Deep dives and aortic temperatures of emperor penguins: new directions for bio-logging at the isolated dive hole

In order to document deep (>100 m) dives and aortic temperature responses of emperor penguins (Aptenodytes forsteri) at an isolated dive hole, and also to evaluate a new catheterization technique, three birds were equipped with time depth recorders, temperature data loggers, and percutaneously-inserted aortic thermistors. After recovery from anesthesia, they were provided access for one day to the dive hole. The birds tolerated the experiment without complication. Mean diving duration (+ SE) of 83 dives was 5.9 + 3.1 min; 55% of dives were > 5.6 min, the previously determined aerobic dive limit; 36% were > 100 m in depth. Mean aortic temperatures during 3-h rest periods ranged from 37.3 + 0.2oC to 38.0 + 0.1oC. Mean dive temperature did not correlate with dive duration, and the grand mean of mean dive temperatures in each bird ranged from 38.3 + 0.2oC to 39.0 + 0.2oC; there was no evidence of core hypothermia during dives. Reliable, safe catheterizations, and the large percentage of deep/long dives of these birds should provide the basis both for future studies of pressure adaptation and hypoxemic tolerance in diving emperor penguins, and for investigation of deep-dive foraging behavior

The icing of external recorders during the polar winter

Recorders and transmitters are commonly attached to suitable polar species of vertebrates. When using these devices, power and memory are two of the most limiting factors in successful experiments. To conserve power and memory the units are often programmed to record or transmit at designated times. A commonly used sensor is operational only when the animal is in sea water. For this procedure to function properly, exposed electrodes close a circuit when the attached device is wet. Using satellite transmitters that were programmed to transmit only after they were dry for a prescribed time, we noted an uncommon number of failures in transmission. On later controlled experiments using captive emperor penguins, Aptenodytes forsterii, we found that mock transmitters formed a glaze of ice over their surface while the birds were diving freely into an ice hole cut in two meter thick sea ice. We concluded that the icing caused the sensor to fail in detecting when the birds had re-entered the water. Icing could be an important factor in successful use of attached recorders and transmitters on polar animals, especially in winter

Three-dimensional use of marine habitats by juvenile emperor penguins Aptenodytes forsteri

International audienceThe juvenile phase is poorly known in Antarctic seabirds, despite being a critical period for individual survival. To better understand the ecology of young Antarctic seabirds, we surveyed for the first time the three-dimensional habitat use of six juvenile emperor penguins during their post-natal dispersal from Terre Ade'lie, using bio-telemetric tags. The tags transmitted location and activity data for nearly 100 days on average. One individual was followed during eight months and covered 7000 km, which represents the longest continuous individual survey for the species. Studied individuals first dispersed away from Antarctica, up to 54.78S and 1250 km north of the pack-ice edge, in the Polar Frontal Zone. This highlighted a much looser association with sea ice and a greater at-sea range compared to previous knowledge on breeding adults. Juvenile penguins then moved southwards close to the extending pack-ice during autumn and winter. Over the survey duration, juveniles showed a contrasting use of marine habitats, with less mobility, less time underwater, and shallower dives (generally not over 50-100 m) in the pack ice, versus greater distances travelled, more time spent underwater, especially deeper than 100m (up to 250-300 m) in open water. We discuss hypotheses which could explain the northward exodus of juvenile emperor penguins across contrasting habitats

Blood Oxygen Depletion Is Independent of Dive Function in a Deep Diving Vertebrate, the Northern Elephant Seal

Although energetics is fundamental to animal ecology, traditional methods of determining metabolic rate are neither direct nor instantaneous. Recently, continuous blood oxygen (O2) measurements were used to assess energy expenditure in diving elephant seals (Mirounga angustirostris), demonstrating that an exceptional hypoxemic tolerance and exquisite management of blood O2 stores underlie the extraordinary diving capability of this consummate diver. As the detailed relationship of energy expenditure and dive behavior remains unknown, we integrated behavior, ecology, and physiology to characterize the costs of different types of dives of elephant seals. Elephant seal dive profiles were analyzed and O2 utilization was classified according to dive type (overall function of dive: transit, foraging, food processing/rest). This is the first account linking behavior at this level with in vivo blood O2 measurements in an animal freely diving at sea, allowing us to assess patterns of O2 utilization and energy expenditure between various behaviors and activities in an animal in the wild. In routine dives of elephant seals, the blood O2 store was significantly depleted to a similar range irrespective of dive function, suggesting that all dive types have equal costs in terms of blood O2 depletion. Here, we present the first physiological evidence that all dive types have similarly high blood O2 demands, supporting an energy balance strategy achieved by devoting one major task to a given dive, thereby separating dive functions into distinct dive types. This strategy may optimize O2 store utilization and recovery, consequently maximizing time underwater and allowing these animals to take full advantage of their underwater resources. This approach may be important to optimizing energy expenditure throughout a dive bout or at-sea foraging trip and is well suited to the lifestyle of an elephant seal, which spends > 90% of its time at sea submerged making diving its most “natural” state

High peripheral temperatures in king penguins while resting at sea: thermoregulation versus fat deposition

Marine endotherms living in cold water face an energetically challenging situation. Unless properly insulated, these animals will lose heat rapidly. The field metabolic rate of king penguins at sea is about twice that on land. However, when at sea, their metabolic rate is higher during extended resting periods at the surface than during foraging, when birds descend to great depth in pursuit of their prey. This is most likely explained by differences in thermal status. During foraging, peripheral vasoconstriction leads to a hypothermic shell, which is rewarmed during extended resting bouts at the surface. Maintaining peripheral perfusion during rest in cold water, however, will greatly increase heat loss and, therefore, thermoregulatory costs. Two hypotheses have been proposed to explain the maintenance of a normothermic shell during surface rest: (1) to help the unloading of N2 accumulated during diving; and (2) to allow the storage of fat in subcutaneous tissue, following the digestion of food. We tested the latter hypothesis by maintaining king penguins within a shallow seawater tank, while we recorded tissue temperature at four distinct sites. When king penguins were released into the tank during the day, their body temperature immediately declined. However, during the night, periodic rewarming of abdominal and peripheral tissues occurred, mimicking temperature patterns observed in the wild. Body temperatures, particularly in the flank, also depended on body condition and were higher in ‘lean’ birds (after 10 days of fasting) than in ‘fat’ birds. While not explicitly tested, our observation that nocturnal rewarming persists in the absence of diving activity during the day does not support the N2 unloading hypothesis. Rather, differences in temperature changes throughout the day and night, and the effect of body condition/mass supports the hypothesis that tissue perfusion during rest is required for nutritional needs

Relationship between red blood cell lifespan and endogenous carbon monoxide in the common bottlenose dolphin and beluga

Certain deep-diving marine mammals (i.e., northern elephant seal (Mirounga angustirosis), Weddell seal (Leptonychotes weddellii)) have blood carbon monoxide (CO) levels that are comparable to those of chronic cigarette smokers. Most CO produced in humans is a by-product of heme degradation, which is released when red blood cells (RBC) are destroyed. Elevated CO can occur in humans when RBC lifespan decreases. The contribution of RBC turnover to CO concentrations in marine mammals is unknown. Here, we report the first RBC lifespans in two healthy, marine mammal species with different diving capacities and heme stores, the shallow diving bottlenose dolphin (Tursiops truncatus) and deep-diving beluga (Delphinapterus leucas) and relate the lifespans to the levels of CO in blood and breath. The belugas, with high blood heme stores, had the longest mean RBC lifespan compared to humans and bottlenose dolphins. Both cetacean species were found to have three times higher blood CO content compared to humans. The estimated CO production rate from heme degradation indicates some marine mammals may have additional mechanisms for CO production, or delay CO removal from the body, potentially from long duration breath-holds

Taking movement data to new depths : Inferring prey availability and patch profitability from seabird foraging behavior

Funded byNatural Environment Research Council. Grant Number: NE/K007440/1 and Marine Scotland Science and Seabird Tracking and Research (STAR) Project led by the Royal Society for the Protection of Birds (RSPB)Peer reviewedPublisher PD