Impact of thermal convection on air circulation in a mammalian burrow under arid conditions

Microclimates in mammal burrows depend on a critical balance between production, consumption and ventilation. This study investigates one, potentially dominant, advective ventilation mechanism: thermal convective venting (TCV). Temperature profiles were monitored continuously inside artificial mammalian burrows that were dug in the central Negev Desert of Israel, representing a typical arid environment. Using a heat transfer numerical model, it was found that heat transfer by TCV occurs regularly during nights and early mornings, driven by a thermal gradient between the burrow's soil and the atmosphere. The venting properties of TCV were tested using tracer visualization experiments in a climate-controlled laboratory under controlled conditions mimicking field thermal gradients. An inclined burrow produced convective venting rates two orders of magnitude higher than the calculated CO ₂ production rate of Sundevall's jird (Meriones crassus, the case-study mammal); i.e., TCV can support the mammal's respiratory needs, even when neglecting other potential venting mechanisms like diffusion and wind-driven venting. Our calculations suggest that TCV can also support the respiration needs of larger mammals since venting by TCV increases as the burrow radius increases.