Foraging of multimammate mice, Mastomys natalensis, under different predation pressure: cover, patch‐dependent decisions and density‐dependent GUDs

Abstract

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 assess under which predation pressure they live. We investigated patch use of Mastomys natalensis 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 one‐week periods in late 1999, we measured rodent feeding decisions with the giving‐up density (GUD) method. Trays with known amounts of millet seeds in sand were placed in pairs, one of them under a cover, the other one in the open. M. natalensis mice were expected to give up sooner in the open trays than in those with cover. We hypothesised that M. natalensis mice could assess the ambient predation pressure leading to larger difference in GUD between covered and non‐covered trays in the plots where predators were attracted. We also made video recordings of the rodent activity at a pair of trays in each treatment. The GUD‐values were significantly lower for the covered trays but predation pressure did not affect this difference. The video observations showed that in the control and netted 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. However, the variation in predation pressure in our experiment was not obvious from the GUD. Moreover, we found a strong relation between rodent density and GUD, which may mask variations in perceived predation pressure. Similar GUD values may be reached in different ways and we present models to investigate whether animals’ decision to forage at a food patch is only affected by the seed density at that patch, not by that at a neighbour patch.

Rodent abundance, stone bund density and its effects on crop damage in the Tigray highlands, Ethiopia

“…Predator impacts on rodent populations can be direct or indirect. In the former, predators influence population dynamics by physically removing individuals, whereas in the latter case the presence of predators induces behavioral or physiological responses on the prey due to perceived risk, reducing the probability of being captured (Mohr et al, 2003;Vibe-Petersen et al, 2006).…”

Invasive plant species alters consumer behavior by providing refuge from predation

“…This tradeoff is manifested as a dependence of the time allocated for foraging on perceived predation risk (Lima and Dill 1990;Brown et al 1992;Kotler 1997;Mohr et al 2003;Verdolin 2006). The decision can apparently be influenced by weather conditions that might change the Communicated by Janne Sundell.…”

Foraging efficiency of Akodon azarae under different plant cover and resource levels

“…Although feeding patches may be visited by many individuals, the GUD value reflects the feeding decision of a single animal, the last one to visit the patch (Brown 1988;Kotler 1997;Morris 1997;Mohr et al 2003). On the other hand, GUDs can be compared between related situations despite different densities when the same number of individuals have access to the different types of foraging patches (Ziv et al 1995).…”