E-Thesis 223 views 81 downloads
The functionality of Eurasian otters (Lutra lutra) as top-down predators in marine ecosystems / JASMINE KNIGHT
Swansea University Author: JASMINE KNIGHT
Abstract
Ecological niche (Elton, 1927) has been adapted over the years to fit the various definitions within the broad spectrum of an ecological niche. The term ‘trophic niche’ is referred to most commonly now and can be measured by width/ breadth using various diversity indices to determine whether a speci...
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Swansea, Wales, UK
2023
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| Institution: | Swansea University |
| Degree level: | Master of Research |
| Degree name: | MRes |
| Supervisor: | Forman, Dan. W. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa64022 |
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| Abstract: |
Ecological niche (Elton, 1927) has been adapted over the years to fit the various definitions within the broad spectrum of an ecological niche. The term ‘trophic niche’ is referred to most commonly now and can be measured by width/ breadth using various diversity indices to determine whether a species is a generalist or a specialist (Hutchinson, 1957). This study explores the methodology utilised by existing literature for Lutra lutra spraint analysis and subsequent dietary studies. The data from seven studies in the UK and Europe in the last 40 years has been extracted and processed to create a meta-dataset of the relative frequency of occurrence (R.F.O %) of prey within spraints, and four selected prey characteristics or traits; body form, ecosystem type, habitat classification and prey type. Trophic niche analysis using Shannon- Weiner diversity index and Levins measure of niche breadth index indicates the hypothesis that the diet of Lutra lutra is more likely to be generalist than specialist is correct (Mean J’ = 0.75 (± 0.08), mean Levins = 0.35 (± 0.05)). Prey trait analysis demonstrates that the most prevalent body form is fusiform (39.6%), ecosystem type with prey presence at two interfaces was most frequent, (36.4%) demersal is the most common habitat classification (48.7%) and type of food (prey) consumed by the prey species/group is small invertebrates, small crustaceans, fish fry (type 3, 43.5%). Furthermore, Welch’s two sample t-test indicates that there is no significant difference between the mean R.F.O (%) of marine prey and non-marine prey at family level (t= 1.97, p= 0.06). The clear need for the standardisation of current approaches towards spraint analysis to improve our understanding of Lutra lutra’s diet and by extension ecological niche, to ultimately protect this semi-aquatic mammal from potential threats in rapidly changing dynamic coastal and marine environments (Gutiérrez, et al., 2019). |
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| Keywords: |
Eurasian otter, Lutra lutra, marine ecosystems, marine prey, top-down predator, trophic niche, spraint analysis |
| College: |
Faculty of Science and Engineering |