174 The Mammalia of Essex ; a Contribution towards a 



the great and easily distinguishing feature separating 

 Muridfe and ArvicoUdae. The Water Kat, for its size and 

 numbers, does less damage to man than any other member 

 of the family, its prmcipal food being aquatic vegetables, 

 and it only takes what man can well spare. Occasionally, 

 when they are abundant and the weather is severe, they do 

 a little mischief to osier beds, but the injury they inflict 

 on the farmer is so small as not to be worth consideration. 

 The little animal is common in all parts of Essex, wherever 

 there are sluggish streams or stagnant water in sufficient 

 quantity to hide it. It will be well to bear in mind that it is 

 sometimes quite black in colour, and has been described (by 

 Macgillivray, ' Nat. Lib.' xvii. 257) under the name of 

 Arvicola ater, but this is merely a variety. This dark variety 

 has occasionally been mistaken for the old English Black Rat 

 (Musrattus), and many of the supposed appearances of the 

 latter animal can thus be explained. 



Arvicola agrestis. Common Field Vole. — Bell says that 

 A. agrestis may always be distinguished by the character of 

 its second upper molar, which has five cemental spaces, 

 whereas the same tooth in A. arvalis (which has not yet been 

 found in Britain), as in all the other European voles, presents 

 four spaces. This vole abounds sometimes to such an extent 

 as entirely to destroy the herbage, and from the quantity it 

 consumes (in confinement I have known one eat six drachms 

 of clover in twenty-four houi-s) one can quite understand 

 the devastation caused by it when existing in numbers. Not 

 only is herbage eaten, but, according to Bell, " many years 

 since the plantations of young oaks in New and Dean 

 Forests were destroyed." Its insatiable appetite compels it 

 to be abroad at all seasons of the year and all hours of the 

 day, but I have noticed those I have kept in confinement to 

 be more active towards and during the evening. I never 

 could make them very tame, and they appeared to me to be 

 rather stupid. The nest is usually placed amongst the roots 

 of the grass, sometimes under fallen timber. The young are 

 from four to six in number, and there are generally three or 

 four broods in a year. Weasels, owls, and kestrels are their 



