If you filter any list then navigate to another page, then return to the first list, the filter parameters that you had previously applied will be maintained. We refer to this as Sticky Filters.
The reason for this is because the filters are quite comprehensive! So imagine if you apply a complex filter to your Mouse List (like filter for all males, of a certain mouseline of a certain genotype, of a certain age, etc.), then if you navigate to another list to enter a new mating record for example and then return to the Mouse List to deal with your filtered males, you wouldn't want the filter to reset or else you would have to apply it all over again!
So we made the filters "stick" so that no matter where you go, your filters will be maintained to the last filtered state. And you simply need to click "Reset Filter" in order to restore the default and view all records.