The burrow system of the African ice rat Otomys sloggetti robertsi

Abstract

We studied the architecture of the burrow system of the African ice rat Otomys sloggetti robertsi, a non-hibernating, diurnal murid rodent endemic to the sub-alpine and alpine regions of the southern African Drakensberg and Maluti mountains. In our study site we found ice rat burrows in two substrates (organic and mineral soils). The structure of the burrow system was similar in both soil types, comprising several interlinking tunnels, numerous burrow entrances and 1-2 nest chambers. However, the surface area of the burrow systems in organic soils was larger, the tunnels were deeper, and some of the systems contained two levels, all of which was contrary to our assumption that digging would be more difficult in the compact organic soils. Ice rats occur in colonies of up to 17 individuals, and the collected efforts of several individuals are required for constructing complex burrow systems. The burrow structure is similar to those of two arid-adapted relatives, Parotomys brantsii and Parotomys littledalei, suggesting that the burrow architecture among these three taxa may reflect the similar functions of burrows in extreme environments. For ice rats, burrows could provide a suitable microhabitat in which to escape adverse environmental conditions, particularly during winter. Moreover, ice rat burrows contained far fewer nest chambers than those of both Parotomys species, indicating that members in a colony share nest chambers, thereby facilitating huddling. Finally, the extensive interlinking tunnels may provide underground routes to aboveground feeding sites, thereby reducing exposure to adverse conditions.

Reproduction and ontogeny of Mastacomys fuscus (Rodentia: Muridae) in the Australian Alps and comparisons with other small mammals living in alpine communities

“…All three species of rodents from other alpine regions show that different strategies in alpine and subalpine regions are possible; however, there is no long-term information on inter-annual variation in production, nor on inter-annual changes in demography. Of these three species, O. sloggetti robertsi shows remarkable similarity to M. fuscus in many aspects of its biology, including size, diet, morphology, reproductive characteristics, and R e (Hinze 2005;Schwaibold and Pillay 2006;Willan 1990). However, unlike M. fuscus, it appears to be capable of 3-4 litters/year.…”

“…However, unlike M. fuscus, it appears to be capable of 3-4 litters/year. Also, unlike M. fuscus, O. sloggetti robertsi has a communal social behaviour (Hinze 2005;Schwaibold and Pillay 2006), a characteristic that may contribute to its higher reproductive capacity. However, compared with this study, none of these studies on other continents consider the inter-specific differences within communities.…”

Behavioural correlates of group size and group persistence in the African ice rat Otomys sloggetti robertsi

“…Ice rats have small litters with a short inter-litter interval (38-300 49 days, Willan 1990). Juveniles were always closely associated (physically and spatially) 301 with the mother (which was marked), including many instances of nipple-clinging even after 302 weaning (Hinze 2005). Adult ice rats never overlap spatially aboveground in a colony, so we 303 could accurately determine the number offspring per female.…”

“…were present above-ground, which would have represented the last litters born in the austral 297 summer in February and March (Hinze 2005). Like the number of adults, the maximum 298 number of juveniles observed during 3-5 days was considered to be the total number of 299 juveniles present in that colony.…”

Spatial dichotomy of sociality in the African ice rat

“…obs.). Colony members (kinship unknown) collectively construct an intricate interlinking tunnel system 280–357 mm belowground, consisting of ≥25 entrance holes and one to two nesting chambers, providing refuge at night and during adverse weather (Hinze, Pillay & Grab, ). Ice rats are vulnerable to thermoregulatory stress due to their high surface area to volume ratio, which creates greater heat exchange with the environment (McNab, ).…”