Pacific pocket mice make burrows in their habitat’s substrate. In these burrows they rest, store caches, and raise young. Being nocturnal means also needing a place to retreat into darkness during the day. Therefore, digging a burrow is an invaluable trait to have for survival.
Our pocket mice are provided with artificial burrows that allow us to check on each individual to monitor their health and reproductive status. However, these burrows take away from each individual needing to use his or her skills to create their own, but they still put personal touches to each artificial burrow. They do this by using nesting material to create a comfortable nest and by covering up the ends of burrow entrances with sand to eliminate light during the day.
Some are starting to completely cover their burrows with sand, while others build a separate dense nest out of nesting material and use their artificial burrows for seed caching.
To our surprise, one of the juveniles born last summer at our facility began developing a more elaborate burrow than the others. At first he made a dense nest from the nesting material, but then he began covering it with sand. Now it looks incredible!
His neighbor—a little girl—took his idea and started making her own like his, but then decided against it. She destroyed it and went back to using her artificial burrow.
The fact that even though there was no need for the male to create this burrow, he still had the resources available for him to do so, which lends credence to the appropriateness of the environment we are providing them and potentially the essential traits that are being maintained because of this environment.
Amaranta Kozuch is a senior research technician at the San Diego Zoo Institute for Conservation Research. Read her previous post, Let a Sleeping Pocket Mouse Sleep.