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Ancestor: Mus musculus interstellaris (Ship Mouse)

Descendants 2 Myh:
Snail-punching Mice 

Size: Around 10 cm minus the tail (about 15-16 cm with the tail)

Dietary Needs: Omnivorous generalist, though particularly inclined to forage in freshwater for newborn snails, fish spawn and crayfish larvae that have lost their parental protection. They may also nibble on freshwater colonial microalgae. Out of the water they are more insectivorous than their ancestors, but still partial to grains, fruits and seeds.

Life Cycle: Reproduction is seasonal. Females go into short oestrus cycles in the spring and early summer when they are able to smell male urine in the area, but they will postpone this cycle to preserve their longevity if there are no males for miles - a rare occurrence. Males leave a trail of urine everywhere they go during the breeding season, so that their presence in an area can be easily detected by a female. His ultrasonic chirps help her home in on where he is. Once mating is complete there is no further involvement from the male. females either make nests in dense ground vegetation like grass, moss and herbs. If this is absent she may dig a small burrow a few metres higher than the water and line it with moss and fur. The blind, helpless, naked babies grow their fur in within about a week, are weaned within 3-4 weeks and are gone from the nest within 1 and a half months. Females may have two or more litters on a good year. 

Other: While they are capable of living without access to freshwater, they prefer to have access to the water. While cats can swim in this part of the planet, they may choose not to waste energy and warmth on such small escaping prey, if they should dash into the cold water. This is also because the cat may lose sight of the mouse under the rippling and reflective water surface, and will have to locate the mouse again if it should continue the pursuit into the water. Because of this, the water is a place of relative safety for the mouse when they can smell cats around. But it's not completely safe. Their long whiskers can read a lot of information about the water currents and vibrations, and they have shorter sensitive whiskers all over their body. This can alert them to large approaching fish. But their aquatic nemesis is the adult crayfish, which often ambush these mice.