Field Evidence for Colony Size and Aseasonality of Breeding and in Ansell's Mole-Rat,Fukomys anselli(Rodentia: Bathyergidae)

Abstract

Ansell's mole-rat, Fukomys anselli, is a cooperatively breeding bathyergid endemic to the Lusaka Province of Zambia. During a 12-month field study involving the capture of 33 colonies of mole-rats, the number of occupants, breeding females and sex ratio within colonies were recorded. While thirty of these social groups contained a single breeding queen, three were found to exhibit plural breeding among females, having two queens present simultaneously. Mean ± S.E.M. colony size was 8.7 ± 2.2 (range 6-16, n = 33). The occurrence of plural breeding and small group size is consistent with the predictions of the aridity food distribution hypothesis for social species inhabiting mesic habitats. The sex ratio of the population was skewed towards females at 1.2:1. The mean mass of adult males was 63.0 ± 18.3 g (range 36.7-110.3, n = 87) while that for adult females was 52.9 ± 11.8 g (range 35.1-77.8, n = 86). Pregnant and lactating females were found throughout the study period from February 2009 to February 2010, indicating an aseasonal pattern of breeding in this species. Autopsy of individuals (n = 288) from the 33 colonies revealed a total of 19 pregnant females. Nine of these were in the latter stages of pregnancy and mean litter size was determined as 2.7 pups (range 1-4). Collectively, these new data reveal that Fukomys anselli share many similarities in life history and reproductive traits with the phylogentically closely related giant Zambian mole-rat, Fukomys mechowii.

A maze-lover's dream: Burrow architecture, natural history and habitat characteristics of Ansell's mole-rat (Fukomys anselli)

“…Similarly, not even one case of plural breeding (two or more breeding females per group) was found, which contradicts with Sichilima et al (2011). The absence of any breeding animal in an isolated burrow system, as in H, indicates that the group might be formed by dispersers (in this case, they were probably sisters) who have not yet encountered a mate.…”

“…In the recent study of Sichilima et al (2011) males were also larger (up to 110 g) but the females were slightly smaller (up to 78 g). Our data shows that the largest individuals are usually breeding males followed by breeding females, but the difference in body mass of a breeding pair and the rest of the group was not always conspicuous and exceptions occurred.…”

“…The examined population of the Ansell's mole rat had a mean group size of 9.7 individuals (and maximum of 13). This is only slightly more that the value by Sichilima et al (2011), which was computed without exclusion of incomplete family groups (mean 8.7; range 6-16). Similarly, a mean group size of around ten is reported for F. mechowii (Scharff et al, 2001;Sichilima et al, 2008b;Šumbera et al, 2012).…”

Plasticity and constraints on social evolution in African mole-rats: ultimate and proximate factors

“…In some species this appears to be in response to a reduction in seasonality at lower latitudes in habitats where rainfall is relatively high (e.g. F. mechowii and F. anselli) [20,77]. Comparative phylogenetic analysis has revealed a positive correlation between seasonality in breeding and induced ovulation.…”

Reproduction in the East African root rat (Tachyoryctes splendens; Rodentia: Spalacidae) from Tanzania: the importance of rainfall

“…All solitary southern African species of bathyergid mole rats are seasonal breeders with their reproduction acutely tied to rainfall Herbst et al, 2004;Sandwyk & Bennett, 2005;Hart et al, 2006). In marked contrast, the majority of social bathyergids reproduce throughout the year Sichilima, Faulkes & Bennett, 2008;Sichilima, Bennett & Faulkes, 2011). Two social species, one from a winter rainfall region, the common mole rat Cryptomys hottentotus hottentotus (Spinks, Van der Horst & Bennett, 1997;Spinks, Bennett & Jarvis, 1999) and one from a summer rainfall region, the highveld mole rat Cryptomys hottentotus pretoriae (van Rensburg et al, 2002) are unusual in exhibiting seasonal reproduction, with the former also occurring sympatrically with solitary species (Bathyergus; Bennett & Faulkes, 2000).…”