The burrow structure, colony composition and reproductive biology of the giant mole-rat (Fukomys mechowii) Peters 1881 from the Copperbelt of Zambia

African mole-rats (Bathyergidae) are subterranean hystricomorph rodents offering an excellent system with which to test theories relating to the evolution and maintenance of sociality in mammals. The aridity food distribution hypothesis (AFDH) suggests that, within the bathyergids, sociality has evolved in response to patterns of rainfall, its effects on food distribution, and the subsequent costs and risks of foraging and dispersal. Here, in the first detailed study of burrow architecture in a social mole-rat species, with data from 32 burrows, we show that in the giant mole-rat Fukomys mechowii, burrow fractal dimension increases with colony size and is higher during the rainy season than during the dry season. The mass of food in the burrow increases with fractal dimension and is higher during the rainy season than during the dry season. These results link for the first time colony size, burrow architecture, rainfall and foraging success and provide support for two assumptions of the AFDH, namely that (1) in arid conditions burrowing may be severely constrained by the high costs of digging; and (2) the potential risks of failing to locate food may be mitigated by increases in colony size. It was also fundamental in this study to assess whether the Fukomys mechowii is (1) An aseasonal or seasonal breeder (2) To investigate whether non-reproductive female giant mole-rats exhibit induced or spontaneous ovulation and finally (3) To estimate the age variation and sexual dimorphism of this little studied giant mole-rat species. Thus in a field study that involved the complete excavation of 32 burrow systems with a mean colony size of 9.9 individuals (range 7-16), it was evident that Fukomys mechowii is a cooperatively breeding mole-rat exhibiting a reproductive division of labour in which usually one, or occasionally two, females are responsible for procreation. Pregnant reproductive females were found throughout the study period (September 2005 until June 2006), supporting preliminary evidence that reproduction occurs throughout the year. Of the 32 colonies sampled, 14 of 18 (87.5%) in which the reproductive female could be identified as pregnant contained a single reproductive female, while four (12.5%) had two females breeding simultaneously (plural breeding). The population sex ratio was skewed towards females at 1:1.46. Autopsy of pregnant reproductive females (n=18) revealed that the production of two (10/18 pregnancies) or three (7/18) offspring was the norm, with one case of four embryos being present. These new data increase our fragmentary knowledge of the natural history of this little studied species. Six non-reproductive females were removed from their natal colonies and housed individually without a male for a period of 12 weeks as a control group. They were then subsequently housed for a further 6 weeks as experiment 1, on their own before being allowed non-physical contact in experiment 2, with a mature adult male for a further 6 weeks. The non-reproductive females were given a further period of isolation for a month prior to being physically paired with vasectomized males, in experiment 3. Urine was collected every second day for all three experiments and urinary progesterone profiles were generated. The progesterone values measured during the first part of Experiment 2 and 3 were markedly higher than those measured during the first part of Experiment 1 (Z= -2.201, p=0.028 for both comparisons), however, this was not significant after Bonferroni correction. Similarly progesterone values tended to be elevated during the second phase of Experiment 2 and 3 but not significantly so (Experiment 1 vs. 2: Z=-1.782, p=0.075, Experiment 1 vs. 3: Z=-2.201, p=0.028). Thus, chemical or physical stimulation by a male does not appear to be necessary for ovulation in female giant mole-rats. The giant mole-rat is a spontaneous ovulator. Due to difficulties in estimating absolute age in mammals, different methods for its estimation have been proposed, and among these, the degree of molar eruption and wear are considered to be one of the most reliable indicators of relative age. Consequently, maxillary molar tooth-row eruption and wear were used to assign individuals of the giant mole-rat, Fukomys mechowii (Peters, 1881) from two geographically proximal and ecologically similar localities in the Copper-belt Province of Zambia to 9 relative age classes. These were in turn used to assess the nature and extent of sexual dimorphism and age variation in this little-studied social mole-rat based on cranial morphometric data, reference to body mass and a series of both univariate and multivariate statistical analyses. Both univariate and multivariate analyses showed morphological differences between individuals of age classes 1–3 and those of age classes 5–9, while individuals of age class 4 were intermediate between these age class groupings, suggesting that this age class lies at a point on a hypothetical growth curve where it begins to stabilize. The analysis of the nature and extent of sexual dimorphism revealed its absence in the younger individuals of age classes 1–4 and its presence in older age classes 5–9. These results may allow an insight into our understanding of the population social structure, and reproductive strategies in the giant mole-rat. In conclusion, it is worth mentioning that; (1) A number of studies have examined burrow architecture, although not necessarily fractal dimensions in the Bathyergidae but the majority of these have concentrated on solitary species in which when there is plural occupancy it is during the breeding season or when the mother has a litter. This study is thus the first to examine in detail the dynamic nature of social mole-rat burrows, with respect to seasonal changes. The burrow fractal dimension is a good indication of the mole-rats ability to burrow to find food and thus results support the critical assumption which underlies the aridity food distribution hypothesis. The results accord well with previous data in social mole-rats indicating that larger colonies have greater survival and link colony size, burrow architecture and foraging success for the first time; (2) the giant mole-rat is an aseasonal breeder which in a few instances can have two queens per colony; (3) the giant mole-rat is a spontaneous ovulator and finally (4) the giant mole-rat Fukomys mechowii exhibits a sexual dimorphism amongst its older age classes 5-9. Suggesting that there are different growth curves in males versus females, whereby males attain much larger size (skull size and body mass) than females after puberty and finally intimating that opportunistic mating competition among males is very high.Thesis (PhD)--University of Pretoria, 2011.Zoology and EntomologyUnrestricte

Field evidence for colony size and aseasonality of breeding and in Ansell’s mole-rat, Fukomys anselli (Rodentia: Bathyergidae)

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 Department of Science and Technology and National Research Foundation SARChI Chair in Mammal Behavioural Ecology and Physiology to NCB. AMS was the recipient of a postdoctoral fellowship from the SARChI chair.http://www.bioone.org/loi/afzoab201

Patterns of habitat selection and use by Macaca mulatta tcheliensis in winter and early spring in temperate forest, Jiyuan, China

The chosen habitat of any animal species comprises a range of environmental features that provide adequate resources for its continuous survival. Consequently, the criteria of habitat selection by animals, combines a wider spectrum of both environmental and extrinsic factors, with major prerequisites based on food resources, availability of shelter and suitable ethics for procreation. From this study, conducted in winter and early spring, at Mt. Wangwushan area, located on N 35°05′-35°15′, E 112°12′-112°22′, in Taihangshan Macaque National Nature Reserve (TMNNR), Jiyuan, Henan Province, we show by elaborative results that Macaca mulatta tcheliensis was specifically associated with the following habitat characteristics: 1) the average tree DBH (diameter at breast height) with over 15 cm; 2) the distance from human disturbance of less than 2000 m; 3) the distance to water with less than 1000 m; 4) the gradient of mountain slope of 15°~40°; 5) which was markedly tarrying with the altitude ranges from 1000 m to 1300 m; and 6) where the canopy coverage was less than 60%. In addition, during this study, rhesus macaque mostly inhabited the sunny slopes of mountains than the shady areas. Results of the first five principal components analysis (PCA) accounted for the total variance of 68.88%, while the other factors showed insignificant effects on habitat selection by rhesus macaque in the temperate forest. In conclusion, these new results increase our understanding on the living status, under the harshest condition, in winter and early spring of Macaca mulatta tcheliensis, the sub-species of rhesus macaques as may be linked to its habitat selection and utilization, in the temperate forest.National Natural Science Foundation of China (No. 30770381 and 30970378).http://www.springer.com/life+sciences/journal/11756ab201

Field evidence for aseasonality of reproduction and colony size in the Afrotropical giant mole-rat Fukomys mechowii (Rodentia: Bathyergidae)

The giant mole-rat, Fukomys mechowii is a cooperatively breeding subterranean mole-rat exhibiting a reproductive division of labour in which usually one, or occasionally two, females are responsible for procreation. In a field study that involved complete excavation of 32 burrow systems, mean colony size was 9.9 individuals (range 7-16). Pregnant reproductive females were found throughout the study period (September 2005 until June 2006), supporting preliminary evidence that reproduction occurs throughout the year. Of the 32 colonies sampled, 10 of 14 in which the reproductive female could be identified as pregnant contained a single reproductive female, while four had two females breeding simultaneously (plural breeding). The population sex ratio was skewed towards females at 1:1.46. Autopsy of pregnant reproductive females (n = 18) revealed that the production of two (10 / 18 pregnancies) or three (7 / 18) offspring was the norm, with one case of four embryos being present. These new data increase our fragmentary knowledge of the natural history of this little-studied species

Circadian rhythms of locomotor activity in Ansell's mole-rat : are mole-rat's clocks ticking?

Circadian rhythms of locomotor activity have been investigated in several African mole-rat species. Even though mole-rats spend most of their lives in underground burrows devoid of light, studies have shown that they do possess circadian rhythms to some extent. We investigated the circadian rhythms of locomotor activity in 11 male Ansell's mole-rats Fukomys anselli from Zambia. In order to determine whether these animals can entrain to light and have endogenous rhythms, they were subjected to different light regimes: first, 12 h light/12 h dark, followed by constant darkness, then returned to 12 h light/12 h dark, which was later inversed to 12 h dark/12 h light. Only two individuals displayed arrhythmic activity patterns whereas the other nine (81.8%) exhibited entrainment of their activity to the light regimes. Locomotory activity of Ansell's mole-rat was predominantly during the dark phase in all light regimes. During constant darkness (DD), only five individuals (45.5%) displayed very weak circadian rhythms that free ran but became more indistinct towards the end of the cycle. Under the second LD light cycle, 90.1% of the animals were active during the night phase of the cycle and when placed under an inverse light cycle, seven individuals still displayed activity predominantly during the dark phase. In conclusion, these results suggest that Ansell's mole-rat does have a weak circadian clock and is able to perceive light and entrain to light cycles

Ontogenetic variation and craniometric sexual dimorphism in the social giant mole-rat, Fukomys mechowii (Rodentia: Bathyergidae), from Zambia

The degree of maxillary molar tooth-row eruption and wear were used to assign samples of the social giant mole-rat, Fukomys mechowii, from Zambia, into nine relative age classes in order to assess ontogenetic (age) variation and craniometric sexual dimorphism, with reference to body mass. Univariate and multivariate statistical analyses showed craniometric differences between age classes 1–3 and age classes 5–9, with age class 4 being intermediate between these two age class groupings. This suggests that age class 4 lies at a point on a hypothetical growth curve where growth begins to stabilize. The intermediate placement of age class 4 in multivariate space broadly coincided with body mass categorizations into juveniles (age classes 1–3; <100 g), subadults (age class 4; c. 100–150 g), and adults (age classes 5–9; >150 g). The analyses also revealed the absence of sexual dimorphism in the relatively younger age classes 1–4 but its presence in the relatively older age classes 5–9, and these results are supported by data on body mass. These results may have implications in our understanding of the population and social structures, and reproductive strategies in this little-studied giant mole-rat

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

African mole rats (Bathyergidae) offer an excellent system with which to test theories relating to the evolution and maintenance of sociality in mammals. The aridity food distribution hypothesis (AFDH) suggests that, within the bathyergids, sociality has evolved in response to patterns of rainfall, its effects on food distribution, and the subsequent costs and risks of foraging and dispersal. Here, in the first detailed study of burrow architecture in a social mole-rat species, with data from 32 burrows, we show that in the giant mole-rat Fukomys mechowii burrow fractal dimension increases with colony size and is higher during the rainy season than during the dry season. The mass of food in the burrow increases with fractal dimension and is higher during the rainy season than during the dry season. These results link for the first time colony size, burrow architecture, rainfall and foraging success and provide support for two assumptions of the AFDH, namely that (1) in arid conditions burrowing may be severely constrained by the high costs of digging; and (2) the potential risks of failing to locate food may be mitigated by increases in colony size

Socially induced infertility in Ansell's mole-rat : are there depressed hormone levels in non-reproductive males and females?

Ansell’s mole-rat, Fukomys anselli, is a social subterranean mammal and exhibits an extreme reproductive division of labour. Reproduction in the colony appears to be restricted usually to a single female. Complete colonies captured throughout an entire calendar year were euthanased and the histology of the gonads and plasma hormone concentrations were measured in reproductive and non-reproductive members of both sexes. In males, the circulating levels of testosterone were highest in the reproductive male. The mean testes mass for male corrected for body mass was lower than that of the non-reproductive male. However, the mean testes volume of reproductive males was greater than that for the non-reproductive males and the seminiferous tubule diameter was greater in reproductive males. Reproductive females characteristically possessed corpora lutea of ovulation and pregnancy in their ovaries and this was met with much elevated progesterone concentrations in these females. In contrast, non-reproductive females showed a complete range of follicular genesis, but they did not possess corpora lutea of ovulation or pregnancy, in turn they show depressed progesterone concentrations. The current available evidence suggests that in Ansell’s mole-rats, the non-reproductive males and females refrain from sexual activity by being subordinate and moreover related to the breeding pair.The research was funded by the SARCHI Chair of mammal behavioural ecology and physiology from the Department of Science and Technology and the National Research Foundation, South Africa (to N.C Bennett). We also acknowledge a bursary from the NRF (to P.R de Bruin).http://www3.interscience.wiley.com/journal/118535410/home-8369nf201