Mortality transmitters--new instrument for animal loss research on Norwegian ranges

In 1988, 315 lambs from 4 sheep (Ovis aries) herds comprised of 1003 animals were marked with silent mortality transmitters in Gammeldalen in Hedmark County, southern Norway. The aim was to identify causes of death and the so-called "hidden loss" of lambs on summer range. A total of 22 animals, 19 lambs and 3 ewes were found dead. Of these, 18 lambs were marked with radio transmitters. A total of 10 animals died of disease (45.5%) and 12 were killed by predators (54.5%). Of the 18 radio-located lambs, 6 died of disease (33.3%) and 12 due to predators (66.7%). Various common lamb diseases were diagnosed, e.g. lung, thoracic and intestinal infections. Eleven lambs were killed by lynx (Lynx lynx), a 12th was found chased to exhaustion, presumably by a predator. Use of mortality transmitters is concluded to be useful in investigating sheep losses on Norwegian ranges.