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Ancestor: Dash Mouse
Temporal Range:
Temporal Range:
Evolved: By 2 Myh
Extinct: Not yet
Geographical Range:
Geographical Range:
Location: East Catland continent in the South West in river, wetland and other freshwater habitats
Viable Habitat: Flooded wetlands, rivers and lakes in temperate to semi-tropical climate
Size: Smallest species: 32 cm with tail (20 cm without), Largest species: 42 cm with tail (27 cm without)
Dietary Needs: Carnivores that eat invertebrates and also small vertebrates. Prey include snails, juvenile crayfish, small fish, small lizards and smaller species of mice. If they find bird eggs they will also eat those.
Life Cycle: Mating can occur year-round as the female can get pregnant twice in one year, sometimes to different males. So males are always making their near-ultrasonic calls, keeping up the hustle to spread his genes. Males and females don't form strong attachments as they end up competing with each other for food. Once a female is pregnant she rejects all males.
Pregnant females make their nests deep within large tufts of tough, dense grass. When her pups are born they don't stay pink, blind and helpless for long. Very soon they join her in the water, sometimes in a nose-to-tail line, sometimes by using her as floatation or hanging on to her when she dives. An amphibious life is complicated, especially for a carnivore, so the pups begin learning survival early. She starts with up to 10 pups, but many are lost to predators, accidents and disease before they mature. Sometimes survival involves luck, but most survivors are the strongest and healthiest pups, the ones with the best combination of their parent's genes.
Larger species take longer to reach physical maturity and in the most seasonal parts of their range can only manage to raise one litter per year. They can take up to 3 months to mature, not leaving enough time to raise another litter before a major seasonal change. However there are smaller species within this genus who can produce two litters a year before the season becomes unfavourable.
Other: These mice spend more time underwater than any other mouse evolved on this planet so far. They live alongside another mouse species that regularly swims, but that other mouse mainly swims to cross water and spends less time underwater.
Their webbed feet greatly improve their swimming speed over their ancestors. Their slightly more splayed limb positioning allows them to easily push aside submerged water weeds all around them, which often choke the water and make it difficult to swim through in places. Waterproofing is enhanced by a good strong sebum, secreted by glands attached to the follicle of the over-coat hair type, so that hair grows out sebum-coated. Meanwhile under-coat hairs have no such glands. This also ensures the fluffy undercoat has minimal sebum, as sebum reduces the under-coat's qualities. Their under-coat's fur is also so dense that water takes a while to soak in if their waterproof layer is breached by water.
Their incisors continuously grow but at a much reduced rate compared to their ancestors' teeth, as their diet and lifestyle don't cause them to wear their teeth down as intensively. Most wear comes from the incisors rubbing together. The incisors also don't grow tightly together. On upper and lower jaws they are visible as separate left and right teeth with a gap in the middle. This gives the mouth two separate stabbing hold points, giving the mouse more control over prey than if the left and right incisors were together as one. They can use their incisors to take chunks of prey into the mouth by processing the meat first through repeated perforation until it starts to separate.
Molars have also changed. The large molar closer to the mouth opening has become flatter and bumpier, and is mostly used for breaking exoskeletons and grinding up pieces of shell that are small enough to consume. Towards the back the two smaller molars become narrower and pointier for shredding up meat.
Although these mice spend much of their life hunting in the water they are also capable of a terrestrial existence. They do not thrive this way and are more vulnerable, but it allows them to find alternative water sources if their home dries up. Without a water source they are restless. They won't settle down and females won't mate until they have secured a territory near water.
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