Sweeping the house clean : burrow architecture and seasonal digging activity in the East African root rat from Tanzania

We investigated changes in burrow architecture and fractal dimension across seasons and between the sexes in the solitary East African root rat Tachyoryctes splendens over an entire calendar year. The basic burrow system comprised a main tunnel reticulating into foraging tunnels, a nest consisting of food store chamber, latrine and sleeping area, and a bolt hole. Main tunnel length was strongly affected by sex, and contrary to expectations, it was longer for females than for males (during both the dry and the wet seasons). The number and the length of foraging tunnels were affected by both sex and season, with females’ burrows having more foraging tunnels than males in both the dry and the wet seasons. Females also had burrows with higher fractal dimension than males, while fractal dimension increased with burrow length for both sexes. We suggest that unlike the solitary bathyergid mole-rats, male T. splendens do not construct larger burrows than females in the search for mates, but rather females have larger burrows with more foraging tunnels resulting from the increased need for provisioning of their young.University of Dar es Salaam (UDSM) World Bank Fund (C1B1 of the University of Dar as Salaam, Tanzania. NCB acknowledges funding from the South African DST/NRF SARChI Chair for Mammal Behavioural Ecology and Physiology,University of Pretoria.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1469-79982015-08-31hb201

Burrow fractal dimension and foraging success in subterranean rodents: a simulation

For animals that forage underground, the success with which food items are located may be closely related to burrow architecture. Fractal dimension, which describes how a burrow explores the surrounding area in a way that is independent of burrow length, is an obvious choice for a single metric describing burrow shape. Although it is often assumed that burrows of high fractal dimension will be associated with greater foraging success, this has not previously been demonstrated. In this study, we use computer simulations to study the success with which burrows of different fractal dimensions locate randomly distributed food items. In addition, we examine the effect of different patterns of food distribution (in particular the patchiness with which food items are distributed) and consider how using different criteria for locating food items affects the relationship between fractal dimension and foraging success. We conclude that, under a wide range of plausible assumptions about the ways in which subterranean rodents forage, burrows of high fractal dimension are more successful at locating food items than burrows of lower fractal dimension. Copyright 2006.burrow architecture; computer model; food distribution; food patchiness; shape

Cladogenesis and endemism in Tanzanian mole-rats, genus Fukomys: (Rodentia: Bathyergidae): a role for tectonics?

Biological Journal of the Linnean Society, 2010; 100: 337–352.African mole-rats of the family Bathyergidae are subterranean hystricomorph rodents found throughout sub- Saharan Africa, where the distributional ranges of the most speciose taxa are divided by the African Rift Valley. In particular, mole-rats of the genera Heliophobius and Fukomys are distributed widely, and their adaptive radiation appears to have been strongly influenced by the geological process of rifting. As a result, virtually all members of the genus Fukomys occur in locations west of the Rift Valley. However, a small number of isolated populations occur east of the Rift Valley in Tanzania, where Heliophobius is widespread and is the predominant bathyergid rodent. Phylogenetic analysis of mitochondrial cytochrome b sequences of previously unstudied Tanzanian mole-rats (genus Fukomys) and geographically adjacent populations strongly suggests that vicariance in the Western Rift Valley has subdivided populations of mole-rats and, together with climatic changes, played a role in the isolation of extralimital populations of Fukomys in Tanzania. Together with molecular clock-based estimates of divergence times, these results offer strong support for the hypothesis that the observed patterns of cladogenesis are consistent with tectonic activity in the ‘Mbeya triple junction’ and Rungwe volcanic province between Lakes Rukwa and Nyasa

Cladogenesis and endemism in Tanzanian mole-rats, genus Fukomys: (Rodentia: Bathyergidae): a role for tectonics?

Biological Journal of the Linnean Society, 2010; 100: 337–352.African mole-rats of the family Bathyergidae are subterranean hystricomorph rodents found throughout sub- Saharan Africa, where the distributional ranges of the most speciose taxa are divided by the African Rift Valley. In particular, mole-rats of the genera Heliophobius and Fukomys are distributed widely, and their adaptive radiation appears to have been strongly influenced by the geological process of rifting. As a result, virtually all members of the genus Fukomys occur in locations west of the Rift Valley. However, a small number of isolated populations occur east of the Rift Valley in Tanzania, where Heliophobius is widespread and is the predominant bathyergid rodent. Phylogenetic analysis of mitochondrial cytochrome b sequences of previously unstudied Tanzanian mole-rats (genus Fukomys) and geographically adjacent populations strongly suggests that vicariance in the Western Rift Valley has subdivided populations of mole-rats and, together with climatic changes, played a role in the isolation of extralimital populations of Fukomys in Tanzania. Together with molecular clock-based estimates of divergence times, these results offer strong support for the hypothesis that the observed patterns of cladogenesis are consistent with tectonic activity in the ‘Mbeya triple junction’ and Rungwe volcanic province between Lakes Rukwa and Nyasa

Burrow architecture and digging activity in the Cape dune mole rat

While females are traditionally thought to invest more time and energy into parentalcare than males, males often invest more resources into searching and displaying formates, obtaining mates and in male–male conflict. Solitary subterranean mammalsperform these activities in a particularly challenging niche, necessitating energeticallyexpensive burrowing to both search for mates and forage for food. This restrictionpresumably affects males more than females as the former are thought to dig longertunnels that cover greater distances to search for females. We excavated burrowsystems of male and female Cape dune mole rats Bathyergus suillus the, largest trulysubterranean mammal, to investigate whether male burrows differ from those offemales in ways that reflectmate searching bymales. We consider burrow architecture(length, internal dimensions, fractal dimension of tunnel systems, number of nestingchambers and mole mounds on the surface) in relation to mating strategy. Malesexcavated significantly longer burrow systems with higher fractal dimensions andlarger burrow areas than females.Male burrow systems were also significantly fartherfrom one another than females were from other females’ burrow systems. However,no sex differences were evident in tunnel cross-sectional area, mass of soil excavatedper mound, number of mounds produced per unit burrow length or mass of soilexcavated per burrow system. Hence, while males may use their habitat differentlyfrom females, they do not appear to differ in the dimensions of the tunnels they create.Thus, exploration and use of the habitat differs between the sexes, which may be aconsequence of sex differences in mating behaviour and greater demands for food

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