5 JANUARY 1929, Page 19

Country Life

To LOCAL NATURALISTS Will the countryman please co-operate ? Zoological authori- ties at Oxford want- information from the annals of the past, as well as.from recent observation aboutcertain of our common animals, especially field voles and brown squirrels. The theory is-that `! there isa certain definite cycle in the numbers of all rodefits, the-period differing with the different species." It is even claimed that an exact cycle has been discovered in reference.'to' field voles and Norwegian lemmings, which rise to an excess every four years. An information bureau has been established for the purpose of collecting information about past years ; and it is hoped to comb out accumulated information of such events during the last hundred years or so. There is-probably a mass of it. It used to be a much More common habit on country estates to keep exact records of natural historY. observations, eSpecially the killing of vermin, than it is to-day ; and one would like to- see the old habit revived.