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.

The effects of age and previous experience on social rank in female red junglefowl, Gallus gallus spadiceus

“…Unlike the studies conducted with Damaraland mole-rats, Cryptomys damarensis (Gaylard et al 1998), Highland ponies and cows (Clutton-Brock et al 1976), boat-tailed grackles, Quiscallus major (Poston 1997) or even the domestic chicken, (Masure & Allee 1934), we did not find a correlation between the age of the individual and the social rank attained in red junglefowl females. Our results do agree with Collias (1943;domestic chicken) and Wallace & Bennett (1998;Zambian mole-rats, C. mechowi), who found that age did not influence dominance status. Older birds did attain dominant ranks more often than the 1-year-olds ( Fig.…”

Extended Longevity of Reproductives Appears to be Common in Fukomys Mole-Rats (Rodentia, Bathyergidae)

“…To disentangle the potential effects of reproductive status and social rank on ageing, we excluded breeders from analysis and assigned each non-breeder to one of two groups: a) “dominant” individuals that attained maturity when no dominant siblings were present; and b) “subdominant” individuals that attained maturity when one or more dominant siblings were present. This allocation is possible because in F. mechowii families, relative rank of each individual depends mainly on body mass ( [11] and own unpublished data). Males become larger than females [10] , thus fully grown males >3 years usually dominate adult females irrespective of the female's age.…”

Evolution of African mole‐rat sociality: burrow architecture, rainfall and foraging in colonies of the cooperatively breeding Fukomys mechowii

“…There is reproductive division of labour, with breeding typically restricted to a single female and a number of male consorts (Bennett & Aguilar, 1995). In most cases, all other individuals are the offspring of the reproductive cohort (Wallace & Bennett, 1998).…”