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1.
The fine link between a particular dive pattern and a specific prey item represents a challenging task in the analysis of
marine predator–prey relationships. There is growing evidence that prey type affects diving seabirds’ foraging strategies,
dive shapes and underwater activity costs. This study investigates whether a generalist diver, the Great Cormorant Phalacrocorax carbo, modifies the time budget allocated to prey-capture behaviour and breathing strategies (reactive vs. anticipatory) with respect
to the prey type (pelagic vs. benthic). Video recordings of 91 Great Cormorants show how the ecology and behaviour of their
main prey, Mullets (Mugilidae) and Flounders Platichthys flesus, affect dive/surface durations and the diving pattern. The demersal habit and the low mobility of Flounders leads to an easy
access to prey with an anticipatory strategy. Moreover, the patchy distribution of this fish species increases prey-capture
rates. Conversely, Mullets exploit the whole water column and are highly mobile, and this is reflected in the need of performing
two sequential dives to capture a prey, both longer and likely more expensive, with a consequent switch of strategy from reactive
in the searching phase to anticipatory breathing during prey-capture events. This study provides evidence that a generalist
diver may switch between different foraging strategies, and it shows how each of them may be optimal under particular ecological
conditions. These constraints influence the dynamics that operate within the marine food chains and have relevant implications
in managing lagoon areas, including fish ponds. 相似文献
2.
Steven L. H. Teo Andre Boustany Heidi Dewar Michael J. W. Stokesbury Kevin C. Weng Shana Beemer Andrew C. Seitz Charles J. Farwell Eric D. Prince Barbara A. Block 《Marine Biology》2007,151(1):1-18
Electronic tags were used to examine the biology of Atlantic bluefin tuna (Thunnus thynnus L.) on their breeding grounds in the Gulf of Mexico (GOM). The hypothesis that movement patterns, diving behavior, and thermal
biology change during different stages of the breeding migration was tested. Mature Atlantic bluefin tuna tagged in the western
Atlantic and the GOM, were on their breeding grounds from February to June for an average of 39 ± 11 days. The bluefin tuna
experienced significantly warmer mean sea surface temperatures (SSTs) within the GOM (26.4 ± 1.6°C) than outside the GOM (20.2 ± 1.9°C).
As the bluefin tuna entered and exited the GOM, the fish dove to daily maximum depths of 568 ± 50 and 580 ± 144 m, respectively,
and exhibited directed movement paths to and from the localized breeding areas. During the putative breeding phase, the bluefin
tuna had significantly shallower daily maximum depths (203 ± 76 m), and exhibited shallow oscillatory dives during the night.
The movement paths of the bluefin tuna during the breeding phase were significantly more residential and sinuous. The heat
transfer coefficients (K) were calculated for a bluefin tuna in the GOM using the recorded ambient and body temperatures. The K for this fish increased rapidly at the high ambient temperatures encountered in the GOM, and was significantly higher at
night in the breeding phase when the fish was exhibiting shallow oscillatory dives. This suggests that the fish were behaviorally
and physiologically thermoregulating in the Gulf of Mexico. This study demonstrates that the movement patterns, diving behavior,
and thermal biology of Atlantic bluefin tuna change significantly at different stages of the breeding migration and can be
used to define spawning location and timing.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
3.
Jamie N. Womble Gail M. Blundell Scott M. Gende Markus Horning Michael F. Sigler David J. Csepp 《Marine Biology》2014,161(6):1361-1374
Foraging theory predicts that animals will adjust their foraging behavior in order to maximize net energy intake and that trade-offs may exist that can influence their behavior. Although substantial advances have been made with respect to the foraging ecology of large marine predators, there is still a limited understanding of how predators respond to temporal and spatial variability in prey resources, primarily due to a lack of empirical studies that quantify foraging and diving behavior concurrently with characteristics of prey fields. Such information is important because changes in prey availability can influence the foraging success and ultimately fitness of marine predators. We assessed the diving behavior of juvenile female harbor seals (Phoca vitulina richardii) and prey fields near glacial ice and terrestrial haulout sites in Glacier Bay (58°40′N, ?136°05′W), Alaska. Harbor seals captured at glacial ice sites dived deeper, had longer dive durations, lower percent bottom time, and generally traveled further to forage. The increased diving effort for seals from the glacial ice site corresponded to lower prey densities and prey at deeper depths at the glacial ice site. In contrast, seals captured at terrestrial sites dived shallower, had shorter dive durations, higher percent bottom time, and traveled shorter distances to access foraging areas with much higher prey densities at shallower depths. The increased diving effort for seals from glacial ice sites suggests that the lower relative availability of prey may be offset by other factors, such as the stability of the glacial ice as a resting platform and as a refuge from predation. We provide evidence of differences in prey accessibility for seals associated with glacial ice and terrestrial habitats and suggest that seals may balance trade-offs between the costs and benefits of using these habitats. 相似文献
4.
Sixty-eight yellowfin tuna, Thunnus albacares, (60-135 cm fork length) were caught and released with implanted archival tags offshore off Baja California, Mexico, during
October 2002 and October 2003. Thirty-six fish (53%) were recaptured and the data were downloaded from all 36 recovered tags.
Time at liberty ranged from 9 to 1,161 days, and the data were analyzed for the 20 fish that were at liberty for 154 or more
days. The accuracy in the position estimates, derived from light-level longitude data and sea-surface temperatures (SSTs)
based latitude, is about 0.41° in longitude and 0.82° in latitude, in this region. The movement paths, derived from position
estimates, for the 20 yellowfin indicated that 19 (95%) remained within 1,445 km of their release locations. The estimated
mean velocity along movement paths was 77 km/day. The southern and northern seasonal movement paths observed for yellowfin
off Baja California are influenced by the seasonal movements of the 18°C SST isotherm. Cyclical movements to and from suitable
spawning habitat (≥24°C SST) was observed only for mature fish. For the 12 fish that demonstrated site fidelity, the mean
95 and 50% utilization distributions were 258,730 km2 and 41,260 km2, respectively. Evaluations of the timed depth records resulted in discrimination of four distinct behaviors. When exhibiting
type-1 diving behavior (78.1% of all days at liberty) the fish remained at depths less than 50 m at night and did not dive
to depths greater than about 100 m during the day. Type-2 diving behavior (21.2% of all days at liberty) was characterized
by ten or more dives in excess of 150 m during the day. Type-2 diving behavior is apparently a foraging strategy for fish
targeting prey organisms of the deep-scattering layer during the day, following nighttime foraging within the mixed layer
on the same prey. Yellowfin tuna exhibited occasional deep-diving behavior, and some dives exceeded 1,000 m, where ambient
temperatures were less than 5°C. Surface-oriented behavior, defined as the time fish remained at depths less than 10 m for
more than 10 min, were evaluated. The mean number and duration of surface-oriented events per day for all fish was 14.3 and
28.5 min, respectively. Habitat utilization of yellowfin, presented as monthly composite horizontal and vertical distributions,
indicates confined geographical distributions, apparently resulting from an affinity to an area of high prey availability.
The vertical distributions indicate greater daytime depths in relation to a seasonally deeper mixed layer and a greater proportion
of daytime at shallower depths in relation to a seasonally shallower mixed layer. 相似文献
5.
Carey E. Kuhn 《Marine Biology》2011,158(3):649-663
In the heterogeneous marine environment, predators can increase foraging success by targeting physical oceanographic features,
which often aggregate prey. For northern fur seals (Callorhinus ursinus), two prevalent oceanographic features characterize foraging areas during summer in the Bering Sea: a stable thermocline
and a subsurface “cold pool”. The objective of this study was to examine the influence of these features on foraging behavior
by equipping fur seals from St. Paul Island (Alaska, USA) with time-depth recorders that also measured water temperature.
Foraging bout variables (e.g., mean dive depth and percent time diving in a bout) were compared with respect to subsurface
thermal characteristics (thermocline presence and strength and cold pool presence). Over 74% of bouts occurred in association
with strong thermoclines (temperature change > 5°C). Few differences were found for dive behavior in relation to the presence
of a thermocline and the cold pool, but for epipelagic bouts, a strong thermocline resulted in increased bottom times, number
of dive wiggles, and percent time diving when compared to moderate thermoclines. There was also a positive relationship between
mean dive depth and thermocline depth. The combination of increasing foraging effort in areas with strong thermoclines and
diving to depths closely related to the thermocline indicates this feature is important foraging habitat for northern fur
seals and may act to concentrate prey and increase foraging success. By recognizing the environmental features northern fur
seals use to find prey, managers will be better equipped to identify and protect foraging habitat that is important to northern
fur seals, and possibly other marine predators in the Bering Sea. 相似文献
6.
L. Silva F. Saporit D. Vales M. Tavares P. Gandini E. A. Crespo L. Cardona 《Marine Biology》2014,161(5):1195-1206
In diving seabirds, sexual dimorphism in size often results in sex-related differences of foraging patterns. Previous research on Magellanic penguins, conducted during the breeding season, failed to reveal consistent differences between the sexes on foraging behavior, despite sexual dimorphism. In this paper, we tested the hypothesis that male and female Magellanic penguins differ in diet and foraging patterns during the non-breeding period when the constraints imposed by chick rearing activities vanish. We used stable isotope ratios of carbon and nitrogen in feather and bone to characterize the diet and foraging patterns of male and female penguins in the South Atlantic at the beginning of the 2009–2010 and 2010–2011 post-breeding seasons (feathers) and over several consecutive breeding and migratory seasons (bone). The mean δ13C and δ15N values of feathers showed no differences between the sexes in any of the three regions considered or in the diet composition between the sexes from identical breeding regions; however, Bayesian ellipses showed a higher isotopic niche width in males at the beginning of the post-breeding season. Stable isotope ratios in bone revealed the enrichment of males with δ13C compared with females across the three regions considered. Furthermore, the Bayesian ellipses were larger for males and encompassed those of females in two of the three regions analyzed. These results suggest a differential use of winter resources between the sexes, with males typically showing a larger diversity of foraging/migratory strategies. The results also show that dietary differences between male and female Magellanic penguins may occur once the constraints imposed by chick rearing activities cease at the beginning of the post-breeding season. 相似文献
7.
Holly F. Swift William M. Hamner Bruce H. Robison Laurence P. Madin 《Marine Biology》2009,156(5):1049-1056
Behavioral observations using a remotely operated vehicle (ROV) in the Gulf of California in March, 2003, provided insights
into the vertical distribution, feeding and anatomy of the rare and delicate ctenophore Thalassocalyce inconstans. Additional archived ROV video records from the Monterey Bay Aquarium Research Institute of 288 sightings of T. inconstans and 2,437 individual observations of euphausiids in the Gulf of California and Monterey Canyon between 1989 and 2005 were
examined to determine ctenophore and euphausiid prey depth distributions with respect to temperature and dissolved oxygen
concentration [dO]. In the Gulf of California most ctenophores (96.9%) were above 350 m, the top of the oxygen minimum layer.
In Monterey Canyon the ctenophores were more widely distributed throughout the water column, including the hypoxic zone, to
depths as great as 3,500 m. Computer-aided behavioral analysis of two video records of the capture of euphausiids by T. inconstans showed that the ctenophore contracted its bell almost instantly (0.5 s), transforming its flattened, hemispherical resting
shape into a closed bi-lobed globe in which seawater and prey were engulfed. Euphausiids entrapped within the globe displayed
a previously undescribed escape response for krill (‘probing behavior’), in which they hovered and gently probed the inner
surfaces of the globe with antennae without stimulating further contraction by the ctenophore. Such rapid bell contraction
could be effected only by a peripheral sphincter muscle even though the presence of circumferential ring musculature was unknown
for the Phylum Ctenophora. Thereafter, several live T. inconstans were collected by hand off Barbados and microscopic observations confirmed that assumption. 相似文献
8.
The behaviour of the oral arms of Pelagia noctiluca (Forsskål) has been investigated in open sea predation and in predation induced both in the laboratory and the natural environment. Specimens were first studied in the field and then collected from coastal aggregations in the Gulf of Trieste, North Adriatic Sea, in December 1985 (Lat. 13°40 E, Long. 45°42 N) and in June 1986 (Lat. 13°39 E, Long. 45°43 N). The results of laboratory experiments and in situ observations, recorded on videotapes and photographs, show that the marginal tentacles are utilized to: (1) paralyze the prey; (2) contract and bend inward towards the nearest oral arm. Occasionally the tentacle does not contract and the prey is released; thus prey selection may occur. The oral arms are therefore involved in the: (1) transport of prey from the tentacle to the gastric cavity; (2) catching of motionless prey; (3) anchoring the medusa to the substratum. A similar feeding pattern can explain the survival of several specimens of P. noctiluca near the bottom during the winter of 1985/1986 in the Gulf of Trieste (North Adriatic Sea) in spite of the severe climatic conditions. 相似文献
9.
André Chiaradia Yan Ropert-Coudert Akiko Kato Thomas Mattern Julija Yorke 《Marine Biology》2007,151(4):1535-1542
Little Penguins, Eudyptula minor, breed in several small colonies in New Zealand and Australia. In this study, we compare the birds’ diving performances at
different sites situated throughout their breeding range. Environmental conditions and breeding success vary drastically amongst
colonies, but all birds feed on similar types of prey and face similar limitations on their foraging range. We examined several
diving parameters and calculated the proportion of foraging zone available during breeding to examine whether oceanographic
and geographic factors in the foraging zone can explain variations in diving behaviour and fledging success among the different
colonies. In colonies with high fledging success, Penguin Island and Oamaru, penguins made shallow dives <50 m depth and had
lower diving effort. More than 90% of the foraging zone was in waters <50 m depth in these colonies. Motuara Island also has
shallow waters with 95% <50 m depth, but the fledging success was low. Phillip Island has only 42% of waters <50 m and comparatively
low fledging success. Thus, penguins dived deeper and showed a higher diving effort in colonies with lower fledging success
(Motuara Island and Phillip Island), indicating that they were disadvantaged compared to conspecifics from other colonies
that dived shallower and with a lesser diving effort. We concluded that bathymetry is an important factor, but not the only
one, which influences fledging success. 相似文献
10.
How energy costs affect foraging decisions is poorly understood for marine animals. To provide data relevant to this topic,
we examined the relationship between activity levels and foraging behavior by attaching activity recorders to 29 chick-rearing
wing-propelled diving birds (thick-billed murres, Uria lomvia) in 1999–2000. We connected the activity during the final dive bout with the prey item we observed being fed to the chicks.
After accounting for changes in activity level with depth, activity was highest during the final dive of a dive bout, reflecting
maneuvring during prey capture. Pelagic prey items, especially invertebrates (amphipods), were associated with higher depth-corrected
activity, leading to shorter dives for a given depth (presumably due to higher oxygen consumption rates) and, thus, shorter
search times (lower bottom time for a given depth). Pelagic prey items were likely captured during active pursuit, with the
birds actively seeking and pursuing schooling mid-water prey. In contrast, benthic prey involved low activity and extended
search times, suggesting that the birds slowly glided along the bottom in search for prey hidden in the sediments or rocks.
We concluded that activity levels are important in determining the foraging tactics of marine predators.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
11.
Penguins may exhibit plasticity in their diving and foraging behaviors in response to changes in prey availability. Chinstrap
penguins are dependent predators of Antarctic krill in the Scotia Sea region, but krill populations have fluctuated in recent
years. We examined the diet of chinstrap penguins at Livingston Island, South Shetland Islands, in relation to their diving
and foraging behavior using time-depth recorders over six breeding seasons: 2002–2007. When krill were smaller, more chinstrap
penguins consumed fish. In these years, chinstrap penguins often exhibited a shift to deep dives after sundown, and then resumed
a shallower pattern at sunrise. These night dives were unexpectedly deep (up to 110 m) and mean night dive depths sometimes
exceeded those from the daytime. The average size of krill in each year was negatively correlated to mean night dive depths
and the proportion of foraging trips taken overnight. Based on these patterns, we suggest that when krill were small, penguins
increasingly targeted myctophid fish. The average krill size was negatively correlated to the time chinstrap penguins spent
foraging which suggests that foraging on smaller krill and fish incurred a cost: more time was spent at sea foraging. 相似文献
12.
Contrasting conditions at-sea are likely to affect the foraging behaviour of seabirds. However, the effect of season on the dive parameters of penguins is poorly known. We report here on an extensive study of the diving behaviour of king penguins (Aptenodytes patagonicus) over the bird's complete annual cycle at the Crozet Islands. Time-depth recorders were used to record dive duration, bottom duration, post-dive interval, ascent rate and descent rate in breeding adults during different seasons in 1995 and 1996. Seasons included summer (n=6, incubation; n=6, chick brooding), autumn and winter (n=5 and n=3, respectively, chick at the crèche stage), and spring (n=4, birds at the post-moult stage). In all seasons dive duration increased with dive depth, but, for a given depth, dives were longer in winter (6.8 min when averaged over the 100-210 m depth layer) than in spring (4.6 min) and summer (4.4 min). The time spent at the bottom of the dives, which probably represents a substantial part of the feeding time, was much longer in winter (2.5 min per dive for dives over the 100-210 m layer) than during other seasons (1.0-1.4 min), i.e. there was a 2.5-fold augmentation for similar diving depths. Ascent and descent rates increased with increasing dive depth, but no difference in the relationships between rates of ascent and descent and dive depth was found among seasons. Furthermore, for all dive depths, ascent and descent rates were independent of the bottom duration. In all seasons post-dive intervals increased with dive duration and with dive depth, but they were longer in spring (2.3 min for dives over the 100-210 m layer) and summer than in autumn and winter (1.6-1.8 min). The diving efficiency decreased with increasing dive depth and was higher in autumn and winter (0.22-0.29) than in summer and spring (0.15-0.18). The large increase in bottom and dive duration from spring to winter is in agreement with the seasonal drop in prey density, with penguins spending more time searching for prey. In contrast, the consistency of the vertical velocity during contrasting conditions at-sea suggests that the transit time to depth is an important component of the foraging behaviour (scanning of the water column) that is independent of the prey availability. The time budget of the penguins during diving in a fluctuating environment appears to vary primarily during the bottom phase of the dives, with bottom duration increasing with diminishing prey supplies, while post-dive intervals shorten in the same time. 相似文献
13.
F. Daunt V. Afanasyev J. R. D. Silk S. Wanless 《Behavioral ecology and sociobiology》2006,59(3):381-388
In temperate regions, winter presents animals with a number of challenges including depressed food abundance, increased daily
energy requirements, higher frequency of extreme weather events and shortened day length. Overcoming these constraints is
critical for overwintering survival and scheduling of future breeding of long-lived species and is likely to be state dependent,
associated with intrinsic abilities such as food acquisition rates. We examined the relationship between environmental and
intrinsic factors on overwintering foraging and subsequent breeding phenology of the European shag Phalacrocorax aristotelis, a diurnal marine predator. We tested a range of hypotheses relating to overwintering foraging time and location. We found
that individuals greatly increased their foraging time in winter to a peak of more than 90% of available daylight at the winter
solstice. The seasonal patterns of foraging time appear to be driven by a combination of light levels and weather conditions
and may be linked to the availability of the shag's principal prey, the lesser sandeel Ammodytes marinus. There was no evidence that shags dispersed south in winter to increase potential foraging time. Foraging time decreased
after the winter solstice and, crucially, was correlated with subsequent breeding phenology, such that individuals that spent
less time foraging in February bred earlier. The relationship was much stronger in females than males, in line with their
more direct control of timing of breeding. Our results demonstrate that pre-breeding intrinsic foraging ability is critical
in determining breeding phenology. 相似文献
14.
Akiko Shoji Ellie Owen Mark Bolton Ben Dean Holly Kirk Annette Fayet Dave Boyle Robin Freeman Chris Perrins Stéphane Aris-Brosou Tim Guilford 《Marine Biology》2014,161(9):2121-2129
How central-place foragers change search strategy in response to environmental conditions is poorly known. Foragers may vary the total distance travelled and how far they range from the central place in response to variation in the distribution of their prey. One potential reason as to why they would extend the length of their foraging trip and its distance from the colony would be to increase prey quality or quantity, despite incurring higher transit costs. To test this trade-off hypothesis in a species with high flight costs, we recorded the foraging behaviour of razorbills (Alca torca) using state-of-the-art techniques that log both individual horizontal (flight activity) and vertical (dive activity) movements. We show that the distance that razorbills travelled to foraging locations increased with sea-surface temperature, which may relate to higher prey quality or quantity. This relation is supported by an indirect index of patch quality, based on dive profiles, which also increased with travel distance from the colony. Furthermore, we show that this index was highest during the daily peak in diving activity, around midday. Taken together, these results suggest that razorbills are capable of adjusting their search strategies sensitively in response to proximate environmental cues. 相似文献
15.
Sebastián P. Luque John P. Y. Arnould Edward H. Miller Yves Cherel Christophe Guinet 《Marine Biology》2007,152(1):213-224
The duration of periods spent ashore versus foraging at sea, diving behaviour, and diet of lactating female Antarctic (Arctocephalus gazella, AFS) and subantarctic (A. tropicalis, SFS) fur seals were compared at Iles Crozet, where both species coexist. The large disparity in lactation duration (SFS:
10 months, AFS: 4 months), even under local sympatry, has led to the expectation that AFS should exhibit higher foraging effort
or efficiency per unit time than SFS to allow them to wean their pups in a shorter period of time. Previous evidence, however,
has not supported these expectations. In this study, the distribution of foraging trip durations revealed two types of trips:
overnight (OFT, <1 day) and long (LFT, >1 day), in common with other results from Macquarie Island. However, diving behaviour
differed significantly between foraging trip types, with greater diving effort in OFTs than in LFTs, and diving behaviour
differed between fur seal species. OFTs were more frequent in SFS (48%) than in AFS (28%). SFS performed longer LFTs and maternal
attendances than AFS, but spent a smaller proportion of their foraging cycle at sea (66.2 vs. 77.5%, respectively). SFS dove
deeper and for longer periods than AFS, in both OFTs and LFTs, although indices of diving effort were similar between species.
Diel variation in diving behaviour was lower among SFS, which foraged at greater depths during most of the night time available
than AFS. The diving behaviour of AFS suggests they followed the nychthemeral migration of their prey more closely. Concomitant
with the differences in diving behaviour, AFS and SFS fed on the same prey species, but in different proportions of three
myctophid fish (Gymnoscopelus fraseri, G. piabilis, and G. nicholsi) that represented most of their diet. The estimated size of the most important fish consumed did not vary significantly between
fur seal species, suggesting that the difference in dive depth was mostly a result of changes in the relative abundance of
these myctophids. The energy content of these fish at Iles Crozet may thus influence the amount and quality of milk delivered
to pups of each fur seal species. These results contrast with those found at other sites where both species coexist, and revealed
a scale of variation in foraging behaviour which did not affect their effort while at sea, but that may be a major determinant
of foraging efficiency and, consequently, maternal investment. 相似文献
16.
I. J. Staniland N. Gales N. L. Warren S. L. Robinson S. D. Goldsworthy R. M. Casper 《Marine Biology》2010,157(11):2383-2396
Foragers show adaptive responses to changes within their environment, and such behavioural plasticity can be a significant
driving force in speciation. We investigated how lactating Antarctic fur seals, Arctocephalus gazella, adapt their foraging within two contrasting ecosystems. Location and diving data were collected concurrently, between December
2003 and February 2004, from 43 seals at Bird Island, where krill, Euphausia superba, are the main prey, and 39 at Heard Island, where mostly fish are consumed. Seals at Heard Island were shorter and lighter
than those at Bird Island and they spent longer at sea, dived more frequently and spent more time in the bottom phase of dives.
Generalized additive mixed effects models showed that diving behaviours differed between the islands. Both populations exploited
diel vertically migrating prey species but, on average, Heard Island seals dived deeper and exceeded their estimated aerobic
dive limits. We propose that the recovery of the Heard Island population may be limited by the relative inaccessibility and
scarcity of food, whereas at Bird Island, the presence of abundant krill resources helps sustain extremely high numbers of
seals, even with increased intra- and inter-specific competition. Both populations of fur seals appear to be constrained by
their physiological limits, in terms of their optimal diving behaviour. However, there does appear to be some flexibility
in strategy at the level of trip with animals adjusting their time at sea and foraging effort, in order to maximize the rate
of delivery of energy to their pups. 相似文献
17.
We performed field and laboratory studies to investigate how large adult Leptasterias polaris detect and locate their major prey, large infaunal bivalves, in the sediment bottom community. A field survey using SCUBA diving showed that 95% of the locations where L. polaris dug into the sediment bottom were over bivalves and this success rate was much greater than if digging was done at random (22%). Furthermore, when sea stars were provided with a low density of randomly distributed prey in a laboratory arena, they dug exclusively in locations where a clam had been buried. These observations indicated that L. polaris locates infaunal prey prior to investing energy into digging. Studies in a laboratory flow tank showed that L. polaris readily detected and moved towards its preferred prey Ensis directus whereas its responses to less preferred prey Mya truncata and Spisula polynyma were much weaker. The degree to which it oriented towards these three common prey seemed to reflect potential energy intake relative to foraging costs (which likely increase with the depth of the different prey) and risks from interactions with other carnivores (which are greatest when feeding on large prey). This is the first study to clearly demonstrate that sea stars use prey odours to locate infaunal prey.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00227-004-1497-1Communicated by R.J. Thompson, St. Johns 相似文献
18.
Timothée Romuald Cook Frédéric Bailleul Amélie Lescroël Yann Tremblay Charles-André Bost 《Marine Biology》2008,154(2):383-391
Knowing the depth zone of neutral buoyancy of divers is important because buoyancy can determine how animals manage their
energy budget. In this study, we estimate the depth zone of neutral buoyancy of free-ranging cormorants for the first time,
using time-depth recorders. We discovered that vertical ascent rates of 12 Crozet and 15 Kerguelen diving blue-eyed shags
(respectively Phalacrocorax
melanogenis and P.
verrucosus) slowed down considerably at the 50–60 m depth zone. We suggest this was due to birds trying to reach the surface from that
point upwards using reduced locomotor activity because the force of buoyancy becomes greater than the force of gravity at
that depth. The results show a shift of this depth zone in relation to maximum targeted dive depth, suggesting cormorants
may control buoyancy through respiratory air volume adjustment. Interestingly, 60 m is close to the maximum depth zone reached
by these two species during dives lasting 4 min, their estimated behavioural aerobic dive limit. This suggests that the decision
to swim deeper has a direct consequence on the energy budget, with time spent recovering at the surface (time thus lost to
foraging) strongly increasing relative to the preceding time of submergence. Resources found in deeper waters must be of sufficient
quantity or quality to justify crossing the frontier of physical neutral buoyancy. 相似文献
19.
Aaron D. Spares Michael J. W. Stokesbury Ron K. O’Dor Terry A. Dick 《Marine Biology》2012,159(8):1633-1646
The influence of salinity, temperature and prey availability on the marine migration of anadromous fishes was determined by describing the movements, habitat use and feeding behaviours of Arctic char (Salvelinus alpinus). The objectives were to determine whether char are restricted to the upper water column of the inter-/subtidal zones due to warmer temperatures. Twenty-seven char were tracked with acoustic temperature/pressure (depth) transmitters from June to September, 2008/2009, in inner Frobisher Bay, Canada. Most detections were in surface waters (0–3 m). Inter-/subtidal movements and consecutive repetitive dives (maximum 52.8 m) resulted in extreme body temperature shifts (−0.2–18.1 °C). Approximately half of intertidal and subtidal detections were between 9–13 °C and 1–3 °C, respectively. Stomach contents and deep diving suggested feeding in both inter-/subtidal zones. We suggest that char tolerate cold water at depth to capture prey in the subtidal zone, then seek warmer water to enhance feeding/digestion physiology. 相似文献
20.
Seasonally breeding predators, which are limited in the time available for provisioning young at a central location, and
by the fasting abilities of the young, are likely to maximize energy delivery to the young by maximizing the rate of energy
delivery averaged over the whole period of investment. Reduction in food availability or increased foraging costs will alter
the optimal behavior of individuals. This study examined the behavioral adaptations of a diving predator, the Antarctic fur
seal, to increased foraging costs during lactation. One group of mothers (n=5, treatment) was fitted with additional drag to increase the cost of transport in comparison with a control group (n=8). At the scales of the individual dives, the treatment group made more shorter, shallower (< 30 m) dives. Compensation for
slower swimming speeds was achieved by diving at a steeper angle. Overall, diving behavior conformed to several specific theoretical
predictions but there were also departures from theory, particularly concerning swimming speed during diving. Diving behavior
appears to be adjusted to maximize the proportion of time spent at the bottom of dives. At the scale of diving bouts, no difference
was observed between the treatment and control groups in terms of the frequency and duration of bouts and there was also no
difference between the two groups in terms of the proportion of time spent diving. At the scale of complete foraging cycles,
time taken to return to the pup was significantly longer in the treatment group but there was no difference in the rate of
delivery of energy (measured from pup growth rate) to the pups in each group. Since mothers in the treatment group did not
use significantly more body reserves, we conclude that behavioral adjustments at the scale of individual dives allowed mothers
in the treatment group to compensate for the additional foraging costs. Pup growth rate appears to be less sensitive to the
foraging conditions experienced by mothers than foraging trip duration.
Received: 14 June 1996 / Accepted after revision: 16 November 1996 相似文献