Theses and Dissertations Collection

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Browsing Theses and Dissertations Collection by Author "Mohr, Katrine"

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    Feeding decisions as an anti-predation strategy in the African multimammate rat (Mastomys natalensis)
    (University of Copenhagen, 2001-06) Mohr, Katrine
    Patch use under predation risk often results in a change of feeding behaviour in the prey animals. However, such changes only appear if the animals are able to asses under which predation pressure they live. We investigated whether Mastomys natalensis changes its feeding decisions under different conditions of avian predation pressure. In replicated maize field plots in Morogoro, Tanzania, avian predators were allowed under natural conditions (control), attracted with perches and nest boxes or kept out with nets. During four periods of one week each in late 1999, we measured rodent feeding decisions with the giving-up density (GUD) method. Trays with known concentrations of millet seeds in sand were placed in pairs, one of them under a cover, the other one in the open. Since rodents give up foraging in a feeding patch when the risk of being taken by a predator starts outweighing the expected benefit of searching for food items, they were expected to give up sooner in the open trays than in those with cover. Under the hypothesis that the rodents could assess the ambient predation pressure the difference in GUD between covered and non-covered trays would be larger in the plots where predators were attracted. During the same research period, we also made video recordings of rodent activity at a pair of trays in each treatment. The GUD-values were significantly lower under the covers, as expected, however, predation pressure did not affect this difference or the actual GUD-values. The video observations, on the other hand, showed that in the control and net plots the animals visited trays equally frequently regardless of the cover, while the visits in the predator-attracted plots occurred significantly more often in the covered trays. We conclude that M. natalensis can assess the ambient predation pressure and adapt its behaviour at a feeding patch. The variation in predation pressure in our experiment was not reflected in the GUD. We found a strong relation between rodent density and GUD, which may overshadow perceived variations in predation pressure.