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Investigations of diving behavior of the Atlantic walrus ( Odobenus rosmarus rosmarus ) in the high Arctic Greenland and Canada are important for understanding behavioral adaptations and area utilization of this Arctic benthic feeder. Furthermore, such information along with estimations of annual consumption and carrying capacity of walruses are needed in management decisions of this utilized species. Satellite-linked transmitters deployed on 27 walruses from 2010 to 2013 provided data for investigations of diving behavior in three predefined main areas: NW Greenland, Smith Sound and NE Canada. Sub-areas within each main area were also compared. Depth of dives, dive rates, time at depth of dives, haul-out periods and vertical speeds were estimated. Majority of dives targeted depths from 10 to 100 m, which corresponds to the distribution of walrus preferred food items. Four dives to depths > 500 m occurred and are the deepest ever documented for a walrus. Dive rates and time at depth of dives were significantly different between sub-areas (p < 0.0001), whereas haul-out periods were not (p = 0.072). Mean vertical speeds to destination depths ranged from 1.0 m s − 1 (95% CI: 0.8–1.2) to 1.8 m s − 1 (95% CI: 1.0–2.6). Based on dive rates, time at depth, haul-out and percentage of feeding dives Alexandra Fjord and Princess Mary Bay in NE Canada and Carey Island in NW Greenland were identified as the most important areas for walrus feeding during summer. Walrus predation on the standing bivalve biomass in NW Greenland (within 5–100 m of depth) was estimated to 3.2% annually based on assessments of mean biomass of walrus preferred prey items. From a simple relationship between available shallow water habitat, current population size ( n = 2544) and walrus pre-exploitation population sizes it is furthermore proposed that the carrying capacity in the Smith Sound region does not exceed 5000 walruses. [ABSTRACT FROM AUTHOR]

The breeding success, foraging strategies and abundance of penguin species are thought to vary according to the quality of near-shore marine environments. Little blue penguins (LBP), Eudyptula minor, in particular, are considered a candidate species for assessing near-shore marine productivity and integrity due to their limited foraging ranges and reliance on local resources, particularly during breeding. However, to assess their ability to be near-shore ecosystem indicators an understanding of what their 'normal' dive patterns and population parameters from across New Zealand are needed. This research investigates diving behaviours and feather stable isotope values (as indicators of diet) of LBPs from southern (Pearl Island, Stewart Island/Rakiura, Nov. 2011) and central (Adele Island, Abel Tasman, Nov. 2012) New Zealand (NZ), two areas not previously studied, and compares them with LBPs from other areas of NZ. The diving behaviours of LBPs across NZ, are highly variable, not obviously linked with local geography and bathometry. These results and the NZ wide comparison indicates that LBPs are environmentally adaptable, which may make them difficult to use as ecosystem indicators across sites. However, with increasing knowledge of diving behaviours and population parameters of LBPs within a region, they are likely to be indicators of local changing marine environment. [ABSTRACT FROM AUTHOR]

The development of high-resolution archival tag technologies has revolutionized our understanding of diving behavior in marine taxa such as sharks, turtles, and seals during their wide-ranging movements. However, similar applications for large whales have lagged behind due to the difficulty of keeping tags on the animals for extended periods of time. Here, we present a novel configuration of a transdermally attached biologging device called the Advanced Dive Behavior ( ADB) tag. The ADB tag contains sensors that record hydrostatic pressure, three-axis accelerometers, magnetometers, water temperature, and light level, all sampled at 1 Hz. The ADB tag also collects Fastloc GPS locations and can send dive summary data through Service Argos, while staying attached to a whale for typical periods of 3-7 weeks before releasing for recovery and subsequent data download. ADB tags were deployed on sperm whales ( Physeter macrocephalus; N = 46), blue whales ( Balaenoptera musculus; N = 8), and fin whales ( B. physalus; N = 5) from 2007 to 2015, resulting in attachment durations from 0 to 49.6 days, and recording 31 to 2,539 GPS locations and 27 to 2,918 dives per deployment. Archived dive profiles matched well with published dive shapes of each species from short-term records. For blue and fin whales, feeding lunges were detected using peaks in accelerometer data and matched corresponding vertical excursions in the depth record. In sperm whales, rapid orientation changes in the accelerometer data, often during the bottom phase of dives, were likely related to prey pursuit, representing a relative measure of foraging effort. Sperm whales were documented repeatedly diving to, and likely foraging along, the seafloor. Data from the temperature sensor described the vertical structure of the water column in all three species, extending from the surface to depths >1,600 m. In addition to providing information needed to construct multiweek time budgets, the ADB tag is well suited to studying the effects of anthropogenic sound on whales by allowing for pre- and post-exposure monitoring of the whale's dive behavior. This tag begins to bridge the gap between existing long-duration but low-data throughput tags, and short-duration, high-resolution data loggers. [ABSTRACT FROM AUTHOR]

Background: In animals, recoil motion resulting from underwater propulsion can destabilise trajectory and decrease locomotory performance. The posture of diving seabirds fluctuates simultaneously with their appendage beat, especially in the vertical plane, because of the recoil force of the beat. Seabirds that fly and swim face trade-offs between maximising their locomotory performance in one medium relative to the other, and flightless penguins were hypothesised to have higher underwater pitching stability than alcids that fly and swim. To test this hypothesis, we investigated the in situ pitching stability of three species of diving seabirds, including a penguin, Pygoscelis adeliae, and two species of alcids, Cerorhinca monocerata and Uria lomvia. A high-resolution gyroscope data logger was attached to the back of each bird and recorded the angular velocity of the body during the descent phase of dives. Results: For all three species, the root mean square (RMS) of the angular velocity, which indicated the level of angular fluctuation, was negatively correlated with the depth. Many factors, such as the dorsoventral acceleration resulting from wing beat, dive angle, speed, and current depth, as well as the maximum depth in each dive, significantly affected the angular velocity RMS. The angular velocity RMS at a given depth (e.g. 5 and 10 m) significantly increased with the maximum depth of the dives, suggesting buoyancy regulation relative to the target depth to reduce the destabilising angular momentum in all three species. During entire descent periods, the angular fluctuation was generally lower in P. adeliae than in the two species of alcids, supporting the hypothesis of a higher pitching stability in penguins. Furthermore, the angular fluctuation of U. lomvia was lower than that of C. monocerata at deeper depths, suggesting higher pitching stability and more efficient underwater locomotion in U. lomvia. Conclusions: This study demonstrated a difference in the pitching stability, which is an important component of underwater locomotory efficiency, of a penguin and two alcid species while diving freely in natural conditions. In situ angular fluctuation data obtained by gyroscope would be useful to understand the locomotory strategy of swimming animals. [ABSTRACT FROM AUTHOR]

As the Antarctic Circumpolar Current crosses the South-West Indian Ocean Ridge, it creates an extensive eddy field characterised by high sea level anomaly variability. We investigated the diving behaviour of female southern elephant seals from Marion Island during their post-moult migrations in relation to this eddy field in order to determine its role in the animals' at-sea dispersal. Most seals dived within the region significantly more often than predicted by chance, and these dives were generally shallower and shorter than dives outside the eddy field. Mixed effects models estimated reductions of 44.33 ± 3.00 m (maximum depth) and 6.37 ± 0.10 min (dive duration) as a result of diving within the region, along with low between-seal variability (maximum depth: 5.5 % and dive duration: 8.4 %). U-shaped dives increased in frequency inside the eddy field, whereas W-shaped dives with multiple vertical movements decreased. Results suggest that Marion Island's adult female elephant seals' dives are characterised by lowered cost-of-transport when they encounter the eddy field during the start and end of their post-moult migrations. This might result from changes in buoyancy associated with varying body condition upon leaving and returning to the island. Our results do not suggest that the eddy field is a vital foraging ground for Marion Island's southern elephant seals. However, because seals preferentially travel through this area and likely forage opportunistically while minimising transport costs, we hypothesise that climate-mediated changes in the nature or position of this region may alter the seals' at-sea dispersal patterns. [ABSTRACT FROM AUTHOR]

Evidence is presented from publicly available remotely operated vehicle ( ROV) footage that suggests deep-water ranging in ocean sunfishes (family Molidae) is more common than typically thought, including a new maximum depth recorded for the southern sunfish Mola ramsayi. [ABSTRACT FROM AUTHOR]

Studies of seabird-prey interactions often focus on biotic factors, such as prey abundance, seabird biomechanics and competition. In contrast, we examined the influence of abiotic factors, particularly weather, light and tide, on the diving behaviour of thick-billed murre ( Uria lomvia) foraging in the Canadian Low Arctic. We found little evidence that tide and weather influenced dive behaviour. As visual predators, light availability limits foraging opportunities; however, prey often surface at night so there may be a trade-off between increased food availability and reduced foraging ability during low-light conditions. Our data lent support to both ideas, as dive depth increased with light availability and the proportion of vertically migrating schooling prey was highest during sunup and sundown. There was no difference in dive depth between sexes outside the period of sundown; males, which forage at night, dove shallower than females in the late afternoon, which we suggest is because they specialize on shallow prey often caught at night. Apparently, adaptation for higher oxygen stores or lower oxygen consumption in deeper-diving females overrode any adaptation for improved vision in night-specialist males. We concluded that light availability interacted with prey vertical migration to impact underwater foraging abilities of breath-hold divers. [ABSTRACT FROM AUTHOR]

Many marine birds dive to catch prey in water. The gentoo penguin (Pygoscelis papua), a specialized diving seabird that preys on krill and fish, is distributed from the sub-Antarctic islands to Antarctic regions. Here, we observed the diving behavior of breeding gentoo penguins on King George Island, South Shetland Islands, Antarctica. Using a time–depth recorder, we collected diving depths every second from seven gentoo breeders for 5–21 days during the chick-rearing period and analyzed their diving characteristics. Most dives occurred in shallow water, although the dive efficiency (=bottom duration time/[dive duration + post-dive surface time]) was highest at depths of 30–35 m and decreased as the penguins dove deeper. Gentoo penguins did not dive more frequently during the day than at night, but during nighttime, most dives occurred in shallow water (<20 m) and the dive efficiency was also higher at this time. As penguins repeated their foraging trips, the number of dives, depth of dives, and trip duration did not change significantly. Our results suggest that the diel dive patterns of gentoo penguins might be related to the vertical migration of krill (upward to the surface at night). In addition, we observed that gentoo penguins could perform active diving behavior even at night, possibly aided by civil twilight during the chick-rearing period in Antarctic regions. [ABSTRACT FROM AUTHOR]

While it is widely known that marine mammals possess adaptations which allow them to make repetitive and extended dives to great depths without suffering ill effects seen in humans, the response of marine mammal immune cells to diving is unknown. Renewed interest in marine mammal dive physiology has arisen due to reports of decompression sickness-like symptoms and embolic damage in stranded and by-caught animals, and there is concern over whether anthropogenic activities can impact marine mammal health by disrupting adaptive dive responses and behavior. This work addresses the need for information concerning marine mammal immune function during diving by evaluating granulocyte and monocyte phagocytosis, and granulocyte activation in belugas (n = 4) in comparison with humans (n = 4), with and without in vitro pressure exposures. In addition, the potential for additional stressors to impact immune function was investigated by comparing the response of beluga cells to pressure between baseline and stressor conditions. Granulocyte and monocyte phagocytosis, as well as granulocyte activation, were compared between pressure exposed and non-exposed cells for each condition, between different pressure profiles and between conditions using mixed generalized linear models (a = 0.05). The effects of pressure varied between species as well by depth, compression/decompression rates, and length of exposures, and condition for belugas. Pressure induced changes in granulocyte and monocyte function in belugas could serve a protective function against dive-related pathologies and differences in the response between humans and belugas could reflect degrees of dive adaptation. The alteration of these responses during physiologically challenging conditions may increase the potential for dive-related in jury and disease in marine mammals. [ABSTRACT FROM AUTHOR]

Marine tetrapods represent powerful models for studying how evolutionary transitions shape the life history traits, physiology and behaviour of animals. Whereas adaptations to diving are driven primarily by the need to secure underwater food, diving in the pelagic sea snake, Hydrophis ( Pelamis ) platurus , seems less foraging-dependent. Indeed, this reptile captures fish while floating at the sea surface. Despite knowledge about its surface ecology, its underwater behaviour remains mostly unknown. Yet, study of this life phase is a key to understanding how and why this snake dives. In this study, we reanalysed published data on its diving behaviour. The pelagic sea snake spends 95% of its time underwater, where it can dive to 50 m and stay for 3.5 h without breathing. Dives are S-shaped, with a long phase of gradual ascent during which the snake is neutrally buoyant. Snake lungs deflate slowly during this phase at a rate that increases with water temperature, and thus metabolism. Dive duration is linked to inferred lung volume at the start of the dive, suggesting aerobic diving. We propose that pelagic sea snakes dive for multiple reasons, but primarily to avoid sea surface turbulence. Underwater, they can reduce metabolism by targeting cooler water layers. By hovering in the water column, they reduce energy expenditure and escape both surface and bottom predators, while more easily locating their own prey from underneath. Some marine turtles occasionally display S-shaped dives, but the role of such dives remains under debate. We suggest the study of sea snakes can help interpret diving behaviour in other lineages of marine reptiles. [ABSTRACT FROM AUTHOR]

The sperm whales (Physeter macrocephalus) within the Kaikoura Canyon (New Zealand) have a regular spatio-temporal pattern between their time spent at the surface and the time diving for food. We built a spatio-temporal model that tracks the identity of individuals from a dataset of sperm whale sightings collected from a shore-based station. The model was built on the hypothesis that an individual should surface inside a spatio-temporal buffer of 30 to 60 min and 3 km around its last dive position. In order to validate the model, we correlated photo-identification of sperm whales collected from a boat-based station with the predictive identification made by the model. With the simultaneously recorded shore- and boat-based observations, a total of 160 sightings of sperm whales were made. We found that on average, 88% of our observed (boat-based) data were correctly predicted by the model. [ABSTRACT FROM AUTHOR]

The article investigates the diving skill development and potential inter-sex differences of fledgling brown boobies (Sula leucogaster) populating the Central Gulf of California, Mexico. Observations showed that the birds' maximum diving depth and duration increased notably between 21 and 25 days after first flight. It was also noted that maximum dive depth was not influenced by time or by sex difference while diving abilities can be a driver for post-fledgling parental care.

Locomotion accounts for a significant proportion of the energy budget in birds, and selection is likely to act on its economy, particularly where energy conservation is essential for survival. Birds are capable of different forms of locomotion, such as walking/running, swimming, diving and flying, and adaptations for these affect the energetic cost [cost of locomotion (CoL)] and kinematics of terrestrial locomotion. Furthermore, seasonal changes in climate and photoperiod elicit physiological and behavioural adaptations for survival and reproduction, which also influence energy budget. However, little is understood about how this might affect the CoL. Birds are also known to exhibit sex differences in size, behaviour and physiology; however, sex differences in terrestrial locomotion have only been studied in two cursorially adapted galliform species in which males achieved higher maximum speeds, and in one case had a lower mass-specific CoL than females. Here, using respirometry and high-speed video recordings, we sought to determine whether season and sex would affect the CoL and kinematics of a principally aquatic diving bird: the circumpolar common eider ( Somateria mollissima). We demonstrate that eiders are only capable of a walking gait and exhibit no seasonal or sex differences in mass-specific CoL or maximum speed. Despite sharing identical limb morphometrics, the birds exhibited subtle sex differences in kinematic parameters linked to the greater body mass of the males. We suggest that their principally aquatic lifestyle accounts for the observed patterns in their locomotor performance. Furthermore, sex differences in the CoL may only be found in birds in which terrestrial locomotion directly influences male reproductive success. [ABSTRACT FROM AUTHOR]

Optimal diving theory predicts that animals make decisions that maximize their foraging profitability subject to the constraint of oxygen stores. We examined the temporal pattern of prey encounters within a dive from concurrently collected dive data and animal-borne video from a free-ranging pinniped to test predictions of optimal diving theory. C rittercams were deployed on 32 adult male harbour seals ( Phoca vitulina concolor De Kay, 1842) at Sable Island, Nova Scotia, Canada, for 3 days each. Deployments resulted in approximately 3 h of video per seal and a total of 2275 capture attempts for 1474 prey encounter events recorded. We found support for seven of the nine selected predictions of optimal diving theory. As predicted, prey encounters increased with bottom duration; dive duration increased with dive depth; and travel duration, bottom duration, and percent bottom duration decreased over a wide range of travel durations. Descent duration did increase with dive depth, and seals terminated dives earlier when no prey were encountered and when prey were encountered later in a dive. Contrary to prediction, bottom duration did not increase and then decrease for short travel durations and dives were not terminated earlier when travel durations were short and prey encounter rate was low. [ABSTRACT FROM AUTHOR]

Leatherback sea turtles, Dermochelys coriacea, are highly migratory predators that feed exclusively on gelatinous zooplankton, thus playing a unique role in coastal and pelagic food webs. From 2007 to 2010, we used satellite telemetry to monitor the movements and dive behavior of nine adult and eleven subadult leatherbacks captured on the Northeast USA shelf and tracked throughout the Northwest Atlantic. Leatherback movements and environmental associations varied by oceanographic region, with slow, sinuous, area-restricted search behavior and shorter, shallower dives occurring in cool (median sea surface temperature: 18.4°C), productive (median chlorophyll a: 0.80 mg m−3), shallow (median bathymetry: 57 m) shelf habitat with strong sea surface temperature gradients (median SST gradient: 0.23°C km−1) at temperate latitudes. Leatherbacks were highly aggregated in temperate shelf and slope waters during summer, early fall, and late spring and more widely dispersed in subtropical and tropical oceanic and neritic habitat during late fall, winter and early spring. We investigated the relationship of ecoregion, satellite-derived surface chlorophyll, satellite-derived sea surface temperature, SST gradient, chlorophyll gradient and bathymetry with leatherback search behavior using generalized linear mixed-effects models. The most well supported model showed that differences in leatherback search behavior were best explained by ecoregion and regional differences in bathymetry and SST. Within the Northwest Atlantic Shelves region, leatherbacks increased path sinuosity (i.e., looping movements) with increasing SST, but this relationship reversed within the Gulf Stream region. Leatherbacks increased path sinuosity with decreasing water depth in temperate and tropical shelf habitats. This relationship is consistent with increasing epipelagic gelatinous zooplankton biomass with decreasing water depth, and bathymetry may be a key feature in identifying leatherback foraging habitat in neritic regions. High-use habitat for leatherbacks in our study occurred in coastal waters of the North American eastern seaboard and eastern Caribbean, putting turtles at heightened risk from land- and ocean-based human activity. [ABSTRACT FROM AUTHOR]

The diving ability of juvenile animals is constrained by their physiology, morphology and lack of experience, compared to adults. We studied the influences of age and mass on the diving behaviour of juvenile (2-3-year-old females, n = 12; 3-5-year-old males, n = 7) New Zealand (NZ) sea lions ( Phocarctos hookeri) using time-depth recorders (TDRs) from 2008 to 2010 in the NZ subantarctic Auckland Islands. Diving ability (e.g. dive depth, duration and bottom time per dive) improved with age and mass. However, the percentage of each dive spent at the bottom, along with percentage time at sea spent diving, was comparable between younger and lighter juveniles and older and heavier juveniles. These suggest that younger and older juveniles expend similar foraging effort in terms of the amount of time spent underwater. Only, 5-year-old male juveniles dove to adult female depths and durations and had the highest foraging efficiency at depths >250 m. It appears that juvenile NZ sea lions attain adult female diving ability at around 5 years of age (at least in males), but prior to this, their performance is limited. Overall, the restricted diving capabilities of juvenile NZ sea lions may limit their available foraging habitat and ability to acquire food at deeper depths. The lower diving ability of juvenile NZ sea lions compared to adults, along with juvenile-specific constraints, should be taken into consideration for the effective management of this declining, nationally critical species. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

With the exception of relatively brief periods when they reproduce and moult, hooded seals, Cystophora cristata, spend most of the year in the open ocean where they undergo feeding migrations to either recover or prepare for the next fasting period. Valuable insights into habitat use and diving behaviour during these periods have been obtained by attaching Satellite Relay Data Loggers (SRDLs) to 51 Northwest (NW) Atlantic hooded seals (33 females and 18 males) during ice-bound fasting periods (2004−2008). Using General Additive Models (GAMs) we describe habitat use in terms of First Passage Time (FPT) and analyse how bathymetry, seasonality and FPT influence the hooded seals’ diving behaviour described by maximum dive depth, dive duration and surface duration. Adult NW Atlantic hooded seals exhibit a change in diving activity in areas where they spend >20 h by increasing maximum dive depth, dive duration and surface duration, indicating a restricted search behaviour. We found that male and female hooded seals are spatially segregated and that diving behaviour varies between sexes in relation to habitat properties and seasonality. Migration periods are described by increased dive duration for both sexes with a peak in May, October and January. Males demonstrated an increase in dive depth and dive duration towards May (post-breeding/pre-moult) and August–October (post-moult/pre-breeding) but did not show any pronounced increase in surface duration. Females dived deepest and had the highest surface duration between December and January (post-moult/pre-breeding). Our results suggest that the smaller females may have a greater need to recover from dives than that of the larger males. Horizontal segregation could have evolved as a result of a resource partitioning strategy to avoid sexual competition or that the energy requirements of males and females are different due to different energy expenditure during fasting periods. [ABSTRACT FROM AUTHOR]

Abstract: Hawksbill sea turtles (Eretmochelys imbricata) nesting in Barbados were outfitted with time-depth recorders (TDRs) with temperature sensors to investigate the form and patterns of diving behaviour during the inter-nesting interval (INI; average 14.7days). All females, regardless of size, surfaced infrequently during dives of average 56min duration, and the majority of dives (90%) were spent in the bottom phase at 15–25m depths, which corresponded to the depth of benthic habitat at each location. Diving activity was highest while commuting to and from the nesting beach (about 1–2days each way), with a level of quiescence during the intermediate period (i.e. the majority of the INI). Despite little thermal variation in seawater at this latitude (13.1°N), the length of the INI was influenced by ambient sea water temperature. Diving behaviour was consistent with females conserving energy reserves built up at foraging grounds prior to arrival at the nesting beach and minimising time spent in the water column away from safe refuge at night. The frequency of surfacing and the depths at which females spend most of their time varies between sites even within one species and may be crucial in managing the risks to animals temporarily residing offshore from important nesting beaches. [Copyright &y& Elsevier]

Highlights: [•] During surveys, diving taxa must often be at or near the surface to be detected. [•] We studied effects of variation in sea turtle diving on analyses of sightings data. [•] Several analyses were biased or confounded by spatiotemporal variation in diving. [•] Long winter dives led to negative detection bias and density underestimates. [•] Diving and depth use studies are needed for the conservation of diverse divers. [ABSTRACT FROM AUTHOR]

The diving capacity of marine mammals is typically defined by the aerobic dive limit (ADL) which, in lieu of direct measurements, can be calculated (cADL) from total body oxygen stores (TBO) and diving metabolic rate (DMR). To estimate cADL, we measured blood oxygen stores, and combined this with diving oxygen consumption rates (VO) recorded from 4 trained Steller sea lions diving in the open ocean to depths of 10 or 40 m. We also examined the effect of diving exercise on O stores by comparing blood O stores of our diving animals to non-diving individuals at an aquarium. Mass-specific blood volume of the non-diving individuals was higher in the winter than in summer, but there was no overall difference in blood O stores between the diving and non-diving groups. Estimated TBO (35.9 ml O kg) was slightly lower than previously reported for Steller sea lions and other Otariids. Calculated ADL was 3.0 min (based on an average DMR of 2.24 L O min) and was significantly shorter than the average 4.4 min dives our study animals performed when making single long dives-but was similar to the times recorded during diving bouts (a series of 4 dives followed by a recovery period on the surface), as well as the dive times of wild animals. Our study is the first to estimate cADL based on direct measures of VO and blood oxygen stores for an Otariid and indicates they have a much shorter ADL than previously thought. [ABSTRACT FROM AUTHOR]

Understanding the links between foraging behaviour and habitat use of key species is essential to addressing fundamental questions about trophic interactions and ecosystem functioning. Eight female grey seals (Halichoerus grypus) were equipped with time-depth recorders linked to Fastloc GPS tags following the annual moult in southwest Ireland. Individual dives were coupled with environmental correlates to investigate the habitat use and dive behaviour of free-ranging seals. Dives were characterised as either pelagic, benthic, or shallow (where errors in location and charted water depth made differentiating between pelagic and benthic dives unreliable). Sixty-nine percent of dives occurring in water >50 m were benthic. Pelagic dives were more common at night than during the day. Seals performed more pelagic dives over fine sediments (mud/sand), and more benthic dives when foraging over more three-dimensionally complex rock substrates. We used Markov chain analysis to determine the probability of transiting between dive states. A low probability of repeat pelagic dives suggests that pelagic prey were encountered en route to the seabed. This approach could be applied to make more accurate predictions of habitat use in data-poor areas, and investigate contentious issues such as resource overlap and competition between top predators and fisheries, essential for the effective conservation of these key marine species. [ABSTRACT FROM AUTHOR]

Identification of Area-restricted search (ARS) behaviour is used to better understand foraging movements and strategies of marine predators. Track-based descriptive analyses are commonly used to detect ARS behaviour, but they may be biased by factors such as foraging trip duration or non-foraging behaviours (i.e. resting on the water). Using first-passage time analysis we tested if (I) daylight resting at the sea surface positions falsely increase the detection of ARS behaviour and (II) short foraging trips are less likely to include ARS behaviour in Masked Boobies Sula dactylatra. We further analysed whether ARS behaviour may be used as a proxy to identify important feeding areas. Depth-acceleration and GPS-loggers were simultaneously deployed on chick-rearing adults to obtain (1) location data every 4 minutes and (2) detailed foraging activity such as diving rates, time spent sitting on the water surface and in flight. In 82% of 50 foraging trips, birds adopted ARS behaviour. In 19.3% of 57 detected ARS zones, birds spent more than 70% of total ARS duration resting on the water, suggesting that these ARS zones were falsely detected. Based on generalized linear mixed models, the probability of detecting false ARS zones was 80%. False ARS zones mostly occurred during short trips in close proximity to the colony, with low or no diving activity. This demonstrates the need to account for resting on the water surface positions in marine animals when determining ARS behaviour based on foraging locations. Dive rates were positively correlated with trip duration and the probability of ARS behaviour increased with increasing number of dives, suggesting that the adoption of ARS behaviour in Masked Boobies is linked to enhanced foraging activity. We conclude that ARS behaviour may be used as a proxy to identify important feeding areas in this species. [ABSTRACT FROM AUTHOR]

For many marine organisms, especially large whales that cannot be studied in laboratory settings, our ability to obtain basic behavioral and physiological data is limited, because these organisms occupy offshore habitats and spend a majority of their time underwater. A class of multisensor, suction-cup-attached archival tags has revolutionized the study of large baleen whales, particularly with respect to the predatory strategies used by these gigantic bulk filter feeders to exploit abundant oceanic resources. By integrating these data with those from other disciplines, researchers have uncovered a diverse and extraordinary set of underwater behaviors, ranging from acrobatic diving maneuvers to extreme feeding events during which whales engulf volumes of prey-laden water that are much larger than their own body. This research framework not only improves our knowledge of the individual performance and behavior of these keystone predators but also informs our ability to understand the dynamics of complex marine ecosystems. [ABSTRACT FROM AUTHOR]

Understanding the solubility of nitrogen gas in tissues is a crucial aspect of diving physiology, especially for air-breathing tetrapods. Adipose tissue is of particular interest because of the high solubility of nitrogen in lipids. Surprisingly, nothing is known about nitrogen solubility in the blubber of any marine mammal. We tested the hypothesis that N2 solubility is dependent on the lipid composition of blubber; most blubber is composed of triacylglycerols, but some toothed whales deposit large amounts of waxes in blubber instead. The solubility of N2 in the blubber of 13 toothed whale species ranged from 0.062 to 0.107 ml N2ml-1 oil. Blubber with high wax ester content had higher N2 solubility, observed in the beaked (Ziphiidae) and small sperm (Kogiidae) whales, animals that routinely make long, deep dives. We also measured nitrogen solubility in the specialized cranial acoustic fat bodies associated with echolocation in a Risso's dolphin; values (0.087 ml N2ml~1 oil) were 16% higher here than in its blubber (0.074 ml N2ml-1 oil). As the acoustic fats of all Odontocetes contain waxes, even if the blubber does not, these tissues may experience greater interaction with N2. These data have implications for our understanding and future modeling of diving physiology in Odontocetes, as our empirically derived values for nitrogen solubility in toothed whale adipose were up to 40% higher than the numbers traditionally assumed in marine mammal diving models. [ABSTRACT FROM AUTHOR]

Sperm whales have depredated black cod (Anoplopoma fimbria) from demersal longlines in the Gulf of Alaska for decades, but the behavior has recently spread in intensity and geographic coverage. Over a three-year period 11 bioacoustic tags were attached to adult sperm whales off Southeast Alaska during both natural and depredation foraging conditions. Measurements of the animals' dive profiles and their acoustic behavior under both behavioral modes were examined for statistically significant differences. Two rough categories of depredation are identified: 'deep' and 'shallow.' 'Deep depredating' whales consistently surface within 500 m of a hauling fishing vessel, have maximum dive depths greater than 200 m, and display significantly different acoustic behavior than naturally foraging whales, with shorter inter-click intervals, occasional bouts of high 'creak' rates, and fewer dives without creaks. 'Shallow depredating' whales conduct dives that are much shorter, shallower, and more acoustically active than both the natural and deep depredating behaviors, with median creak rates three times that of natural levels. These results suggest that depredation efforts might be measured remotely with passive acoustic monitoring at close ranges. [ABSTRACT FROM AUTHOR]

ABSTRACT Species of petrels and shearwaters with high diving ability could facilitate the catch of albatrosses in pelagic longline fisheries, because they retrieve bait to the surface from depths that albatrosses cannot reach. Once on the surface, large seabirds such as albatrosses can easily displace smaller species thus gaining access to baited hooks which increases their likelihood of getting caught., This paper evaluates the extent to which diving species (i.e. Procellaria aequinoctialis, Procellaria conspicillata and Puffinus gravis) increase the susceptibility of albatross to bycatch in pelagic longline fisheries. In 48 sets, attacks on baits were quantified. When more than one bird (of the same or different species) tried to attack the same bait this was defined as a multiple attack., There were 384 attacks on baits, of which 260 were made by a single individual and 124 by more than one. Multiple attacks were the largest source of bycatch of albatrosses (22 of 27 albatrosses whose attacks were observed)., Of the baits attacked by albatrosses (n = 244), 17% were indirectly facilitated by diving medium-sized petrels. Considering only the multiple attacks in which albatrosses participated (n = 114), 36% were initiated by these medium-sized petrels. Eleven (41%) of the albatrosses captured, and whose attacks were observed, resulted from a diving medium-sized seabird species first having contacted the terminal tackle., This paper shows that medium-sized petrels, with a strong ability to dive, increase considerably the access to bait, and indirectly, the incidental bycatch of albatrosses. Observations made in the absence of mitigation measures also provide useful information to improve the performance of tori lines. Based on the seabird behaviour, it is recommended that tori lines should have a minimum aerial coverage of 50 m. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We examined depth preference in adult zebrafish in a modified visual cliff apparatus, in which distance from the water surface and distance from the substrate could be independently manipulated. In one condition, when the two sides of the apparatus genuinely differed in depth, subjects showed a powerful preference for the deeper side. In another condition, both sides of the tank were set to the same depth using a glass insert, but one side was made to appear deeper by placing gravel substrate just below the glass floor on one side, and far below the glass floor on the other, in an analogue of the visual cliff paradigm. Although terrestrial animals tend to avoid the ‘deeper’-looking side of a visual cliff apparatus, zebrafish preferred the side that appeared deeper. They showed no preference for the side in which they could be closer to the gravel substrate. This effect appeared whether or not the gravel represented a novel stimulus for the fish. We conclude that escape from the surface, rather than approach to the substrate, motivates the diving response in zebrafish. [Copyright &y& Elsevier]

Surfacing behaviour is fundamental in the ecology of aquatic air-breathing organisms; however, it is only in vertebrates that the evolutionary ecology of diving has been well characterized. Here, we explore the diving behaviour of dytiscid beetles, a key group of surface-exchanging freshwater invertebrates, by comparing the dive responses of 25 taxa ( Deronectes and Ilybius spp.) acclimated at two temperatures. The allometric slopes of dive responses in these dytiscids appear similar to those of vertebrate ectotherms, supporting the notion that metabolic mode shapes the evolution of diving performance. In both genera, beetles spend more time submerged than on the surface, and surface time does not vary with the temperature of acclimation. However, presumably in order to meet increased oxygen demand at higher temperatures, Deronectes species increase surfacing frequency, whereas Ilybius species decrease dive time, an example of 'multiple solutions.' Finally, widespread northern species appear to possess higher diving performances than their geographically restricted southern relatives, something which may have contributed to their range expansion ability. [ABSTRACT FROM AUTHOR]

The article presents a study on the association between hunting strategy and dive profiles in the Australasian gannet using underwater videography. The researchers recorded 50 minutes of underwater video footage of Australasian gannet dive behavior from 11 stationary dusky dolphin Lagenorhynchus obscurus feeding bouts. They also used the water bubble trajectory and the water surface as horizontal and vertical references. They found that U- and V-shaped dives could be related indirectly to the foraging behaviors of conspecifics and of other marine predators.

The article presents a study which examines the relationship between the dive characteristics of southern elephant seals in Marion Island, Prince Edward Islands, and environmental variables including ocean temperature and bathymetry. The study placed 59 satellite-relay data loggers (SRDLs) on elephant seals from 2004-2008, and animal location was obtained through Service Argos. Findings revealed that ocean temperature significantly affects the dive depths and dive duration of elephant seals.

The structural features of the venous system of seals, including such specialties as a caval sphincter, a huge posterior caval vein and hepatic sinuses, venous plexuses and a huge extradural intravertebral vein, are described and functional aspects of these features in relation to diving habits are discussed. A number of old concepts are discarded and new ones are proposed, particularly with regard to the significance of the extradural intravertebral vein, which, contrary to common current belief, probably is of little importance during diving. [ABSTRACT FROM AUTHOR]

The article discusses a study on the effect of diverse oceanographic conditions and prey communities on the foraging behavior of little auks Alle alle in Greenland Sea. The study used time-depth recorders to compare the diving behavior and time allocation of little auks breeding adjacent to the East Greenland Current (EGC), the Sørkapp Current (SC), and West Spitsbergen Current (WSC). The study found that EGC is a favorable foraging environment than WSC and SC.

Abstract: In 1960, C.G. Wilber in a laboratory-based study described for the first time the changes in heart rate with submergence in the American alligator noting in particular the marked bradycardia that occurred during forced dives. This short review summarizes the major advances in our understanding of diving and the responses and role of the cardiovascular system of crocodilians during submergence in the 50years since Wilber published his findings. These advances are attributable in part to the technological advances made in physiological monitoring devices and wildlife telemetry that have not only provided greater elucidation of the hemodynamics of the unique crocodilian cardiovascular system but also allowed the natural diving behaviors and heart rates in free-ranging crocodiles to be recorded. Of note, telemetric field-based studies have revealed that wild free-ranging crocodiles typically undertake only short dives, less than 20min, yet crocodiles are also capable of dives of many hours in duration. In contrast to Wilber''s study, dives recorded from free-ranging crocodiles were found to be accompanied by only a modest bradycardia, highlighting the often confounding effects associated with captive animals monitored under laboratory conditions. More recent studies have also documented the complex central flow and pressure patterns of crocodilians, including a pulmonary to systemic shunt that can be initiated by a unique intracardiac valve located in the subpulmonary conus. The role and significance of this cardiac shunt remains controversial and the focus of recent lab-based studies. We contend that elucidation of the role and significance of the cardiac shunt in crocodilians will only be achieved by monitoring telemetrically the central cardiovascular flows and pressures in non-captive animals that are undisturbed and free-ranging. This presents the challenge ahead in the next 50years. [Copyright &y& Elsevier]

Many birds and mammals forage under water and have to return to the surface to breathe. Models of optimal diving attempt to explain the behaviour of such animals in terms of selection for successful foraging given the constraints imposed by physiology. Several recent papers have questioned the accuracy of both the assumptions and the predictions of these models. Here, I provide a critical review of these papers, arguing that they misrepresent both the models and the data. As a result, they focus on inappropriate tests. I use the debate to suggest various new models and to explore the general relationship between theory and data in behavioural ecology. In particular, I consider the merits of qualitative and quantitative predictions. [ABSTRACT FROM AUTHOR]

Abstract: Whale flukeprints are an often observed, but poorly understood, phenomenon. Used by whale researchers to locate whales, flukeprints refer to a strikingly smooth oval-shaped water patch which forms behind a swimming or diving whale on the surface of the ocean and persists up to several minutes. In this paper we provide a description of hydrodynamic theory and related experiments explaining the creation and evolution of these “whale footprints.” The theory explains that the motion of the fluke provides a mechanism for shedding of vortex rings which subsequently creates a breakwater that damps the short wavelength capillary waves. The theory also suggests that the role of natural surfactants are of secondary importance in the early formation of these prints. [Copyright &y& Elsevier]

Abstract: The diving response in marine mammals results in bradycardia and peripheral vasoconstriction, with blood flow redistributing preferentially to nervous and cardiac tissues. Therefore, some tissues are rendered ischemic during a dive; with the first breath after a dive, blood flow to all tissues is reestablished. In terrestrial mammals, reactive oxygen species (ROS) production increases in response to ischemia/reperfusion and oxidative damage can occur. The capacity of marine mammals to tolerate repeated ischemia/reperfusion cycles associated with diving appears to be due to an enhanced antioxidant system. However, it is not known if diving depth and/or duration elicit differences in tissue capacity to produce ROS and antioxidant defenses in marine mammals. The objective of this study was to analyze ROS production, antioxidant defenses and oxidative damage in marine mammal species that perform shallow/short vs. deep/long dives. We measured production of superoxide radical (O2 •−), oxidative damage to lipids and proteins, activity of antioxidant enzymes, and glutathione levels in tissues from shallow/short divers (Tursiops truncatus) and deep/long divers (Kogia spp.). We found that differences between the diving capacity of dolphins and Kogia spp. are reflected in O2 •− production and antioxidant levels. These differences suggest that shallow/short and deep/long divers have distinct mechanisms to successfully maintain redox balance. [Copyright &y& Elsevier]

The article presents a study on the diving behaviour and lunar responses of the Northern fur seal (NFS) Callorhinus ursinus. For the study, researchers deployed 64 SPASH dive tags on the seal pups from four North American breeding locations during the autumn season of 2005 and 2006. They observed that the pups showed nocturnal diving patterns similar to adults during the first month at sea. They found that the diving capacity of seals increasd linearly with age until 8 to 10 months of age in association with maximum depths and durations. They observed that pups have a tendency to dive deeper and for longer periods during full moons compared to other lunar stages.

Abstract: Understanding food web functioning through the study of natural bio-indicators may constitute a valuable and original approach. In the context of jellyfish proliferation in many overexploited marine ecosystems studying the spatio-temporal foraging patterns of the giant “jellyvore” leatherback turtle turns out to be particularly relevant. Here we analyzed long-term tracking data to assess spatio-temporal foraging patterns in 21 leatherback turtles during their pluri-annual migration in the Northern Atlantic. Through an analytical approach based on the animal''s own motion (independent of currents) and diving behavior distinct zones of high and low foraging success were identified. High foraging success occurred in a sub-equatorial zone spanning the width of the Atlantic and at high (>30°N) latitudes. Between these zones in the centre of North Atlantic gyre there was low foraging success. This “ocean desert” area was traversed at high speed by leatherbacks on their way to more productive areas at higher latitudes. Animals traveled slowly in high foraging success areas and dived shallower (17.2±8.0kmday−1 and 53.6±33.1m mean±SD respectively) than in low foraging success areas (51.0±13.1kmday−1 and 81.8±56.2m mean±SD respectively). These spatio-temporal foraging patterns seem to relatively closely match the main features of the integrated meso-zooplankton distribution in the North Atlantic. Our method of defining high foraging success areas is intuitive and relatively easy to implement but also takes into account the impact of oceanic currents on animal''s behavior. [Copyright &y& Elsevier]

Chinstrap, Pygoscelis antarctica, and gentoo, P. papua, penguins are sympatric species that inhabit the Antarctic Peninsula. To evaluate differences in the foraging habitat of these two species, we recorded their foraging locations and diving behavior using recently developed GPS-depth data loggers. The study was conducted on King George Island, Antarctica during the chick-guarding period of both species, from December 2006 to January 2007. The area used for foraging, estimated as the 95% kernel density of dive (>5 m) locations, overlapped partially between the two species (26.4 and 68.5% of the area overlapped for chinstrap and gentoo penguins, respectively). However, the core foraging area, estimated as the 50% kernel density, was mostly separate (12.8 and 25.0% of the area overlapped for chinstrap and gentoo penguins, respectively). Chinstrap penguins tended to use off-shelf (water depth > 200 m) regions (77% of the locations for dives >5 m), whereas gentoo penguins mainly used on-shelf (water depth < 200 m) areas (71% of dive locations). The data on foraging locations, diving behavior, and bathymetry indicated that gentoo penguins often performed benthic dives (28% of dives >5 m), whereas chinstrap penguins almost always used the epipelagic/mid-water layer (96% of dives >5 m). Diving parameters such as diving bottom duration or diving efficiency differed between the species, reflecting differences in the use of foraging habitat. The diving parameters also suggested that the on-shelf benthic layer was profitable foraging habitat for gentoo penguins. Conversely, the relationship between trip duration, date, and stomach content mass suggested that the chinstrap penguins went further from the colony to forage as the season progressed, possibly reflecting a reduction in prey availability near the colony. Our results suggest that chinstrap and gentoo penguins segregated their foraging habitat in the Antarctic coastal marine environment, possibly due to inter- and intra-specific competition for common prey resources. [ABSTRACT FROM AUTHOR]

Abstract: Time-depth-recorders were used to determine the contribution of U-dives in 5 green turtles (Chelonia mydas) during the internesting interval at Wan-an Island, Penghu Archipelago, Taiwan in 2004 and 2005. All turtles had a high incidence of long U-dives (dive duration up to 68min), characterized by constant bottom depth that indicated turtles residing on the seabed. In many cases, these U-dives were inferred to serve a resting function. While there were differences in the incidence of U-dives among individuals, a consistent feature was that U-dive frequency and depth decreased in the days immediately preceding their nesting event. This pattern suggests that preparation for the subsequent nesting event may be a normal process. This observation seems to occur widely among sea turtle species. [Copyright &y& Elsevier]

The article presents a study on the swimming effort of the female green turtles Chelonia mydas with reference to body angle, flipper beat frequency, and swimming speed. It mentions that turtles change their flipper beat frequency along with the current buoyancy just like other diving mammals. It notes that body angles were steepest in the first phases of descent and ascent while swimming speed was associated with current buoyancy and flipper beat frequency. The study also measured the dynamic body acceleration (DBA) as an indicator of its descent and ascent phase activities which revealed an association between DBA and maximum dive depth.

Differences in predation intensity experienced by organisms can lead to divergent natural selection, driving evolutionary change. Western mosquitofish ( Gambusia affinis) exhibit larger caudal regions and higher burst-swimming capabilities when coexisting with higher densities of predatory fish. It is hypothesized that a trade-off between steady (constant-speed cruising; important for acquiring resources) and unsteady (rapid bursts and turns; important for escaping predators) locomotion, combined with divergent selection on locomotor performance (favouring steady swimming in high-competition scenarios of low-predation environments, but unsteady swimming in high-predation localities) has caused such phenotypic divergence. Here, I found that morphological differences had a strong genetic basis, and low-predation fish required less hydromechanical power during steady swimming, leading to increased endurance. I further found individual-level support for cause-and-effect relationships between morphology, swimming kinematics and endurance. Results indicate that mosquitofish populations inhabiting low-predation environments have evolved increased steady-swimming abilities via stiffer bodies, larger anterior body/head regions, smaller caudal regions and greater three-dimensional streamlining. [ABSTRACT FROM AUTHOR]

The article offers information on role of carbon monoxide in enabling elephant seals make deep dives in the ocean and mentions presence of high carbon monoxide levels in the animal's blood, which binds to red blood cells to slow oxygen delivery resulting in increased oxygen supply.