Windsor, Z. 2021. Refinements in head plate mouse nesting: Using composite nests to enhance welfare. Animal Technology and Welfare 20(2), 135-141.

When given the opportunity, mice will choose to build nests using multiple different materials. Studies indicate that providing mice with choices which mimic the natural environment allows laboratory mice to build the best quality nests and mice have also been shown to go to considerable effort to gather and combine multiple nesting materials to construct a nest. These types of nests are referred to as composite nests and are typically higher quality nests than those built of only one material. Special consideration must be given to head plate mice which invariably face restrictions on enrichment items such as nesting material, as long and fibrous products are liable to become tangled around the head implant device and cause entrapment and injury. Only materials made up of short fibres are recommended for head plate mice. It has been demonstrated that single short fibre materials can be used to construct high quality nests by head plate mice, however it is not known whether a combination of short fibre materials can be used to construct a higher quality nests than one single short fibre materials. I hypothesize that the simple addition of a second nesting material will allow for the construction of a higher quality composite nest which will have the potential to refine basic husbandry and enhance head plate mouse welfare in the laboratory. This study used Fifteen singly housed C57BL/6J mice (3M; 12F). The three test groups were: Pure Comfort White (PCW, n=5), Nestlets (Control) (n=5) and Composite (a combination of both PCW and Nestlets) (n=5). No tangling was observed in any of the groups, therefore Nestlets, Pure Comfort White and a combination of both (Composite) are all safe for use with head plate mice. The Pure Comfort White group produced the second highest and most stable scores throughout the trial. This is consistent with previous findings. The Nestlet group produced more variable, lower scores which did not improve significantly over time as the trial went on. Mice in the Composite group produced the highest scoring nests of the three groups. The quality of these nests remained consistent on an individual basis throughout the trial. The most structurally sound nests were recorded in this group. Head plate mice are able to safely construct higher quality nests when given both a Nestlet and Pure Comfort White in conjunction with each other. The provision of more than one nesting material fulfils the mouse’s biological motivation to create composite nests and serves as an enhancement to welfare.