Pre‐natal and Infant Mortality in a Laboratory Population of Voles {Microtus agrestis).

Summary. A technique for estimating the pre‐natal mortality in the vole, Microtus agrestis, by palpating the embryos, is described. The results obtained from a laboratory stock of voles show a mortality of at least 21‐07 per cent. 14–20 per cent, of the young born alive die during the 14 days between birth and weaning, giving an accumulated loss of at least 32‐28 per cent, for the first 35 days of existence. The sex ratio at weaning was 50–89 2‐22 males per cent.