Naked mole-rats recruit colony mates to food sources

Naked mole-rats, Heterocephalus glaber, are eusocial, subterranean rodents that inhabit arid regions of northeastern Africa. They feed on bulbs and tubers that are patchily distributed. Nests are often located far from the nearest food source through a labyrinth of tunnels. Two captive colonies were studied to determine whether successful foragers recruit colony mates and, if so, how. Individuals that found a new food source typically gave a special vocalization on their way back to the nest and waved the food around once they got there. Colony mates preferentially visited the site where the initial forager had obtained food, often bypassing alternative sites containing the same type of food. Recruits preferred to use tunnels that had been traversed by the ‘scout’ rather than an alternative pathway to the same food, regardless of whether they had to turn in the same or the opposite direction from that of the scout to enter the previously used pathway. Recruits preferred tunnels that the scout had recently used over tunnels that were recently traversed by another colony mate carrying the same type of food. When tunnels traversed by the scout were replaced with clean substitutes or with tunnels that were recently traversed by another colony mate carrying the same type of food, recruits showed no pathway preferences. Results indicate that naked mole-rats follow each other’s (odour) trails to food. There are intriguing parallels between the foraging recruitment system of H. glaber and those of other social vertebrates and insects. ? 1996 The Association for the Study of Animal Behaviour Foragers in many species of social vertebrates and invertebrates face the dual challenges of locating patchy, unpredictable food sources and transmitting the information to other group members. Individuals advertise the locations of superabundant food sources with special vocalizations in some birds (e.g. cliff swallows, Hirundo pyrrhonota: Brown et al. 1991; ravens, Corvus corax: Heinrich & Marzluff 1991) and mammals (e.g. chimpanzees, Pan troglodytes: Wrangham 1977; cotton-top tamarins, Saguinus oedipus: Cleveland & Snowdon 1982; Elowson et al. 1991; toque macaques, Macaca sinica: Dittus 1984; spider monkeys, Ateles geoffroyi: Chapman & Lefebvre 1990; and greater spear-nosed bats, Phyllostomus hastatus: Wilkinson & Boughman, in press), whereas Norway rats (Rattus norvegicus) leave odour trails to preferred food sources (Galef & Buckley, 1996). Foraging recruitment systems of social insects also take several forms. In many species of stingless bees (e.g. Trigona cufira: Michener 1974) and some ants (e.g. Leptothorax acervorum: Möglich 1978), foragers lead recruits to food. In many other ant species (reviewed by Gabba & Pavan 1970; Hölldobler & Wilson 1990, pp. 265–273; Hölldobler 1995), a few species of stingless bees (Michener 1974; Lindauer 1961) and most species of tent caterpillars (Fitzgerald 1995), foragers lay chemical trails to food. Finally of course, the dance language of honey bees, Apis mellifera, is legendary for its precision and accuracy (von Frisch 1967; Seeley 1995). Naked mole-rats are eusocial, subterranean rodents that inhabit arid regions of northeastern Africa (Sherman et al. 1991; Jarvis et al. 1994). On average, colonies contain 70–80 mole-rats (range=2–295 or more: Braude 1991; Lacey & Sherman, 1996), among which only one female and one to three males breed (Lacey & Sherman 1991; Sherman et al. 1992). Colony mates are closely related owing to natal philopatry and Correspondence: P. W. Sherman, Section of Neurobiology & Behavior, Cornell University, Ithaca, NY 14853, U.S.A. T. M. Judd is at the Biology Department, Oakland University, Rochester, MI 48309, U.S.A. 0003–3472/96/110957+13 $25.00/0 ? 1996 The Association for the Study of Animal Behaviour