9. How many mice are on the South Farallon Islands?

The invasive house mouse population fluctuates seasonally and annually, but a recent sample of mouse density on Southeast Farallon Island suggests a density of up to 1,270 mice per acre at certain times of the year. The population of mice on the Farallon Islands can reach plague levels and is among the highest mouse densities reported on any island worldwide. The density is such that, according to researchers on the island, the ground appears to “move” with mice.

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