Stenella Longirostris Research Articles

Age and growth of some delphinids in south-eastern Brazil

This study provides the first compilation on age and growth of some delphinids in south-eastern Brazil (18°25′S–25°45′S). A total of 154 delphinids were reported: 44 Atlantic spotted dolphin Stenella frontalis; 36 bottlenose dolphin Tursiops truncatus; 26 ‘Brazilian’ common dolphin Delphinus sp.; 20 rough-toothed dolphin Steno bredanensis; 16 Fraser's dolphin Lagenodelphis hosei; 3 false killer whale Pseudorca crassidens; 3 unidentified Stenella sp.; 2 pantropical spotted dolphin Stenella attenuata; 2 short-finned pilot whale Globicephala macrorhynchus; 1 spinner dolphin Stenella longirostris; and 1 striped dolphin Stenella coeruleoalba. Age was estimated by counting the number of growth layer groups present in the dentine in 74.5% of the sample. The growth of 92 individuals of the first five species was determined by the Gompertz model to length-at-age data. Stenella frontalis—the oldest specimen was 23 y and the asymptotic length of 224.4 cm predicted by growth curve occurred at about 20 y; T. truncatus—the oldest specimen was 26 y and the asymptotic length of 301.3 cm predicted by growth curve occurred at about 20 y; Delphinus sp.—the oldest dolphin was 18 y and the asymptotic length of 215.9 cm predicted by growth curve occurred at about 5–6 y; S. bredanensis—the oldest specimen was 24 y and the asymptotic length of 258.1 cm predicted by growth curve occurred at about 10 y; L. hosei—the oldest specimen was 19 y and the asymptotic length of 231.2 cm predicted by growth curve occurred at about 7–8 y. Only age was estimated for the other species. The age-at-length data for S. frontalis, Delphinus sp., S. bredanensis and L. hosei were consistent, suggesting a good agreement with previous work on these species. For T. truncatus, the age at asymptotic length obtained in this study might be confirmed by increasing the sample size. The information currently presented will contribute to further life history research of delphinids on the western south Atlantic coast.

Report on the collision between a spinner dolphin and a boat in the Fernando de Noronha Archipelago, Western Equatorial Atlantic, Brazil

This paper reports a case of collision between an individual spinner dolphin and a boat in the Fernando de Noronha Archipelago, as an example of disturbance potentially caused by tourism industry activities. Photos illustrating the inflicted injuries on the animal are presented, and preventive measures to avoid this kind of accidents are proposed. This is the first report on a collision between spinner dolphins and boats.

Fishes associated with spinner dolphins at Fernando de Noronha Archipelago, tropical Western Atlantic: an update and overview

An update is presented for fish species associated with spinner dolphins at Fernando de Noronha Archipelago, tropical Western Atlantic, providing a general view of their diversity. The associates are mostly reef-dwelling fishes that feed on the dolphin wastes. Twelve species are habitual or occasional plankton-eaters and two species are herbivores that occasionally forage on floating pieces of algae. One species is a strict carnivore, one species is a hitchhiker that forages on a variety of foods including parasites and dead tissue from the dolphins, and one species is a carnivore that joins the dolphin groups to forage on schools of small fishes or squids. We predict that the list of fish associated with spinner dolphins will expand mostly with addition of habitual or occasional plankton-eaters.

Species records, mistaken identifications, and their further use: the case of the diskfish Echeneis naucrates on a spinner dolphin

The single record of the sharksucker (Echeneis naucrates) attached to a spinner dolphin (Stenella longirostris) is based on a photograph taken at Fernando de Noronha Archipelago, off northeast Brazil. A careful examination of this photograph demonstrates that the diskfish attached to the dolphin is the whalesucker (Remora australis), a species so far recorded on cetaceans only. Thus, the record of S. longirostris as a host for E. naucrates is here invalidated and the value of vouched records is reiterated. The exaggerated reliance even on refereed papers dealing with species records and checklists that lack or have dubious vouchers and their further use is commented upon.

Whistle variability in South Atlantic spinner dolphins from the Fernando de Noronha Archipelago off Brazil

A series of quali- and quantitative analyses were conducted to evaluate the variability of spinner dolphin whistles from the Fernando de Noronha Archipelago off Brazil. Nine variables were extracted from each whistle contour, and the whistle contours shapes were classified into the seven categories described in Driscoll (1995). The analysis showed mean beginning and ending frequencies values of 10.78 and 12.74 kHz, respectively. On average, whistle duration was relatively short, with mean values around 0.495 s (N=702). Comparative analyses were also conducted to investigate the relationship between the obtained results and those presented in previous studies. When comparing averages, the results of the study of Oswald et al.(2003) in the Tropical Eastern Pacific (TEP) presented less significant differences in relation to this study; only whistle duration differed significantly between both works. The results of multivariate classification tests also pointed TEP population as the closest related to the population studied here. The similarities between such disjunct populations might be attributed to a more recent isolation event (the closing of the Panama Isthmus) than the divergence that has driven North and South Atlantic populations apart.

Environmental Variables Affecting the Residence of Spinner Dolphins (<I>Stenella longirostris</I>) in a Bay of Tahiti (French Polynesia)

The spinner dolphin (Stenella longirostris) is the most common among 16 species in the Society Islands (French Polynesia). They are observed yearround during daytime in sheltered bays or within lagoons. From 1995 to 2002, we studied spinner dolphins from a shore site in Baie des Pecheurs, a bay on the west coast of Tahiti, performing 1,033 sighting sessions with binoculars. Presence, position, and school size were noted, as well as various behavioral and environmental variables. Human presence also was recorded. Dolphins were present on average 73.3% of the days, with a higher presence rate from May to November (81.0%) than from December to April (66.7%). Dolphins stayed within the bay from early morning until 1200 to 1500 h and had school sizes ranging from as small as 15 to 30 to as large as 100 to 140 individuals. Dolphins began to move slowly offshore after 1100 h. On average, they stayed 400 m from shore, although they approached as close as 100 to 150 m. Dolphin presence and residence time seemed to be negatively affected by surface water turbidity (river flow) and lagoon current strength. Recreational dolphin watching was low from Monday to Thursday (0.20 to 0.35 boat per sighting session) and high on Sunday, with an average of 1.67 boats per session. There was a lower dolphin presence rate from Monday to Thursday (69%) than from Friday to Sunday (78%). Presence patterns were similar to those found in Hawaii, accounting for differences in environmental characteristics.

Oceanographic influences on seabirds and cetaceans of the eastern tropical Pacific: A review

This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific, the oceanic region centered on the eastern Pacific warm pool, but also including the equatorial cold tongue and equatorial current system, and summarizes what is known about oceanographic influences on seabirds and cetaceans there. The eastern tropical Pacific supports on the order of 50 species of seabirds and 30 species of cetaceans as regular residents; these include four endemic species, the world’s largest populations for several others, three endemic sub-species, and a multi-species community that is relatively unique to this ecosystem. Three of the meso-scale physical features of the region are particularly significant to seabirds and cetaceans: the Costa Rica Dome for blue whales and short-beaked common dolphins, the Equatorial Front for planktivorous seabirds, and the countercurrent thermocline ridge for flocking seabirds that associate with mixed-species schools of spotted and spinner dolphins and yellowfin tuna. A few qualitative studies of meso- to macro-scale distribution patterns have indicated that some seabirds and cetaceans have species-specific preferences for surface currents. More common are associations with distinct water masses; these relationships have been quantified for a number of species using several different analytical methods. The mechanisms underlying tropical species–habitat relationships are not well understood, in contrast to a number of higher-latitude systems. This may be due to the fact that physical variables have been used as proxies for prey abundance and distribution in species–habitat research in the eastern tropical Pacific. Though seasonal and interannual patterns tend to be complex, species–habitat relationships appear to remain relatively stable over time, and distribution patterns co-vary with patterns of preferred habitat for a number of species. The interactions between seasonal and interannual variation in oceanographic conditions with seasonal patterns in the biology of seabirds and cetaceans may account for some of the complexity in species–habitat relationship patterns. Little work has been done to investigate effects of El Niño-Southern Oscillation cycles on cetaceans, and results of the few studies focusing on oceanic seabirds are complex and not easy to interpret. Although much has been made of the detrimental effects of El Niño events on apex predators, more research is needed to understand the magnitude, and even direction, of these effects on seabirds and cetaceans in space and time.

The spatial context of free-ranging Hawaiian spinner dolphins (Stenella longirostris) producing acoustic signals

To improve our understanding of how dolphins use acoustic signals in the wild, a three-hydrophone towed array was used to investigate the spatial occurrence of Hawaiian spinner dolphins (Stenella longirostris) relative to each other as they produced whistles, burst pulses, and echolocation clicks. Groups of approximately 30 to 60 animals were recorded while they traveled and socialized in nearshore waters off Oahu, Hawaii. Signaling animals were localized using time of arrival difference cues on the three channels. Sequences of whistles occurred between dolphins separated by significantly greater distances than animals producing burst pulses. Whistles typically originated from dolphins spaced widely apart (median = 23 m), supporting the hypothesis that whistles play a role in maintaining contact between animals in a dispersed group. Burst pulses, on the other hand, usually came from animals spaced closer to one another (median = 14 m), suggesting they function as a more intimate form of signaling between adjacent individuals. The spacing between echolocating animals was more variable and exhibited a bimodal distribution. Three quarters of echolocating animals were separated by 10 m or more, suggesting that the task of vigilance in a pod may not be shared equally by all members at all times.

Geographical distribution of polybrominated diphenyl ethers (PBDEs) and organochlorines in small cetaceans from Asian waters

Polybrominated diphenyl ethers (PBDEs) are one of the flame retardants widely used in plastics, textiles, electronic appliances, and electrical household appliances. In this study, PBDEs and organochlorine compounds (OCs) were determined in the archived samples from the Environmental Specimen Bank for Global Monitoring ( es-BANK) at Ehime University. The blubber of cetaceans found stranded along the coasts of Japan, Hong Kong, the Philippines and India during the period from 1990 to 2001 were employed for chemical analysis to understand the present status of contamination and the specific accumulation of PBDEs. PBDEs were detected in all the cetacean samples analyzed, and concentrations were one or two orders of magnitude lower than for PCBs and DDTs. Concentrations of PBDEs ranged from a low value of 6.0 ng/g lipid wt. in spinner dolphin ( Stenella longirostris) from India to a high value of 6000 ng/g lipid wt. in Indo-Pacific humpback dolphin ( Sousa chinensis) from Hong Kong. No difference in PBDE levels between coastal and offshore species from Japan was observed, implying the existence of pollution sources in this region other than Japan. Highest concentrations of PBDEs were found in animals from Hong Kong, followed by Japan, and much lower levels from the Philippines and India, suggesting that developing nations may also have pollution sources of PBDEs. Geographical distribution of PBDEs in Asian waters was different from PCBs but similar to DDTs.

Abstracts of Papers, Thirtieth Annual Albert L. Tester Memorial Symposium, 16-18 March 2005

Abstracts of Papers Thirtieth Annual Albert L. Tester Memorial Symposium, 16-18 March 2005 Abstract The Albert L. Tester Memorial Symposium is held in honor of Professor Albert Tester, who, at the time of his death in 1974, was Senior Professor of Zoology at the University of Hawai'i at Mānoa. The faculty and students of the Department of Zoology proposed an annual symposium of student research papers as a means of honoring, in a continuing and active way, Dr. Tester's lively encouragement of student research in a broad range of fields within marine biology. Papers reporting original research on any aspect of science are solicited from students at the university and these papers are presented at the symposium, which takes place during the spring semester. Income from contributions to the Albert L. Tester Memorial Fund of the University of Hawai'i Foundation is used to provide prizes for the three best papers, judged on quality, originality, and importance of research reported, as well as the quality of the public presentation. Judges include Department of Zoology faculty members and the previous year's student award winners. In addition, a distinguished scholar from another university or research institution is invited to participate in the symposium as a judge and to present the major symposium address. In 2005 the distinguished visitor and judge was Dr. Stephen Palumbi, Stanford University, Hopkins Marine Station, Pacific Grove, California. A Proposal to Study Connectance of Pollination Systems in Dry Forests of Hawai'i Patrick Aldrich2 Traditionally, mutualistic plant-animal interactions have been placed in a dichotomy of specialized versus generalized relationships within a community. Recently ecologists have become aware that this split is artificial, and most systems are made up of connections and networks analogous to food webs. Using network theory and connectivity to describe species interactions can help explain the structural organization of the species richness of communities and how introduced pollinator species in the system can affect its stability. Hawaiian dry forests located at Pu'uwa'awa'a on the island of Hawai'i provide a system to study networks of native and introduced pollinators in a fragmented, altered landscape. Because most of the understory of the Hawaiian dry forests is a matrix of grasses, only the overstory trees will be used in this study. Observations will be made at inflorescences of all dominant tree species within the dry forest system. Each day a single species will be selected, based on phenology, and observed from sunrise to sunset. Data will be entered into a binary-coded matrix to examine interactions and connections between pollinators and plants. Analyses, following food web and network theory, will be used to test whether the connectivity is structured or random. [End Page 305] Ecological and Behavioral Factors Influencing Patterns of Interbreeding and Genetic Diversity in the Hawaiian Spinner Dolphin3 Kimberly R. Andrews4 In many cetacean populations, reproductively isolated subgroups exist within populations even when these subgroups live in the same geographic range or are capable of traveling to other subgroups' ranges. The factors that lead to reproductive isolation in these cetacean populations are often complex. For the Hawaiian spinner dolphin (Stenella longirostris), there is variability throughout the Hawaiian Archipelago in factors such as geographic distance between suitable habitat, prey distribution, habitat type and availability, population size, and social structure. To investigate whether these factors have led to reproductive isolation between subgroups and influenced genetic diversity, genetic structure and genetic diversity of the spinner dolphin throughout Hawai'i were investigated. Genetic samples were collected from Kure Atoll (34 samples), Midway Atoll (57), Pearl and Hermes Reef (21), French Frigate Shoals (13), Ni'ihau (39), O'ahu (47), Maui (60), and the Big Island (77). A 429-base pair region of the mitochondrial DNA (mtDNA) control region and 12 microsatellite loci were used to evaluate genetic structure and diversity. Analysis of molecular variance (AMOVA) indicated significant genetic structure for the spinner dolphin within Hawai'i for both mtDNA and microsatellites. The pattern of genetic structure could not be explained only by geographic distance between populations, indicating the presence of additional, more complex factors influencing patterns of interbreeding. An unexpected peak in genetic diversity was found at...

Dynamics of the aerial maneuvers of spinner dolphins

The spinner dolphin (Stenella longirostris) performs spectacular leaps from the water while rotating around its longitudinal axis up to seven times. Although twisting of the body while airborne has been proposed as the mechanism to effect the spin, the morphology of the dolphin precludes this mechanism for the spinning maneuver. A mathematical model was developed that demonstrates that angular momentum to induce the spin was generated underwater, prior to the leap. Subsurface corkscrewing motion represents a balance between drive torques generated by the flukes and by hydrodynamic forces at the pectoral fins, and resistive torques, induced by the drag forces acting on the rotating control surfaces. As the dolphin leaps clear of the water, this balance is no longer maintained as the density of the air is essentially negligible, and a net drive torque remains, which permits the dolphin's rotation speed to increase by as much as a factor of three for a typical specimen. The model indicates that the high rotation rates and orientation of the dolphin's body during re-entry into the water could produce enough force to hydrodynamically dislodge unwanted remoras.

Patterns of Use of Maku'a Beach, O'ahu, Hawai'i, by Spinner Dolphins (<I>Stenella longirostris</I>) and Potential Effects of Swimmers on Their Behavior

Spinner dolphins (Stenella longirostris) use Maku’a Beach, a small bight along the Waianae coast of O’ahu, as a rest site. Behavior and use patterns of Maku’a Beach by spinner dolphins and swimmers were studied in July and August of 1995 to provide baseline data on the dolphin population and to assess potential impacts of swimmers on the dolphins’ resting behavior. Dolphins were observed on 52 out of 53 days, and they entered the area between 0545 and 0845 h. Their departure time varied widely. Average school size was 67 ± 0.6 SE and decreased with time of day. The most common aerial behaviors were slaps, leaps, and spins, respectively, with a peak in aerial behavior in late afternoon associated with schools moving offshore. The number of swimmers in the study area was highest on weekend mornings (X – = 12 ± 0.6 SE), with a maximum of 63 people in the water at the same time. Rest appeared delayed and compressed in this population of dolphins as compared to other studies and may be a response to the presence of swimmers in the morning. The results suggest a potential adverse impact of swimmers on the dolphins’ resting patterns, with earlier departure times and shorter periods of dive behavior indicative of rest.

Two Presumed Interspecific Hybrids in the Genus <I>Stenella</I> (Delphinidae) in the Tropical West Atlantic

We describe and comment on two aberrant individuals of the genus Stenella from Fernando de Noronha Archipelago, tropical West Atlantic, which we regard as interspecific hybrids. Each dolphin was found living with a large group of the spinner dolphins, Stenella longirostris. One of the aberrant dolphins is a presumed hybrid between S. longirostris and S. attenuata, and the second one is possibly a hybrid between S. longirostris and S. clymene. Each of the hybrids was accompanied by a spinner female. The S. longirostris × S. attenuata was first sighted as a calf and was re-sighted several times over two years. This individual was recorded being nursed by the female. The other hybrid was re-sighted a few times over three months.

Application of a diver-operated 4-channel acoustic/video recording device to study wild dolphin echolocation and communication

Despite decades of research on captive dolphins, there still is much to learn about dolphin echolocation and communication in the wild. This is mainly due to the difficulties associated with recording dolphin signals accurately in the wild, such as their broadband (with frequencies over 200 kHz) and directional nature, the difficulty of identifying vocalizing dolphins, and being confined to equipment aboard a vessel. To resolve these difficulties, an underwater portable battery-operated digital recording device was developed that is capable of simultaneously capturing acoustic signals up to 220 kHz on 4 channels as well as video. It consists of a custom-made underwater housing, containing two batteries, a digital camcorder, and an acoustic recording unit with signal conditioning board, 4-channel data acquisition card, PC/104-plus single board computer and power supply, and a notebook hard disk. Attached to the housing is a 4-hydrophone star array. Post-recording, acoustic signals recorded within 15 m are accurately localized in 3-D and attributed to individual dolphins on the video. Thus, acoustic signal features are correlated with different echolocation behaviors and communicative signal exchanges among dolphins are assessed. The system has been successfully field tested with spinner dolphins (Stenella longirostris) along the leeward coast of Oahu, Hawaii.

Organochlorine residues in odontocete species from the southeast coast of India

Blubber from bottle-nose dolphins, spinner dolphins, humpback dolphin ( Tursiops truncatus, Stenella longirostris and Sousa chinensis) were collected from the Bay of Bengal (southeast coast of India) and analyzed for the organochlorine pesticides hexachlorocyclohexane (HCHs), p, p′-dichlorodiphenyl trichloroethane (DDTs), and polychlorinated biphenyls (PCBs). All nine specimens analyzed contained considerable levels of all the three chemical classes where DDT was in the range of 3330–23 330 ng/g; HCHs in the range of 95–765 ng/g; and PCBs in the range of 210–1220 ng/g (wet weight basis). The reasons for this and the variations in the isomer pattern of HCHs and DDT and its metabolites in marine mammal tissues are discussed.

Spinner dolphins in a remote Hawaiian atoll: social grouping and population structure

Spinner dolphins (Stenella longirostris) commonly use inshore island and atoll habitats for daytime rest and social interactions and forage over deep waters at night. In Hawaii, they occur througho ...

Non-recovery of two spotted and spinner dolphin populations in the eastern tropical Pacific Ocean

Populations of northeastern offshore spotted dolphins Stenella attenuata attenuata and eastern spinner dolphins S. longirostris orientalis have been reduced because the dolphins are bycatch in the purse-seine fishery for yellowfin tuna in the eastern tropical Pacific Ocean (the 'tuna-dolphin issue'). Abundance and trends of these dolphin stocks were assessed from 12 large-scale pelagic surveys carried out between 1979 and 2000. Estimates of abundance were based on a multivariate line-transect analysis, using covariates to model the detection process and group size. Current estimates of abundance are about 640 000 northeastern offshore spotted dolphins (CV = 0.17) and 450 000 eastern spinner dolphins (CV = 0.23). For the whole period from 1979 to 2000, annual estimates of abundance ranged from 494 000 to 954 000 for northeastern offshore spotted dolphins and from 271000 to 734 000 for eastern spinner dolphins. Management actions by USA and international fishing agencies over 3 decades have successfully reduced dolphin bycatch by 2 orders of magnitude, yet neither stock is showing clear signs of recovery. Possible reasons include underreporting of dolphin bycatch, effects of chase and encirclement on dolphin survival and reproduction, long-term changes in the ecosystem, and effects of other species on spotted and spinner dolphin population dynamics.

Odontocete Stranding Patterns in the Main Hawaiian Islands (1937-2002): How Do They Compare with Live Animal Surveys?

ABSTRACT In this study we (1) synthesized 65 yr of odontocete stranding data around the main Hawaiian Islands (1937–2002); (2) analyzed stranding patterns and trends over time; and (3) compared occurrence patterns based on sightings of live animals with stranding data and evaluated the compatibility of these data sets. From 1937 to 2002, 202 odontocete strandings were recorded by the National Marine Fisheries Service, Pacific Islands Regional Office. Strandings increased through time due to increased reporting effort and occurred throughout the year. The four most common of 16 species reported were Kogia spp. (18%), spinner dolphins (Stenella longirostris) (15%), striped dolphins (Stenella coeruleoalba) (11%), and sperm whales (Physeter macrocephalus) (10%). The highest proportion of strandings was recorded on O‘ahu (48%), followed by Maui/Lāna‘i (24%), Kaua‘i (12%), Hawai‘i (11%), and Moloka‘i (5%). Comparison with four previously published live animal survey studies suggests that stranding records are a...

Distribution and habitat characteristics of dolphins of the genus Stenella (Cetacea: Delphinidae) in the southwest Atlantic Ocean

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 300:229-240 (2005) - doi:10.3354/meps300229 Distribution and habitat characteristics of dolphins of the genus Stenella (Cetacea: Delphinidae) in the southwest Atlantic Ocean Ignacio B. Moreno1,2,7,*, Alexandre N. Zerbini3, Daniel Danilewicz1,2, Marcos C. de Oliveira Santos4, Paulo C. Simões-Lopes5, Jose Lailson-Brito Jr.6, Alexandre F. Azevedo6 1Grupo de Estudos de Mamíferos Aquáticos do Rio Grande do Sul (GEMARS), Rua Felipe Neri 382/203, Porto Alegre, Rio Grande do Sul 90440-150, Brazil2Centro de Estudos Costeiros, Limnológicos e Marinhos (CECLIMAR) & Universidade Federal do Rio Grande do Sul (UFRGS), Avenida Tramandaí 976, Imbé, Rio Grande do Sul 95625-000, Brazil3Washington Cooperative Fish and Wildlife Research Unit, School of Aquatic and Fishery Sciences, Box 355020, University of Washington, Seattle, Washington 98195-5020, USA4Projeto Atlantis—Departamento de Ecologia Geral, Instituto de Biociências—USP, Rua do Matão 321, Cidade Universitária, São Paulo, São Paulo 05508-900, Brazil5Laboratório de Mamíferos Aquáticos, Departamento de Ecologia e Zoologia, Universidade Federal de Santa Catarina, Caixa Postal 5102, Florianópolis, Santa Catarina 88040-970, Brazil6Laboratório de Mamíferos Aquáticos (MAQUA)/UERJ, Rua São Francisco Xavier 524/4018E, Rio de Janeiro,Rio de Janeiro 20550-013, Brazil7Present address: Pós-Graduação em Biociências, Laboratório de Ictiologia, Museu de Ciências e Tecnologia/PUCRS, Avenida Ipiranga 6681, Caixa Postal 1429, Porto Alegre, Rio Grande do Sul 90619-900, Brazil *Email: iggy.moreno@gmail.com ABSTRACT: The distribution of dolphins of the genus Stenella is poorly known in the southwest Atlantic Ocean. A complete review of records (n = 311) of these dolphin species was performed to describe distribution and habitat. Atlantic spotted dolphins S. frontalis occur in both southern (21 to 33°S) and northern Brazil (north of 06°S), with a hiatus in its distribution off eastern South America. This species presents the highest preference for nearshore habitats, restricted to waters within the 1000 m isobath. Pantropical spotted dolphins S. attenuata are found in tropical waters as far south as 22°S and are mainly observed off northeastern South America. They occur beyond the continental shelf break in depths >850 m. Clymene dolphins S. clymene are distributed in deep waters (1390 to 4500 m) as far south as 30°S. Strandings are more common where the continental shelf is narrower. Spinner dolphins S. longirostris are found in oceanic waters as far south as 30°S. They inhabit tropical waters over the shelf and slope (depths ranging from 170 to 2700 m). The striped dolphin S. coeruleoalba is the least known species of the genus in the western South Atlantic. Most records are from temperate waters in southern Brazil and Argentina. The distributions of S. attenuata, S. clymene and S. longirostris overlap to a great extent and are predominantly oceanic and associated with warm ocean currents. S. frontalis seems to prefer a different, coastal habitat, influenced both by warm currents and upwelling areas. The discontinuous distribution of this species suggests that an isolated population inhabits the southern coast of Brazil. KEY WORDS: Stenella · Atlantic Ocean · Brazil · Uruguay · Argentina · Distribution · Habitat characteristics Full text in pdf format Supplemental Appendix PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 300. Online publication date: September 16, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.

Geographic variations in the whistles of spinner dolphins (Stenella longirostris) of the Main Hawai‵ian Islands

Geographic variations in the whistles of Hawai'ian spinner dolphins are discussed by comparing 27 spinner dolphin pods recorded in waters off the Islands of Kaua'i, O'ahu, Lana'i, and Hawai'i. Three different behavioral states, the number of dolphins observed in each pod, and ten parameters extracted from each whistle contour were considered by using clustering and discriminant function analyses. The results suggest that spinner dolphin pods in the Main Hawai'ian Islands share characteristics in approximately 48% of their whistles. Spinner dolphin pods had similar whistle parameters regardless of the island, location, and date when they were sampled and the dolphins' behavioral state and pod size. The term "whistle-specific subgroup" (WSS) was used to designate whistle groups with similar whistles parameters (which could have been produced in part by the same dolphins). The emission rate of whistles was higher when spinner dolphins were socializing than when they were traveling or resting, suggesting that whistles are mainly used during close-range interactions. Spinner dolphins also seem to vary whistle duration according to their general behavioral state. Whistle duration and the number of turns and steps of a whistle may be more important in delivering information at the individual level than whistle frequency parameters.