Switch to non-toxic shot in the Camargue, France: effect on waterbird contamination and hunter effectiveness

The use of lead shot for wildfowling is a severe threat to waterbirds through ingestion of toxic lead pellets. Consequently, lead shot has been banned in many countries since the late 1990s and on Tour du Valat estate since 1994 (Camargue, France). An experimental study was undertaken to check if hunters would habituate to this new type of cartridge and consequently improve their effectiveness (average number of shots per bagged animal), assess the factors influencing effectiveness, and assess the trend of contamination in shot waterbirds and the estate sediment. From 1995 to 2005, we monitored hunting bags, spent cartridges, and the gizzards of shot ducks. Using generalized mixed effect models, we assessed the factors influencing hunter effectiveness. Instances of non-toxic pellets in duck gizzards increased, probably as a result of rapid accumulation in the sediments. We estimated that between 1995 and 2005, the lead shot ban spared 456 kg of lead from entering 403 ha of temporary marshes and avoided the contamination of 8 % of the ducks foraging on Tour du Valat. After 11 years of hunting with non-toxic shot, there was unexpectedly no clear pattern in trends of individual effectiveness among hunters. Hunter effectiveness was instead positively influenced by game abundance and hunter assiduity and negatively influenced by wind and number of shots, suggesting a lassitude effect. Our results suggest crippling loss can be reduced through regular practice, self-limitation of shooting intensity to below 20 shots to avoid lassitude effects, and self-limitation of shooting distance under strong wind conditions.