An Assessment of Spatial and Temporal Variation in the Diet of Cape Clawless Otters (Aonyx capensis) in Marine Environments

Jordaan, Rowan K.; McIntyre, Trevor; Somers, Michael J.; Bester, Marthán N

doi:10.3957/056.045.0342

Cited by 8 publications

(14 citation statements)

References 34 publications

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“…Grant and Harrington () assumed that the reduced consumption of fish during summer may be related to the effects of water temperature on fish metabolism: fish swim faster in summer, thus being more difficult to catch, whereas their slower metabolism in winter reduces their swimming speed, which makes them more vulnerable to predation. This pattern has been observed even in marine environments in a study on African Cape clawless otters, Aonyx capensis (Schinz, 1821) (Jordaan, McIntyre, Somers, & Bester, ).…”

Section: Discussionmentioning

confidence: 66%

Diet of the Eurasian otter (Lutra lutra) on the River Gradac, Serbia: Predation in a brown trout‐dominated stream

Krpo‐Ćetković

Subotić

Skorić

et al. 2019

Aquatic Conservation

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1. Prey preference and seasonal variation in the diet of the Eurasian otter, Lutra lutra (Linnaeus, 1758), were examined by the analysis of 789 spraint samples collected along a 10-km section of a small lowland salmonid river in Serbia, with a trout farm situated in its lower part, from June 2009 to March 2012. Of particular interest was any possible impact of the otter on brown trout, which is important to investigate for preventing and managing any potential conflicts with fishers and fish farmers. 2. Fish were by far the most important otter prey, followed by crayfish. Cottus gobio Linnaeus, 1758 (the European bullhead) was the most common prey species, probably because of the combination of its abundance and easy catchability. Other prey contributed very little to the diet of the otters. Of 11 fish species present in the river, five were found in the otter diet: the European bullhead, Salmo trutta Linnaeus, 1758 (brown trout), Squalius cephalus (Linnaeus, 1758) (chub), Barbus balcanicus Kotlík, Tsigenopoulos, Ráb & Berrebi, 2002 (the Danube barbel), and Phoxinus phoxinus (Linnaeus, 1758) (the Eurasian minnow). The bullhead was the only positively selected species, however. The share of fish prey in the otter diet was stable throughout the year, except for a decrease noticed during the summer.3. The results suggest that otters on the River Gradac target smaller, sedentary, and less nutritious prey. Owing to a small percentage of brown trout in otter spraints, we surmise that otters do not represent a major biological or economic threat, either to the native trout population in the river or to the trout from the nearby fish farm.4. Although there are no reports of otters causing damage to the trout population in the local fish farm, it is advisable to establish mechanisms for the compensation of fish farmers in case such damage does occur.5. The data presented in this paper can be used to contribute to the conservation of the otter in stream habitats, especially because there are no published studies on the dietary requirements of otter in Serbia.

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Section: Discussionmentioning

confidence: 66%

Diet of the Eurasian otter (Lutra lutra) on the River Gradac, Serbia: Predation in a brown trout‐dominated stream

Krpo‐Ćetković

Subotić

Skorić

et al. 2019

Aquatic Conservation

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“…The present study sheds new insight on our knowledge of the diet composition of the African clawless otters. Previously, crabs and other crustaceans were regarded as the preferred and primary prey while fish, mollusks, and frogs were secondarily important (Rowe-Rowe, 1977;van der Zee, 1981;Arden-Clarke, 1986;Kruuk and Goudswaard, 1990;Nowak, 1991;Butler and du Toit, 1994;Ligthart et al, 1994;Kingdon, 1997;Somers, 2000;Lariviere, 2001;Somers and Nel, 2003;Emmerson and Philip, 2004;Ogada, 2006;Jordaan et al, 2015). Our study showed that fish was the dominant prey item in and around Lake Tana during both wet and dry seasons.…”

Section: Discussionmentioning

confidence: 80%

“…The diet of African clawless otter has been studied by Kruuk and Goundswaard (1990) in Lake Victoria, Butler and du Toit (1994) in Zimbabwe, Rowe-Rowe (1977), van der Zee (1981), Verwoerd (1987), Perrin and Carugati (2000), Somers (2000), Somers and Nel (2003), Watson and Lang (2003), Jordaan et al (2015) in South Africa and Ogada (2006) in Kenya. However, scientific data on the ecology of the species in Lake Tana is not available and elsewhere in Ethiopia is not available.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the objective of this study was first; to add on the available data on the feeding diet of African clawless otter in African. Our current knowledge is inconclusive and mainly based on research conducted on South Africa populations (van der Zee, 1981;Verwoerd, 1987;Perrin and Carugati, 2000;Somers, 2000;Somers and Nel, 2003;Watson and Lang, 2003;Jordaan et al, 2015). We attempted to test if crabs are the preferred prey as observed in previous studies (Rowe-Rowe, 1977;Nowak, 1991;Butler and du Toit, 1994;Lavriviere, 2001;Carugati and Perrin, 2003;Somers and Nel, 2003) or there is a potential to shift to other prey such as fish as reported in others (Verwoerd, 1987;Somers, 2000).…”

Section: Introductionmentioning

confidence: 99%

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Diet analysis of the African clawless otter (Aonyx capensis) in and around Lake Tana

Andarge¹,

Wube²,

Balakrishnan³

2017

J. Ecol. Nat. Environ.

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The diet composition of the African clawless otter (Aonyx capensis) was studied by analyzing of 440 spraint samples collected during January, 2014 and December, 2015 in both dry and wet seasons from eight sites in and around Lake Tana, North West Ethiopia. Percentage frequency of occurrence and relative percentage frequency of diet items in the spraint samples were calculated.The statistical analysis was conducted using chi-square and one-way ANOVA tests.The number of diet categories per spraint ranged from 1 to 4 with a mean of 1.42 ± 0.591. Fish was the dominant prey item in all sites with an overall frequency of occurrence of 84.77% and a relative percentage frequency of 59.68%. Labeobarbus spp. was the most frequent fish prey (35.45%). Crabs were the second most frequent prey items with percentage frequency of 33.41% and a relative percentage frequency of 23.52%, while small mammals and birds were the least frequent dietary items with percentage frequency of 0.45 and 0.23%, respectively. Other identified diet items and the respective percentage frequency were plant matter (6.17%), insects (5.68%), amphibians (5%), mollusks (2.5%) and unidentified items (3.86%). Variation on fish and crab prey items were observed between seasons and sites, while no variation was observed for other prey items. The results suggested a dietary flexibility and shift in the African clawless otter from crabs to fish that can be explained by availability and accessibility.

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“…According to studies based primarily on scat (spraint) analysis, African clawless otters (Aonyx capensis) feed predominantly on fish, frogs and crabs and occasionally other taxa such as insects (Rowe-Rowe and Somers, 1998;Somers and Nel, 2003). In marine locations, crabs dominate the diet of this species with fish present in lower proportions (van der Zee, 1981;Somers, 2000;Emmerson & Phillip, 2004;Jordaan et al, 2015). This pattern is also observed in freshwater locations (Rowe-Rowe, 1977b;Kruuk and Goudswaard, 1990;Somers and Purves, 1996;Somers and Nel, 2003) which suggests a preference for benthic and/or slow-moving prey.…”

Section: Introductionmentioning

confidence: 79%

Plasticity and specialisation in the isotopic niche of African clawless otters foraging in marine and freshwater habitats

et al. 2019

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Individual-level behavioural plasticity resulting from differences in environmental conditions is prevalent in many organisms and may result in phenomena such as dietary-or habitat specialisation. The isotopic niche of African clawless otters, Aonyx capensis, occupying different habitats was investigated with the use of stable isotope techniques. Stable isotope analyses revealed that African clawless otter isotopic niche varied between, as well as within, individuals and varied when compared to conspecifics occupying different habitats. Some otters varied their isotopic niche and foraging areas temporally, whilst others did not. The isotopic niche of African clawless otters in a coastal habitat overlapped substantially with previous reports on otter diet, but illustrated that otters eat more shark and molluscs than previously estimated. In freshwater habitats, not all otters had trout in their isotopic niche, although this prey item was abundantly available in the study area. Our results suggest that the African clawless otters can exhibit substantial behavioural plasticity. Such evident adaptability is likely to benefit otters and allow for extended use of non-pristine environments affected by human disturbance when sufficient quantities of prey remain available.

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An Assessment of Spatial and Temporal Variation in the Diet of Cape Clawless Otters (Aonyx capensis) in Marine Environments

Cited by 8 publications

References 34 publications

Diet of the Eurasian otter (Lutra lutra) on the River Gradac, Serbia: Predation in a brown trout‐dominated stream

Diet of the Eurasian otter (Lutra lutra) on the River Gradac, Serbia: Predation in a brown trout‐dominated stream

Diet analysis of the African clawless otter (Aonyx capensis) in and around Lake Tana

Plasticity and specialisation in the isotopic niche of African clawless otters foraging in marine and freshwater habitats

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