Université de Fribourg

Diet choice of a predator in the wild: overabundance of prey and missed opportunities along the prey capture sequence

Brechbühl, Rolf ; Casas, Jérôme ; Bacher, Sven

In: Ecosphere, 2011, vol. 2, no. 12, p. art133

Optimal diet theory (ODT) postulates that predators adjust their foraging decisions by calculating a prey value from the potential biomass gain, handling time, prey vulnerability and encounter rate. Tests of ODT have however so far mainly been restricted to laboratory settings. By video surveillance, we gathered a large data set of more than 2000 field observations of crab spider (Misumena vatia)...

Université de Fribourg

Impact of flower-dwelling crab spiders on plant-pollinator mutualisms

Brechbühl, Rolf ; Kropf, Christian ; Bacher, Sven

In: Basic and Applied Ecology, 2009///10.1016/j.baae.2009.07.001

Indirect effects in interactions occur when a species influences a third species by modifying the behaviour of a second one. It has been suggested that indirect effects of crab spiders (Thomisidae) on pollinator behaviour can cascade down the food web and negatively affect plant fitness. However, it is poorly understood how different pollinator groups react to crab spiders and, thus, when a...

Université de Fribourg

Ineffective crypsis in a crab spider: a prey community perspective

Brechbühl, Rolf ; Casas, Jérôme ; Bacher, Sven

In: Proceedings of the Royal Society B: Biological Sciences, 2009///doi: 10.1098/rspb.2009.1632

Cryptic coloration is assumed to be beneficial to predators because of an increased encounter rate with unwary prey. This hypothesis is, however, very rarely, if ever, studied in the field. The aim of this study was to quantify the encounter rate and capture success of an ambush predator, in the field, as a function of its level of colour-matching with the background. We used the crab spider...