Effects of geographical location and size on the functional properties of harvest mouse Micromys minutus nests in Great Britain

Abstract

Nest construction is a feature of a range of taxa, yet the functional properties of nests are poorly understood. Avian nests offer thermal insulation, structural support and protection from rain, but to date there are few studies that have explored these functions for mammal nests. Here nests constructed by harvest mice (Micromys minutus) were studied ex situ to determine the thermal insulation provided by the nest wall and the degree to which simulated rainfall was absorbed. Nests were collected from across Great Britain and analysis explored whether nest size and geographical location affected insulation or rainproofing. Nests were constructed from grass leaves woven into an outer wall that surrounded smaller pieces of grass that filled the interior of the nest. Nest mass was positively related to thermal insulation but unrelated to geographical location. By contrast, nest mass was positively related to the amount of water nest absorbed after simulated rain but volume and longitude were inversely related to the time it took the nest to dry out. In many ways, harvest mice nests had similar functional properties to those of small songbirds, i.e., to provide thermal insulation and rainproofing. This study was the first to explore the environmental protection potentially offered to harvest mice by their nests. The study has highlighted our poor understanding of the factors that determine the function of mammal nests. There is scope for more research into the functional properties, e.g., thermal insulation or rainproofing, of a wide variety of mammal nests.