Kenyan mangrove crabs: feeding ecology and behavioural ecology of some selected species
Dahdouh-Guebas, F. (1994). Kenyan mangrove crabs: feeding ecology and behavioural ecology of some selected species. MSc Thesis. Vrije Universiteit Brussel: Brussel. 76 + ann. pp.
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Document type: Dissertation
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| Abstract |
This thesis is concentrating on two aspects of Kenyan mangrove crabs. Starting from several crab species (Cardisoma carnifex, Epixanthus dentatus, Eurycarcinus natalensis, Metopograpsus oceanicus, Metopograpsus thukukhar, Selatium elongatum, Sesarma guttatum, Sesarma leptosoma, Sesarma ortmanni, Neosarmatium meinerti and Thalamita crenata) it tries to understand which species are eating which food items. One species is investigated in particular, namely Thalamita crenata and in a second part of this thesis its orientational capacities are investigated. The investigation of the natural diets was done through stomach content analysis using the percentage occurence method. For the initial crab species a significant correlation was found between the stomach fullness and the herbivority (and hence also carnivority), when they were classified in four groups : 100% herbivore (C. carnifex, S. elongatum, S. guttatum, S. ortmanni and N. meinerti), 75% herbivore (M. oceanicus, M. thukukhar and S. leptosoma), 25% herbivore (E. dentatus and T. crenata) and 0% herbivore (E. natalensis). The diet of T. crenata in particular revealed that this species ingests a variety of food items (Algae, Anomura, Brachyura and other Crustacea, Bivalvia, Foraminifera, Gastropoda, Pisces, Polychaeta, Polyplacofora, mangrove detritus and sand). Also significant differences were found when confronting stomach fullness and herbivority at low/high tide, spring/neap tide and day/night time. Its diet contains more in quantity and more animal matter at spring tide, low tide and during daytime. For the orientational capacities of T. crenata a series of homing experiments were designed based on removal of the crab from its home hole using different distances, transporting means, terrain alternations, and so forth, while variables such as homing performance, walking behaviour, straightness index of the walk and homeward component were investigated. It was found that vision of the terrain closeby was a major help in going back to its home range. |
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