Adverse effects of instrumentation in incubating Adélie penguins (Pygoscelis adeliae)

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 Adélie 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 Adélie 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.     

Human-induced behaviour in Adélie penguins Pygoscelis adeliae

Summary Adélie penguins Pygoscelis adeliae appear to be little perturbed by man. We examined the incidence of nest desertion and duration of foraging trip in Adélie penguins when manipulated and fitted with devices of differing sizes. Birds with ca. 1 cm clipped from their tail feathers stayed at sea 50% longer than unmarked controls. The length of foraging trip and incidence of nest desertion increased with increasing device volume. Penguins fitted with devices did not reduce foraging trip length to that of unpackaged birds for at least 19 days. The susceptibility of Adélie penguins to disturbance should be carefully considered when activity patterns are being studied.     

Satellite telemetry of the winter migration of Adélie penguins (Pygoscelis adeliae)

Adélie penguins (Pygoscelis adeliae), after breeding in Antarctica during the austral summer, undergo a winter migration before returning to the breeding grounds 8 months later. It is the major source of adult mortality, with about a quarter of them not returning. Here we describe the first attempt to track the winter migration of Adélie penguins using satellite telemetry. Transmitters were attached to two penguins on 16 February 1991 after their post-breeding moult at Cape Bird, Ross Island, Antarctica. Transmissions were received from one penguin (bird #1) for 4.4 months, during which time it travelled 2792.6 km from the rookery (nearly 1500 km straight-line distance). Transmissions were received from the other penguin (bird #2) for 2.5 months during which time it followed a path remarkably similar to that of bird #1. The penguins travelled northwards up the coast of Victoria Land, keeping within 100 km of the coast, rounding Cape Adare soon after 29 March and were midway between the Balleny Islands and the Antarctic coast on 3 May. Thereafter, the record from bird #1 shows that it travelled further westwards until, when opposite the Mastusevich Glacier Tongue of the Mastusevich Glacier, it turned due north and moved away from the coast. By 29 June, when transmissions ended, its progression had slowed and it was northwest of the Balleny Islands near a zone where pack ice covered 75% of the surface of the sea. Two novel points that arise from this study are: (1) that Adélie penguins from Cape Bird undergo winter migrations of not less than 5000 km, and (2) that they may be travelling to common overwinter feeding grounds.     

Observations on the thermal conductance of Adélie (Pygoscelis adeliae) and Humboldt (Spheniscus humboldti) penguins

 Analyses of cooling rates in one Adélie and one Humboldt penguin yielded calculated thermal conductance values of 0.1040 and 0.1672 W(kg ^°C)^-1, respectively. We review the methods used to calculate penguin surface area, an important component in calculating conductance values, and suggest that, in comparative studies of thermal balance, the use of body mass is a better estimator of body size than surface area. Using previously published data on penguin species, we found a significant model to predict thermal conductance from body mass according to: log C= log 0.1083−0.474 log M, where C is minimal specific thermal conductance in W(kg ^°C)^-1 and M is body mass in kilograms. Received: 13 June 1995/Accepted: 11 March 1996     

Energy requirements of Adélie penguin (Pygoscelis adeliae) chicks

Summary The energy requirements of Adélie penguin (Pygoscelis adeliae) chicks were analysed with respect to body mass (W, 0.145–3.35 kg, n=36) and various forms of activity (lying, standing, minor activity, locomotion, walking on a treadmill). Direct respirometry was used to measure O₂ consumption ( ) and CO₂ production. Heart rate (HR, bpm) was recorded from the ECG obtained by both externally attached electrodes and implantable HR-transmitters. The parameters measured were not affected by hand-rearing of the chicks or by implanting transmitters. HR measured in the laboratory and in the field were comparable. Oxygen uptake ranged from in lying chicks to at maximal activity, RQ=0.76. Metabolic rate in small wild chicks (0.14–0.38 kg) was not affected by time of day, nor was their feeding frequency in the colony (Dec 20–21). Regressions of HR on were highly significant (p< 0.0001) in transmitter implanted chicks (n=4), and two relationships are proposed for the pooled data, one for minor activities ( ), and one for walking ( ). Oxygen consumption, mass of the chick (2–3 kg), and duration of walking (T, s) were related as , whereas mass-specific O₂ consumption was related to walking speed (S, m·s^-1) as .Abbreviations bpm beats per minute - D distance walked (m) - ECG electrocardiogram - HR heart rate (bpm) - ns number of steps - RQ respiratory quotient - S walking speed (m·s^-1) - T time walked (s) - W body mass (kg)     

Feeding strategies of free-ranging Adélie penguins Pygoscelis adeliae analysed by multiple data recording

The fine-scale feeding behaviour of free-ranging Adélie penguins (Pygoscelis adeliae) during a single foraging trip was investigated by monitoring three parameters simultaneously at a frequency of 1 Hz, these being depth, swim speed and oesophagus temperature. Ingestion events were detected as abrupt drops in the oesophageal temperature and related to the birds' foraging behaviour. Although a high percentage of oesophageal temperature loggers were rejected, 1 complete foraging trip was recorded for all the 3 parameters from 1 bird while 92% and 67% of the foraging trip was recorded for 2 other birds; 12.3% of the temperature drops occurred at the surface but they were mainly small, except 61 of them probably representing snow ingestion while the birds were on land. All other drops were observed during dives, 88% of them during the undulatory (and occasionally the ascent) phase of dives deeper than 40 m. The mean swim speed during non-feeding shallow and exploratory dives was relatively constant throughout the dive, around 2.1 m s^-1, whereas during feeding deep dives, swim speed during the undulatory phase was lower (1.71 m s^-1) than during the descent and ascent and was characterised by a series of rapid accelerations and decelerations; 42.6% of these accelerations were followed by one or more ingestion events and birds swam upward in 60% of the accelerations. Such multiple data recording opens new paths for the examination of the decision-making processes in foraging penguins.     

Fluoride turnover in adélie penguins (Pygoscelis adeliae) and other brid species

Summary Fluoride concentrations found in soft tissues of free ranging birds are below 10 mg/kg d.w. In ducks (Anas platyrhynchos) 99.5% of all fluoride is bound in the skeleton. Krill-eating adélie penguins (Pygoscelis adeliae) reached equilibrium concentrations in the order of 10000 mg F/kg d.w. in femur. Fluoride uptake with the diet is buffered by the skeleton where it has a half-life of 3–4 weeks. Fluoride from fresh krill does not reach the organs of adélie penguins to the same extent as NaF. Most fluoride remains bound to the krill cuticle and is not absorbed by the penguin gut during digestion. The availability of krill fluoride was in the range of 21%–30% for muscle and 48%–68% for femur of adélie penguins as compared to NaF (100%). The role of the salt glands in fluoride excretion is neglegible. The uptake of approx. 240 mg F daily with the krill diet is balanced by excretion via the cloaca.This work was supported by a grant from the DFG Nr. MZ-AD 24/9 and by a stipend from the Studienstiftung des deutschen Volkes     

Using logistic regression models to predict breeding success in male Adélie penguins (Pygoscelis adeliae)

Measures of breeding success are traditionally derived using the proportion of total nests that successfully reach strategic stages across a breeding season, such as pair formation, egg laying or fledging chicks. The use of logistic regression has recently become a popular tool in avian literature for identifying influential factors that predict nest and/or individual breeding success. In this study, we use logistic regression models to assess the importance of a range of factors affecting male Adélie penguin (Pygoscelis adeliae) breeding success during the 2002–2003 austral summer, when the presence of icebergs and extensive sea-ice meant overall breeding success of Adélie penguins was low (16/51 focal males had chicks reach fledging point). Logistic regression models for the early breeding season showed that good/average nest quality and central/middle nest location within the sub-colony were the best predictors of successful pair formation. Later, during incubation, the most successful males were those that not only returned earlier but were also heavier upon arrival and built nests of at least average quality. During the final stage when chicks had begun to fledge, the combined parameters of heavier male weight, early arrival time and good nest quality were the best predictors of breeding success. The logistic regression approach used here showed that the predictive ability of these parameters varied as the season progressed. However, most importantly, our logistic models fit the data well across all breeding stages.     

Foraging rhythms in Adélie penguins (Pygoscelis adeliae) at hope bay,Antarctica; determination and control

Summary We studied diel periodicity in activity of Adélie penguins (Pygoscelis adeliae) during the austral summer solstice and one month later by counting, hourly, numbers of birds leaving colonies to forage, numbers arriving back after foraging, numbers in a colony and numbers resting outside the colonies. During the solstice large numbers of birds were arriving at and departing from the colony at all times of the day although there was a tendency for more birds to be at sea when light intensity was highest at mid-day. Generally, birds not brooding chicks did not rest on land. A month later, when visibility was poor at mid-night, the percentage of birds at sea was highly positively correlated with light intensity. Birds returning from foraging in the evening fed chicks immediately and then either rested in the colonies or on snow patches between the colonies and the sea until the following morning.     

Delayed laying and prolonged fasting in Adélie Penguins Pygoscelis adeliae

Observations of nesting Adélie Penguins (Pygoscelis adeliae) were made at Ardley Island during spring 1990 when snow cover was unusually thick at some subcolony sites. Adélie Penguins at these sites had to delay egg laying until the snow melted. Maximum length of fasting periods comprising pre-breeding and incubation was 50 days. Long fasting seemed to have no detrimental effect on breeding. Furthermore, there was no relationship between penguin arrival mass and duration of fast. Even birds with small mass had sufficient reserves to undergo long fasting periods.In spring 1990, when we started with a monitoring study for CEMP (CCAMLR 1990) at Ardley Island, there were still high quantities of snow at the subcolony sites. Adélie Penguins at Ardley Island inhabit both small rocky outcrops and flat, stony hillocks (storm bars). The latter had a distinctly thicker snow cover at this time so that the pebbles necessary for nest building were unattainable. Consequently, we observed the behaviour of the penguins in this situation, recorded the laying dates and lengths of fasting periods.     

Fluoride excretion in adélie penguins (Pygoscelis adeliae) and mallard ducks (Anas platyrynchos)

• 1.1. Chronic F⁻ doses of NaF (40 and 80mg F⁻/kg per day) given to adélie penguins for 6–7 weeks led to a significant increase in F⁻ concentrations of nasal salt secretions with 1.16 and 2.22μg F⁻/g (wet wt) respectively as opposed to 0.66 μg F⁻/g in controls.
• 2.2. Single oral administration of 6 mg fluoride as NaF to mallard ducks led to increased F⁻ concentrations in the nasal salt secretions, with a mean of 0.67μg F⁻/g as opposed to 0.11 μg F⁻/g in controls.
• 3.3. In mallard ducks as well as in adélie penguins the amount of F⁻ excreted via the cloaca was 10³-10⁴ times that excreted via the nasal salt glands.

     

Satellite tracking of Adélie penguins

Summary Female Adélie penguins (Pygoscelis adeliae) that take too long on their first post-laying foraging trip are a major cause of breeding failure, but in the ice-filled waters of Antarctica, determining where they go and why they are away so long has proved difficult. Here we describe the first successful attempt to track penguins at sea using satellite telemetry. Four females foraged in different locations, dispelling the notion of a common feeding ground. They moved up to 272 km from the rookery and covered from 551 to 1,121 km on their trips, swimming at minimum average speeds around 1.2 m/s. The birds were most likely to be in the water between 0630 and 1430 when light intensity, important for a visual predator, was greatest. Carrying the transmitters reduced rates of fat deposition (weight gain), increasing the duration of foraging trips of females, and suggested that they may forage until their fat depots reach a minimum threshold level. This has two implications: (i) durations of these postlaying foraging trips could potentially be used as an indicator of krill abundance (Euphausia sp), the almost exclusive food of Adélie penguins during this period, and (ii) any reduction in krill stocks caused by harvesting could increase foraging trip durations with a concomitant increase mi breeding failures.     

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

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

Factors affecting fledging weight of Adélie penguin (Pygoscelis adeliae) chicks: a modeling study

An individual-based model is developed to examine mechanisms that potentially underlie the observed constancy in fledging weight (2.8-3.2 kg) of Adélie (Pygoscelis adeliae) penguin chicks, in spite of large variability in the abundance of Antarctic krill (Euphausia superba), the primary food source. The model describes the energetic requirements of the chick, with growth resulting from the difference between assimilated energy and respiration. Parameterizations of these metabolic processes are based upon experimental and field observations. Ingestion of Antarctic krill by the chick is dependent on the frequency of food delivery to the chick by the adults, which is based on measured foraging times. The mass, size, and size frequency distribution of Antarctic krill fed to the chick are specified using empirical data. The energy content of the Antarctic krill provided to the chick is taken to be constant or allowed to vary with size. The simulations show that food availability is most critical in the latter portion of chick development, when growth rates and food demands are high. Low food availability during this time must be compensated by either feeding chicks with larger krill of higher caloric value or by increased assimilation efficiency. Periods when small krill with lower caloric value dominate require more frequent feeding of the chicks in order to attain their observed fledging weight. Thus, although the total food energy given to the chick is the main factor determining chick growth, the distribution of food availability relative to chick size (i.e., different net growth rates) and food quality are also factors influencing the fledging weight of penguin chicks. The simulations provide insight into the compensating effects of food delivery, food quality, and metabolic processes that allow Adélie penguin chicks to reach their observed fledging weight in spite of considerable environmental variability in food supply.     

Synchronous diving behavior of Adélie penguins

Synchronizing behavior with other conspecifics has been suggested as serving a function of increased foraging efficiency. However, the potential costs associated with synchronization of behavior have rarely been studied. Adélie penguins Pygoscelis adeliae sometimes dive synchronously in small open waters surrounded by fast sea ice. We examined the diving behavior of three couples and one trio, which were observed to dive synchronously among groups of 12–47 birds for 1.7–4.5 h duration, with time-depth recorders. Timing of diving and surfacing differed slightly between individuals, and one bird tended to initiate diving earlier than the other. Although the duration of the dives differed only slightly between these birds, the maximum depth of the dives differed to a large extent, with one member tending to dive consistently deeper than the other bird in two out of the four cases. Vertical distances between tagged birds in the undulatory phases of the dives (presumed feeding time) were greater than those in the descent and ascent phases, suggesting independent foraging by group members. Duration of the undulatory phase of the dives tended to be shorter in deeper-diving individuals than the others in the synchronously diving group, suggesting a potential cost of reduced feeding time to synchronize diving and surfacing with other birds. A digital video image relating to the article is available at .     

Diet of Adélie penguins Pygoscelis adeliae during the post-hatching period at Esperanza Bay,Antarctica, 1987/88

The diet of the Adélie penguin Pygoscelis adeliae was studied at Esperanza Bay, Antarctic Peninsula, during the post-hatching period by quantitative analysis of adult stomach contents. Euphausiids constituted on average 96% by mass, while fish contributed 4% by mass. Amphipods were present in small amounts. Antarctic krill Euphausia superba was the predominant component throughout the sampling period. In contrast, Euphausia crystallorophias occurred rarely. Differences in the size of krill taken by Adélie penguins appear to reflect either local changes in the availability of certain age classes at various times in the breed ing season, or differences in foraging areas, or are due to year-to-year differences in prey availability and abundance, possibly caused by variations in seasonal ice cover. Pleuragramma antarcticum constituted the bulk of the fish portion, particularly during the guard period.     

Sea ice affects the population dynamics of Adélie penguins in Terre Adélie

Overall Adélie penguin population size in Pointe Géologie Archipelago increased between 1984 and 2003 at a rate of 1.77% per year, and averaged 33,726±5,867 pairs. As predicted by the optimum model proposed by Smith et al. (Bioscience 49:393–404, 1999). Adélie penguin population size increased when sea ice extent and concentration (SIE and SIC) decreased six years earlier, indicating that the conditions around reproduction or first years at sea, were determinant. The breeding success averaged 85.2±35.45% and was not related to environmental variables. Adult survival probability varied between years from 0.64 to 0.82. Southern oscillation index (SOI) had a strong negative effect on adult annual survival. Adult survival of Adélie penguins increased during warmer events, especially during winter and spring at the beginning of reproduction. Therefore, we speculate that the rapid decreases in 1988–1991 and 1996 of the breeding population size were related to a decrease in adult mortality. However, adult survival varied little, and could not explain the strong increasing population trend. The sea ice conditions during breeding or during the first year at sea appeared determinant and influenced the population dynamics through cohort effects, probably related to the availability of productive feeding habitats.     

People in Antarctica — how much do Adélie Penguins Pygoscelis adeliae care?

Summary In the course of physiological field studies, we opportunistically examined the effects of humans and aircraft on breeding Adélie Penguins Pygoscelis adeliae. Proximity to both aircraft and humans caused substantial increases in penguin heart rate even when no external stress was manifest. A solitary human at 20 m distance from commuting penguins on a well-used pathway caused the birds to deviate by 70 m. Birds at nests exposed to a single human fled much more readily when the brood consisted of large chicks (critical distance 6.1 m) rather than small chicks (critical distance 1.3 m) or eggs (critical distance 0.3 m). Aircraft caused birds to panic at distances greater than 1,000 m and 3 days exposure to a helicopter inhibited birds that had been foraging from returning to their nests, caused bird numbers in the colonies to decrease by 15% and produced an active nest mortality of 8%. Based on this data, we make recommendations to minimize stress on Adélie Penguin colonies exposed to man.     

The gastrointestinal tract of Adélie penguins – morphology and function

The aim of this study was to provide data on the morphology of the gastrointestinal tract of Adélie penguins (Pygoscelis adeliae). It was found to consist of a long oesophagus, a two-chambered stomach, a small intestine measuring only 5.22body length, two rudimentary caeca and a short colon, typical of carnivorous birds. The stomach comprised a glandular proventriculus and a muscular gizzard that frequently contained grit. An acidic pH was recorded in both chambers. Ultrastructural studies of the small intestinal mucosal membrane revealed epithelial cells with elongated, irregular microvilli and high affinity for toluidine blue, absorptive intestinal epithelial cells and goblet cells. Numerous large lymphocyte-like cells were observed close to the brush border of the epithelium, and empty spaces on the epithelial surface reflected normal cell loss in the small intestine. The rudimentary caeca and colon provide relatively little volume and time for symbiotic bacteria to aid the digestion of crustacean chitin.     

Strategic allocation of ejaculates by male Adélie penguins

Sperm competition theory suggests that males should strategically allocate sperm to those females that will bring them the best possible genetic returns. Although males of a number of species of insects and fishes have been shown to allocate sperm strategically, we provide, to our knowledge, the first evidence that an avian species is also capable of allocating ejaculates. Male Adélie penguins (Pygoscelis adeliae) are more likely to transfer sperm during extra-pair copulations (EPCs) than during pair copulations. We investigated the question of how males allocate ejaculates within the constraints of limited sperm availability and found (i) that males that engaged in EPC attempts ejaculated less often when copulating with their social partner than males that made no EPC attempts, and (ii) that there was no difference between males that were involved in failed EPC attempts and those that were involved in successful EPCs in the proportion of copulations that resulted in sperm transfer. These results indicate that males achieve strategic allocation of sperm within the constraints of limited sperm availability by withholding ejaculates from their social partners.