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Guido J. Parra - One of the best experts on this subject based on the ideXlab platform.
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Demographic collapse and low genetic diversity of the Irrawaddy dolphin population inhabiting the Mekong River.
PloS one, 2018Co-Authors: Michael Krützen, Guido J. Parra, Isabel Beasley, Arne Ludwig, Corinne Y. Ackermann, Lars Bejder, Dietmar Lieckfeldt, Gerard E. Ryan, Rebekka Wolfensberger, Peter B. S. SpencerAbstract:In threatened wildlife populations, it is important to determine whether observed low genetic diversity may be due to recent anthropogenic pressure or the consequence of historic events. Historical size of the Irrawaddy dolphin (Orcaella brevirostris) population inhabiting the Mekong River is unknown and there is significant concern for long-term survival of the remaining population as a result of low abundance, slow reproduction rate, high neonatal mortality, and continuing anthropogenic threats. We investigated population structure and reconstructed the demographic history based on 60 Irrawaddy dolphins samples collected between 2001 and 2009. The phylogenetic analysis indicated reciprocal monophyly of Mekong River Orcaella haplotypes with respect to haplotypes from other populations, suggesting long-standing isolation of the Mekong dolphin population from other Orcaella populations. We found that at least 85% of all individuals in the two main study areas: Kratie and Stung Treng, bore the same mitochondrial haplotype. Out of the 21 microsatellite loci tested, only ten were polymorphic and exhibited very low levels of genetic diversity. Both individual and frequency-based approaches suggest very low and non-significant genetic differentiation of the Mekong dolphin population. Evidence for recent bottlenecks was equivocal. Some results suggested a recent exponential decline in the Mekong dolphin population, with the current size being only 5.2% of the ancestral population. In order for the Mekong dolphin population to have any potential for long-term survival, it is imperative that management priorities focus on preventing any further population fragmentation or genetic loss, reducing or eliminating anthropogenic threats, and promoting connectivity between all subpopulations.
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Population Differentiation and Hybridisation of Australian Snubfin (Orcaella heinsohni) and Indo-Pacific Humpback (Sousa chinensis) Dolphins in North-Western
2016Co-Authors: Er M. Brown, Carol Palmer, Deborah Thiele, Guido J. Parra, Lars Bejder, Simon J. Allen, Bethan Littleford-colquhoun, Daniele Cagnazzi, Celine H. FrèreAbstract:Little is known about the Australian snubfin (Orcaella heinsohni) and Indo-Pacific humpback (Sousa chinensis) dolphins (‘snubfin ’ and ‘humpback dolphins’, hereafter) of north-western Australia. While both species are listed as ‘near threatened’ by the IUCN, data deficiencies are impeding rigorous assessment of their conservation status across Australia. Understanding the genetic structure of populations, including levels of gene flow among populations, is important for the assessment of conservation status and the effective management of a species. Using nuclear and mitochondrial DNA markers, we assessed population genetic diversity and differentiation between snubfin dolphins from Cygnet (n = 32) and Roebuck Bays (n = 25), and humpback dolphins from the Dampier Archipelago (n = 19) and the North West Cape (n = 18). Al
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Corrigendum to: Estimates of abundance and apparent survival of coastal dolphins in Port Essington harbour, Northern Territory, Australia (Wildlife Research (2014) 41:1 (35-45) DOI: 10.1071/WR14031)
Wildlife Research, 2015Co-Authors: Carol Palmer, Guido J. Parra, Tracey L. Rogers, Lyndon O Brooks, Debra Glasgow, John C. Z. WoinarskiAbstract:Context Three dolphin species occur in coastal waters of monsoonal northern Australia: the Australian snubfin (Orcaella heinsohni), humpback (Sousa sp.) and the bottlenose (Tursiops sp.). Their overall population size and trends are poorly known, and their conservation status has been difficult to resolve, but can be expected to deteriorate with likely increased development pressures. Aims We sought to provide an estimate of abundance, and apparent survival, of the three dolphin species at the largely undeveloped harbour of Port Essington (325km2), Northern Territory, with repeated sampling over a 2.9-year period. Given increasing obligations to undertake population assessments for impact studies at proposed development sites, we assess the strengths and limitations of a systematic sampling program.
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Population Differentiation and Hybridisation of Australian Snubfin (Orcaella heinsohni) and Indo-Pacific Humpback (Sousa chinensis) Dolphins in North-Western Australia
PloS one, 2014Co-Authors: A. Brown, Carol Palmer, Deborah Thiele, Guido J. Parra, Lars Bejder, Simon J. Allen, Daniele Cagnazzi, Anna M Kopps, Bethan L. Littleford‐colquhoun, Celine H. FrèreAbstract:Little is known about the Australian snubfin (Orcaella heinsohni) and Indo-Pacific humpback (Sousa chinensis) dolphins (‘snubfin’ and ‘humpback dolphins’, hereafter) of north-western Australia. While both species are listed as ‘near threatened’ by the IUCN, data deficiencies are impeding rigorous assessment of their conservation status across Australia. Understanding the genetic structure of populations, including levels of gene flow among populations, is important for the assessment of conservation status and the effective management of a species. Using nuclear and mitochondrial DNA markers, we assessed population genetic diversity and differentiation between snubfin dolphins from Cygnet (n = 32) and Roebuck Bays (n = 25), and humpback dolphins from the Dampier Archipelago (n = 19) and the North West Cape (n = 18). All sampling locations were separated by geographic distances >200 km. For each species, we found significant genetic differentiation between sampling locations based on 12 (for snubfin dolphins) and 13 (for humpback dolphins) microsatellite loci (FST = 0.05–0.09; P
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Collation and review of sightings and distribution of three coastal dolphin species in waters of the Northern Territory, Australia
Pacific Conservation Biology, 2014Co-Authors: Carol Palmer, Guido J. Parra, Tracey L. Rogers, John C. Z. WoinarskiAbstract:On a global scale, the coastal waters of the Northern Territory (NT), Australia, are relatively undisturbed, but the pace and extent of coastal development is increasing. Three species of dolphin occur in these waters: the Australian snubfin Orcaella heinsohni, Indo-Pacific humpback Sousa chinensis and bottlenose Tursiops sp., but their distribution is poorly documented. To provide a broader distributional context and complement recent local-scale population studies (Palmer in press), we review the broader distribution of these coastal dolphins, via the collation of historic and contemporary data from sighting surveys, stranding and museum records, and a community sighting programme. Records spanned 1948 to 2010, with Sousa (44%) the most frequently recorded followed by Orcaella and Tursiops (both 28%). The compiled records indicate that the three species are widely distributed along the NT coast but with some apparent differences in habitat use. All species were recorded within 20 km of a major tidal river; but fewer than 3% of Tursiops records were from within tidal rivers, whereas nearly a quarter of Orcaella and Sousa records were as far as 20 to 50 km upstream. Differences in environmental settings between Orcaella and Sousa were less pronounced, but a lower proportion of Orcaella were recorded within 20 km of a river mouth. There are probable but unquantifiable biases in the record sources, but most records of dolphins were from estuaries, tidal rivers and coastal areas within 20 km of river mouths, and these sites probably represent important habitat for these species. The NT’s remote and relatively pristine waters likely hold significant subpopulations of all three species. The information provided here should aid future research efforts, however; further information on the dolphins’ population size, trend and structure are needed to resolve their conservation status at state and national jurisdictions, inform environmental impact assessments and species management.
Carol Palmer - One of the best experts on this subject based on the ideXlab platform.
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Population Differentiation and Hybridisation of Australian Snubfin (Orcaella heinsohni) and Indo-Pacific Humpback (Sousa chinensis) Dolphins in North-Western
2016Co-Authors: Er M. Brown, Carol Palmer, Deborah Thiele, Guido J. Parra, Lars Bejder, Simon J. Allen, Bethan Littleford-colquhoun, Daniele Cagnazzi, Celine H. FrèreAbstract:Little is known about the Australian snubfin (Orcaella heinsohni) and Indo-Pacific humpback (Sousa chinensis) dolphins (‘snubfin ’ and ‘humpback dolphins’, hereafter) of north-western Australia. While both species are listed as ‘near threatened’ by the IUCN, data deficiencies are impeding rigorous assessment of their conservation status across Australia. Understanding the genetic structure of populations, including levels of gene flow among populations, is important for the assessment of conservation status and the effective management of a species. Using nuclear and mitochondrial DNA markers, we assessed population genetic diversity and differentiation between snubfin dolphins from Cygnet (n = 32) and Roebuck Bays (n = 25), and humpback dolphins from the Dampier Archipelago (n = 19) and the North West Cape (n = 18). Al
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Corrigendum to: Estimates of abundance and apparent survival of coastal dolphins in Port Essington harbour, Northern Territory, Australia (Wildlife Research (2014) 41:1 (35-45) DOI: 10.1071/WR14031)
Wildlife Research, 2015Co-Authors: Carol Palmer, Guido J. Parra, Tracey L. Rogers, Lyndon O Brooks, Debra Glasgow, John C. Z. WoinarskiAbstract:Context Three dolphin species occur in coastal waters of monsoonal northern Australia: the Australian snubfin (Orcaella heinsohni), humpback (Sousa sp.) and the bottlenose (Tursiops sp.). Their overall population size and trends are poorly known, and their conservation status has been difficult to resolve, but can be expected to deteriorate with likely increased development pressures. Aims We sought to provide an estimate of abundance, and apparent survival, of the three dolphin species at the largely undeveloped harbour of Port Essington (325km2), Northern Territory, with repeated sampling over a 2.9-year period. Given increasing obligations to undertake population assessments for impact studies at proposed development sites, we assess the strengths and limitations of a systematic sampling program.
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Conservation biology of dolphins in coastal waters of the Northern Territory, Australia
2014Co-Authors: Carol PalmerAbstract:In a global context, the tropical coastal waters around much of northern Australia are exceptional in their relatively unmodified condition, due largely to the limited amount of coastal development and relatively low human population size in coastal lands. These waters offer a significant opportunity for the conservation of coastal biodiversity. However, increasing development pressures may jeopardise this opportunity and adding to this risk there is little information on distribution, population size and trends for much of the marine biodiversity in the region. This data deficiency has constrained the assessment of the conservation status of marine species and hence compromised conservation planning, management and security. This study assessed aspects of the status of three species of coastal dolphin – the Australian snubfin (Orcaella heinsohni), the recently described Australian humpback (Sousa sahulensis) and bottlenose (either or both Tursiops truncatus or T. aduncus) – in coastal waters of the Northern Territory (NT), Australia. Serendipitously, I also considered aspects of the status and distribution of the false killer whale (Pseudorca crassidens), a delphinid species that uses NT coastal waters to a much greater extent than was previously known. This study helped clarify the taxonomy and distribution of Orcaella in these waters, documented the broad distributional patterns of the three dolphin species in this region, and provided the first estimates of abundance and apparent survival for all three species for a site in monsoonal northern Australia. The three species were found to be widely distributed along the Northern Territory coast, but showed some significant differences in habitat use. At my main study site in Port Essington, the population sizes of the three species were determined by Pollock’s robust capture–recapture design modeling over 2.9 years. The estimated number of individuals varied per sampling episode from 136 (s.e. 62) to 222 (s.e. 48) for Orcaella, 48 (s.e. 17) to 207 (s.e. 65) for Sousa and 34 (s.e. 16) to 75 (s.e. 26) for Tursiops. Apparent annual survival for Orcaella was 0.81 (s.e. 0.11), Sousa 0.59 (s.e. 0.12) and Tursiops 0.51 (s.e. 0.17). Satellite tracking of four false killer whales demonstrated that this species is recorded in these coastal waters, but at a very different scale to the coastal dolphins. The study findings are interpreted with respect to the conservation status of the four species, and I draw some recommendations for their conservation management.
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Population Differentiation and Hybridisation of Australian Snubfin (Orcaella heinsohni) and Indo-Pacific Humpback (Sousa chinensis) Dolphins in North-Western Australia
PloS one, 2014Co-Authors: A. Brown, Carol Palmer, Deborah Thiele, Guido J. Parra, Lars Bejder, Simon J. Allen, Daniele Cagnazzi, Anna M Kopps, Bethan L. Littleford‐colquhoun, Celine H. FrèreAbstract:Little is known about the Australian snubfin (Orcaella heinsohni) and Indo-Pacific humpback (Sousa chinensis) dolphins (‘snubfin’ and ‘humpback dolphins’, hereafter) of north-western Australia. While both species are listed as ‘near threatened’ by the IUCN, data deficiencies are impeding rigorous assessment of their conservation status across Australia. Understanding the genetic structure of populations, including levels of gene flow among populations, is important for the assessment of conservation status and the effective management of a species. Using nuclear and mitochondrial DNA markers, we assessed population genetic diversity and differentiation between snubfin dolphins from Cygnet (n = 32) and Roebuck Bays (n = 25), and humpback dolphins from the Dampier Archipelago (n = 19) and the North West Cape (n = 18). All sampling locations were separated by geographic distances >200 km. For each species, we found significant genetic differentiation between sampling locations based on 12 (for snubfin dolphins) and 13 (for humpback dolphins) microsatellite loci (FST = 0.05–0.09; P
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First report of a lacaziosis-like disease (LLD) observed in the Australian Snubfin Dolphin ('Orcaella heinsohni') in Darwin Harbour, Northern Territory, Australia
2014Co-Authors: Carol Palmer, Amanda PetersonAbstract:A lacaziosis-like disease (LLD) was photographed on the skin of three Australian Snubfin Dolphins (Orcaella heinsohni) in Darwin Harbour in 2008 and 2010, and this represents the first report of the skin disease recorded in Australia on this species of dolphin. Lacaziosis-like disease is considered non-lethal, but it could be indicative of decreasing water quality and/or exposure to potentially immunosuppressive anthropogenic or environmental pressures. Photo-identification data provides an efficient and cost-effective approach for documenting the occurrence of LLD and monitoring for the prevalence and incidence of skin lesions in a dolphin population.
A. Brown - One of the best experts on this subject based on the ideXlab platform.
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Shark bite injuries on three inshore dolphin species in tropical northwestern Australia
Marine Mammal Science, 2017Co-Authors: Felix Smith, Lars Bejder, Simon J. Allen, A. BrownAbstract:Predation risk has a profound influence on the behavior of marine mammals, affecting grouping patterns and habitat use. Dolphins frequently bear evidence of shark bites, which can provide an indirect measure of predation pressure. Using photo-identification data, we investigated the prevalence of shark bites on three sympatric species of inshore dolphin, the Australian snubfin (Orcaella heinsohni), Australian humpback (Sousa sahulensis), and Indo-Pacific bottlenose dolphin (Tursiops aduncus), among four study sites in northwestern Australia. Bite prevalence varied markedly between species, with 72% of snubfin, 46% of humpback, and 18% of bottlenose dolphins exhibiting evidence of shark bites. Binomial logistic regression confirmed a high likelihood of bite presence on snubfin dolphins, and at one particular site for snubfin and bottlenose dolphins. The prevalence of tiger shark (Galeocerdo cuvier) bites on snubfin dolphins was high, and bites attributed to other carcharhinid sharks were observed on all species. While acknowledging methodological differences with other studies, the prevalence of shark bites on snubfin dolphins is among the highest reported for any dolphins, suggesting predation risk represents an important but varying influence thereon. This study provides a baseline for future investigations into the affect of predation risk on the behavioral ecology of these sympatric species.
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Population Differentiation and Hybridisation of Australian Snubfin (Orcaella heinsohni) and Indo-Pacific Humpback (Sousa chinensis) Dolphins in North-Western Australia
PloS one, 2014Co-Authors: A. Brown, Carol Palmer, Deborah Thiele, Guido J. Parra, Lars Bejder, Simon J. Allen, Daniele Cagnazzi, Anna M Kopps, Bethan L. Littleford‐colquhoun, Celine H. FrèreAbstract:Little is known about the Australian snubfin (Orcaella heinsohni) and Indo-Pacific humpback (Sousa chinensis) dolphins (‘snubfin’ and ‘humpback dolphins’, hereafter) of north-western Australia. While both species are listed as ‘near threatened’ by the IUCN, data deficiencies are impeding rigorous assessment of their conservation status across Australia. Understanding the genetic structure of populations, including levels of gene flow among populations, is important for the assessment of conservation status and the effective management of a species. Using nuclear and mitochondrial DNA markers, we assessed population genetic diversity and differentiation between snubfin dolphins from Cygnet (n = 32) and Roebuck Bays (n = 25), and humpback dolphins from the Dampier Archipelago (n = 19) and the North West Cape (n = 18). All sampling locations were separated by geographic distances >200 km. For each species, we found significant genetic differentiation between sampling locations based on 12 (for snubfin dolphins) and 13 (for humpback dolphins) microsatellite loci (FST = 0.05–0.09; P
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Distribution and abundance of tropical inshore dolphins in Cygnet Bay, Western Australia
2013Co-Authors: A. Brown, Lars Bejder, Kenneth H. Pollock, Simon J. AllenAbstract:Little is known of inshore dolphin populations, particularly snubfin (Orcaella heinsohni) and humpback (Sousa chinensis) dolphins, in tropical north-western Australia. Studies elsewhere suggest that they are sensitive to habitat modification and vulnerable to localised extinctions. Both species are listed ‘near-threatened’ by the IUCN. In north-western Australia, large-scale industrial development is ongoing, but a complete absence of quantitative data on dolphin abundance and distribution precludes assessment of their conservation status. Here, we report initial results from systematic boat-based photo-identification surveys of ca. 130 km2 of the near-shore waters (
Isabel Beasley - One of the best experts on this subject based on the ideXlab platform.
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Demographic collapse and low genetic diversity of the Irrawaddy dolphin population inhabiting the Mekong River.
PloS one, 2018Co-Authors: Michael Krützen, Guido J. Parra, Isabel Beasley, Arne Ludwig, Corinne Y. Ackermann, Lars Bejder, Dietmar Lieckfeldt, Gerard E. Ryan, Rebekka Wolfensberger, Peter B. S. SpencerAbstract:In threatened wildlife populations, it is important to determine whether observed low genetic diversity may be due to recent anthropogenic pressure or the consequence of historic events. Historical size of the Irrawaddy dolphin (Orcaella brevirostris) population inhabiting the Mekong River is unknown and there is significant concern for long-term survival of the remaining population as a result of low abundance, slow reproduction rate, high neonatal mortality, and continuing anthropogenic threats. We investigated population structure and reconstructed the demographic history based on 60 Irrawaddy dolphins samples collected between 2001 and 2009. The phylogenetic analysis indicated reciprocal monophyly of Mekong River Orcaella haplotypes with respect to haplotypes from other populations, suggesting long-standing isolation of the Mekong dolphin population from other Orcaella populations. We found that at least 85% of all individuals in the two main study areas: Kratie and Stung Treng, bore the same mitochondrial haplotype. Out of the 21 microsatellite loci tested, only ten were polymorphic and exhibited very low levels of genetic diversity. Both individual and frequency-based approaches suggest very low and non-significant genetic differentiation of the Mekong dolphin population. Evidence for recent bottlenecks was equivocal. Some results suggested a recent exponential decline in the Mekong dolphin population, with the current size being only 5.2% of the ancestral population. In order for the Mekong dolphin population to have any potential for long-term survival, it is imperative that management priorities focus on preventing any further population fragmentation or genetic loss, reducing or eliminating anthropogenic threats, and promoting connectivity between all subpopulations.
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Australian snubfin dolphin
2018Co-Authors: Isabel Beasley, Alexander M. BrownAbstract:[Extract] The Australian snubfin dolphin (Orcaella heinsohm) is a coastal dolphin species in the family Delphinidae, within the genus Orcaella. The other species within the genus is the Irrawaddy dolphin (0. brevirostris). The closest relative to Orcaella is the killer whale Orcinus orca. The Australian snubfin dolphin was first recorded in Australia in 1964 [previously considered Irrawaddy dolphin], when anthropologists found skulls of two Australian snubfin dolphins that had been eaten by Indigenous people in Arnhem land in 1948. The name "snubfin dolphin" was first suggested in 1981, as an alternative common name. This name highlights a diagnostic external character, is appropriate to all populations, and has previously been included in general field guides. The common name, the Australian snubfin dolphin, reflects that the majority of known specimens and morphological work are based on Australian populations.
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Australian Snubfin Dolphin: Orcaella heinsohni
Encyclopedia of Marine Mammals, 2018Co-Authors: Isabel Beasley, Alexander M. BrownAbstract:Abstract The Australian snubfin dolphin is a close relative of the Irrawaddy river dolphin and occurs largely in nearshore areas, as does the latter. It was only recently described as a separate species, largely by skull morphology and recent genetics.
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Observations on Australian Humpback Dolphins (Sousa sahulensis) in Waters of the Pacific Islands and New Guinea.
Advances in marine biology, 2015Co-Authors: Isabel Beasley, Maria Jedensjö, Gede Mahendra Wijaya, Jim Anamiato, Benjamin Kahn, D. KrebAbstract:The Australian humpback dolphin, Sousa sahulensis, has recently been described to occur in northern Australian coastal waters. However, its distribution in adjacent waters of the Pacific Islands and New Guinea remains largely unknown. Although there have been few studies conducted on inshore dolphins in these regions, the available information records humpback dolphins primarily from the Kikori Delta in Papua New Guinea, and Bird's Head Seascape in West Papua. Research in southern Papua New Guinea indicates that humpback dolphins are indeed S. sahulensis, based on cranial and external morphometrics, external colouration and the preliminary genetic analysis presented here. A similar situation exists for the Australian snubfin dolphin, Orcaella heinsohni, where it is assumed that the species also occurs along the Sahul Shelf coastal waters of northern Australia and New Guinea. There are anecdotal reports of direct catch of Australian humpback dolphins for use as shark bait, coastal development is increasing, and anthropogenic impacts will continue to escalate as human populations expand into previously uninhabited regions. Future research and management priorities for the Governments of the Pacific Islands and Indonesia will need to focus on inshore dolphins in known regional hotspots, as current bycatch levels appear unsustainable.
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Markedly reduced genetic variation and population collapse of the Irrawaddy dolphin (Orcaella brevirostris)
2013Co-Authors: K. Krützen, Guido J. Parra, Isabel Beasley, Arne Ludwig, Peter B. S. Spencer, Corinne Y. Ackermann, Lars Bejder, B. BrownellAbstract:Irrawaddy dolphins Orcaella brevirostris are small cetaceans distributed in coastal, lake and riverine waters in Southeast Asia. Riverine populations include those in the Mekong River in Cambodia and southern Laos. All populations are small (
Lars Bejder - One of the best experts on this subject based on the ideXlab platform.
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Demographic collapse and low genetic diversity of the Irrawaddy dolphin population inhabiting the Mekong River.
PloS one, 2018Co-Authors: Michael Krützen, Guido J. Parra, Isabel Beasley, Arne Ludwig, Corinne Y. Ackermann, Lars Bejder, Dietmar Lieckfeldt, Gerard E. Ryan, Rebekka Wolfensberger, Peter B. S. SpencerAbstract:In threatened wildlife populations, it is important to determine whether observed low genetic diversity may be due to recent anthropogenic pressure or the consequence of historic events. Historical size of the Irrawaddy dolphin (Orcaella brevirostris) population inhabiting the Mekong River is unknown and there is significant concern for long-term survival of the remaining population as a result of low abundance, slow reproduction rate, high neonatal mortality, and continuing anthropogenic threats. We investigated population structure and reconstructed the demographic history based on 60 Irrawaddy dolphins samples collected between 2001 and 2009. The phylogenetic analysis indicated reciprocal monophyly of Mekong River Orcaella haplotypes with respect to haplotypes from other populations, suggesting long-standing isolation of the Mekong dolphin population from other Orcaella populations. We found that at least 85% of all individuals in the two main study areas: Kratie and Stung Treng, bore the same mitochondrial haplotype. Out of the 21 microsatellite loci tested, only ten were polymorphic and exhibited very low levels of genetic diversity. Both individual and frequency-based approaches suggest very low and non-significant genetic differentiation of the Mekong dolphin population. Evidence for recent bottlenecks was equivocal. Some results suggested a recent exponential decline in the Mekong dolphin population, with the current size being only 5.2% of the ancestral population. In order for the Mekong dolphin population to have any potential for long-term survival, it is imperative that management priorities focus on preventing any further population fragmentation or genetic loss, reducing or eliminating anthropogenic threats, and promoting connectivity between all subpopulations.
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Shark bite injuries on three inshore dolphin species in tropical northwestern Australia
Marine Mammal Science, 2017Co-Authors: Felix Smith, Lars Bejder, Simon J. Allen, A. BrownAbstract:Predation risk has a profound influence on the behavior of marine mammals, affecting grouping patterns and habitat use. Dolphins frequently bear evidence of shark bites, which can provide an indirect measure of predation pressure. Using photo-identification data, we investigated the prevalence of shark bites on three sympatric species of inshore dolphin, the Australian snubfin (Orcaella heinsohni), Australian humpback (Sousa sahulensis), and Indo-Pacific bottlenose dolphin (Tursiops aduncus), among four study sites in northwestern Australia. Bite prevalence varied markedly between species, with 72% of snubfin, 46% of humpback, and 18% of bottlenose dolphins exhibiting evidence of shark bites. Binomial logistic regression confirmed a high likelihood of bite presence on snubfin dolphins, and at one particular site for snubfin and bottlenose dolphins. The prevalence of tiger shark (Galeocerdo cuvier) bites on snubfin dolphins was high, and bites attributed to other carcharhinid sharks were observed on all species. While acknowledging methodological differences with other studies, the prevalence of shark bites on snubfin dolphins is among the highest reported for any dolphins, suggesting predation risk represents an important but varying influence thereon. This study provides a baseline for future investigations into the affect of predation risk on the behavioral ecology of these sympatric species.
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Population Differentiation and Hybridisation of Australian Snubfin (Orcaella heinsohni) and Indo-Pacific Humpback (Sousa chinensis) Dolphins in North-Western
2016Co-Authors: Er M. Brown, Carol Palmer, Deborah Thiele, Guido J. Parra, Lars Bejder, Simon J. Allen, Bethan Littleford-colquhoun, Daniele Cagnazzi, Celine H. FrèreAbstract:Little is known about the Australian snubfin (Orcaella heinsohni) and Indo-Pacific humpback (Sousa chinensis) dolphins (‘snubfin ’ and ‘humpback dolphins’, hereafter) of north-western Australia. While both species are listed as ‘near threatened’ by the IUCN, data deficiencies are impeding rigorous assessment of their conservation status across Australia. Understanding the genetic structure of populations, including levels of gene flow among populations, is important for the assessment of conservation status and the effective management of a species. Using nuclear and mitochondrial DNA markers, we assessed population genetic diversity and differentiation between snubfin dolphins from Cygnet (n = 32) and Roebuck Bays (n = 25), and humpback dolphins from the Dampier Archipelago (n = 19) and the North West Cape (n = 18). Al
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Population Differentiation and Hybridisation of Australian Snubfin (Orcaella heinsohni) and Indo-Pacific Humpback (Sousa chinensis) Dolphins in North-Western Australia
PloS one, 2014Co-Authors: A. Brown, Carol Palmer, Deborah Thiele, Guido J. Parra, Lars Bejder, Simon J. Allen, Daniele Cagnazzi, Anna M Kopps, Bethan L. Littleford‐colquhoun, Celine H. FrèreAbstract:Little is known about the Australian snubfin (Orcaella heinsohni) and Indo-Pacific humpback (Sousa chinensis) dolphins (‘snubfin’ and ‘humpback dolphins’, hereafter) of north-western Australia. While both species are listed as ‘near threatened’ by the IUCN, data deficiencies are impeding rigorous assessment of their conservation status across Australia. Understanding the genetic structure of populations, including levels of gene flow among populations, is important for the assessment of conservation status and the effective management of a species. Using nuclear and mitochondrial DNA markers, we assessed population genetic diversity and differentiation between snubfin dolphins from Cygnet (n = 32) and Roebuck Bays (n = 25), and humpback dolphins from the Dampier Archipelago (n = 19) and the North West Cape (n = 18). All sampling locations were separated by geographic distances >200 km. For each species, we found significant genetic differentiation between sampling locations based on 12 (for snubfin dolphins) and 13 (for humpback dolphins) microsatellite loci (FST = 0.05–0.09; P
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Markedly reduced genetic variation and population collapse of the Irrawaddy dolphin (Orcaella brevirostris)
2013Co-Authors: K. Krützen, Guido J. Parra, Isabel Beasley, Arne Ludwig, Peter B. S. Spencer, Corinne Y. Ackermann, Lars Bejder, B. BrownellAbstract:Irrawaddy dolphins Orcaella brevirostris are small cetaceans distributed in coastal, lake and riverine waters in Southeast Asia. Riverine populations include those in the Mekong River in Cambodia and southern Laos. All populations are small (