Diet overlap between harbour porpoise and bottlenose dolphin: An argument in favour of interference competition for food?

In summer 2001, members of the public in south-west Scotland were interviewed to determine their knowledge of the diversity and occurrence of cetaceans in the region. Interviews were conducted in both rural island and coastal communities and a major city.The majority of interviewees (46%) underestimated the number of cetacean species occurring in western Scottish waters (i.e. <10 species). Only 4·4% gave the correct answer (24). Location of the participant affected the level of knowledge. Photographs were presented of the four most commonly occurring cetacean species: only 30·2% correctly identified one or more of the species. The species most frequently identified correctly was the bottlenose dolphin (19% of interviewees) followed by the harbour porpoise (17·5%), minke whale (10·7%) and, lastly, the common dolphin (7·1%).Interviewees were also asked whether certain cetacean species occurred in local waters or not. The level of awareness was generally low. The most common positive answers involved the bottlenose dolphin, harbour porpoise, and minke whale. Only one in five were aware of killer whales and 13·1% believed that grey whales occurred in Scottish waters. Knowledge of species occurrence showed statistically significant relationships with age, gender, level of environmental interest and location, but not occupation (teachers, tourism professionals and marine stakeholders did not show greater levels of cetacean knowledge). The study identified target groups and locations where knowledge of cetaceans is low and environmental education efforts should be concentrated.

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An intraspecific and interspecific comparison of raptor diets in the south-west of the Northern Territory, Australia

Wildlife Research ◽

10.1071/wr99092 ◽

2001 ◽

Vol 28 (4) ◽

pp. 379 ◽

Cited By ~ 19

Author(s):

Tom Aumann

Keyword(s):

Northern Territory ◽

Diet Overlap ◽

Large Mammals ◽

Interspecific Comparison ◽

Important Food ◽

The South ◽

South West ◽

Eastern Australia ◽

Competition For Food ◽

Central Australia

Dietary information, collected during 1995–97 in the south-west of the Northern Territory, is presented for 11 raptor species. Unlike better-studied populations of these species in south-eastern and eastern Australia, most of the raptors in the arid inland were found to depend heavily on reptiles and birds, the budgerigar (Melopsittacus undulatus) being a particularly important food for many species during those periods when it was plentiful. Between-territory, between-year and seasonal differences in diet are quantified for most species. The raptor assemblages in central Australia included specialists on medium-sized to large mammals, small to medium-sized birds, and small reptiles/invertebrates, as well as several generalists. Indices of prey diversity and evenness were calculated for each species, and diet overlap between them was used to investigate aspects of interspecific competition for food. Overall, diet overlap was greatest among the bird specialists and between some of the generalists. It increased in 1997, a year of comparative plenty, possibly because several species exploited an abundance of some prey taxa and competitive pressure eased.

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Don’t forget the porpoise: acoustic monitoring reveals fine scale temporal variation between bottlenose dolphin and harbour porpoise in Cardigan Bay SAC

Marine Biology ◽

10.1007/s00227-017-3081-5 ◽

2017 ◽

Vol 164 (3) ◽

Cited By ~ 12

Author(s):

Hanna K. Nuuttila ◽

Winnie Courtene-Jones ◽

Sarah Baulch ◽

Malene Simon ◽

Peter G. H. Evans

Keyword(s):

Temporal Variation ◽

Bottlenose Dolphin ◽

Acoustic Monitoring ◽

Harbour Porpoise ◽

Fine Scale

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Estimates of cetacean by-catch in the turbot fishery on the Turkish Western Black Sea Coast in 2007 and 2008

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315416000060 ◽

2016 ◽

Vol 96 (4) ◽

pp. 993-998 ◽

Cited By ~ 4

Author(s):

Arda M. Tonay

Keyword(s):

Black Sea ◽

Bottlenose Dolphin ◽

Harbour Porpoise ◽

Catch Rate ◽

Fishing Boat ◽

Black Sea Coast ◽

By Catch ◽

Age Range ◽

Sea Coast

This is the first study estimating cetacean by-catch in the Turkish western Black Sea turbot fishery. One turbot fishing boat was observed during two fishing seasons, from April through July 2007 and April through mid-September 2008. During this time, 24 harbour porpoises and one bottlenose dolphin were caught in turbot trammel nets. The by-catch rate was found to be 0.18 for harbour porpoise and 0.01 for bottlenose dolphin individuals per kilometre in 2007, and 0.19 for harbour porpoise individuals in 2008. It is estimated that the total numbers of harbour porpoises killed in the Turkish western Black Sea during the legal fishing period (April and July) were 167 ± 153 (CV: 0.92) in 2007 and 329 ± 220 (CV: 0.67) in 2008, and the number killed during both legal and illegal periods of turbot fishing were 2011 ± 742 (CV: 0.37) in 2007 and 2294 ± 806 (CV: 0.35) in 2008. The estimated range of harbour porpoise by-catch in the turbot fishery on the Turkish western Black Sea coast is between these two estimates. The by-caught harbour porpoises were between 1–8 years of age. About half of them were within the age range of 4 (26%) and 5 (21%) years old, and 78% were physically immature individuals. Turbot fishing carried out with bottom nets, especially in May and June, when turbot fishing is banned, is a threat to the sustainability of harbour porpoise stocks.

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Diet overlap of collared lemmings and tundra voles at Pearce Point, Northwest Territories

Canadian Journal of Zoology ◽

10.1139/z93-241 ◽

1993 ◽

Vol 71 (9) ◽

pp. 1703-1709 ◽

Cited By ~ 6

Author(s):

Carita M. Bergman ◽

Charles J. Krebs

Keyword(s):

Northwest Territories ◽

Food Preferences ◽

Faecal Pellet ◽

Diet Overlap ◽

Exploitative Competition ◽

Microtus Oeconomus ◽

Pellet Analysis ◽

Competition For Food

We used a combination of faecal pellet analysis and feeding enclosure trials to determine the diets of collared lemmings (Dicrostonyx kilangmiutak) and tundra voles (Microtus oeconomus) at Pearce Point, Northwest Territories, and we looked for evidence of exploitative competition between the two species. Voles preferred monocotyledons (Carex and Eriophorum spp.) and lemmings preferred Dryas integrifolia. We found that there was little overlap in the natural diets of the two species, but that overlap was increased experimentally when both species were forced to forage in the same habitats. However, food preferences generally did not change. The diet of collared lemmings at Pearce Point was similar to that found in all other studies except those done in Alaska, where Dryas is uncommon. We conclude that exploitative competition for food is unlikely to be an important factor in interspecific relations between collared lemmings and tundra voles.

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Passive acoustic monitoring of bottlenose dolphin and harbour porpoise, in Cardigan Bay, Wales, with implications for habitat use and partitioning

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315409991226 ◽

2010 ◽

Vol 90 (8) ◽

pp. 1539-1545 ◽

Cited By ~ 30

Author(s):

Malene Simon ◽

Hanna Nuuttila ◽

Mercedes M. Reyes-Zamudio ◽

Fernando Ugarte ◽

Ursula Verfub ◽

...

Keyword(s):

Habitat Use ◽

Bottlenose Dolphin ◽

Harbour Porpoise ◽

Habitat Partitioning ◽

Specific Interactions ◽

Special Area ◽

One Year ◽

The One ◽

Species Specific ◽

Passive Acoustic

Knowledge about harbour porpoise and bottlenose dolphin occurrence in Cardigan Bay Special Area of Conservation (SAC), Wales, is limited to daylight hours during summer, when conditions are suitable for traditional visual surveys. T-PODs are autonomous instruments programmed to log time-cues of species-specific echolocation signals for long periods of time. Here we investigated bottlenose dolphin and harbour porpoise habitat use and partitioning by deploying ten calibrated T-PODs in Cardigan Bay SAC for one year. The T-PODs detected both species all year round with a peak of detections in April–October for dolphins and in October–March for porpoise, revealing a previously unknown importance of the place to harbour porpoise during winter. Though the two species are sympatric, simultaneous detections of both species were rare and indication of temporal habitat partitioning between the two species in some parts of the SAC was observed. The one location where simultaneous detections were not as rare was close to the stretch of shoreline where stranding of porpoises killed by dolphins are most common, suggesting that the observed spatiotemporal overlap leads to inter-specific interactions, in some cases fatal for the porpoise.

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Cetacean sightings and strandings: evidence for spatial and temporal trends?

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315411000464 ◽

2011 ◽

Vol 92 (8) ◽

pp. 1809-1820 ◽

Cited By ~ 19

Author(s):

Stephen K. Pikesley ◽

Mathew J. Witt ◽

Tom Hardy ◽

Jan Loveridge ◽

Jeff Loveridge ◽

...

Keyword(s):

Bottlenose Dolphin ◽

Temporal Trends ◽

Minke Whale ◽

Harbour Porpoise ◽

Mitigation Strategies ◽

North Coast ◽

Positive Trend ◽

Common Dolphin ◽

Cetacean Species ◽

Key Species

Cetacean species and their habitats are under threat and effective marine management mitigation strategies require knowledge and understanding of cetacean ecology. This requires data that are challenging and expensive to obtain; incidental sightings/strandings data are potential underused resources. In this study, incidental cetacean sightings (N = 6631) and strandings (N = 1856) in coastal waters of Cornwall, south-west Britain (1991 to 2008) were analysed for evidence of spatial and temporal patterns or trends. Eighteen species were recorded sighted and/or stranded; key species were identified as bottlenose dolphin (Tursiops truncatus), harbour porpoise (Phocoena phocoena), common dolphin (Delphinus delphis), Risso's dolphin (Grampus griseus) and minke whale (Balaenoptera acutorostrata). There were significant decreases in bottlenose dolphin sightings and pod size but an increase in harbour porpoise and minke whale sightings. Cetacean strandings showed a recent decrease over time although there was a significant positive trend in harbour porpoise strandings that correlated with sightings. Incidence of sightings and strandings were both greater on the south coast than the north coast. When Marine Tour Operator data were analysed, distinct species-specific inshore and offshore habitat use was evident. With rigorous interrogation and editing, significant patterns and trends were gained from incidentally collected data, highlighting the importance of public engagement with such recording schemes and the potential of these underused resources.

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