Burrow architecture and digging activity in the Cape dune mole rat

While females are traditionally thought to invest more time and energy into parental care than males, males often invest more resources into searching and displaying for mates, obtaining mates and in male-male conflict. Solitary subterranean mammals perform these activities in a particularly challenging niche, necessitating energetically expensive burrowing to both search for mates and forage for food. This restriction presumably affects males more than females as the former are thought to dig longer tunnels that cover greater distances to search for females. We excavated burrow systems of male and female Cape dune mole rats Bathyergus suillus the, largest truly subterranean mammal, to investigate whether male burrows differ from those of females in ways that reflect mate searching by males. We consider burrow architecture (length, internal dimensions, fractal dimension of tunnel systems, number of nesting chambers and mole mounds on the surface) in relation to mating strategy. Males excavated significantly longer burrow systems with higher fractal dimensions and larger burrow areas than females. Male burrow systems were also significantly farther from one another than females were from other females' burrow systems. However, no sex differences were evident in tunnel cross-sectional area, mass of soil excavated per mound, number of mounds produced per unit burrow length or mass of soil excavated per burrow system. Hence, while males may use their habitat differently from 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 a consequence of sex differences in mating behaviour and greater demands for food.

The cost-effectiveness of the SPHERE intervention for the secondary prevention of coronary heart disease

Objectives: The Secondary Prevention of Heart disEase in geneRal practicE (SPHERE) trial has recently reported. This study examines the cost-effectiveness of the SPHERE intervention in both healthcare systems on the island of Ireland. Methods: Incremental cost-effectiveness analysis. A probabilistic model was developed to combine within-trial and beyond-trial impacts of treatment to estimate the lifetime costs and benefits of two secondary prevention strategies: Intervention - tailored practice and patient care plans; and Control - standardized usual care. Results: The intervention strategy resulted in mean cost savings per patient of 512.77 (95 percent confidence interval [CI], 1086.46-91.98) and an increase in mean quality-adjusted life-years (QALYs) per patient of 0.0051 (95 percent CI, 0.0101-0.0200), when compared with the control strategy. The probability of the intervention being cost-effective was 94 percent if decision makers are willing to pay €45,000 per additional QALY. Conclusions: Decision makers in both settings must determine whether the level of evidence presented is sufficient to justify the adoption of the SPHERE intervention in clinical practice. Copyright © Cambridge University Press 2010.