On the importance of shelter availability for reptiles provided by burrow‐digging ecosystem engineers: A systematic review and a case study

By altering habitat characteristics, ecosystem engineers influence coexisting species, which is often reflected in their population parameters. The magnitude and direction of these effects may depend on several factors, but identifying and understanding the underlying processes are necessary to develop and execute conservation measures aiming to protect endangered species or communities. In grasslands, often only ground burrows provide suitable shelter, hibernacula or microhabitat for the thermoregulation of poikilotherms. Here, we present the results of a systematic review of studies as well as a case study examining the effects of ground burrows on reptile populations. The case study presents a 5‐year long investigation on the relationship between ground burrow availability (used burrow density as a proxy, categorized by entrance size) and the population parameters (occupancy, colonization, extinction) of five reptile species ( Lacerta agilis , Lacerta viridis , Podarcis tauricus , Vipera ursinii , Coronella austriaca ) inhabiting grasslands of Central Hungary. The systematic review indicates that although reptiles widely use burrows created by ecosystem engineers in open habitats, their effects on occupancy and abundance are highly variable and context‐dependent, with predominantly positive, but also neutral and occasional negative outcomes, potentially influenced by environmental factors and publication bias. The case study found that ground burrow densities generally have negligible effects, although in some cases they negatively or positively influenced certain reptile population parameters. For V. ursinii , greater burrow‐size diversity reduced local extinction probability, while some burrows showed marginal effects. Wider, ground‐squirrel burrows negatively affected L. agilis , whereas L. viridis and C. austriaca showed no consistent responses. Our results imply that although ecosystem engineers might have significant impacts on regulating the population dynamics of reptiles through altering habitats, this cannot be generalized across ecosystems and taxa. Conservation strategies for reptiles would need to account for the intricacies underlying the interactions between ecosystem engineers and reptiles.