Identification of the Filial Relationships of Free-Living Small Mammals by 35Sulfur

Abstract

A technique for determining the filial relationships of free-living small mammals is described. The radioisotope 35*sulfur is injected into a lactating mother, and this passes from the milk and is incorporated in the growing hairs of the young. In three species, Mus musculus and Rattus fuscipes (Rodentia) and Antechinus stuartii (Marsupialia), radioactivity in the hairs of the young was detected for up to 130 days after injection of the mother. The technique has the following advantages: (1) the half-life of 35*S is only 87.4 days; (2) 35*S had no evident adverse effects; (3) different treatments, ranging from 0.75 µCi [27.75 kBq] g-¹ to 4.25 µCi [157.25 kBq] g-¹ body weight of the mothers, resulted in different levels of radioactivity in the hair of the juveniles; consequently, the filial relationships of several mothers and their young may be established. The application of this technique to field studies of small mammals is outlined.