Size dependency of patch departure behavior: evidence from granivorous rodents

Abstract

Citation: Cozzoli, F., V. Gjoni, and A. Basset. 2019. Size dependency of patch departure behavior: evidence from granivorous rodents. Ecology 100(10):Abstract. Individual size is a major determinant of mobile organisms' ecology and behavior. This study aims to explore whether allometric scaling principles can provide an underlying framework for general patterns of resource patch use. To this end, we used giving-up densities (GUDs), that is, the amount of resources remaining in a patch after a forager has quit feeding, as a comparative measure of the amount of resources exploited by a forager of any given size. We specifically tested the hypothesis that size-dependent responses to both internal (energy requirement) and external (risk management) forces may have an effect on GUDs. We addressed this topic by conducting an extensive meta-analysis of published data on granivorous rodents, including 292 GUD measurements reported in 25 papers. The data set includes data on 22 granivorous rodent species belonging to three taxonomic suborders (Castorimorpha, Myomorpha, and Sciuromorpha) and spans three habitat types (desert, grassland, and forest). The observations refer to both patches subject to predation risk and safe patches. Pooling all data, we observed positive allometric scaling of GUDs with average forager size (scaling exponent = 0.45), which explained 15% of overall variance in individual GUDs. Perceived predation risk during foraging led to an increase in GUDs independently of forager size and taxonomy and of habitat type, which explained an additional 12% of overall GUD variance. The size scaling exponent of GUDs is positive across habitat types and taxonomic suborders of rodents. Some variation was observed, however. The scaling coefficients in grassland and forest habitat types were significantly higher than in the desert habitat type. In addition, Sciuromorpha and Myomorpha exhibited a more pronounced size scaling of GUDs than Castorimorpha. This suggests that different adaptive behaviors may be used in different contexts and/or from different foragers. With body size being a fundamental ecological descriptor, research into size scaling of GUDs may help to place patch-use observations in a broader allometric framework.

A process based model of cohesive sediment resuspension under bioturbators' influence

“…We showed that the effect of bioturbators on cohesive sediment resuspension can be described by bioturbators' population metabolic rate, with minor variations across different bioturbation modalities. This finding is in-line with other studies showing that indicators based on community size structure, rather than on species-specific characteristics, can be used to describe functional ecological processes or patterns such as community interactions (McGill, et al, 2006) and structure (Gjoni, et al, 2017;Gjoni & Basset, 2018), resource exploitation (Basset, et al, 2012a;Cozzoli, et al, 2018b;Cozzoli, et al, 2019), species coexistence (Canavero, et al, 2014), habitat carrying capacity (Edgar, 1993) and ecological status (Mouillot, et al, 2006;Menezes, et al, 2010;Basset, et al, 2012b).…”

Relationship between individual metabolic rate and patch departure behaviour: evidence from aquatic gastropods

“…The intrinsic inclination of larger foragers to leave the resource patch earlier because of their inherently greater readiness to perceive resource limitation sooner has been theoretically hypothesized (Holling 1992, Basset 1995) and empirically observed (Brown et al 1988, Kotler and Brown 1990, Bowers et al 1993, Vasquez 1996, Searle et al 2005, Stenberg and Persson 2006, Cozzoli et al 2018, 2019). In this study, we show that not only larger individuals, but also individuals of the same size and species but with higher standard metabolic rates, are more likely to abandon the resource patch earlier, rather than face increasing competition for the remaining resources (Fig.…”

“…Under conditions of resource abundance and without considering the effect of extrinsic factors such as the risk of predation (Ward et al 2000), vagile foragers tend to persist on a resource patch and to avoid energy‐expensive behaviours such as exploration, which are in contrast adopted when the resource becomes scarce (Killen et al 2007). Patch departure decisions have been observed to be related to individual body mass: larger organisms abandon a resource patch earlier and at a resource density that is still exploitable for small foragers (Brown et al 1988, Kotler and Brown 1990, Bowers et al 1993, Vasquez 1996, Searle et al 2005, Stenberg and Persson 2006, Cozzoli et al 2018, 2019). The size dependency of an animal's propensity to abandon resource patches may be due to a number of mechanisms acting in synergy.…”

“…Therefore, it could be more convenient for them to allocate time to discovering and moving to new and more proficient resource patches, rather than further exploiting the patch in use (Charnov 1976, Brown et al 1994). Thirdly, foragers are expected to exploit a resource patch only until the energy gain in terms of ingested resource per unit of time balances the costs of foraging (Brown et al 1988): since larger organisms have higher metabolic costs and require a higher rate of resource ingestion to sustain themselves (Peters 1983, Brown et al 1988, Hendriks 1999), it follows that on depletion of patch profitability due to resource consumption and the consequent drop in ingestion rates (Holling 1959a, b1959b), larger foragers perceive scarcity and abandon the patch at a higher resource density than smaller foragers (Kotler and Brown 1990, Basset 1995, Cozzoli et al 2018, 2019). Tradeoffs between resource exploitation efficiency and harvest rates may allow coexistence on a resource whose abundance varies spatially due to depletion and renewal (Schmitt 1985, Wilson et al 1999, Richards et al 2000).…”

Impact of Predator Exclusion and Habitat on Seroprevalence of New World Orthohantavirus Harbored by Two Sympatric Rodents within the Interior Atlantic Forest

“…However, following the exclusion of both generalist and specialist predators, the abundance of montane voles ( Microtus montanus ) increased [ 122 ]. Where predator presence was found to affect rodent prey abundance, reports have indicated that the effects may be complexly interrelated with habitat, existing rodent densities, season, individual species behavioral characteristics, and type of predator [ 122 , 124 , 125 , 126 ]. These potential interactions are difficult to tease apart, both conceptually and statistically, and their resolution will require intensive long-term studies in natural and managed field conditions.…”