this period of general food scarcity and slow-down of growth. They also experience short-term heterothermy below 20 °C in the lower abdomen during the intense (re)feeding period in spring, induced by cold meals and adverse weather. The heterothermic response involves reductions in peripheral temperature, reductions in thermal core volume and temporal abandonment of high core temperature. Among climate variables, air temperature and wind speed show the strongest effect on body temperature, but their effect size depends on physiological state. The observed heterothermy is remarkable for such a large bird (10 kg before fasting), which may account for its unrivalled fasting capacity among birds.
Full-text · Article · Aug 2011 · Nature Communications
[Show abstract][Hide abstract] ABSTRACT: 1. A major hypothesis of life-history theory is that conditions of early development affect future survival and reproductive success. Responses to detrimental environments during early ontogeny may involve trade-offs between current and future fitness. Yet, the functional mechanisms involved in such evolutionary trade-offs remain poorly documented.
2. The physiological and behavioural ontogeny of diving abilities was examined in subantarctic fur seal (Arctocephalus tropicalis Gray) pups to assess whether the repeated extreme fasts they naturally endure throughout the period of maternal dependence impacts on their development.
3. The ontogeny of pup body oxygen storage capacity was slow, in particular for the muscle compartment, which shows limited increase in myoglobin content (0·23–0·85 g 100 g wet muscle−1). As a consequence, by the time of weaning, mass-specific oxygen stores had only reached 76%, 24% and 61% of adult female capacity for blood, muscle and total, respectively. Concomitantly, in marked contrast to other pinniped infants, they spent decreasing amounts of time in water (16–7%) with age and exhibited very little diving experience and skills.
4. Overall, in addition to experiencing the longest fasting durations throughout the maternal dependence period, subantarctic fur seal pups demonstrate the lowest levels of mass-specific total oxygen stores and maximum dive duration of any otariid near the age of weaning reported to date.
5. Furthermore, dives that exceeded the calculated aerobic dive limit occurred with a very low frequency (0·04%), suggesting that behavioural limitations linked to the necessity to conserve energy to survive repeated fasting, rather than restricted oxygen storage capacity, constrained pup diving behaviour.
6. Hence, these animals appear to trade-off the early development of both their physiological and behavioural diving abilities in favour of body fat accumulation to survive the prolonged fasts they must endure and, potentially, provide a nutritional buffer while they locate appropriate food patches after weaning. While promoting pre-weaning survival, this strategy renders pups more vulnerable to unpredictable changes in environmental conditions and food availability at the transition to independent foraging and, thus, could have negative impact on post-weaning survival.
Full-text · Article · Aug 2011 · Functional Ecology
[Show abstract][Hide abstract] ABSTRACT: Birds may allocate a significant part of time to comfort behavior (e.g., preening, stretching, shaking, etc.) in order to eliminate parasites, maintain plumage integrity, and possibly reduce muscular ankylosis. Understanding the adaptive value of comfort behavior would benefit from knowledge on the energy costs animals are willing to pay to maintain it, particularly under situations of energy constraints, e.g., during fasting. We determined time and energy devoted to comfort activities in freely breeding king penguins (Aptenodytes patagonicus), seabirds known to fast for up to one month during incubation shifts ashore.
A time budget was estimated from focal and scan sampling field observations and the energy cost of comfort activities was calculated from the associated increase in heart rate (HR) during comfort episodes, using previously determined equations relating HR to energy expenditure. We show that incubating birds spent 22% of their daily time budget in comfort behavior (with no differences between day and night) mainly devoted to preening (73%) and head/body shaking (16%). During comfort behavior, energy expenditure averaged 1.24 times resting metabolic rate (RMR) and the corresponding energy cost (i.e., energy expended in excess to RMR) was 58 kJ/hr. Energy expenditure varied greatly among various types of comfort behavior, ranging from 1.03 (yawning) to 1.78 (stretching) times RMR. Comfort behavior contributed 8.8-9.3% to total daily energy expenditure and 69.4-73.5% to energy expended daily for activity. About half of this energy was expended caring for plumage.
This study is the first to estimate the contribution of comfort behavior to overall energy budget in a free-living animal. It shows that although breeding on a tight energy budget, king penguins devote a substantial amount of time and energy to comfort behavior. Such findings underline the importance of comfort behavior for the fitness of colonial seabirds.
[Show abstract][Hide abstract] ABSTRACT: Aggressive behaviour associated with the defence of a territory is thought to impose substantial energy costs and thus to represent a trade-off with other energy-demanding activities. The energy costs of aggressive behaviours, however, have rarely been estimated in the wild, and the overall contribution of territorial defence to daily energy expenditure has never been determined. We studied the activity budget of breeding king penguins, Aptenodytes patagonicus, equipped with heart rate data loggers to estimate the energy costs associated with territory defence in this colonial bird exhibiting very high rates of agonistic interactions. We also assessed whether threat displays imposed lower energy costs than attacks with body contact. During territorial defence (i.e. threats and physical attacks combined), energy expenditure averaged 1.27 times resting metabolic rate. Defence accounted for 13% of the daily time budget and contributed to 2.7% of the total daily energy expenditure. Interactions with body contact cost three times more than threat displays, but accounted for only 16% of the aggressive behaviours recorded. Neither did body mass, body size, penguin sex or breeding stage affect the cost of aggressiveness. Our results are consistent with previous research reporting that fighting imposes significant metabolic costs. However, we found that aggressive behaviour in king penguins was not an expensive activity compared to the total energy budget. Because king penguins go without food and are sleep deprived while breeding, they may have developed behavioural strategies (e.g. lower rates of attacks with body contact) allowing them to defend their territory efficiently at a low energy cost.
[Show abstract][Hide abstract] ABSTRACT: Continuous growth, associated with a steady parental food supply, is a general pattern in offspring development. So that young chicks can acquire their locomotor independence, this period is usually marked by a fast maturation of muscles, during which different myosin heavy chain (MyHC) isoforms are expressed. However, parental food provisioning may fluctuate seasonally, and offspring therefore face a challenge to ensure the necessary maturation of their tissues when energy is limited. To address this trade-off we investigated muscle maturation in both the pectoral and pelvic girdles of king penguin chicks. This species has an exceptionally long rearing period (1 year), which is prolonged when parental food provisioning is drastically reduced during the sub-Antarctic winter. Approximately 1 month post hatching, chicks acquire a functional pedestrian locomotion, which uses pelvic muscles, whereas swimming, which uses the pectoral muscles, only occurs 1 year later. We therefore tested the hypothesis that the MyHC content of the leg muscles reaches a mature state before those of the pectoral muscles. We found that leg muscle MyHC composition changed with the progressive acquisition of pedestrian locomotion, whereas pectoral muscle fibres reached their mature MyHC profile as early as hatching. Contrary to our predictions, the acquisition of the adult profile in pectoral muscles could be related to an early maturation of the contractile muscular proteins, presumably associated with early thermoregulatory capacities of chicks, necessary for survival in their cold environment. This differential maturation appears to reconcile both the locomotor and environmental constraints of king penguin chicks during growth.
Full-text · Article · Jun 2011 · Journal of Experimental Biology
[Show abstract][Hide abstract] ABSTRACT: Fasting is common in many seabird species including penguins and Procellariiforme seabirds, due to food availability, moult, migration and reproduction. In this study we focused our attention on penguins fasting during moult. In the past many studies have focused their attention on understanding the physiology of fasting and re-feeding. However, little attention has been paid to the affects of fasting on the gastrointestinal microbiota.
Recent studies on the affects of fasting in mammalian species, has shown that long-term fasting not only alters the diversity and species richness of the gut microbiota, but also affects the host’s immune systems response and ability to prevent infection and disease.
Therefore the aims of this study were to examine: 1) the affect that fasting has on the gastrointestinal microbiota of penguins; 2) the presence of mucin-degrading bacteria; and 3) The changes in the number of pathogens increase during moult, increasing the risk of infection and disease. Utilising group specific 16S rRNA DNA primers changes in diversity, species richness and quantity of the major bacterial phyla were analysed in moulting and non moulting King, Gentoo and Little penguins using PCR- Denaturing Gradient Gel Electrophoresis (DGGE) and quantitative Real Time PCR.
Results have indicated that fasting during moult alters the diversity and species richness in the gastrointestinal microbiota of penguins, with an increase in the total number of bacteria recorded in the moulting birds.
[Show abstract][Hide abstract] ABSTRACT: The gastrointestinal tract is a diverse and complex ecosystem is colonised by hundreds of different species of micro-organisms. The microbiota provides nutrition to the host by the secretion of nutrients, vitamins, amino acids and short chain fatty acids. These compounds contribute to the energy supply for the animal and can also influence the type of microbiota present. The intestinal flora is also responsible for the establishment and maintenance of the host’s immune system.
Because of the importance that the gut microbiota plays in the conversion of food to energy and immune system function, it is important to understand what influences the gut microbiota of penguins. It has been established that dietary changes, antibiotics and the environment we live in can influence the composition of the gastrointestinal microbiota of humans and avian species of commercial importance. However, there is little to no literature that has investigated what influences the gastrointestinal microbiota in penguins. The gastrointestinal microbiota of king penguins was examined to determine the dominant microbiota and to see if whether geographical separation influences the microbiota of two king penguin populations.
Faecal samples from two king penguin populations with considerable geographical separation (~6000km) but consume a similar diet were analysed using 16S rRNA group specific primers. A database of bacteria present in the gastrointestinal tract has been developed using the 454 sequencer, which has yielded over 50,000 bacteria sequences from each location. The predominant bacterial groups isolated from the samples were from the phyla Bacteroidetes and Firmicutes. Escherichia coli, Bifidobacteria, Staphylococcus and Lactobacillus spp were present but not are considered to be predominant groups. Differences in diversity, species richness and quantification of the predominant bacteria groups were examined using PCR-DGGE, and quantitative Real Time PCR.
[Show abstract][Hide abstract] ABSTRACT: Heart rate (f(H)) measurement offers the possibility to monitor energy expenditure (EE) in wild animals if the EE/f(H) relationship for the species, physiological stages and activities of interest is known. This relationship has been extensively studied using oxygen consumption rate ( ) measurement in captive, repeatedly handled king penguins (Aptenodytes patagonicus). Unfortunately, the potential effects of stress on the observed relationships resulting from handling and confinement were not considered. This study is the first involving undisturbed animals, and determines the EE/f(H) relationship in naturally fasting and freely incubating or captivity-acclimatized male and female king penguins. EE determination was based on (1) the measurement of body mass loss during periods of phase II fasting, and (2) the calculation of its energy equivalent from changes in body composition, i.e. 23.9 kJ g(-1). f(H) levels in freely incubating and captivity-acclimatized birds were found to be 50-70% lower than those previously reported for resting king penguins during measurements. Significant EE/f(H) relationships were found in freely incubating and captive males and females (R(2)=0.59 to 0.84), with no difference observed between genders. The best overall relationship was obtained by including fasting duration (t, days) in the model: EE=818+43.7xf(H)+36.3t-1.4txf(H) (R(2)=0.91). This equation yielded EE estimates approximately 26% higher than the previously reported 'best' predictive equation in king penguins, and even more so when f(H) was low. This result suggests that stress induces a disproportionate increase of f(H) vs O(2) consumption, and that the use of EE/f(H) relationships obtained in stressed birds could lead to underestimated EE values.
Preview · Article · Jan 2010 · Journal of Experimental Biology