Increases in glucocorticoids are sufficient but not necessary to increase cooperative burrowing in Damaraland mole-rats

Despite widespread interest in the evolution of cooperative behaviour, the physiological mechanisms shaping their expression remain elusive. We tested the hypothesis that glucocorticoid (GC) hormones affect cooperative behaviour using captive Damaraland mole-rats (Fukomys damarensis), a cooperatively breeding mammal. Within groups, individuals routinely contribute to public goods that include foraging tunnels, which provide all group members access to the tubers of desert plants they feed on, communal food stores and nests. We found that experimental increases in glucocorticoid concentration (GCc) in non-breeding female helpers led them to be active for longer and to burrow more while active, raising their daily contributions to burrowing, but not food carrying or nest building. However, experimentally induced increases in burrowing did not lead to elevated GCc in helpers of both sexes. These results suggest that heightened GCc may stimulate some cooperative behaviours that are energetically demanding (a characteristic shared by many types of cooperative activities across species) but that the cooperative behaviours affected by GCc can also be regulated by other mechanisms.An Advanced Grant awarded by the European Research Council to Tim Clutton-Brock (Grant agreement No. 294494) and relied on records of individuals maintained by the Kalahari Mole-Rat Project. This research is part of a project that has received funding from the European Research Council (Grant agreement No. 294494 and 742808 to Tim Clutton-Brock), the Human Frontier Science Program (funding reference RGP0051/2017), the University of Zurich, the Swiss National Science Foundation and the Mammal Research Institute at the University of Pretoria, South Africa.https://www.elsevier.com/locate/yhbehhj2022Mammal Research InstituteZoology and Entomolog