21,927 research outputs found
The scaling of diving time budgets : insights from an optimality approach
No full textThe authors acknowledge the Natural Environment Research Council for support with this work (grant NER/A/S/2003/00616).Simple scaling arguments suggest that, among air-breathing divers, dive duration should scale approximately with mass to the one-third power. Recent phylogenetic analyses appear to confirm this. The same analyses showed that duration of time spent at the surface between dives has scaling very similar to that of dive duration, with the result that the ratio of dive duration to surface pause duration is approximately mass invariant. This finding runs counter to other arguments found in the diving literature that suggest that surface pause duration should scale more positively with mass, leading to a negative scaling of the dive-pause ratio. We use a published model of optimal time allocation in the dive cycle to show that optimal decisions can predict approximate mass invariance in the dive-pause ratio, especially if metabolism scales approximately with mass to the two-thirds power (as indicated by some recent analyses) and oxygen uptake is assumed to have evolved to supply the body tissues at the required rate. However, emergent scaling rules are sensitive to input parameters, especially to the relationship between the scaling of metabolism and oxygen uptake rate at the surface. Our results illustrate the utility of an optimality approach for developing predictions and identifying key areas for empirical research on the allometry of diving behavior.Peer reviewe
Fishing for drifts : detecting buoyancy changes of a top marine predator using a step-wise filtering method
No full textThis research was partly funded by a Natural Environment Research Council grant [NE/E018289/1]. Further, a PhD studentship in Marine Biology partially funded by the Natural Environment Research Council [NE/L501852/1] and the University of St Andrews 600th Scholarship supported this work.In southern elephant seals (Mirounga leonina), fasting and foraging related fluctuations in body composition are reflected by buoyancy changes which can be monitored by changes in drift rate. Here, we present an improved knowledge-based method for detecting buoyancy changes from compressed and abstracted dive profiles received through telemetry. We applied this step-wise filtering method to the dive records of 11 southern elephant seals, which identified 0.8% to 2.2% of all dives as drift dives. At the beginning of the migration, all individuals were strongly negatively buoyant. Over the following 75 to 150 days, the buoyancy reached a peak close to or at neutral buoyancy, indicative of a seal’s foraging success. Ground-truthing confirmed that this new knowledge-based method is capable to reliably detect buoyancy changes in the dive records of drift diving species using abstracted dive profiles. This affirms that the abstraction algorithm conveys sufficient detail of the geometric shape of drift dives for them to be identified. It also suggest that using this step-wise filtering method, buoyancy changes could be detected even in old datasets with compressed dive information, for which conventional drift dive classification previously failed.Peer reviewe
Changes in dive behaviour during naval sonar exposure in killer whales, long-finned pilot whales, and sperm whales.
No full textAnthropogenic underwater sound in the environment might potentially affect the behavior of marine mammals enough to have an impact on their reproduction and survival. Diving behavior of four killer whales (Orcinus orca), seven long-finned pilot whales (Globicephala melas), and four sperm whales (Physeter macrocephalus) was studied during controlled exposures to naval sonar [low frequency active sonar (LFAS): 1–2 kHz and mid frequency active sonar (MFAS): 6–7 kHz] during three field seasons (2006–2009). Diving behavior was monitored before, during and after sonar exposure using an archival tag placed on the animal with suction cups. The tag recorded the animal's vertical movement, and additional data on horizontal movement and vocalizations were used to determine behavioral modes. Killer whales that were conducting deep dives at sonar onset changed abruptly to shallow diving (ShD) during LFAS, while killer whales conducting deep dives at the onset of MFAS did not alter dive mode. When in ShD mode at sonar onset, killer whales did not change their diving behavior. Pilot and sperm whales performed normal deep dives (NDD) during MFAS exposure. During LFAS exposures, long-finned pilot whales mostly performed fewer deep dives and some sperm whales performed shallower and shorter dives. Acoustic recording data presented previously indicates that deep diving (DD) is associated with feeding. Therefore, the observed changes in dive behavior of the three species could potentially reduce the foraging efficiency of the affected animals.Peer reviewe
How man-made interference might cause gas bubble emboli in deep diving whales
No full textRecent cetacean mass strandings in close temporal and spatial association with sonar activity has raised the concern that anthropogenic sound may harm breath-hold diving marine mammals. Necropsy results of the stranded whales have shown evidence of bubbles in the tissues, similar to those in human divers suffering from decompression sickness (DCS). It has been proposed that changes in behavior or physiological responses during diving could increase tissue and blood N2 levels, thereby increasing DCS risk. Dive data recorded from sperm, killer, long-finned pilot, Blainville's beaked and Cuvier's beaked whales before and during exposure to low- (1–2 kHz) and mid- (2–7 kHz) frequency active sonar were used to estimate the changes in blood and tissue N2 tension (PN2). Our objectives were to determine if differences in (1) dive behavior or (2) physiological responses to sonar are plausible risk factors for bubble formation. The theoretical estimates indicate that all species may experience high N2 levels. However, unexpectedly, deep diving generally result in higher end-dive PN2 as compared with shallow diving. In this focused review we focus on three possible explanations: (1) We revisit an old hypothesis that CO2, because of its much higher diffusivity, forms bubble precursors that continue to grow in N2 supersaturated tissues. Such a mechanism would be less dependent on the alveolar collapse depth but affected by elevated levels of CO2 following a burst of activity during sonar exposure. (2) During deep dives, a greater duration of time might be spent at depths where gas exchange continues as compared with shallow dives. The resulting elevated levels of N2 in deep diving whales might also make them more susceptible to anthropogenic disturbances. (3) Extended duration of dives even at depths beyond where the alveoli collapse could result in slow continuous accumulation of N2 in the adipose tissues that eventually becomes a liability.Peer reviewe
Drift diving by hooded seals (Cystophora cristata) in the Northwest Atlantic Ocean
No full textThis work was funded through the Atlantic Seal Research Programme, International Governance Programme (GBS and MOH), the Greenland Institute of Natural Resources (ARA), and a CFI grant to YFW. The authors also acknowledge the support of the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) in the completion of this study. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions (LB).Many pinniped species perform a specific dive type, referred to as a ‘drift dive’, where they drift passively through the water column. This dive type has been suggested to function as a resting/sleeping or food processing dive, and can be used as an indication of feeding success by calculating the daily change in vertical drift rates over time, which reflects the relative fluctuations in buoyancy of the animal as the proportion of lipids in the body change. Northwest Atlantic hooded seals perform drift dives at regular intervals throughout their annual migration across the Northwest Atlantic Ocean. We found that the daily change in drift rate varied with geographic location and the time of year and that this differed between sexes. Positive changes in buoyancy (reflecting increased lipid stores) were evident throughout their migration range and although overlapping somewhat, they were not statistically associated with high use areas as indicated by First Passage Time (FPT). Differences in the seasonal fluctuations of buoyancy between males and females suggest that they experience a difference in patterns of energy gain and loss during winter and spring, associated with breeding. The fluctuations in buoyancy around the moulting period were similar between sexes.Peer reviewe
Protecting Animals 36: Author Witi Ihimaera
No full textIn this very special episode of Knowing Animals I am joined by beloved New Zealand author Witi Ihimaera. Witi has written many books featuring nonhuman animals. He offers us a non-colonial lens through which to think about the human/nonhuman relationship
I Am Not My Genes: Against Genetic Exceptionalism and Essentialism in Justifying Confidentiality Breaches.
No full textAcoustic and foraging behavior of a Baird’s beaked whale, Berardius bairdii, exposed to simulated sonar
No full textResearch was supported by the US Navy Chief of Naval Operations, Environmental Readiness Program, the Office of Naval Research, the Naval Postgraduate School, and the National Research Council.Beaked whales are hypothesized to be particularly sensitive to anthropogenic noise, based on previous strandings and limited experimental and observational data. However, few species have been studied in detail. We describe the underwater behavior of a Baird's beaked whale (Berardius bairdii) from the first deployment of a multi-sensor acoustic tag on this species. The animal exhibited shallow (23 ± 15 m max depth), intermediate (324 ± 49 m), and deep (1138 ± 243 m) dives. Echolocation clicks were produced with a mean inter-click interval of approximately 300 ms and peak frequency of 25 kHz. Two deep dives included presumed foraging behavior, with echolocation pulsed sounds (presumed prey capture attempts) associated with increased maneuvering, and sustained inverted swimming during the bottom phase of the dive. A controlled exposure to simulated mid-frequency active sonar (3.5–4 kHz) was conducted 4 hours after tag deployment, and within 3 minutes of exposure onset, the tagged whale increased swim speed and body movement, and continued to show unusual dive behavior for each of its next three dives, one of each type. These are the first data on the acoustic foraging behavior in this largest beaked whale species, and the first experimental demonstration of a response to simulated sonar.Peer reviewe
Trackline and point detection probabilities for acoustic surveys of Cuvier’s and Blainville’s beaked whales
No full textAcoustic survey methods can be used to estimate density and abundance using sounds produced by cetaceans and detected using hydrophones if the probability of detection can be estimated. For passive acoustic surveys, probability of detection at zero horizontal distance from a sensor, commonly called g(0), depends on the temporal patterns of vocalizations. Methods to estimate g(0) are developed based on the assumption that a beaked whale will be detected if it is producing regular echolocation clicks directly under or above a hydrophone. Data from acoustic recording tags placed on two species of beaked whales (Cuvier’s beaked whale—Ziphius cavirostris and Blainville’s beaked whale—Mesoplodon densirostris) are used to directly estimate the percentage of time they produce echolocation clicks. A model of vocal behavior for these species as a function of their diving behavior is applied to other types of dive data (from time-depth recorders and time-depth-transmitting satellite tags) to indirectly determine g(0) in other locations for low ambient noise conditions. Estimates of g(0) for a single instant in time are 0.28 [standard deviation (s.d.) ¼ 0.05] for Cuvier’s beaked whale and 0.19 (s.d. ¼ 0.01) for Blainville’s beaked whale.Peer reviewe
I Think I Am Philip K. Dick
No full textFor years, noted writer Laurence A. Rickels often found himself compared to novelist Philip K. Dickthough in fact Rickels had never read any of the science fiction writers work. When he finally read his first Philip K. Dick novel, while researching for his recent book The Devil Notebooks , it prompted a prolonged immersion in Dicks writing as well as a recognition of Rickelss own long-documented intellectual pursuits. The result of this engagement is I Think I Am: Philip K. Dick , a profound thought experiment that charts the wide relevance of the pulp sci-fi author and paranoid visionary. I Think I Am: Philip K. Dick explores the science fiction authors meditations on psychic reality and psychosis, Christian mysticism, Eastern religion, and modern spiritualism. Covering all of Dicks science fiction, Rickels corrects the lack of scholarly interest in the legendary Californian author and, ultimately, makes a compelling case for the philosophical and psychoanalytic significance of Philip K. Dicks popular and influential science fiction.Intro -- Contents -- Introjection -- Part I -- Endopsychic Allegories -- Schreber Guardian -- Belief System Surveillance -- Part II -- Deeper Problems -- Veil of Tears -- Go West -- Dick Manfred -- Timing -- Glimmung -- Part III -- Spiritualism Analogy -- Imitating the Dead -- Indexical Layer -- Ilse -- Hammers and Things -- Crucifictions -- Over There -- Martyrology -- Can't Live, Can't Live -- Lola -- Umwelt, Mitwelt, and Eigenwelt -- Outer Race -- The German Introject -- Part IV -- Materialism, Idealism, and Cybernetics -- Startling Stories -- A Couple of Years -- Android Empathy -- Homunculus and Robot -- ALL OF YOU ARE DEAD. I AM ALIVE. -- Go with the Flow -- Part V -- Room for Thought -- Caduceus -- Jump -- Still -- A Wake -- Spätwerk -- Let the Dead Be -- Play Bally -- Das Hund -- Notes -- BibliographyFor years, noted writer Laurence A. Rickels often found himself compared to novelist Philip K. Dickthough in fact Rickels had never read any of the science fiction writers work. When he finally read his first Philip K. Dick novel, while researching for his recent book The Devil Notebooks , it prompted a prolonged immersion in Dicks writing as well as a recognition of Rickelss own long-documented intellectual pursuits. The result of this engagement is I Think I Am: Philip K. Dick , a profound thought experiment that charts the wide relevance of the pulp sci-fi author and paranoid visionary. I Think I Am: Philip K. Dick explores the science fiction authors meditations on psychic reality and psychosis, Christian mysticism, Eastern religion, and modern spiritualism. Covering all of Dicks science fiction, Rickels corrects the lack of scholarly interest in the legendary Californian author and, ultimately, makes a compelling case for the philosophical and psychoanalytic significance of Philip K. Dicks popular and influential science fiction.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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