Reaching Out for Inaccessible Food Is a Potential Begging Signal in Cooperating Wild-Type Norway Rats, Rattus norvegicus.

Niklas I Paulsson,Michael Taborsky

doi:10.3389/fpsyg.2021.712333

Abstract

Begging is widespread in juvenile animals. It typically induces helpful behaviours in parents and brood care helpers. However, begging is sometimes also shown by adults towards unrelated social partners. Adult Norway rats (Rattus norvegicus) display a sequence of different behaviours in a reciprocal food provisioning task that have been interpreted as such signals of need. The first behaviour in this sequence represents reaching out for a food item the animal cannot obtain independently. This may reflect either an attempt to grasp the food object by itself, or a signal to the social partner communicating the need for help. To distinguish between these two possibilities, we tested in female wild-type Norway rats if the amount of reaching performed by a food-deprived rat changes with the presence/absence of food and a social partner. Focal rats displayed significantly more reaching behaviour, both in terms of number and total duration of events, when food and a potentially helpful partner were present compared to when either was missing. Our findings hence support the hypothesis that rats use reaching behaviour to signal need to social partners that can help them to obtain food.

Highlights

The ability to comprehend the need of others is widespread in the context of brood care, where variation in offspring begging allows parents to adaptively modulate food provisioning (Grodzinski and Lotem, 2007)
Rats (N = 25) showed more reaching behaviours when a partner capable of providing food was present than when none was present (i.e., Food treatment; general linear mixed models (GLMM): ß = 0.887 ± 0.164 SE, p ≤ 0.001), but not in the presence of only a partner without food that it could have fetched for the focal subject (GLMM: ß = 0.083 ± 0.170 SE, p = 0.624; Figure 2A; Table 1)
As with the number of reaching behaviours, the total duration of reaching by focal rats in the presence of a partner and food was significantly longer than when no partner was present (i.e., Food treatment; GLMM: ß = 0.729 ± 0.207 SE, p

Summary

Introduction

The ability to comprehend the need of others is widespread in the context of brood care, where variation in offspring begging allows parents to adaptively modulate food provisioning (Grodzinski and Lotem, 2007). Begging signals are frequently used by offspring towards their brood caring parents in mammals (e.g., Kunc et al, 2007; Fröhlich et al, 2020), birds (e.g., Leech and Leonard, 1996) and insects (e.g., Mattey et al, 2018). If animals respond to the need of prospective receivers of help by increasing their generosity (Schneeberger et al, 2020), this would select for the evolution of signals of demand (Kilner and Johnstone, 1997; Grodzinski and Lotem, 2007), among unrelated adults (Carter and Wilkinson, 2016; Schweinfurth and Taborsky, 2018a). During reciprocal exchange of goods and services begging can increase the propensity of a previous receiver

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