A Lavellan, làbh-allan, la-mhalan or la-bhallan etc. is a mythological

Mythology

The term mythology can refer either to the study of myths, or to a body or collection of myths. As examples, comparative mythology is the study of connections between myths from different cultures, whereas Greek mythology is the body of myths from ancient Greece...

/cryptozoological

Cryptozoology

Cryptozoology refers to the search for animals whose existence has not been proven...

 creature from northern Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

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It was generally considered to be a kind of rodent

Rodent

Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

, and indeed the name "làbh-allan" is also used for a water shrew

Eurasian Water Shrew

The Eurasian Water Shrew, Neomys fodiens, known in the United Kingdom as the Water Shrew, is a relatively large shrew, up to long, with a tail up to three-quarters as long again. It has short dark fur, often with a few white tufts, a white belly, and a few stiff hairs around the feet and tail...

 or water vole in Scottish Gaelic. It was however, reportedly larger than a rat

Rat

Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...

, very noxious, and lived in deep pools in rivers. Its poisonous abilities were legendary, and it was said to be able to injure cattle over a hundred feet away.

Some sources claim that it was mostly to be found in Caithness

Caithness

Caithness is a registration county, lieutenancy area and historic local government area of Scotland. The name was used also for the earldom of Caithness and the Caithness constituency of the Parliament of the United Kingdom . Boundaries are not identical in all contexts, but the Caithness area is...

. Thomas Pennant

Thomas Pennant

Thomas Pennant was a Welsh naturalist and antiquary.The Pennants were a Welsh gentry family from the parish of Whitford, Flintshire, who had built up a modest estate at Bychton by the seventeenth century...

 made enquiries about the animal while in Ausdale in the county, and it is also mentioned in the work of Rob Donn

Rob Donn

Rob Donn was a Scottish Gaelic poet from Sutherland. It is generally assumed that his surname was MacKay , but this has been disputed, so he is sometimes referred to as "Rob Donn MacAoidh".-Biography:...

, the Scottish Gaelic poet from Sutherland

Sutherland

Sutherland is a registration county, lieutenancy area and historic administrative county of Scotland. It is now within the Highland local government area. In Gaelic the area is referred to according to its traditional areas: Dùthaich 'IcAoidh , Asainte , and Cataibh...

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Pennant claims the locals preserved the skin, and, as a cure for their sick beasts, gave them the water in which it had been dipped.