[1] Univ St Andrews, Ctr Res Ecol & Environm Modelling, St Andrews KY16 9LZ, Fife, Scotland
[2] Univ St Andrews, Res Unit Wildlife Populat Assessment, St Andrews KY16 9LZ, Fife, Scotland
[3] Univ Lisbon, Ctr Estat & Aplicacoes, P-1749016 Lisbon, Portugal
[4] US Geol Survey, Patuxent Wildlife Res Ctr, Laurel, MD 20708 USA