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1.
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
2.
The pattern and characteristics of diving in 14 female northern rockhopper penguins, Eudyptes chrysocome moseleyi, were studied at Amsterdam Island (37°50′S; 77°31′E) during the guard stage, using electronic time–depth recorders. Twenty-nine
foraging trips (27 daily foraging trips and two longer trips including one night) with a total of 16 572 dives of ≥3 m were
recorded. Females typically left the colony at dawn and returned in the late afternoon, spending an average of 12 h at sea,
during which they performed ∼550 dives. They were essentially inshore foragers (mean estimated foraging range 6 km), and mainly
preyed upon the pelagic euphausiid Thysanoessa gregaria, fishes and squid being only minor components of the diet. Mean dive depth, dive duration, and post-dive intervals were 18.4 m
(max. depth 109 m), 57 s (max. dive duration 168 s), and 21 s (37% of dive duration), respectively. Descent and ascent rates
averaged 1.2 and 1.0 ms−1 and were, together with dive duration, significantly correlated with dive depth. Birds spent 18% of their total diving time
in dives reaching 15 to 20 m, and the mean maximum diving efficiency (bottom time:dive cycle duration) occurred for dives
reaching 15 to 35 m. The most remarkable feature of diving behaviour in northern rockhopper penguins was the high percentage
of time spent diving during daily foraging trips (on average, 69% of their time at sea); this was mainly due to a high dive
frequency (∼44 dives per hour), which explained the high total vertical distance travelled during one trip (18 km on average).
Diving activity at night was greatly reduced, suggesting that, as other penguins, E. chrysocome moseleyi are essentially diurnal, and locate prey using visual cues.
Received: 9 December 1998 / Accepted: 3 March 1999 相似文献
3.
Gentoo penguins Pygoscelis papua show considerable plasticity in their diet, diving, and foraging behaviors among colonies; we expected that they might exhibit
similar variability over time, at a single site, since flexible foraging habits would provide a buffer against changes in
prey availability. We examined interannual changes in the foraging strategies and diet of gentoo penguins in the South Shetland
Islands, Antarctica, over 5 years with variable prey abundance. Antarctic krill Euphausia superba was the primary diet item, and fish the secondary, though the importance of these items varied among years. Diving behavior
also varied over time: different dive depth distributions were observed among years. Nonetheless, chick-rearing success remained
relatively constant, indicating that gentoo penguins were able to maintain chick provisioning by altering their foraging strategy
among years. Variable abundance of krill in the region did not have observable impacts on the diet, foraging behaviors or
chick-rearing success of gentoo penguins. We suggest that foraging plasticity may be one reason that gentoo penguin populations
have remained stable in the region, while their congeners (P. antarctica and P. adeliae) with less flexible foraging strategies have declined. 相似文献
4.
The diving behaviour of king penguins (Aptenodytes patagonicus) was studied on the Falkland Islands, where a small population (ca. 300 fledglings year–1) is located at the geographical limit of their breeding range. King penguins rearing newly hatched chicks were equipped with time-depth recorders before leaving for sea. In total, 20,175 dives >3 m were recorded from 12 birds during 15 foraging trips with a mean duration of 5.7±2.3 days. The majority of the trips was directed up to 500 km to the northeast of the breeding colony in slope waters of, and oceanic waters beyond, the Patagonian shelf. Mean time spent underwater accounted for 42±9% of the foraging trip. Mean dive depth achieved was 55±16 m; maximum dive depth recorded was 343 m. Mean dive duration was 159±25 s; maximum dive duration was 480 s. The mean vertical distance covered was 140±65 km trip–1; and on average birds covered 25 km day–1. Synchronous diving behaviour was observed in two birds for a period of about 24 h after leaving the colony. Dive depth correlated positively with: (1) light intensity, (2) dive duration and (3) vertical velocities, thus confirming previous findings obtained from conspecifics at other breeding sites and indicating comparable diving behaviour. However, separation of dives according to their profile—V-, U-, or W-shaped—revealed significant differences between certain dive parameters. For a given depth range, bottom time was longer and vertical velocities higher in W-dives than in U-dives. This, together with a higher number of W-dives at dawn and dusk, suggests that foraging is more effective during W-dives than U-dives, and during twilight. These findings imply that king penguins have to make more complex decisions, individually and socially, on the performance of the subsequent dive than previously thought.Communicated by O. Kinne, Oldendorf/Luhe 相似文献
5.
Timothée R. Cook Maike Hamann Lorien Pichegru Francesco Bonadonna David Grémillet Peter G. Ryan 《Marine Biology》2012,159(2):373-387
Knowledge on how divers exploit the water column vertically in relation to water depth is crucial to our understanding of
their ecology and to their subsequent conservation. However, information is still lacking for the smaller-bodied species,
due mostly to size constraints of data-loggers. Here, we report the diving behaviour of a flying diving seabird, the Cape
Cormorant Phalacrocorax capensis, weighing 1.0–1.4 kg. Results were obtained by simultaneously deploying small, high resolution and high sampling frequency
GPS and time-depth loggers on birds breeding on islands off Western South Africa (34°S, 18°E) in 2008. In all, dive category
was assigned to all dives performed by 29 birds. Pelagic dives occurred almost as frequently as benthic dives. Pelagic dives
were shallow (mean: 5 m) and took place over seafloors 5–100 m deep. Benthic dives were deeper, occurring on seafloors mainly
10–30 m deep. Dive shape was linked to dive category in only 60% of dives, while the descent rate, ascent rate and bottom
duration/dive duration ratio of a dive best explained its dive category. This shows that only the concomitant use of tracking
and depth tags can adequately classify diving strategies in a diver like the Cape Cormorant. Diet was mainly Cape Anchovy
Engraulis encrasicolis, suggesting that birds probably displayed two contrasted strategies for capturing the same prey. Flexible foraging techniques
represent an important key to survival inside the highly productive but heterogeneous Benguela upwelling ecosystem. 相似文献
6.
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
7.
During the El Niño of 1982/1983, the Humboldt penguin population diminished dramatically in the whole distributional area of the species. Recovery of the population was slow since 1983 and it has been suggested that large numbers of Humboldt penguins die at sea, entangled in nets, or starve to death, even during non-“El Niño” years. We were able to determine for the first time, how Humboldt penguins on Pan de Azúcar Island (26°S; 72°W) utilize their marine habitat and where their feeding areas lie. For this purpose we employed two streamlined Argos satellite transmitters during the 1994/1995 and 1995/1996 breeding seasons, respectively. Mean travelling speed of Humboldt penguins during foraging trips was 0.94?m s?1 and 50% of bird positions were located within 5?km of the island (90% within 35?km). Total area covered by Humboldt penguins foraging from Pan de Azúcar Island was 12?255?km2. Satellite transmitters also recorded dive duration; penguins spent on average 7.8 to 9?h diving per foraging day but showed no preferences for particular feeding areas. Mean daily dive durations (4-d mean) recorded during the 1994/1995 breeding season were positively correlated between birds. Significant correlation between dive duration and sea surface temperature anomalies and negative correlation between dive duration and fishery landings at nearby Caldera harbour indicate that the 1994/1995 increase in foraging effort was a response to deteriorating prey availability. Sea surface temperatures during the 1995/1996 breeding season were colder than average, and we observed no trends in bird diving activities. 相似文献
8.
April Hedd P. M. Regular W. A. Montevecchi A. D. Buren C. M. Burke D. A. Fifield 《Marine Biology》2009,156(4):741-751
Owing to the necessity of delivering food to offspring at colonies, breeding seabirds are highly constrained in their foraging
options. To minimize constraints imposed by central-place foraging and to optimize foraging behavior, many species exhibit
flexible foraging tactics. Here we document the behavioral flexibility of pursuit-diving common murres Uria aalge when foraging on female capelin Mallotus villosus in the northwest Atlantic. Quite unexpectedly, being visual foragers, we found that common murres dived throughout the day
and night. Twenty-one percent of recorded dives (n = 272 of 1,308 dives) were deep (≥50 m; maximum depth = 152 m, maximum duration = 212 s), bringing murres into sub-0°C water
in the Cold Intermediate Layer (CIL; 40–180 m) of the Labrador Current. Deep dives occurred almost exclusively during the
day when murres would have encountered spatially predictable aggregations of capelin between 100 and 150 m in the water column.
Temperatures within the CIL shaped trophic interactions and involved trade-offs for both predators and prey. Sub-0°C temperatures
limit a fish’s ability to escape from endothermic predators by reducing burst/escape speeds and also lengthening the time
needed to recover from burst-type activity. Thus, while deep diving may be energetically costly, it likely increases certainty
of prey capture. Decreased murre foraging efficiency at night (indicated by an increase in the number of dives per bout) reflects
both lower light conditions and changing prey behavior, as capelin migrate to warmer surface waters at night where their potential
to escape from avian predators could increase. 相似文献
9.
Klemens Pütz Andrea Raya Rey Nic Huin Adrian Schiavini Andrea Pütz Bernhard H. Lüthi 《Marine Biology》2006,149(2):125-137
The diving behaviour of southern rockhopper penguins (Eudyptes c. chrysocome) was studied at two breeding sites in the Southwest Atlantic: the Falkland Islands and Staten Island, Argentina. Incubating and brooding birds were equipped with time-depth recorders to monitor their foraging activities. Rockhopper penguins from Staten Island started their breeding season about 3 weeks earlier than their conspecifics from the Falkland Islands. The foraging area used by incubating males from the Falkland Islands comprised about 150,000 km² to the northeast of the breeding site and was characterised by shelf and slope waters, whereas the foraging area of incubating males from Staten Island comprised 350,000 km² of oceanic waters to the southeast of the breeding site. A number of dive parameters were measured and compared between the four study groups: Incubating males and brooding females from the Falkland Islands, and incubating males and females from Staten Island. In all study groups, dive depth correlated positively to light intensity, dive duration and vertical velocity. However, significant differences between various diving parameters of the study groups were noted, not only in terms of diving performance, but also as regards diving efficiency (DE). A principal component analysis (PCA) on 16 variables revealed that 75% of the variance could be explained by only two principal components: diving pattern (PC1) and diving effort (PC2). PC1 indicated that the birds from Staten Island, both males and females, dived deeper, covered a greater vertical distance per hour and had higher ascent rates, but spent less time underwater and at the bottom of a dive, and had a lower DE than conspecifics from the Falkland Islands. PC2, which included the percentage of foraging dives, the number of dives per hour, dive duration, bottom time and descent rate, differed significantly between incubating males from the Falkland Islands and the other three groups, which were all very similar. Overall, the diving behaviour was notably similar to that of conspecifics from the Indian and Pacific Oceans. The implications of the results in terms of intra-specific adaptations as well as potential threats from human activities are discussed. 相似文献
10.
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
11.
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
12.
The foraging ecology of seven Gentoo penguins,Pygoscelis papua, breeding at Ardley Island, Antarctica was studied using animal-attached devices which recorded swimming speed, heading and dive depth. Reconstruction of the foraging routes by vectorial analysis of the data indicated that at no time did the birds forage on the sea bed. Swimming speed was relatively constant at 1.7 m s-1, but rates of descent and ascent in the water column during dives increased with increasing maximum dive depth due to changes in descent and ascent angles. The amount of time spent discending and ascending in the water column increased with maximum dive depth as did the duration spent at the point of maximum depth. Dive profiles were essentially either U-shaped (flat-bottomed dives), or V-shaped (bounce dives). Development of a model based on simple probability theory indicated that the optimal dive profile to maximize the chances of prey acquisition depends on vertical prey distribution and on the visual capabilities of the birds with respect to descent and ascent angles. 相似文献
13.
Trevor McIntyre Horst Bornemann Joachim Plötz Cheryl A. Tosh Marthán N. Bester 《Marine Biology》2011,158(9):2125-2139
The at-sea behaviour of marine top predators provides valuable insights into the distribution of prey species and strategies
used by predators to exploit patchily distributed resources. We describe the water column usage and dive strategies of female
southern elephant seals from Marion Island tracked between 2004 and 2008. Dives representing increases in forage effort were
identified using a method that combines dive type analyses and the calculation of relative amounts of time that animals spend
in the bottom phases of dives. Results from this analysis indicate that female elephant seals from Marion Island tend to display
lower levels of forage effort closer to the island and display intensive opportunistic forage bouts that occur at a minimum
distance of approximately 215 km from the island. Females from Marion Island dived deeper and for longer periods of time,
compared to females from other populations. Most animals displayed positive diel vertical migration, evidently foraging pelagically
on vertically migrating prey. A few animals displayed periods of reverse (negative) diel vertical migration, however, diving
to deeper depths at night, compared to daytime. This behaviour is difficult to explain and prey species targeted during such
periods unknown. Our results illustrate plasticity in foraging behaviour of southern elephant seals, as well as inter-population
differences in forage strategies. 相似文献
14.
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
15.
There is little information on the effort put into foraging by seabirds, even though it is fundamental to many issues in behavioural ecology. Recent researchers have used changes in the underwater cruising speed of penguins to allude to prey ingestion since accelerations are thought to reflect the encounter and pursuit of prey. In this study, we attached minute accelerometers, to determine flipper beat frequency as a proxy for prey pursuit, to Little Penguins Eudyptula minor foraging in shallow waters in Western Australia. During diving, Little Penguins flapped continuously and at a regular pace of 3.16 Hz while descending the water column and throughout the bottom phase of most dives. However, the frequency and amplitude of wingbeats increased transitorily, reaching 3.5–5.5 Hz, during some dives indicating prey pursuit. Pursuit phases lasted a mean of 2.9±3.3 s and occurred principally during the bottom phases of dives (75.4%). Most dives in all birds (86%) had a clear square-shaped depth profile indicating feeding activity near the seabed in the shallow waters of the bays. Hourly maximum depth, time spent underwater, percentage of dives with pursuit events and catch per unit effort showed an overall increase from zero at ca. 0500 h to a maximum during the hours around mid-day before decreasing to zero by 1900 h. During pursuit phases, Little Penguins headed predominantly downward, probably using the seabed to assist them in trapping their prey. In the light of our results, we discuss depth use by Little Penguins and their allocation of foraging effort and prey capture success as a function of environmental conditions. 相似文献
16.
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
17.
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
18.
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
19.
Evan A. Howell Peter H. Dutton Jeffrey J. Polovina Helen Bailey Denise M. Parker George H. Balazs 《Marine Biology》2010,157(5):1011-1026
Satellite telemetry data from 17 juvenile loggerhead turtles (43.5–66.5 cm straight carapace length) were used in conjunction with oceanographic data to analyze the influence of regional and seasonal oceanography on dive behavior in the North Pacific Ocean. Combined dive behavior for all individuals showed that turtles spent more than 80% of their time at depths <5 m, and more than 90% of their time at depths <15 m. Multivariate classifications of dive data revealed four major dive types, three representing deeper, longer dives, and one representing shallower dives shorter in duration. Turtles exhibited variability in these dive types across oceanographic regions, with deeper, longer dives in the Hawaii longline swordfish fishing grounds during the first quarter of the year, as well as in the Kuroshio Extension Bifurcation Region and the region near the Baja California Peninsula, Mexico. Turtles in the Kuroshio Extension Bifurcation Region also exhibited dive variability associated with mesoscale eddy features, with turtles making deeper, longer dives while associated with the strongest total kinetic energy. Turtles in the central North Pacific exhibited seasonality in dive behavior that appeared to reflect synchronous latitudinal movements with the North Pacific Subtropical Front and the associated seasonal, large-scale oceanography. Turtles made deeper, longer dives during the first quarter of the year within this region, the reported time and area where the highest loggerhead bycatch occurs by the longline fishery. These results represent the first comprehensive study of dive data for this species in this region. The increased understanding of juvenile loggerhead dive behavior and the influences of oceanography on dive variability should provide further insight into why interactions with longline fisheries occur and suggest methods for reducing the bycatch of this threatened species. 相似文献
20.
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