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Otter density is significantly higher in the Burguret river

Effects of the Louisiana crayfish. invasion and other human impacts. on the African Clawless otter in the. Ewaso. Ng’iro. ecosystem. Otter density is significantly higher in the Burguret river. Mordecai O. Ogada. ,. Department of Zoology. Kenyatta. University, Nairobi, Kenya. Email:.

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Otter density is significantly higher in the Burguret river

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  1. Effects of the Louisiana crayfish invasion and other human impacts on the African Clawless otter in the Ewaso Ng’iro ecosystem Otter density is significantly higher in the Burguret river Mordecai O. Ogada , Department of Zoology Kenyatta University, Nairobi, Kenya Email: mordyogada @yahoo.com The Study Area. Thanks for your support! • Prof. P. Aloo - Obudho & Prof. R. O. Okelo • Whitley Laing / Rufford Foundation • Wildlife Conservation Society • Mpala Wildlife Foundation • Columbus Zoo & Aquarium • Lincoln Park Zoo • Kenyatta University Biological Sciences Dept. Crayfish - Invaded Ecosystem… ‘Pristine’ Ecosystem… (Here at Mpala ) (at Burguret River) Crayfish exposed • Availability of food (crab exposure) does to Herons, genets, Dry Season. Low baboons, etc not change significantly with river level. water level due to (Otters’ niche Drought, Water invaded) Extraction • Otter diet is relatively constant (97.25 - 100% crab content in faeces ). Otters experience food stress & Territorial • No significant seasonal change in otter Behaviour breaks down. territorial behaviour / marking. Rainy Season. High water level. Otters’ niche re- established. Territorial marking resumes. Dietary Trends…Crayfish percentage in faecal pellets closely tracks river level when analyzed by LOWESS curve, showing that fewer crayfish are available to otters in the Lower Ewaso Ng’iro when river levels are low. Territorial marking… Percentage of aggregated faecal pellets is significantly higher (t=5.030, p <0.0004, n = 2) in the Burguret river 100 90 The Major Species Involved… 80 • Aonyx capensis - The African clawless otter is highly 70 dependent on crustacean prey, because its lack of claws makes it very difficult to catch fish 60 • Potamonautes neumannii - The freshwater crab is the otters’ natural prey. It forms most (>97%) of the otters’ diet in the 50 the Burguret river. • Procambarus clarkii - 40 E.Ngiro The Louisiana crayfish has Burguret invaded the lower Ewaso Ng’iro , supplanted the crab, and now 30 forms >60% of the otters’ diet there. It hasn’t invaded the Burguret river due to low water temperatures there. 20 0 2 4 6 8 10 12 14 month

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