The size dependency of foraging behaviour: an empirical test performed on aquatic amphipods

Abstract

The behavioural choices made by foragers regarding the use of resource patches have a direct influence on the energy balance of the individual. Given that several individual traits linked to the acquisition of spatially distributed resources increase with body size (e.g., energy requirements, resource ingestion rates, and movement capacity), it is reasonable to expect size dependencies in overall foraging behaviour. In this study, we tested how body size influences the number, duration, and frequency of foraging episodes in heterogeneous resource patches. To this end, we performed microcosm experiments using the aquatic amphipod Gammarus insensibilis as a model organism. An experimental maze was used to simulate a habitat characterised by resource-rich, resource-poor, and empty patches under controlled conditions. The patch use behaviour of 40 differently sized specimens foraging alone in the experimental maze was monitored via an advanced camera setup. Overall, we observed that individual body size exerted a major influence on the use of resource patches over time. Larger individuals had stronger preference for the resource-rich patches initially and visited them more frequently than smaller individuals, but for shorter periods of time. However, larger individuals subsequently decreased their use of resource-rich patches in favour of resource-poor patches, while smaller individuals continued to prefer resource-rich patches for the whole experimental time. With body size being a key organismal trait, our observations support the general understanding of foraging behaviours related to preference, patch use, and abandonment.

Metabolic rate and climate change across latitudes: evidence of mass-dependent responses in aquatic amphipods

“…Gammarus insensibilis ( Stock, 1966 ) is an ectotherm Atlantic–Mediterranean species of amphipod living in transitional and coastal waters ( Costello and Emblow, 2001 ). They are important components of aquatic ecosystem trophic webs, feeding mainly on detritus and providing nourishment for secondary consumers ( Cozzoli et al, 2022 ; Nelson, 2011 ; Shadrin et al, 2022 ), with a lifespan of 1 year ( Gerhardt et al, 2011 ; Węsławski et al, 2020 ). The geographical distribution of G. insensibilis is mostly centred on Europe, Southern Greece, i.e.…”

“…ex Steud were supplied as food during the acclimation period in the aquaria and renewed depending on consumption. Phragmites australis is known to be one of the largest sources of organic plant detritus in transitional water ecosystems, providing food for macroinvertebrates ( Able and Hagan, 2000 ), including G. insensibilis ( Cozzoli et al, 2022 ; Shokri et al, 2021 ). Before starting the experiment, specimens were sorted by sex under a Nikon stereoscope (SMZ1270).…”

Metabolic rate and foraging behaviour: A mechanistic link across body size and temperature gradients

“…Gammarus species are selective foragers, feeding preferentially on fungi with high protein content colonizing decomposed leaf litter (Bärlocher and Kendrick 1973). While foraging they scroll the surface of the leaves seeking valuable resources, and when high-quality resources are not available, they consume resources with a lower value (Cozzoli et al 2022). Daily consumption rates are from 46% to 103% of their body mass, depending on the type of exploited resource (Berezina 2007).…”

“…Several studies have investigated the link between individual energy requirements and foraging behaviour, often focusing on one of the main determinants of metabolic rate, e.g. individual body mass (Brose, 2010; Cozzoli et al, 2019, 2022; Petchey et al, 2008) or, more recently, temperature (Abram et al 2017, Cloyed et al 2019, Jermacz et al 2020). However, despite the key importance of body size and temperature per se in predicting behavioural patterns (Brose 2010, Cozzoli et al 2022), they are not sufficient to crystalize the mechanism behind them (Brandl et al 2022).…”

“…individual body mass (Brose, 2010; Cozzoli et al, 2019, 2022; Petchey et al, 2008) or, more recently, temperature (Abram et al 2017, Cloyed et al 2019, Jermacz et al 2020). However, despite the key importance of body size and temperature per se in predicting behavioural patterns (Brose 2010, Cozzoli et al 2022), they are not sufficient to crystalize the mechanism behind them (Brandl et al 2022). The complexity of resource-consumer interactions often hinders the predictive power of mass and temperature-based models (Dell et al 2014b).…”