Reciprocal allogrooming among unrelated Norway rats (Rattus norvegicus) is affected by previously received cooperative, affiliative and aggressive behaviours

Abstract

Reciprocity can generate stable levels of cooperation among unrelated social partners. If individuals interact repeatedly, costs of altruistic acts can be compensated through an exchange of donor and receiver roles. Frequent interactions are conducive to attaining evolutionarily stable reciprocal exchange. High interaction frequencies are typical for group members maintaining close relationships among one another, which may thereby facilitate reciprocity. Norway rats (Rattus norvegicus) are highly social animals that were experimentally shown to reciprocally exchange food donations and allogrooming. Here we tested experimentally the relationship between reciprocal cooperation and other social behaviours exchanged within dyads of wild-type Norway rats. In particular, we asked phase. This suggests that affiliative and aggressive behaviours affect the allogrooming propensity of rats. In particular, higher frequencies of received aggression decreased the propensity to reciprocate previously received cooperation. We provide experimental evidence that rats are more likely to groom partners that pulled a stick to deliver food to them. Reciprocal exchange of allogrooming depends apparently on experienced cooperation, but also on the quality of the social relationship. Significance Statement Close social relationships among individuals may enhance reciprocal exchange of services and thereby ensure long-term cooperation. Thus we tested whether in unrelated and previously unfamiliar Norway rats the quality of social interactions, that is, the amount of exchanged affiliative and aggressive behaviours, affects reciprocal cooperation, and whether received cooperation in turn predicts subsequent social behaviour. Our results show that focal individuals are generally more helpful to previously helpful partners, but that the quality of social interactions may modify their decision to cooperate. Received aggressive and affiliative behaviours affected the subsequent reciprocal exchange of hygienic behaviour. Moreover, received food provisioning affected the exchange of cooperative, affiliative and aggressive behaviours also outside of a food-provisioning context. These data reveal a close relationship between the exchange of social behaviours between individuals and their propensity to cooperate with one another.

Reciprocity: Different behavioural strategies, cognitive mechanisms and psychological processes

“…After a delay of up to six days, the roles are exchanged and the focal rat can provide food to its previous partner (e.g. Stieger, Schweinfurth, & Taborsky, 2017). To ensure that food donations by the focal rats are based on the previous help by a partner, focal rats are always also tested with a defecting partner that did not provide food to them.…”

“…Such reciprocal allogrooming has significant fitness benefits, as reciprocal groomers live longer and suffer less mammary tumours in the lab (Yee, Cavigelli, Delgado, & McClintock, 2008). Finally, female rats also exchange allogrooming for food and vice versa (Schweinfurth & Taborsky, 2018b; Stieger et al, 2017). Besides direct reciprocity, female, but not male, rats engage in generalised reciprocity (Rutte & Taborsky, 2007, 2008; Schweinfurth et al, 2019).…”

“…First, hard-wired reciprocity cannot explain reciprocity among Norway rats because they tailor their help to the partner’s helping quality (Dolivo & Taborsky, 2015) and the partner’s need (Márquez, Rennie, Costa, & Moita, 2015; Schneeberger et al, 2012; Schneeberger, Röder, & Taborsky, submitted; Schweinfurth & Taborsky, 2018a). Furthermore, rats reciprocate help by using different actions (Schweinfurth & Taborsky, 2017) and different commodities (Schweinfurth & Taborsky, 2018b; Stieger et al, 2017), making a fixed response unlikely. Second, emotion-based reciprocity is also unlikely to explain reciprocity in Norway rats.…”

“…They seem not to form social bonds even after being housed together for more than one and a half years (Schweinfurth, Neuenschwander, et al, 2017). They do not accumulate social information with their partners, but rather use the last experience (Schweinfurth & Taborsky, under review; Stieger et al, 2017). Third, there is no evidence for calculated reciprocity either.…”

“…This is in line with their numerical ability being limited to six items, which is below the amount of grooming bouts they are known to reciprocate (cf. Davis & Bradford, 1986; Schweinfurth, Stieger, et al, 2017).…”