A guide to area‐restricted search: a foundational foraging behaviour

Abstract

Area-restricted search is the capacity to change search effort adaptively in response to resource encounters or expectations, from directional exploration (global, extensive search) to focused exploitation (local, intensive search). This search pattern is used by numerous organisms, from worms and insects to humans, to find various targets, such as food, mates, nests, and other resources. Area-restricted search has been studied for at least 80 years by ecologists, and more recently in the neurological and psychological literature. In general, the conditions promoting this search pattern are: (1) clustered resources; (2) active search (e.g. not a sit-and-wait predator); (3) searcher memory for recent target encounters or expectations; and (4) searcher ignorance about the exact location of targets. Because area-restricted search adapts to resource encounters, the search can be performed at multiple spatial scales. Models and experiments have demonstrated that arearestricted search is superior to alternative search patterns that do not involve a memory of the exact location of the target, such as correlated random walks or Lévy walks/flights. Area-restricted search is triggered by sensory cues whereas concentrated search in the absence of sensory cues is associated with other forms of foraging. Some neural underpinnings of area-restricted search are probably shared across metazoans, suggesting a shared ancestry and a shared solution to a common ecological problem of finding clustered resources. Area-restricted search is also apparent in other domains, such as memory and visual search in humans, which may indicate an exaptation from spatial search to other forms of search. Here, we review these various aspects of area-restricted search, as well as how to identify it, and point to open questions.

Evolution of explorative and exploitative search strategies in collective foraging

“…Evidence for simple heuristics like ARS has been found in humans and other animals [Pacheco-Cobos et al, 2019b, Wiesner et al, 2012, Dorfman et al, 2022]. Our results suggest that ARS may confer an evolutionary advantage to social foragers by increasing their share of resources.…”

“…Therefore, it would benefit foragers to make decisions to explore or exploit based on information about the environment. Some foraging models forego the benefits of informed search in favor of cognitively simplified agents that randomly switch between exploration and exploitation [Viswanathan et al, 1996], while others base decisions to switch on information obtained while foraging [Dorfman et al, 2022, Bénichou et al, 2011, Pacheco-Cobos et al, 2019a, Hills et al, 2013, Kerster et al, 2016]. For example, area-restricted search models drive decisions to switch between exploitation and exploration based on resource encounters, which is more efficient than switching at random.…”

When complex movement yields simple dispersal: behavioural heterogeneity, spatial spread and parasitism in groups of micro-wasps

“…Obviously, we did not explicitly track individuals at a very small scale, so we cannot yet ascertain the exact behavioural determinants of the two strategies we indirectly detected. The existence of these two movement strategies is reminiscent of the duality between exploitation/area-restricted and exploration/extensive strategies found in other organisms, including insects [ 50 , 51 ]. Further research will clarify these aspects, by supplementing our large-scale low-frequency tracking pipeline with small-scale video-tracking at different positions along the experimental tunnel.…”

Emergence of spatially structured populations by area‐concentrated search

“…In our simulations, we use a simple movement model (ACS) on the one hand and landscapes with spatially concentrated resource distribution on the other to simulate behavior of foraging individuals; the simulated populations show attributes of a spatially structured population as emergent properties. As such, the emergence of spatial structure cannot be a very surprising outcome as it is already an intrinsic property of the ACS that individuals tend to preferentially stay in areas of high resource concentration (e.g., Dorfman et al, 2022). At the population level, this would make us expect that animals tend to concentrate in areas where critical resources are aggregated; in our simulations, population densities were up to approx.…”

“…Area-concentrated search movement strategies may approach the efficiency of an unconstrained optimal forager (Adler & Kotar, 1999) and seem to occur in many different species (reviewed in Dorfman et al, 2022), like mallards (at very small spatial scale; Klaassen et al, 2006), wandering albatrosses that respond to habitat cues per se (Weimerskirch et al, 2007), amoeba (Van Haastert & Bosgraaf, 2009), where straight movement is triggered by starvation, or ladybird beetles that respond to prey encounters (Nakamuta, 1985).…”