Earless water rat facts for kids
Quick facts for kids Earless water ratTemporal range: Recent
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| Conservation status | |
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| Genus: |
Crossomys
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| Species: |
moncktoni
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The earless water rat (Crossomys moncktoni) is a special type of rodent found in New Guinea. It belongs to a group of Old World rats and mice called the Hydromys group. This animal is the only species in its genus called Crossomys. Scientists believe it is most closely related to another animal called Baiyankamys. The earless water rat is one of the best swimmers among all rodents in the world.
Names
In the Kalam language spoken in Papua New Guinea, this animal is known as kuypep.
History of Discovery
This unique animal was first described in 1907 by a British scientist named Oldfield Thomas. He studied a single animal found by Mr. C. A. W. Monckton. The species was named after Mr. Monckton. This first earless water rat was found near the Brown River in the Central Province of south-east Papua New Guinea.
It took a long time, until July 1950, for a second earless water rat to be found. Since then, a few more have been caught in the mountains of eastern New Guinea. Even today, the earless water rat is still a very rare species. Its scientific name, "Monckton's fringed mouse," refers to the person who found it and the special fringe of hairs on its tail.
Family Tree
Scientists have spent a lot of time trying to figure out where the earless water rat fits in the rodent family tree.
At first, some thought it was closely related to the Hydromys group. However, later studies, including one in 1994, suggested it might be closer to other groups like Leptomys, Pseudohydromys, and Xeromys.
In a big book about mammals, scientists Guy Musser and Michael Carleton placed Crossomys in the Hydromys group. They believed its body shape was more like the animals in that group.
More recently, in 2005, scientist Helgen suggested that the earless water rat is most closely related to Baiyankamys. He also thought the Crossomys-Baiyankamys group is related to Hydromys and Parahydromys.
Amazing Features
The earless water rat is incredibly well-suited for living in water. It has many special features:
- Its back feet are very long and have completely webbed toes, like a duck's foot.
- Its front legs are very small.
- Its ears are either missing or so tiny you can barely see them.
- Its eyes are very small.
- It has a long tail with a special row of hairs underneath. These hairs start as two white rows at the base of the tail and then join into one row that goes all the way to the end.
These features make it look a lot like the elegant water shrew (Nectogale elegans), even though they are not closely related. This is a great example of convergent evolution, where different animals develop similar traits because they live in similar environments.
The fur on its back is grayish-brown, and its belly is white. Its fur is soft and keeps water out. The top of its tail is light gray, and the bottom is white. Its front feet and claws are very small, but its back feet are very large. The earless water rat might use the short, strong bristles on its upper lip to scrape food. Its outer ear is so small it hardly sticks out from its fur. It might even be able to close its ear canal.
Like many animals that live in water, it has a rather large brain. Its nose bones, roof of the mouth, and molars (back teeth) are quite small. The earless water rat is a medium-sized rat, similar in size to its relative Baiyankamys.
Here are some measurements:
- Head and body length: about 175 to 200 mm (7 to 8 in).
- Tail length: about 212 to 260 mm (8 to 10 in).
- Hind foot length: about 44 to 53 mm (2 to 2 in).
- Ear length: about 1 to 4.5 mm (0 to 0 in).
- Weight: around 165 g (5.8 oz).
Female earless water rats have four nipples, which is common for many rodents in Australia and New Guinea.
The earless water rat and Baiyankamys are related because they share several features. For example, their tails are much longer than their bodies, they have soft, thick, grayish fur, and their snouts are long and narrow. One type of Baiyankamys, B. habbema, also has very small outer ears like the earless water rat.
Where it Lives and What it Does
This animal lives in the mountains of Papua New Guinea, including the Huon peninsula. It can be found at high elevations, from 1000 to 2700 meters (about 3,300 to 8,900 feet). Its home is in the cold, fast-flowing streams of these mountains.
During the day, the earless water rat is busy hunting for food. It eats tadpoles, worms, and insects that live in rivers, especially their larvae. At night, it rests and sleeps in holes it makes along the river banks. Female earless water rats usually have only one baby at a time. Local hunters, like the Telefol, can only catch these animals when the river levels are low.
Different local tribes have different names for this animal. The Kalam tribe calls it kwypep. The Telefol people might call it ogoyam, and the Rofaifo people might call it momo. However, momo is also used for other water rats, like the common Rakali. Some local names for the earless water rat can be translated as "water sugar glider". This name comes from how similar its fur feels to that of a sugar glider.
Not much is known about how many earless water rats there are in the wild. However, the IUCN Red List currently lists its conservation status as "least concern." This means scientists are not too worried about it becoming extinct right now.
