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1.
Mónica A. Silva Rui Prieto Sara Magalh?es Maria I. Seabra Ricardo S. Santos Philip S. Hammond 《Marine Biology》2009,156(2):179-192
Very little is known about the ecology of common bottlenose dolphins (Tursiops truncatus) living in oceanic waters. This study investigated the ranging and residence patterns of bottlenose dolphins occurring in
the Azores (Portugal), the most isolated archipelago in the North Atlantic. Data were collected during standardized boat-based
surveys conducted over a 6-year period in an area of approximately 5,400 km2 (main study area). To investigate the extent of movements of individual animals, non-systematic surveys were also conducted
outside this area. Only 44 individuals out of 966 identified were frequently sighted within and between years. The remaining
individuals were either temporary migrants from within or outside the archipelago, or transients. Resident dolphins showed
strong geographic fidelity to the area. Long-distance movements (of almost 300 km), consistent with foraging or exploratory
trips, were observed among non-resident dolphins. Home range size was estimated for 31 individuals sighted ≥10 times. Range
areas of these dolphins varied in size and location, but considerable overlap was observed in the areas used, suggesting the
absence of habitat partitioning between resident and non-resident dolphins. Estimates of home range size of bottlenose dolphins
in the Azores were found to be considerably larger than those previously reported for this species. It is hypothesized that
dolphins living in the Azores carry out extensive movements and have large home ranges in response to the lower density and
patchy distribution of prey compared to other areas. The extensive ranging behaviour and the lack of territoriality provide
an opportunity for interbreeding between dolphins associated with different islands, thus preventing genetic differentiation
within the population of the Azores. 相似文献
2.
Sophie Quérouil Luís Freitas Irma Cascão Filipe Alves Ana Dinis Joana R. Almeida Rui Prieto Silvia Borràs José A. Matos Diogo Mendonça Ricardo S. Santos 《Marine Biology》2010,157(11):2567-2580
Several cetacean species exhibit fine-scale population structure despite their high dispersal capacities and the apparent continuity of the marine environment. In dolphins, most studies have focused on coastal areas and continental margins, and they revealed differentiated populations within relatively small geographic areas, sometimes in conjunction with a specialisation for different habitats (ecotypes). We analysed the population genetic structure of short-beaked common dolphins (Delphinus delphis) and Atlantic spotted dolphins (Stenella frontalis) in the Azores and Madeira, the two most isolated archipelagos of the North Atlantic. The archipelago of the Azores is divided into three groups of islands and stands 900 km away from Madeira. It is not known whether individuals migrate between groups of islands and archipelagos, nor whether distinct ecotypes are present. These questions were investigated by genetic analyses of 343 biopsy samples collected on free-ranging dolphins. The analyses consisted in sequencing part of the mitochondrial hyper-variable region, screening up to 14 microsatellite loci, and molecular sexing. Results did not unravel any population structure at the scale of the study area. Lack of differentiation matches expectations for spotted dolphins, which are transient in both archipelagos, but not for common dolphins, which are present year-round in the Azores and potentially resident. Absence of genetic structure over hundreds and even thousands of kilometres implies the existence of gene flow over much larger distances than usually documented in small delphinids, which could be achieved through individual movements. This finding indicates that population structure in oceanic habitat differs from that observed in coastal habitat. 相似文献
3.
Sophie Quérouil Jeremy Kiszka Ana Rita Cordeiro Irma Cascão Luís Freitas Ana Dinis Filipe Alves Ricardo Serrão Santos Narcisa M. Bandarra 《Marine Biology》2013,160(6):1325-1337
Short-beaked common dolphins (Delphinus delphis) and Atlantic spotted dolphins (Stenella frontalis) are the two most abundant cetacean species in the oceanic waters of Madeira and the Azores. They are of similar size, occur in similar habitats and are regularly observed in mixed-species groups to forage together. Genetic analyses suggested that, within each species, dolphins ranging around both archipelagos belong to the same panmictic population. We tested the hypotheses that (1) within each species, individuals from the two archipelagos belong to a single ecological stock; (2) between species, common and spotted dolphins have distinct trophic niches; using fatty acid (FA) and stable isotope (SI) analyses. Fatty acids and stable isotopes were analysed from 86 blubber and 150 skin samples of free-ranging dolphins, respectively. Sex-related differences were not significant, except for common dolphin FA profiles. In S. frontalis, FA and SI differences between archipelagos suggested that individuals belonged to different ecological stocks, despite the existence of gene flow between the two archipelagos. In D. delphis, differences were more pronounced, but it was not possible to distinguish between stock structure and a seasonal effect, due to differential sampling periods in the Azores and Madeira. Inter-specific comparisons were restricted to the Azores where all samples were collected during summer. Differences in FA proportions, noticeably for FA of dietary origin, as well as in nitrogen SI profiles, confirmed that both species feed on distinct resources. This study emphasizes the need for an integrated approach including both genetic and biochemical analyses for stock assessment, especially in wide-ranging marine top predators. 相似文献
4.
The bottlenose dolphin community of Doubtful Sound features a large proportion of long-lasting associations 总被引:4,自引:0,他引:4
More than 12 studies of different bottlenose dolphin populations, spanning from tropical to cold temperate waters, have shown that the species typically lives in societies in which relationships among individuals are predominantly fluid. In all cases dolphins lived in small groups characterised by fluid and dynamic interactions and some degree of dispersal from the natal group by both sexes. We describe a small, closed population of bottlenose dolphins living at the southern extreme of the species' range. Individuals live in large, mixed-sex groups in which no permanent emigration/immigration has been observed over the past 7 years. All members within the community are relatively closely associated (average half-weight index>0.4). Both male–male and female–female networks of preferred associates are present, as are long-lasting associations across sexes. The community structure is temporally stable, compared to other bottlenose dolphin populations, and constant companionship seems to be prevalent in the temporal association pattern. Such high degrees of stability are unprecedented in studies of bottlenose dolphins and may be related to the ecological constraints of Doubtful Sound. Fjords are low-productivity systems in which survival may easily require a greater level of co-operation, and hence group stability. These conditions are also present in other cetacean populations forming stable groups. We therefore hypothesise that ecological constraints are important factors shaping social interactions within cetacean societies.Communicated by D. Watts 相似文献
5.
Identifying demographic changes is important for understanding population dynamics. However, this requires long-term studies of definable populations of distinct individuals, which can be particularly challenging when studying mobile cetaceans in the marine environment. We collected photo-identification data from 19 years (1992-2010) to assess the dynamics of a population of bottlenose dolphins (Tursiops truncatus) restricted to the shallow (<7 m) waters of Little Bahama Bank, northern Bahamas. This population was known to range beyond our study area, so we adopted a Bayesian mixture modeling approach to mark-recapture to identify clusters of individuals that used the area to different extents, and we specifically estimated trends in survival, recruitment, and abundance of a "resident" population with high probabilities of identification. There was a high probability (p= 0.97) of a long-term decrease in the size of this resident population from a maximum of 47 dolphins (95% highest posterior density intervals, HPDI = 29-61) in 1996 to a minimum of just 24 dolphins (95% HPDI = 14-37) in 2009, a decline of 49% (95% HPDI = approximately 5% to approximately 75%). This was driven by low per capita recruitment (average approximately 0.02) that could not compensate for relatively low apparent survival rates (average approximately 0.94). Notably, there was a significant increase in apparent mortality (approximately 5 apparent mortalities vs. approximately 2 on average) in 1999 when two intense hurricanes passed over the study area, with a high probability (p = 0.83) of a drop below the average survival probability (approximately 0.91 in 1999; approximately 0.94, on average). As such, our mark-recapture approach enabled us to make useful inference about local dynamics within an open population of bottlenose dolphins; this should be applicable to other studies challenged by sampling highly mobile individuals with heterogeneous space use. 相似文献
6.
Many studies have shown that the distribution of cetaceans can be closely linked to habitat, but the underlying function of the preferred habitats often remains unclear. Only when behavioural observations are made in relation to habitat types can functional mechanisms behind the habitat use be revealed. Within the range of a bottlenose dolphin (Tursiops truncatus) population off NE Scotland, dolphins show clear preferences for several discrete areas. If the observed patterns of distribution are related to foraging, we predict that behaviour patterns shown by dolphins would reflect this relationship. In this study we identify behaviours of dolphins at the water surface that were related to feeding events, evaluate whether the patterns of distribution were related to foraging and whether they were related the local submarine habitat characteristics. To investigate whether visible surface evidence of foraging behaviour varied spatially, we analysed data collected from 104 regular boat-based surveys made within the Moray Firth, NE Scotland, between 1990 and 2000. To determine whether underlying bathymetry had any influence on the surface behaviour of dolphins, a land-based observation study was carried out in the populations core region of use. The results of this study show that feeding behaviour by dolphins was significantly higher in areas used intensively by dolphins. Furthermore, there were clear relationships between feeding events and the submarine habitat characteristics; certain forms of feeding occur primarily over steep seabed gradients, and in deeper waters during June and July. These results quantitatively support the hypothesis that the distinctive patterns of distribution shown by these dolphins are related to foraging behaviour or opportunities, and that submarine habitat characteristics may be a significant factor in the foraging efficiency of dolphins. Future work should focus on collecting detailed information on the distribution patterns of prey within the study area to allow direct comparisons between predator and prey distributions.Communicated by J.P. Thorpe, Port Erin 相似文献
7.
Bruno Díaz López 《Marine Biology》2012,159(10):2161-2172
Owing to the worldwide growth of aquaculture over the last years, new habitats have been created through the supplement of nutrients. This addition of nutrients affects the whole marine food web, resulting in predator species such as bottlenose dolphins becoming attracted to these areas. During this 5-year-long study that was carried out along the north-eastern coast of Sardinia (Italy), bottlenose dolphin’s history of exposure to aquaculture perturbations and their effects was documented. The interaction with a fish farm was assessed by studying the site fidelity, group dynamics, and seasonal and yearly occurrence. In all, 1,838 hours were spent in the field. Behavioural observations showed that the predominant activity (89 % of the time) in the fish farm was foraging (predation and depredation). The occurrence of bottlenose dolphins appeared to be related with the seasons and with the fish farm harvesting operations. Thus, the peak dolphin occurrence in the fish farm area throughout Fall coincides with the period in which they spend most of their time foraging. A relatively small community remained resident interacting with the fish farm over a long period of time. Hence, these individuals gained intimate knowledge on how to capitalize on the fish farm industry. This heterogeneity in site fidelity and residence patterns is highly relevant when coastal management initiatives are considered. 相似文献
8.
Seasonal aerial surveys were conducted in the waters of the central Spanish Mediterranean from 2001 to 2003 using the line transect sampling methodology to estimate cetacean abundance. The density of the three most abundant species, striped dolphin (Stenella coeruleoalba), bottlenose dolphin (Tursiops truncatus) and Risso’s dolphins (Grampus griseus), was estimated. In the case of the first two species, the density was estimated accounting for the proportion of submerged animals, while for Risso’s dolphin only the surface density could be estimated. The striped dolphin was the most abundant species in the study area with a mean density of 0.489 dolphins km−2 (95% CI = 0.339–0.705) and a mean abundance of 15,778 dolphins (95% CI = 10,940–22,756). This density is comparable to that obtained in the International Ligurian Sea Cetacean Sanctuary. Striped dolphins were observed throughout the whole year and no seasonal changes in the density were detected. The mean density of bottlenose dolphins was an order of magnitude lower than that of striped dolphins (0.041 dolphins km−2; 95% CI = 0.023–0.075) with a mean abundance of 1,333 dolphins (95% CI = 739–2,407). The Risso’s dolphin had a surface estimated density of 0.015 dolphins km−2 (95% CI = 0.005–0.046) and a mean abundance of 493 dolphins (95% CI = 162–1,498). These results provide valuable biological information useful to develop conservation plans and establish a baseline for future population trend studies. 相似文献
9.
Calving can be a critical period for cetaceans. Areas providing security for vulnerable calves, and high food availability for lactating females can be critical habitats requiring specific conservation measures. Here, we test the hypothesis that calving and nursing habitat could be defined for Risso’s dolphins (Grampus griseus). We investigated the spatial and temporal preferences of this species around Pico Island, Azores, using data gathered from land-based surveys and dedicated at-sea observations between 2004 and 2007. We divided observed pods into three groups: (1) those with newborn and young calves, (2) those with older calves or juveniles and (3) those consisting only of adults or sub-adults. We analysed eco-geographical variables and incorporated them into a presence-only spatial distribution model to evaluate differences in habitat suitability among the groups. We identified 694 pods of Risso’s dolphins overall. On the 267 pods observed in the first and second groups, 136 calves or juveniles were identified, of which 22 were newborns. The peak of the calving season was between June and August. The pods with newborn calves were larger and closer to shore, whereas the other groups were more widely dispersed offshore. Our results support the definition of critical habitat areas for this species, but we suggest widening the geographical coverage for better mapping around the island and throughout the archipelago generally. Conservation measures can, nevertheless, be implemented immediately, in order to reduce human impacts on a vulnerable component of the Risso’s dolphin population 相似文献
10.
Sergi Pérez Ángel García-López Renaud De Stephanis Joan Giménez Susana García-Tiscar Philippe Verborgh Juan Miguel Mancera Gonzalo Martínez-Rodriguez 《Marine Biology》2011,158(7):1677-1680
We tested the possibility of measuring progesterone levels in bubbler samples collected from free-ranging live bottlenose
dolphins (n = 11) and long-finned pilot whales (n = 2) as a tool to evaluate the pregnancy status of individuals. Samples were collected during January 2004 and September–October
2005 in the Strait of Gibraltar and Gulf of Cadiz and used for sex-determination by genetic methods (skin samples) and for
quantification of progesterone levels by enzyme immunoassay. Photo-identification tracking of females after taking the biopsy
was used to observe the presence of newborns and, in this way, to determine if the female was pregnant at the time of sampling.
Mean progesterone levels from pregnant bottlenose dolphins (n = 2) were around 9 times higher than those from non-pregnant females (n = 9), with no overlap between concentration ranges demonstrating that this method could constitute an effective tool for
determining pregnancy in wild populations of bottlenose dolphins and other cetacean species. 相似文献
11.
Heidi C. Pearson 《Behavioral ecology and sociobiology》2009,63(10):1437-1446
In societies characterized by a high degree of fission-fusion dynamics, individuals adjust their grouping patterns according
to the shifting balance of costs and benefits associated with grouping. This study examines influences on fission-fusion dynamics
for dusky dolphins (Lagenorhynchus obscurus) in Admiralty Bay, New Zealand. This area is an important foraging habitat for dusky dolphins during the winter and spring.
Admiralty Bay has little predation risk, but nearshore mussel farms may infringe on available habitat. I used generalized
estimating equations to determine the influences of coordinated foraging, predation risk, and presence of mussel farms on
party size, rate of fission-fusion, and behavioral state. I conducted 168 boat-based group focal follows totaling 168 h. The
proportion of individuals observed foraging was positively related to party size and rate of party fusion. Resting had no
effect on party size and did not vary according to location. Near mussel farms, traveling decreased, and rate of party fission
decreased. I conclude that (1) coordinated foraging strategies are a primary influence on fission-fusion dynamics within this
population, (2) dolphins may respond to decreased predation risk by not adjusting party size or location during resting, and
(3) areas near mussel farms are not used for traveling. 相似文献
12.
Luciana M. Möller Luciano B. Beheregaray Simon J. Allen Robert G. Harcourt 《Behavioral ecology and sociobiology》2006,61(1):109-117
Kinship has been shown to be an important correlate of group membership and associations among many female mammals. In this study, we investigate association patterns in female Indo-Pacific bottlenose dolphins (Tursiops aduncus) inhabiting an embayment in southeastern Australia. We combine the behavioral data with microsatellite DNA and mitochondrial DNA data to test the hypotheses that genetic relatedness and maternal kinship correlate with associations and social clusters. Mean association between females was not significantly different from a random mean, but the standard deviation was significantly higher than a random standard deviation, indicating the presence of nonrandom associates in the dataset. A neighbor-joining tree, based on the distance of associations between females, identified four main social clusters in the area. Mean genetic relatedness between pairs of frequent female associates was significantly higher than that between pairs of infrequent associates. There was also a significant correlation between mtDNA haplotype sharing and the degree of female association. However, the mean genetic relatedness of female pairs within and between social clusters and the proportion of female pairs with the same and different mtDNA haplotypes within and between clusters were not significantly different. This study demonstrates that kinship correlates with associations among female bottlenose dolphins, but that kinship relations are not necessarily a prerequisite for membership in social clusters. We hypothesize that different forces acting on female bottlenose dolphin sociality appear to promote the formation of flexible groups which include both kin and nonkin. 相似文献
13.
Elizabeth J. Berens McCabe Damon P. Gannon Nélio B. Barros Randall S. Wells 《Marine Biology》2010,157(5):931-942
Prey selection was investigated in wild, resident common bottlenose dolphins, Tursiops truncatus, during the summer months in Sarasota Bay, Florida, USA. Stomach content analyses of 15 dolphins with extensive sighting histories and well-documented distributions were used to determine prey use. Prey availability was assessed by purse seine surveys. We compared the relative abundances of prey available to estimates of prey use at closely matching spatial and temporal scales. G-tests determined that dolphins in this study significantly selected for prey at the species, family, and soniferous/non-soniferous prey levels (G adj = 753.98–1,775.93, df = 1–21, p ≤ 0.01). While comprising only 6.3% of the total available prey, soniferous fishes accounted for 51.9% of the total prey consumed. Manly’s standardized forage ratios and 95% Bonferroni confidence intervals determined significant positive selection for soniferous prey and against non-soniferous prey (βS = 0.9461 vs. βNS = 0.0539). Dolphins selected against Gerridae, Clupeidae, and Sparidae (β ≤ 0.0014), as well as against all the species within those families (β ≤ 0.0190). It is likely that passive listening for soniferous prey provides an ecological or energetic advantage to cetaceans utilizing this specific foraging technique. 相似文献
14.
R. M. Wilson J. A. Nelson B. C. Balmer D. P. Nowacek J. P. Chanton 《Marine Biology》2013,160(11):2967-2980
Site-specific differences were found in consumer isotope values among ten sites examined in the northern Gulf of Mexico. Average δ13C values among sites ranged ?21.7 to ?15.7 ‰, δ15N ranged <3 ‰: from 9.8 to 11.5 ‰, and δ34S ranged from 5.9 to 18.3 ‰. Isotope variation among these sites provided insight into the ranging habits of bottlenose dolphins (Tursiops truncatus) sampled in St. George Sound (29.8N, 84.6W), a nearshore seagrass habitat, during May of 2005. Isotope comparisons suggest that the majority of dolphins sampled (average ± one standard deviation: δ13C = ?17.5 ± 0.8, δ15N = 14.5 ± 0.9, and δ34S = 10.6 ± 1.5) did not forage significantly on offshore species which are significantly 34S-enriched, nor is it likely that they ranged either eastward or westward along the coast within the sampling region. Despite their capability for ranging, these dolphins occupied a restricted home range, during the spring before our sampling efforts. These results demonstrate significant fine-scale isotope variation among coastal habitats explained by differences in freshwater inputs, organic matter loading, and modes of primary production that may be used to constrain the foraging ranges of a highly mobile apex predator. 相似文献
15.
Haidi Arbanasić Martina Đuras Martina Podnar Tomislav Gomerčić Snježana Ćurković Ana Galov 《Marine Biology》2014,161(10):2407-2422
The bottlenose dolphin (Tursiops truncatus) is the most common cetacean species worldwide and the only marine mammal species resident in the Croatian part of the Adriatic Sea. To gain insight into genetic diversity of bottlenose dolphins at adaptively important loci relevant to conservation, we analysed the polymorphism of major histocompatibility complex (MHC) genes, which play a key role in pathogen confrontation and clearance. Specifically, we examined the diversity of MHC class II DRA, DQA and DQB alleles in 50 bottlenose dolphins from the Adriatic Sea collected between 1997 and 2011 and in 12 animals from other Mediterranean locations. Notable variation in DQA, DQB and three-locus haplotypes was found, with all 10 DQA and 12 DQB alleles encoding unique protein products. Analysis of the ratio of non-synonymous to synonymous substitution rates suggests that positive selection acts at both highly variable loci. Phylogenetic analyses revealed trans-species polymorphism at the DQB locus, strongly indicating the influence of balancing selection in the long term. In fact, the balancing selection observed in bottlenose dolphins is higher than that reported for most other cetaceans and comparable to that seen in terrestrial mammals. 相似文献
16.
The signature whistle hypothesis states that dolphins produce highly stereotyped, individually distinctive whistles when in isolation. The presence of signature whistles has been called into question by recent studies proposing that dolphins produce a shared, simple upsweep whistle when in isolation, and that whistles produced by socializing dolphins are shared across individuals and social groups. This shared repertoire hypothesis suggests that when two animals produce the same whistle type, it is due to sharing the same common repertoire rather than one animal learning to produce the whistle of another. One difference between studies supporting or denying the existence of signature whistles is the method used to classify whistle types. We examined whistle production by 17 free-ranging bottlenose dolphins while temporarily restrained. We used both a quantitative comparison technique similar to that used to support the shared repertoire hypothesis and human judges to classify whistle types and quantify similarity between types. Contrary to recent studies that emphasize shared whistles, overall whistle sharing between isolated individuals was low (25%) and a simple upsweep did not account for the most common whistle type in half of the animals. Some species of birds, bats, and primates with stable social groups use vocal learning to converge over time to one common group distinctive call type. We examined whistle similarity between adult male dolphins that are partners in a close social alliance in order to test whether vocal learning may enable a similar vocal convergence. Whistle similarity was rated very high between partners and low between non-partners by both the quantitative technique and human observers. This suggests that as in songbirds and some other mammals, adult male bottlenose dolphins may use vocal learning to converge on similar whistles as they develop affiliative social relationships.Communicated by G. Wilkinson 相似文献
17.
In this study, we investigate association patterns of 249 bottlenose dolphin feeding groups off Sardinia Island (Italy) from
January 2000–May 2007 and describe how their association behaviour is related to their response to food patches created by
a marine fin fish farm. We also tested the hypothesis that dolphins have different social structures with different feeding
activities: Associations should decrease during opportunistic feeding behaviours as it is easier to capture prey, and cooperation
is not as necessary. Sixteen individually identified bottlenose dolphins were observed participating in both opportunistic
and not opportunistic feeding activities, with a mean of 30 ± 8 times and 9.6 ± 1 times, respectively. Bottlenose dolphins
show non-random social behaviour during feeding and this behaviour differs depending on their specific foraging activity.
Dolphin associations during feeding can be divided into three categories: acquaintances, affiliates, and feeding associates.
Association behaviour during fish farm feeding is consistent with our hypothesis that during opportunistic behaviours, benefits
from cooperation decrease, as it is easier to capture prey. Group size homogeneity in both feeding activities demonstrates
that the number of dolphins engaging in foraging is not necessarily related with cooperation levels. Moreover, an adult dolphin
may prefer to associate with a specific individual, independent of the sex, who shares the same foraging priorities. This
study is the first to show how aquaculture is not only directly affecting marine predators but could also indirectly affect
their social structure and behaviour. 相似文献
18.
The red porgy, Pagrus pagrus (L.), is a protogynous sparid associated with reefs and hard bottom habitat throughout the warm-temperate Atlantic Ocean.
In this study, the degree of geographic population differentiation in Atlantic populations was examined with microsatellite
and mitochondrial DNA markers (mtDNA). Six microsatellite loci were amplified and scored in 690 individuals from the eastern
North Atlantic (Crete, Madeira, and Azores), western North Atlantic (North Carolina to Florida, and the eastern Gulf of Mexico),
and Brazil. At two loci, fixed allelic differences were found among the three major geographic areas, while frequency differences
were observed at three other loci. The DNA of 371 individuals was amplified at the mtDNA control region, and 526 bp were sequenced.
Tamura–Nei’s D was used as a measure of nucleotide diversity and divergence: diversity averaged 0.011 within samples, while the corrected
divergence averaged 0 between samples within the same area and 0.061 between samples from different areas. Transversion haplotype
minimum spanning networks, nucleotide divergence, and F
ST values all show that the western Atlantic samples were more closely related to each other than any was to samples from the
eastern North Atlantic. Within the western North Atlantic, no significant population differentiation was observed, and within
the eastern North Atlantic, only the Azores sample showed detectable differences from Crete and Madeira. These data indicate
general homogeneity within large areas, and deep divisions between these areas.
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
19.
To exploit resources in their environment, odontocete cetaceans have evolved sophisticated diving abilities to allow effective
foraging. However, data on the diving behaviour and underwater foraging behaviour remains limited. This study made use of
echolocation clicks and other calls to study the diving behaviour of bottlenose dolphins. Dolphins used the full water column
and consistently dived to depths of around 50 m, close to the seabed. However, the majority of their time appeared to be spent
within the surface layers of the water column. In addition, by localising calls that have been associated with prey capture
events (Janik, Proc R Soc Lond Ser B 267:923–927, 2000a), it appeared that certain forms of feeding behaviour occurred primarily
at depths of between 20 and 30 m. Furthermore, data on the depth of clicks made before and after these feeding calls suggested
that during the minute before the calls, dolphins were consistently diving from the surface to depths close to the seabed,
and were subsequently returning to the surface after the calls. This passive acoustic technique proved an accurate method
for studying the depth distribution of dolphin vocalisations. By exploiting the natural sounds made by these wild odontocetes,
this investigation provided a previously unavailable perspective on the the 3D nature of bottlenose dolphins foraging behaviour.
It confirmed that while the dolphins spent the majority of time close to the surface, the full water column was exploited
during foraging events. 相似文献
20.
Elizabeth J. Berens McCabe Damon P. Gannon Nélio B. Barros Randall S. Wells 《Marine Biology》2010,157(5):943-942
Prey selection was investigated in wild, resident common bottlenose dolphins, Tursiops truncatus, during the summer months in Sarasota Bay, Florida, USA. Stomach content analyses of 15 dolphins with extensive sighting
histories and well-documented distributions were used to determine prey use. Prey availability was assessed by purse seine
surveys. We compared the relative abundances of prey available to estimates of prey use at closely matching spatial and temporal
scales. G-tests determined that dolphins in this study significantly selected for prey at the species, family, and soniferous/non-soniferous
prey levels (G
adj
= 753.98–1,775.93, df = 1–21, p ≤ 0.01). While comprising only 6.3% of the total available prey, soniferous fishes accounted for 51.9% of the total prey
consumed. Manly’s standardized forage ratios and 95% Bonferroni confidence intervals determined significant positive selection
for soniferous prey and against non-soniferous prey (βS = 0.9461 vs. βNS = 0.0539). Dolphins selected against Gerridae, Clupeidae, and Sparidae (β ≤ 0.0014), as well as against all the species within those families (β ≤ 0.0190). It is likely that passive listening for soniferous prey provides an ecological or energetic advantage to cetaceans
utilizing this specific foraging technique. 相似文献