Home About us Contact
|
Home About us Contact | ||
|
|
||
Dive Duration (dive + duration)
Selected AbstractsA comparative analysis of the diving behaviour of birds and mammalsFUNCTIONAL ECOLOGY, Issue 5 2006L. G. HALSEY Summary 1We use a large interspecific data set on diving variables for birds and mammals, and statistical techniques to control for the effects of phylogenetic non-independence, to assess evolutionary associations among different elements of diving behaviour across a broad and diverse range of diving species. Our aim is to assess whether the diving ability of homeothermic vertebrates is influenced by factors other than the physiology of the species. 2Body mass is related to dive duration even when dive depth is controlled for and thus for a given dive depth, larger species dive for longer. This implies that larger species have a greater capacity for diving than is expressed in their dive depth. Larger animals that dive shallowly, probably for ecological reasons such as water depth, make use of the physiological advantage that their size confers by diving for longer. 3Dive duration correlates with dive depth more strongly than with body mass. This confirms that some animals are poor divers for their body mass, either because of a lower physiological capacity or because their behaviour limits their diving. 4Surface duration relates not only to dive duration but also to dive depth, as well as to both independently. This indicates a relationship between dive depth and surface duration controlling for dive duration, which suggests that deeper dives are energetically more expensive than shallow dives of the same duration. 5Taxonomic class does not improve any of the dive variable models in the present study. There is thus an unsuspected consistency in the broad responses of different groups to the effects on diving of the environment, which are therefore general features of diving evolution. [source] Red-gartered Coot Fulica armillata feeding on the grapsid crab Cyrtograpsus angulatus: advantages and disadvantages of an unusual food resourceIBIS, Issue 1 2008GERMÁN O. GARCÍA The behaviour of Red-gartered Coots feeding on an unusual food source was examined at Mar Chiquita Coastal Lagoon, Argentina. The grapsid crab Cyrtograpsus angulatus made up all observed prey items, and 61% were small. Both handling and foraging duration increased with the size of captured crabs, but foraging efficiency decreased. Crab availability affected both the dive duration of the Coots and their foraging decisions with regard to prey-size selection. Two species of gull were observed kleptoparasitizing Coots, especially when the Coot was handling medium or large crabs. Feeding by Coots on Cyrtograpsus angulatus has not been previously documented and may be a feeding innovation. Our estimations suggest that Coots were foraging optimally, since smaller crabs were more energetically profitable. [source] Diving in shallow water: the foraging ecology of darters (Aves: Anhingidae)JOURNAL OF AVIAN BIOLOGY, Issue 4 2007Peter G. Ryan Diving birds have to overcome buoyancy, especially when diving in shallow water. Darters and anhingas (Anhingidae) are specialist shallow-water divers, with adaptations for reducing their buoyancy. Compared to closely-related cormorants (Phalacrocoracidae), darters have fully wettable plumage, smaller air sacs and denser bones. A previous study of darter diving behaviour reported no relationship between dive duration and water depth, contrary to optimal dive models. In this study I provide more extensive observations of African darters Anhinga melanogaster rufa diving in water<5 m deep at two sites. Dive duration increases with water depth at both sites, but the relationship is weak. Dives were longer than dives by cormorants in water of similar depth (max 108 s in water 2.5 m deep), with dives of up to 68 s observed in water<0.5 m deep. Initial dives in a bout were shorter than expected, possibly because their plumage was not fully saturated. Dive efficiency (dive:rest ratio) was 5,6, greater than cormorants (2.7±0.4 for 18 species) and other families of diving birds (average 0.2,4.3). Post-dive recovery periods increased with dive duration, but only slowly, resulting in a strong increase in efficiency with dive duration. All dives are likely to fall within the theoretical anaerobic dive limit. Foraging bouts were short (17.8±4.3 min) compared to cormorants, with birds spending 80±5% of time underwater. Darters take advantage of their low buoyancy to forage efficiently in shallow water, and their slow, stealthy dives are qualitatively different from those of other diving birds. However, they are forced to limit the duration of foraging bouts by increased thermoregulatory costs associated with wettable plumage. [source] Tufted ducks Aythya fuligula do not control buoyancy during divingJOURNAL OF AVIAN BIOLOGY, Issue 3 2005Lewis G. Halsey Work against buoyancy during submergence is a large component of the energy costs for shallow diving ducks. For penguins, buoyancy is less of a problem, however they still seem to trade-off levels of oxygen stores against the costs and benefits of buoyant force during descent and ascent. This trade-off is presumably achieved by increasing air sac volume and hence pre-dive buoyancy (Bpre) when diving deeper. Tufted ducks, Aythya fuligula, almost always dive with nearly full oxygen stores so these cannot be increased. However, the high natural buoyancy of tufted ducks guarantees a passive ascent, so they might be expected to decrease Bpre before particularly deep, long dives to reduce the energy costs of diving. Body heat lost to the water can also be a cause of substantial energy expenditure during a dive, both through dissipation to the ambient environment and through the heating of ingested food and water. Thus dive depth (dd), duration and food type can influence how much heat energy is lost during a dive. The present study investigated the relationship between certain physiological and behavioural adjustments by tufted ducks to dd and food type. Changes in Bpre, deep body temperature (Tb) and dive time budgeting of four ducks were measured when diving to two different depths (1.5 and 5.7 m), and for two types of food (mussels and mealworms). The hypothesis was that in tufted ducks, Bpre decreases as dd increases. The ducks did not change Bpre in response to different diving depths, and thus the hypothesis was rejected. Tb was largely unaffected by dives to either depth. However, diving behaviour changed at the greater dd, including an increase in dive duration and vertical descent speed. Behaviour also changed depending on the food type, including an increase in foraging duration and vertical descent speed when mussels were present. Behavioural changes seem to represent the major adjustment made by tufted ducks in response to changes in their diving environment. [source] Swimming speed and foraging strategies of New Zealand sea lions (Phocarctos hookeri)JOURNAL OF ZOOLOGY, Issue 2 2001D. E. Crocker Abstract Lactating New Zealand sea lions (Phocarctos hookeri) have recently been reported to be the longest and deepest-diving otariid. An unusually large proportion of dives exceeded a theoretical aerobic dive limit, predicted from estimated oxygen stores and measurements of diving metabolic rate. We investigated swimming speed, a key variable in both the management of oxygen stores and foraging strategies, and its relation to diving behaviour in New Zealand sea lions. Diving behaviour was nearly continuous with short inter-dive intervals. Mean diving swimming speeds ranged from 1.6 to 2.4 m/s. Mean surface swimming speeds ranged from 0.9 to 1.8 m/s and were significantly lower than diving speeds in all subjects. New Zealand sea lions spend significant but variable amounts of time resting at the surface. Diving and swimming speed patterns were consistent with foraging on the benthos. Time in the foraging zone was maintained in deeper dives by increasing dive duration. This increased duration cannot be accounted for by a decreased metabolic rate resulting from slower swimming speeds, as speeds increased with the maximum depth of dives. Patterns of swimming speed and acceleration suggest the use of a gliding phase during descent. For most females, the extended duration of deeper dives did not impact on surface times, suggesting the use of aerobic metabolism. Females exhibited significantly slower swim speeds during the bottom segments of foraging dives than during descent or ascent. These findings suggest that swimming behaviour should be considered a critical component when modelling energetic costs for diving animals. [source] Activity budget and diving behavior of gray whales (Eschrichtius robustus) in feeding grounds off coastal British ColumbiaMARINE MAMMAL SCIENCE, Issue 3 2008Lei Lani Stelle Abstract Behavior and diving patterns of summer resident gray whales (Eschrichtius robustus) foraging on mysids were studied in coastal bays along the north shore of Queen Charlotte Strait, British Columbia. In this region, gray whales were found to feed primarily on planktonic prey rather than on the benthos as in their primary feeding areas further north. During the summers of 1999 and 2000, whales spent most of their time actively feeding or searching for prey (77%), whereas only 15% of their time was spent traveling and 8% socializing. The majority of the dives were short; the mean dive duration was 2.24 min with approximately three respirations per surfacing and 15 s between blows. Whales dove frequently (26.7 h,1), spending only 17% of their time at the surface with an overall blow rate of 1.14 respirations per minute. Activity states were characterized by significantly different diving and respiratory parameters; feeding whales dove more frequently, with shorter intervals between respirations, thus spending less time at the surface compared to when traveling or searching. This diving pattern differs from benthic-feeding whales and likely optimizes capture of the mobile mysid swarms in shallow waters. [source] REDUCTIONS IN OXYGEN CONSUMPTION DURING DIVES AND ESTIMATED SUBMERGENCE LIMITATIONS OF STELLER SEA LIONS (EUMETOPIAS JUBATUS)MARINE MAMMAL SCIENCE, Issue 2 2007Gordon D. Hastie Abstract Accurate estimates of diving metabolic rate are central to assessing the energy needs of marine mammals. To circumvent some of the limitations inherent with conducting energy studies in both the wild and captivity, we measured diving oxygen consumption of two trained Steller sea lions (Eumetopias jubatus) in the open ocean. The animals dived to predetermined depths (5,30 m) for controlled periods of time (50,200 s). Rates of oxygen consumption were measured using open-circuit respirometry before and after each dive. Mean resting rates of oxygen consumption prior to the dives were 1.34 (±0.18) and 1.95 (±0.19) liter/min for individual sea lions. Mean rates of oxygen consumption during the dives were 0.71 (±0.24) and 1.10 (±0.39) liter/min, respectively. Overall, rates of oxygen consumption during dives were significantly lower (45% and 41%) than the corresponding rates measured before dives. These results provide the first estimates of diving oxygen consumption rate for Steller sea lions and show that this species can exhibit a marked decrease in oxygen consumption relative to surface rates while submerged. This has important consequences in the evaluation of physiological limitations associated with diving such as dive duration and subsequent interpretations of diving behavior in the wild. [source] REACTIONS OF CAPTIVE HARBOR PORPOISES (PHOCOENA PHOCOENA) TO PINGER-LIKE SOUNDSMARINE MAMMAL SCIENCE, Issue 2 2006Jonas Teilmann Abstract Pingers on gill nets can reduce bycatch of harbor porpoises. If harbor porpoises habituate to pingers, the effect may be reduced or lost. Two captive harbor porpoises were exposed to three sound types. All sounds were in the frequency band from 100 kHz to 140 kHz, 200 ms long, and presented once per 4 s. The source level was 153 dB re 1 ,Pa RMS at 1 m. Each session consisted of a 10-min presound, a 5-min sound, and a 10-min postsound period. Behavior was recorded on video and on dataloggers placed on the dorsal fin of one animal. The loggers recorded heart rate, swimming speed, dive duration, and depth. The animals responded most strongly to the initial presentations of a sound. Surface time decreased, the heart rate dropped below the normal bradycardia, and echolocation activity decreased. The reactions of both animals diminished rapidly in the following sessions. Should the waning of responsiveness apply to wild animals, porpoises may adapt to the sounds but still avoid nets, or the bycatch may increase after some time. The success of long-term use of pingers may then depend on the variety of sounds and rates of exposure. [source] Implications of river damming: the influence of aquatic hypoxia on the diving physiology and behaviour of the endangered Mary River turtleANIMAL CONSERVATION, Issue 2 2009N. J. Clark Abstract River impoundments are characterized by low oxygen levels as a result of reduced water velocity and increased water depth. Bimodally respiring turtle species are likely to be highly sensitive to changes in aquatic PO2 with decreases in oxygen levels impacting upon their diving ability. The acute and long-term effects of aquatic hypoxia on dive duration, oxygen consumption and blood respiratory properties were examined in hatchlings of the endangered Mary River turtle Elusor macrurus. It was hypothesized that acute exposure to aquatic hypoxia would cause a decrease in dive duration as a consequence of a decrease in reliance on aquatic respiration. With long-term exposure to hypoxia, we predicted that Elu. macrurus would have the capacity to compensate for the acute effect of hypoxia and that dive duration would increase due to an increase in aquatic respiration, haemoglobin concentration and oxygen affinity (P50). When exposed to hypoxic conditions, aquatic respiration in Elu. macrurus was substantially reduced resulting in a 51% decrease in dive duration. Contrary to our predictions, Elu. macrurus hatchlings did not acclimate, and long-term exposure to hypoxic conditions caused Elu. macrurus to lose significantly more oxygen to the hypoxic water than the normoxic acclimated turtles. The exacerbation of long-term hypoxia on the respiratory physiology and diving ecology of Elu. macrurus raises concerns about the impacts of long-term environmental change as a result of habitat alteration on the survival of freshwater turtle populations. [source] Do alternate escape tactics provide a means of compensation for impaired performance ability?BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010KIMBERLY A. MILLER Whole-animal performance abilities can facilitate the avoidance of predation and consequently influence fitness, but determining the functional significance of antipredation tactics is difficult without understanding how alternate predator escape strategies are related. We measured maximal sprint speed and dive duration in the semi-aquatic skink Oligosoma suteri to determine how morphology and behaviour influence these alternate predator escape techniques and the relationship between the two measures. Gravid females and juveniles ran significantly slower, but had equivalent or longer dive durations than males and nongravid females. The two performance measures were not influenced by the same morphological and behavioural traits, and were not correlated among individuals. Thus, individuals that are poor sprinters because of their state (e.g. gravid or tail-less individuals) would have a greater likelihood of successful escape by adopting an alternate escape strategy. For species that use multiple strategies for the same function, quantifying selection on whole-animal performance will be difficult. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99, 241,249. [source] | ||||||||||