Habitat selection by the Cape clawless otter (<i>Aonyx capensis</i>) in rivers in the Western Cape Province, South Africa

Somers, Michael J.; Nel, J.A.J.

doi:10.1111/j.1365-2028.2004.00526.x

Cited by 15 publications

(25 citation statements)

References 20 publications

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“…This might be due to the decrease in the water level during the dry season that allowed the African clawless otter to find and capture crabs easily to locate and capture under and/or between the rocks near shore. Similar results were reported by Somers and Nel (2003) in the Olifants and Eerste Rivers in the Western Cape Province. Plant matters in the diet were higher in the wet and lower in the dry.…”

Section: Discussionsupporting

confidence: 78%

“…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: 84%

“…Spraints were air dried and stored in polyethylene plastic bags until analysis. Spraints were analyzed at the Zoology Research Laboratory of the Department of Zoological Sciences, Addis Ababa University following Somers and Nel (2003). They were soaked in liquid detergent overnight in 250 ml of beaker to remove sand, debris and other binding mucilages.…”

Section: Methodsmentioning

confidence: 99%

“…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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Section: Discussionsupporting

confidence: 78%

Section: Discussionmentioning

confidence: 84%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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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Otter occupancy in the Cape Peninsula: Estimating the probability of river habitat use by Cape clawless otters, Aonyx capensis, across a gradient of human influence

Okes

O’Riain

2017

Aquatic Conservation

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1. The distribution of Cape clawless otters, Aonyx capensis, in South Africa and their habitat requirements in freshwater and marine systems has been well established. There is, however, a lack of information on how otters are adapting to urban development and the transformation of critical freshwater habitat.2. Within the Western Cape, the Cape Peninsula exhibits substantial variation in levels of human impact over a small geographic range, offering an excellent opportunity to explore the hypothesis that otters are adversely affected by habitat transformation.3. A single season occupancy model was used based on otter sign to determine the probability of otter occupancy across a gradient of habitat transformation at both landscape and local scales.4. The probability of otters occupying river habitat in the Cape Peninsula was low (P = 0.29) but increased with proximity to marine protected areas (MPAs) that included estuaries and wetland habitat. Otter presence was not influenced by proximity to urban areas at the landscape scale, but declined in canalized sections of river that were heavily degraded by human activity. 5. Despite being heavily transformed, lowland aquatic ecosystems may still provide critical resources in the form of fresh water and breeding sites, and together with food within the marine habitat may be sustaining the peninsula's otter population.6. In order for otters to persist on the peninsula, conservation authorities must maintain wetland, estuarine and river habitat in close proximity to MPAs. Further research is needed to determine the long-term impacts on otters persisting in degraded ecosystems. 7. Annual single season occupancy surveys provide a rapid, cost-effective method for monitoring changes in otter occupancy which should be incorporated into current monitoring efforts to provide much needed long-term monitoring of a top predator in freshwater ecosystems.

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Solitary versus group living lifestyles, social group composition and cooperation in otters

et al. 2020

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Increased reproduction success, enhanced foraging and reduced predation risk are usually regarded as major factors favouring the evolution of social behaviour. Here we formulate a series of hypotheses relating sexual, ecological and behavioural factors to evaluate their explanatory value for 13 extant otter species, estimating the extent to which each factor contributes to the sociality of each species. We also compare individual behaviours within some of the species. Four otter species are obligatory social; four are obligatory solitary; five present both types of social organization. Social organizations of otter species are not related to their phylogenetic relationships. However, many otter species exhibit intra-species patterns of flexible social lifestyles. Both solitary and social otters adjust their social patterns in response chiefly to food availability, but also to habitat features and competition.Group living is more common when intraspecific competition is reduced or trophic resources replenish rapidly. Under these circumstances, group members often forage individually. When otters forage individually, they often switch prey type when they compete with other conspecifics. Social structures of otters fall into seven types: (1) family groups; (2) extended family groups, often with an alpha dominant pair; (3) highly social groups with helpers; (4) collective hunting groups; (5) solitary lifestyle; (6) unstable mixed-sex groups; and (7) single-sex bachelor groups. When an individual of a species with variable sociality adopts one type of sociality, this may be only temporary. Variations in social life are actually based on a series of events that induce individuals to make decisions taking ecological factors into account.Although ontogenetic factors can influence delayed dispersal of otters, social factors rather than ecological factors could play an important role in the formation of groups, and cohesiveness and kinship appear to be secondary effects of reduced dispersal more than primary causes for living in a group. Appropriate adjustment of group behaviour reduces the cost of sociality because individuals avoid social interactions when benefits are low but gather together when group living provides real advantages. Although any one model is unlikely to explicate all facets of sociality, evolution towards a social group results mainly from interactions within a family.

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Habitat selection by the Cape clawless otter (Aonyx capensis) in rivers in the Western Cape Province, South Africa

Cited by 15 publications

References 20 publications

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

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

Otter occupancy in the Cape Peninsula: Estimating the probability of river habitat use by Cape clawless otters, Aonyx capensis, across a gradient of human influence

Solitary versus group living lifestyles, social group composition and cooperation in otters

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