The colony structure and social organization of the giant Zambian mole-rat, Cryptomys mechowi

Abstract

Cryptomys mechowi is a social subterranean mole-rat which inhabits the mesic regions of south-eastern and central Africa. Giant mole-rats live in colonies of up to 11 animals in which reproduction is normally restricted to the largest male and female in the colony. In this preliminary study on a laboratory-reared colony, the non-reproductive members of the colony could not be placed into clearly de®ned, work-related groups based on body mass. The colony showed a work frequency related division of labour. Reproductive animals performed little work, 3±4% of the total work. The non-reproductive caste was divided into two groups based on the amount of burrow maintenance activity: those performing between 7±11% of total work and those ranging from 15±22% of total work. Male members of the colony tended to perform more work than the females. The dominance hierarchy of the colony was found to be nearly linear, with a value of 0.83 calculated from Landau's linearity index. The reproductive animals were the most dominant in their respective gender. Dominance was not age-related. However, non-reproductive males tended to be more dominant than non-reproductive females. Social organization within the giant Zambian mole-rat is compared with other southern African Cryptomys species in the light of the eusociality continuum.

Vocalizations of the giant mole-rat (Fukomys mechowii), a subterranean rodent with the richest vocal repertoire

“…Contact calls of the giant mole-rat include many sequences with nonlinear phenomena like sub-harmonics, deterministic chaos and bifurcation ( Figure 5(c),(d)) which, along with the differences in fundamental frequency, are essential cues for individual recognition (Fitch et al 2002). Individual recognition can be relevant in social species with high level of intraspecific interactions, as in the giant mole-rats (Burda and Kawalika 1993;Wallace and Bennett 1998).…”

A review of the evolutionary causes of rodent group-living

“…More direct support of the aridity food-distribution hypothesis comes from the observation that social but not solitary bathyergids tend to occur in xeric habitats , Faulkes et al 1997, and that group size of mole-rat species increases with unpredictability of rainfall and with the size and patchiness of their food supply Knight-Eloff 1988, Faulkes et al 1997). Nonetheless, the aridity food-distribution hypothesis is not supported by the observation that social mole-rats also occur in mesic areas of Africa (Wallace andBennett 1998, Burda et al 2000).…”

Variability of space-use patterns in a free living eusocial rodent, Ansell’s mole-rat indicates age-based rather than caste polyethism

“…Some studies have also revealed differences between males and females, but their results are ambiguous. For example, in F. mechowii the most active non-breeders were males in the study of Wallace and Bennett 12, but females in the study of Dammann et al 19…”

“…In these genera true morphologically distinct castes have not yet been found, although larger body size and prolonged lumbar vertebrae in naked mole-rat queens45 and larger fat reserves in the so-called dispersive morph of the same species6 are sometimes interpreted in this way (but see7 for a criticism). However, many studies define castes in mole-rats on the basis of the amount of work performed or locomotory activity levels (e.g 89101112…”