Radioiodine as an indicator of free-feeding activity of the rabbit, Oryctolagus cuniculus (L.)

Abstract

The use of ¹³¹I to obtain qualitative and rough quantitative data on the intake of carrot bait by individual rabbits, Oryctolagzus cuniculus (L.), during field enclosure experiments on free feeding was investigated. In laboratory tests, the rapid concentration of varying amounts of ¹³¹I in the thyroid, followed by steady loss, was measured with a Geiger counter applled externally to the throat. It was established that oral intake of 2 µc ¹³¹I could be readily detected for 2 days, and that the minimum rate of labelling should be 1 µc of ¹³¹I per 5 g carrot. A successful field enclosure trial was done. Observations of behaviour revealed no adverse effects due to radiation from the larger amounts of ¹³¹I or to capture and handling of the rabbits.