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1.
Foraging and provisioning in Antarctic fur seals: interannual variability in time-energy budgets 总被引:4,自引:0,他引:4
This study examined three competing hypotheses to explain howlactating
Antarctic fur seals (Arctocephalus gazella) respondto changes in the
level of resource availability. Antarcticfur seals have episodic bouts of
suckling (1-3 days), alternatingwith foraging trips (3-10 days). Foraging
time budgets variedsignificantly (p <.001) among 8 consecutive
years at BirdIsland, South Georgia. Foraging trip duration increased during
periodsof relative food shortage. Time spent ashore was more consistentamong
years than foraging trip duration but declined duringa year of particularly
low food availability. In 4 of the 8years, there was a significant positive
correlation betweentime spent ashore and foraging trip duration. In the other
years,the relationship was close to statistical significance. Energydelivery
to pups during suckling bouts followed an asymptoticpower function. Energy
gain during foraging trips was estimatedfrom diving behavior, which suggested
that the energy gain functionwas linear. Distance traveled during foraging
trips was correlatedwith foraging trip duration, and long foraging trips were
associatedwith reduced foraging intensity. There was support for the
hypothesisthat lactating Antarctic fur seals compensate for reduced resources
byincreasing the foraging trip duration rather than working harderand
increasing their energy expenditure. However, there wasmost support for the
hypothesis that lactating Antarctic furseals adjust time spent ashore as well
as foraging trip duration,possibly to maximize the delivery of food to their
offspring.Lactation appears to impose constraints on provisioning of
offspringthat differ from those of seabirds foraging in the same environment
andoften on the same prey. 相似文献
2.
We investigated the variation of Antarctic fur seal (Arctocephalus gazella) pup growth rates in response to sex, breeding season and duration of both maternal foraging trip and attendance bouts. Data
were collected during five consecutive rearing seasons at Cape Shirreff, the most important breeding colony in the South Shetland
Islands, Antarctica. Our results showed significant interannual and sexual variations in pup growth rates. Male pups grew
significantly faster than female pups during 2000, 2001, 2002 and 2004 seasons, whilst during 2003 no difference was found.
The interannual variation in pup growth rates was correlated with the interannual fluctuation in maternal foraging trip and
attendance bouts. There was a significant effect of pup sex and maternal foraging trip duration on pup growth rates, which
varied between years having foraging trip duration a major effect during 2003, when females spent more time at sea and interestingly
on that year there were no sexual differences in pup growth rates. The effect of attendance bout on pup growth rates was not
significant. Diet analysis showed that Antarctic krill (Euphausia superba) was the most frequent prey item during the study period. Analysis of krill size distribution showed a significant difference
in krill length, during 2003, when A. gazella preyed upon the smallest sizes of krill. In this study, sex was the most important factor on pup growth rates, but when prey
availability seemed more limited, there are longer foraging trips and shorter attendance bouts the sex factor became less
significant. 相似文献
3.
Summary Relationships between size, body condition, age and feeding-attendance patterns during pup rearing of female Antacrtic fur seals Arctocephalus gazella and their effects on the timing of birth and weaning, pup weight, growth and condition were studied at South Georgia in 1981–1982. Twenty-seven (6 male, 21 female) mother-pup pairs were followed from birth to weaning. The analysis of maternal effects was limited to female pups because of the small sample size of male weaners. High weaning weight was associated with those female pups whose mothers spent more time ashore attending their offspring. Weaning weight showed no relationship with perinatal duration, number of feeding trips to sea, days at sea or date of weaning. A further 63 mother-pup pairs were analysed for the effects of maternal body condition (weight/length), age and timing of birth on offspring body weight and condition. Pup weight and condition were weakly correlated with maternal age in female pups. Male pups born earlier in the season were heavier and in better condition. Maternal and offspring body weight and condition were unrelated. For the Antarctic fur seal population at South Georgia where the food supply was apparently not limiting in summer, maternal condition and foraging time were subordinate to maternal care on land (as expressed by attendance duration) in determining offspring weight at weaning. 相似文献
4.
Population censuses of the Antarctic fur seal (Arctocephalus gazella) and the sub-Antarctic fur seal (A. tropicalis) were conducted during the 1994/1995 breeding season at Marion Island. Pup numbers, determined from direct counts and a mark-recapture
experiment, were used to estimate population sizes. Pup numbers of A. tropicalis showed a mean annual change of 2.0% over the previous 6 years, culminating in an estimated total population of 49, 523 for
1994/1995. The population appears to be entering the maturity phase of population growth and may therefore have recovered
from the effects of uncontrolled sealing that ended in the early twentieth century. Numbers at the major colonies on Marion
Island showed little change since 1989 and these sites may have reached carrying capacity. The extension of breeding to other
parts of the island continues. Over the same period, A. gazella pup numbers showed a mean annual change of 17% and the total population numbered 1,205 in 1994/1995. This species has possibly
entered the rapid recolonisation phase of population growth. A few hybrid seals were found.
Received: 25 October 1995/Accepted: 14 April 1996 相似文献
5.
Diving behaviour was investigated in female subantarctic fur seals (Arctocephalus tropicalis) breeding on Amsterdam Island, Indian Ocean. Data were collected using electronic Time Depth Recorders on 19 seals during
their first foraging trip after parturition in December, foraging trips later in summer, and during winter. Subantarctic fur
seals at Amsterdam Island are nocturnal, shallow divers. Ninety-nine percent of recorded dives occurred at night. The diel
dive pattern and changes in dive parameters throughout the night suggest that fur seals follow the nycthemeral migrations
of their main prey. Seasonal changes in diving behaviour amounted to the fur seals performing progressively deeper and longer
dives from their first foraging trip through winter. Dive depth and dive duration increased from the first trip after parturition
(16.6 ± 0.5 m and 62.1 ± 1.6 s respectively, n=1000) to summer (19.0 ± 0.4 m and 65 ± 1 s, respectively, n=2000) through winter (29.0 ± 1.0 m and 91.2 ± 2.2 s, respectively, n=800). In summer, subantarctic fur seals increased the proportion of time spent at the bottom during dives of between 10 and
20 m, apparently searching for prey when descending to these depths, which corresponded to the oceanic mixed layer. In winter,
fur seals behaved similarly when diving between 20 and 50 m, suggesting that the most profitable depths for feeding moved
down during the study period. Most of the dives did not exceed the physiological limits of individuals. Although dive frequency
did not vary (10 dives/h of night), the vertical travel distance and the time spent diving increased throughout the study
period, while the post-dive interval decreased, indicating that subantarctic fur seals showed a greater diving effort in winter,
compared to earlier seasons.
Accepted: 1 August 1999 相似文献
6.
Trend changes in sympatric Subantarctic and Antarctic fur seal pup populations at Marion Island,Southern Ocean
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Mia Wege Marie‐Pierre Etienne W. Chris Oosthuizen Ryan R. Reisinger Marthán N. Bester P. J. Nico de Bruyn 《Marine Mammal Science》2016,32(3):960-982
Recent pup population estimates of sympatric Subantarctic (Arctocephalus tropicalis) and Antarctic fur seals (A. gazella) at Marion Island are presented. Published pup population estimates of A. tropicalis (1995 and 2004) with an unpublished total island count in 2013, and annual counts on subsets of rookeries (2007–2015) were analyzed using a hierarchical Bayesian model. The pup population declined by 46% (95% credible interval CI: 43%–48%) between 2004 (mean = 15,260, CI: 14,447–16,169 pups) and 2013 (mean = 8,312, CI: 7,983–8,697), mirrored by a 58%–60% decline at rookeries counted annually (2007–2015). Population decline was highest at high‐density west and north coast rookeries, despite negligible change in female attendance patterns, pup mortality or median pupping date over the previous 25 yr. A better understanding of foraging behavior and its effects on reproductive success and survival in this A. tropicalis population is needed before we can attribute population decline to any external factors. In contrast, total island counts of A. gazella pups in 2007, 2010, and 2013, suggest that this population is still increasing although the annual intrinsic rate of population growth decreased from 17.0% (1995–2004, 744 pups) to 4.0% (2010–2013, 1,553 pups). The slowed growth of A. gazella is likely the result of saturation at the main rookery. 相似文献
7.
A comparative analysis on cranial ontogeny of South American fur seals (Otariidae: Arctocephalus)
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Bárbara A. Tarnawski David Flores Guillermo Cassini Luis H. Cappozzo 《Zoological Journal of the Linnean Society》2015,173(1):249-269
We analysed the cranial ontogeny of male Arctocephalus australis (Zimmermann, 1783) (N = 116), Arctocephalus gazella (Peters, 1875) (N = 69), and Arctocephalus tropicalis (Gray, 1872) (N = 51) to study skull growth and its allometric patterns in the genus. We used 15 metric variables with bivariate and multivariate approaches to detect interspecific similarities and differences between growth trends, which we discussed in the context of phylogeny and life history. We found common trajectories in 20% of variables, detecting that the differences between adults were associated with size. We detected higher growth rates in A. gazella than in A. australis and A. tropicalis, which were associated with shape differences. Amongst the three species, A. tropicalis was morphologically intermediate, showing additional common trends with A. gazella and A. australis, and an intermediate position in the multivariate morphospace. Allometric patterns were also compared with growth trends described for Otaria byronia (Péron, 1816) and Mirounga leonina (Linnaeus, 1758). We detected positive allometry in Arctocephalus for the mastoid width (MW) but negative allometry in O. byronia and M. leonina. This could indicate that males of Arctocephalus exhibited a delayed development of MW. Finally, the presence of common growth trends for the skull length and the postorbital constriction could indicate a conservative pattern within otariids. © 2014 The Linnean Society of London 相似文献
8.
Subantarctic fur seals, Arctocephalus tropicalis, come ashore to breed in dense colonies and lactating females have to alternate foraging trips at sea with periods ashore during which they suckle their pups. The effectiveness of vocal recognition between mothers and pups, has been shown experimentally. To see whether the recognition abilities of females differ from those of their offspring, we investigated how pups recognize their mother's calls. We used artificially modified signals in playback experiments to determine which acoustic parameters support the recognition process. Pups used both the energy spectrum and the ascending frequency modulation occurring at the beginning of each call. However, they seemed to rely mainly on spectral analyses. The vocal identification process at a perceptual level is therefore asymmetrical, as mothers mainly use temporal structures to recognize their pup's calls. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour. 相似文献
9.
Little is known about movement behaviour in terms of route choice in Antarctic fur seals (Arctocephalus gazella). We deployed satellite transmitters and time-depth recorders simultaneously on 11 animals, and time-depth recorders with
a speed recorder on 10 animals, to investigate the foraging routes of Antarctic fur seals belonging to a colony located at
Iles Kerguelen (Southern Indian Ocean). The study took place during the 1997/1998 austral summer, and results indicate a preferred
foraging area, with two main strategies in route choice apparent during foraging trips. In one strategy seals tended to reach
an apparently known foraging ground and stopped there to feed. In the other strategy, animals performed looped trips, foraging
en route and probably searching for a food patch better than the one previously exploited.
Accepted: 13 September 1999 相似文献
10.
Previous studies of fur seals suggest that the attendance patterns and consequent temporal patterning of energy transfer from mother to pup follows a latitudinal cline. While data from subpolar, tropical, and some temperate latitude species support the postulated cline, data for the temperate latitude Juan Fernández fur seal do not. Maternal foraging trips and associated visits ashore were the longest of all otariids studied to date. The first foraging trip postpartum averaged 10.2 d ( n = 51 females, range 1–22.5), foraging trips combined averaged 12.3 d ( n = 100, range 1.0-25.0), and visits ashore averaged 5.3 d ( n = 91, range 0.3-15.8) over the three seasons of study. Only duration of lactation was intermediate between subpolar and tropical strategies as predicted. Dive records suggest that these females feed almost exclusively at night at depths of less than 10 m and at distances of more than 500 km offshore. The prey species of this fur seal, primarily myctophids and squid, migrate to the surface at night and are patchily distributed. Foraging trip length varied between years in conjunction with shifts in seasurface temperature and type of prey consumed. We suggest that distribution of prey, irrespective of latitude, dictates foraging patterns of fur seals and leads to the exceptionally long foraging trips and visits ashore observed in this species. 相似文献
11.
The study of scats of adult male Antarctic fur seals Arctocephalus gazella (AFS) revealed occasional frequent capture of penguins. Although AFS adult males have been occasionally reported to kill
king penguins Aptenodytes patagonicus at the shore, here we report the first observations of at-sea predation by AFS on adult king penguins in the Crozet archipelago,
southern Indian Ocean. During our 20 days survey, we observed 17 penguins attacked and either severely injured or killed and
consumed. Only AFS adult males were seen catching king penguins successfully. Some adult females and sub-adults also attempted
to catch penguins, either at sea or in land, and so did subantarctic fur seals Arctocephalus tropicalis individuals. Our results confirm the ability of fur seals to catch and predate large seabirds, even at sea. 相似文献
12.
Parents of albatross and shearwater species employ a dual foraging strategy, feeding their chicks quickly in repeated short
trips and then restoring their own fuel reserves during longer trips. A decline in parental body condition is believed to
trigger longer trips, but chick body condition and age may also play a role. To investigate these factors in the little-studied
streaked shearwater Calonectris leucomelas, we monitored the nest attendance of 17 pairs on Mikura Island in 2005 using an automated identification system. We also
monitored body mass changes and meal masses of 5 of the 17 pairs using an automated weighing system. Although the birds did
not show a clear dual foraging pattern, trip duration varied widely from 1 to 15 days. On average, the birds fed chicks 67.6 g
during nighttime meals at 2.74-day intervals. Since meal mass did not depend on trip duration, feeding efficiency (meal mass
delivered per unit trip duration) decreased as trip duration increased. Parents accumulated more energy reserves when they
took longer trips. Parents appeared likely to initiate longer trips when their body condition declined or chick body condition
recovered. 相似文献
13.
Vagrant Antarctic pinnipeds at Gough Island 总被引:1,自引:1,他引:0
Opportunistic sightings of Antarctic fur seals Arctocephalus gazella and a leopard seal Hydrurga leptonyx at Gough Island (40°20′S, 09°54′W) in the South Atlantic Ocean represent the northernmost island records for vagrant Antarctic fur seals, and only the second for a vagrant leopard seal at Gough Island. Some ten different individual Antarctic fur seals were sighted on a single day, up to seven on a single beach. An overall total of 18 individuals were recorded over a 7-week period in October/November 2005, before the onset of the breeding (pupping) season of the resident population of Subantarctic fur seals Arctocephalus tropicalis. Most were immature, male and mostly in good condition (n = 11, 61%); one mature male and six putative females were also present. All had departed after 23 November, although only a fraction of the available beaches was searched. 相似文献
14.
Guinet C Servera N Mangin S Georges JY Lacroix A 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2004,137(3):523-531
Lactating fur seals (Arctocephalus tropicalis) alternate foraging trips at sea and pup attendance periods ashore. During the onshore nursing periods, lactating females do not have access to food and meet both their own metabolic requirements and milk production from their body reserve. Blood and milk samples were collected from females captured soon after their arrival ashore from a foraging trip and before their departure. Milk lipid but not milk protein content was positively related to the body condition index (BCI) of the female. During the 4-day attendance period ashore, females lost body mass, and plasma cortisol levels increased, whereas plasma urea concentration decreased and beta-hydroxybutyrate (beta-OHB) remained unchanged. The increase in cortisol level took place while blood urea concentration decreased and beta-OHB remained at a low level suggesting that it was independent from the transition from phase II to phase III that is indicative of the depletion of lipid body store as described in penguins. Thus, our results suggest that the increase in cortisol level in relation to decreasing BCI may either contribute to the mobilization of protein stores to ensure milk production when easily mobilized stores are used and/or could act as a re-feeding signal which is triggered well before females have depleted their body store. 相似文献
15.
David G. Ainley Peter R. Wilson Kerry J. Barton Grant Ballard Nadav Nur Brian Karl 《Polar Biology》1998,20(5):311-319
We investigated the diet and aspects of foraging effort among Adélie penguins (Pygoscelis adeliae) breeding at three colonies on Ross Island, in the southwestern Ross Sea – Capes Royds, Bird and Crozier – during the chick-provisioning
period of three austral summers, 1994–1995, 1995–1996 and 1996–1997. During the study period, pack-ice cover differed in waters
offshore of these colonies, by colony, seasons and year. Diet differed among colonies only slightly. The fish Pleuragramma antarcticum was the most important prey, especially during years or periods within years when little pack ice was present. With respect
to krill, which composed the remainder of diet, juvenile Euphausia crystallorophias were consumed predominantly in a year of heavy pack-ice cover; more adult krill were consumed in 2 years when pack ice was
sparse. Foraging trip duration differed by colony, season and year and was related directly to distance from the colony to
the nearest pack ice. The amount of food brought to chicks increased as trip duration increased, to a point (2 days), but
then decreased as duration increased further (up to 4 days). On the basis of data on mass of parents and of meal sizes to
chicks, it appeared that on the longest trips more of the food gathered by parents was used for self maintenance; on the longest
trips, parents lost body mass. Successful foraging during chick rearing, the period when adult foraging is most intense, appears
to depend on the proximity of pack ice to nesting colonies for this penguin species.
Received: 1 October 1997 / Accepted: 25 April 1998 相似文献
16.
J. R. Clarke 《Polar Biology》2001,24(1):16-20
Analyses of the body masses of Adélie penguins (Pygoscelis adeliae) departing on foraging trips of long and short duration (> and<40 h, respectively) during chick rearing showed that the departure
weights of birds prior to long trips were significantly lighter than were those prior to short trips. Penguins, particularly
males, were significantly heavier at the start of the guard stage than at the end and both sexes gained similar amounts of
body mass during the crèche period. Results support the hypothesis that the foraging effort of Adélie penguins at Béchervaise
Island is partitioned between the sexes, with males accepting a net rate of negative energy gain to provide regular meals
for their offspring during the guard stage. Adélie penguin foraging behaviour may be driven by a trade-off between the allocation
of food to chicks and the storage of parental body reserves, similar to that previously postulated for some species of flying
seabirds. The relevance of such a foraging strategy to the breeding success of penguins in the Mawson region of eastern Antarctica
is discussed in relation to micronekton distribution in the area.
Accepted: 3 June 2000 相似文献
17.
Maternal expenditure in lactating Antarctic fur seals (Arctocephalusgazella) was studied at Heard Island in the 1987 to 1988 summer/autumn.The mean birth mass, growth rate, and mass at 60 days of sonswere significantly greater than those of daughters. Maternalforaging trips lasted on average 5.9 days, and attendance boutslasted 1.5 days. Over the course of this study, foraging tripduration increased from 5.0 to 7.0 days, and attendance durationdeclined from 2.0 to 1.5 days. Pups lost 3.2% of their bodymass/day while their mothers foraged at sea, but gained massrapidly during periods of maternal attendance. Sons gained significantlymore body mass (1.9 kg) compared with daughters (1.3 kg) duringmaternal attendance, suggesting that sons consume more milk.Sex differences in mass gain were unrelated to pup age or bodymass. During 2-day maternal attendance bouts, sons gained mostof their mass (71%) during the first day, and daughters increasedmass at almost the same rate each day. The increase in massby sons during maternal attendance was significantly positivelyrelated to both the duration of their mothers' preceding andsubsequent foraging trips. In contrast, mass gained by daughterswas positively related to the duration of their mothers' attendance.Mass at 60 days age was negatively related to birth date insons, and positively related to birth mass in daughters. Thesedata indicate that (1) greater maternal resources are expendedon sons than on daughters, (2) sons receive greater maternalresources because they are male, and not because of their greaterbirth mass and body size, (3) different factors appear to beimportant in determining high postnatal growth in sons and daughters,and (4) demand for resources by sons can influence maternalbehavior and ultimately the level of resources received. 相似文献
18.
The Antarctic fur seal Arctocephalus gazella at Gough Island (40°20′S, 09°54′W) in the South Atlantic Ocean, first seen in October/November 2005, was recorded again in
September–October 2009. Up to three different individual Antarctic fur seals were sighted on a single day, on a particular
beach. A total of seven different individuals were recorded over a 3-week period, well before the onset of the breeding (pupping)
season of the resident population of Subantarctic fur seals A. tropicalis. Positively identified individuals were all male, mostly subadult and lean. Only a fraction (~20%) of the available beaches
was searched, and it is unknown if the Antarctic fur seals were still present at Gough Island during the austral summer breeding
season of southern fur seals. 相似文献
19.
Background
Individual variations in the use of the species niche are an important component of diversity in trophic interactions. A challenge in testing consistency of individual foraging strategy is the repeated collection of information on the same individuals.Methodology/Principal Findings
The foraging strategies of sympatric fur seals (Arctocephalus gazella and A. tropicalis) were examined using the stable isotope signature of serially sampled whiskers. Most whiskers exhibited synchronous δ13C and δ15N oscillations that correspond to the seal annual movements over the long term (up to 8 years). δ13C and δ15N values were spread over large ranges, with differences between species, sexes and individuals. The main segregating mechanism operates at the spatial scale. Most seals favored foraging in subantarctic waters (where the Crozet Islands are located) where they fed on myctophids. However, A. gazella dispersed in the Antarctic Zone and A. tropicalis more in the subtropics. Gender differences in annual time budget shape the seal movements. Males that do not perform any parental care exhibited large isotopic oscillations reflecting broad annual migrations, while isotopic values of females confined to a limited foraging range during lactation exhibited smaller changes. Limited inter-individual isotopic variations occurred in female seals and in male A. tropicalis. In contrast, male A. gazella showed large inter-individual variations, with some males migrating repeatedly to high-Antarctic waters where they fed on krill, thus meaning that individual specialization occurred over years.Conclusions/Significance
Whisker isotopic signature yields unique long-term information on individual behaviour that integrates the spatial, trophic and temporal dimensions of the ecological niche. The method allows depicting the entire realized niche of the species, including some of its less well-known components such as age-, sex-, individual- and migration-related changes. It highlights intrapopulation heterogeneity in foraging strategies that could have important implications for likely demographic responses to environmental variability. 相似文献20.
Daniel Torres Jorge Acevedo Daniel E. Torres Romeo Vargas Anelio Aguayo-Lobo 《Polar Biology》2012,35(3):469-473
A vagrant adult male Subantarctic fur seal Arctocephalus tropicalis was observed among Antarctic fur seals A. gazella at Cape Shirreff, Livingston Island, Antarctica, which is located to ~4,190 and ~5,939 km from the nearest breeding colonies
of Subantarctic fur seals. Although the colony of origin of this animal and the reason for its movement outside its distribution
range are unknown, this sighting shows the high dispersal capacity of this species and provides an insight into possible changes
in its distribution. Although this vagrant was not observed with females Antarctic fur seal, news sightings in the future
could result in viable hybrid, and introgressive hybridization could represent a threat for Cape Shirreff population recovery,
if still the population way to go to recover to presailing levels. 相似文献