Visit, consume and quit: Patch quality affects the three stages of foraging

Abstract

Foraging is a three-stage process during which animals visit patches, consume food and quit. Foraging theory exploring relative patch quality has mostly focused on patch use and quitting decisions, ignoring the first crucial step for any forager: finding food. Yet, the decision to visit a patch is just as important as the decision to quit, as quitting theories can only be used if animals visit patches in the first place. Therefore, to better understand the foraging process and predict its outcomes, it is necessary to explore its three stages together. We used the common brushtail possum (Trichosurus vulpecula) as a model to investigate foraging decisions in response to food varying in quality. In particular, we tested whether patch nutritional quality affected the following: (1) patch visits; (2) behaviours at the patch during a foraging visit; and (3) patch quitting decisions (quantified using giving up density-GUD). Free-ranging possums were presented with diets varying in nitrogen content and concomitantly volatile organic compound (VOC) composition at feeding stations in the wild. We found that possums were able to distinguish between different quality foods from afar, despite the location of the diets changed daily. Possums used VOC (i.e. odour cues) emitted by the diets to find and select patches from a distance. High-quality diets with higher protein and lower fibre were visited more often and for longer. Possums spent more time foraging on diets high in nutritional content, resulting in lower GUDs. Our study provides important quantitative evidence that foraging efficiency plays out during all the three stages of the foraging process (i.e. visit, consume and quit), and demonstrates the significance of considering all these stages together in future studies and foraging models. Sensory cues such as food odours play a critical role in helping foragers, including mammalian herbivores, find high-quality food. This allows foragers to make quick, accurate and important decisions about food patches well before patch quitting decisions come into play.

Direct and indirect effects of high temperatures on fledging success in a cooperatively breeding bird

“…If such elevated water demand does exist when hot, our data suggest that provisioning adults might be unable to increase biomass provisioned in order meet this demand. This is because biomass caught declined with increasing temperature above 32.3ºC, indicating poorer foraging success (du Plessis et al 2012;Cunningham et al 2015;van de Ven et al 2019) and suggesting that there was probably less biomass available at high temperatures with which to provision to nestlings (Conrey et al 2016;Dodson et al 2016;Mella et al 2018). Adults may also be constrained in their ability to provision more water-rich food to nestlings at high temperatures due to the increased costs of flight at high air temperatures (Klaassen 1995;Powers et al 2017) and the need to attend to their own water demands (Bourne, Ridley, et al 2020;Czenze et al 2020).…”

Size dependency of patch departure behavior: evidence from granivorous rodents

“…Larger foragers may indeed be able to maintain a relatively higher harvest rate by improving their collection behavior (Dukas and Kamil , Catania and Remple , Mella et al. ) and by learning (Ishii and Shimada ). Furthermore, the costs of thermoregulation per unit of mass of rodents decrease as size increases (Bozinovic and Rosenmann ), so that larger individuals are advantaged when foraging in extreme temperatures.…”

The power of odour cues in shaping fine-scale search patterns of foraging mammalian herbivores

“…Although movements that bring animals to a patch are important, foraging is not complete until food is found. Odour cues can guide animal movements from afar [28] and are likely essential in finding food at fine scales (centimetres to metres) too. Food plants for generalist herbivores often occur within metres of each other, and their odour cues could be harnessed for efficient, directed search even at this fine scale.…”