Experience, corpulence and decision making in ant foraging

Abstract

SUMMARYSocial groups are structured by the decisions of their members. Social insects typically divide labour: some decide to stay in the nest while others forage for the colony. Two sources of information individuals may use when deciding whether to forage are their own experience of recent task performance and their own physiology, e.g. fat reserves (corpulence). The former is primarily personal information; the latter may give an indication of the food reserves of the whole colony. These factors are hard to separate because typically leaner individuals are also more experienced foragers. We designed an experiment to determine whether foraging specialisation is physiological or experience based (or both). We invented a system of automatic doors controlled by radio-tag information to manipulate task access and decouple these two sources of information. Our results show that when information from corpulence and recent experience conflict, ants behave only in accordance with their corpulence. However, among ants physiologically inclined to forage (less corpulent ants), recent experience of success positively influenced their propensity to forage again. Hence, foraging is organised via long-term physiological differences among individuals resulting in a relatively stable response threshold distribution, with fine-tuning provided by short-term learning processes. Through these simple rules, colonies can organise their foraging effort both robustly and flexibly.Supplementary material available online at

Resistance to nutritional stress in ants: when being fat is advantageous

“…Ants that possess greater fat reserves might also survive longer when facing adverse conditions. Measures of fat content in our study confirmed the pattern of 'lean forager-corpulent inner-nest worker', which is common in social insects (Seeley, 1995;Schulz et al, 1998;Markiewicz and O'Donnell, 2001;Tschinkel, 1998;Blanchard et al, 2000;Smith et al, 2011;Tibbetts et al, 2011;Robinson et al, 2012;Mersch et al, 2013;Bernadou et al, 2015) and suggests that inner-nest workers survived longer due to their high fat reserves. When fed an imbalanced diet, foragers that remained foragers lost a considerable amount of fat and foragers that reverted to inner-nest tasks did not gain any fat.…”

“…Second, there is a further division of labour among workers depending on genetic components, morphology, age and physiological status (Hölldobler and Wilson, 1990). In many species, for example, older and lean workers are the ones in charge of foraging for the entire colony, whereas younger and corpulent individuals stay in the nest (Seeley, 1995;Schulz et al, 1998;Markiewicz and O'Donnell, 2001;Tschinkel, 1998;Blanchard et al, 2000;Smith et al, 2011;Tibbetts et al, 2011;Robinson et al, 2012;Mersch et al, 2013;Bernadou et al, 2015). Nevertheless, division of labour among workers remains highly flexible in social insects.…”

Worker senescence and the sociobiology of aging in ants

“…1). Ant species may differ substantially in the extent of the influence of age on behavior and its underlying physiological processes (Sendova-Franks and Franks 1993, 1995; Seid and Traniello 2006; Muscedere et al 2009, 2011; Robinson et al 2012, e.g.). The role of age in task performance has sparked controversy (Tofts and Franks 1992; Robson and Beshers 1997; Traniello and Rosengaus 1997); in some ants the effects of age on behavior may be weak (Sendova-Franks and Franks 1993, 1995).…”

Anterior cingulate cortex involved in social food‐foraging decision‐making strategies of rats

“…For example, Heijne and Sanfey (2015) reported that the effect of prior beliefs on stay/leave decision‐making was much less pronounced in a social than in a nonsocial context. For rodents, which are highly social experimental animals, social situations affected their decision‐making including mate choice, territorial scramble and food foraging (Dall & Wright, 2009; Robinson, Feinerman, & Franks, 2012; Westneat, Walters, McCarthy, Hatch, & Hein, 2000). The findings from Hillman and Bilkey (2012) suggested that the anterior cingulate cortex (ACC) is an important cost–benefit domain for encoding spatial and competitive decision‐making in rats.…”