Architecture of Ctenomys mendocinus (Rodentia) burrows from two habitats differing in abundance and complexity of vegetation

Abstract

Architecture ofBurrow systems of the fossorial rodent Ctenomys mendocinus Philippi, 1869 were studied in the Andean Precordillera. These burrows were linear, with laterals and branches forked off the main tunnel. Their size and architecture did not differ between sexes. Burrows showed a constant heading along the main tunnel, with a mean directional angle close to 0°. Most forks of the main tunnel were originated more than expected at plants, indicating a change of search pattern where plants were encountered. This behaviour suggests a tactic consistent with area-restricted search. These systems were compared with others of the same species located in a habitat with higher cover and structural complexity of vegetation, at the Mendoza Piedmont. Female burrows were larger and male burrows more bifurcated in the Precordillera. These burrows were more complex than those from the Piedmont, owing to the presence of secondary tunnels. The mean directional angle close to 0°, orthogonal branches and angles of ascent of laterals close to 40° were attributes shared by the systems of both habitats. C. mendocinus maintains a basic search pattern as an optimal forager, and increases the systems size and complexity probably as an adaptive strategy to optimize the foraging efficiency and minimize the predation risk.

Silvery mole-rats (Heliophobius argenteocinereus, Bathyergidae) change their burrow architecture seasonally

“…Thus it was reported that males trying to encompass more female territories have longer burrows (Reichman et al 1982;Davies and Jarvis 1986;Rosi et al 1996). However, even strong sexual dimorphism may not be reflected in the length and architecture of burrow systems in solitary subterranean rodents (Rosi et al 2000). Higher branching of systems was found at higher population densities (Reichman et al 1982;Cameron et al 1988).…”

“…The architecture (linear versus reticular pattern) of burrow systems was related primarily to density and distribution of food supply (Jarvis and Sale 1971;Reichman et al 1982;Heth 1989;Rosi et al 2000;Spinks et al 2000; but see Cameron et al 1988;Andersen 1988). Recently, Le Comber et al (2002) have correlated the higher fractal dimension (= higher rate of reticulation) of burrow systems among bathyergids with sociality and also with life in a mesic habitat, where a greater food supply is expected.…”

“…A higher rate of soil deposition into older and abandoned tunnels at the peak of the dry season may reflect avoidance of temperature stress and/or higher energetic costs connected with pushing hard soil into mounds (see Vleck 1979Vleck , 1981. The total burrow system length was inversely related to food supply (Jarvis and Sale 1971;Reichman et al 1982;Heth 1989;Rosi et al 2000;Spinks et al 2000), or correlated with duration of occupancy (Brown and Hickman 1973) or energetic requirements of solitary inhabitants (Heth 1989). In our sample, body mass of occupants was the best predictor of the burrow length in most animals.…”

“…Parameters of burrow systems are also affected by environmental factors, particularly availability and distribution of food, soil characteristics, and climate (reviewed in Hickman 1990;Nevo 1999;Bennett and Faulkes 2000). The burrow system is not a rigid and stable entity, but a dynamic structure that is continuously reworked, with new tunnels being opened and previously exploited areas being backfilled (Hickman 1977;Davies and Jarvis 1986;Zuri and Terkel 1996;Jarvis et al 1998;Rosi at al. 2000;Spinks et al 2000).…”

Reactions to disturbances in the context of antipredatory behaviour in a solitary subterranean rodent

“…This fact is often used when attempting to trap these animals (Jarvis 1991;Zuri and Terkel 1996). They often store excavated soil belowground, in older burrows, reducing the aboveground advertisement of their presence and the predation risk associated directly with mound construction (Sparks and Andersen 1988;Rosi et al 2000). Further antipredatory behaviours were described by Jarvis and Sale (1971) in the silvery mole-rat (Heliophobius argenteocinereus) and in the East African mole rat (Tachyoryctes splendens): During excavation of their burrow systems, they retreated into deep tunnels and plugged their entrances thoroughly with soil, thus walling themselves off physically from a danger and confusing the ''predator''.…”