Effectiveness of various cattle ear tags as markers for Weddell seals

Methods for estimating tag loss and sightability of tags are presented. Rates of tag loss were estimated for metal and several varieties of plastic cattle ear tags in a long-term population study of Weddell seals. Tags were lost at a higher rate in the first year after application than in subsequent years, and pups lost tags at a higher rate than older seals given the same tag types. Medium-sized plastic tags (Dalton, Allflex and Fearing) were retained at higher rates and were overlooked less frequently than metal tags on adult seals. Dalton Jumbo Rototags showed the lowest loss rates on pups in comparison to larger, flexible plastic tags, but were harder to read in the field.