Survival rates of cougars in Oregon from 1989 to 2011: A retrospective analysis

Cougar (Puma concolor) management in Oregon is unique because hunting cougars with dogs was allowed through the 1994 hunting season, but thereafter Ballot Initiative Measure 18 prohibited the use of dogs to pursue cougars. Since 1995, hunting seasons have become increasingly longer with more tags sold. The effects of changing management structure on survival rates and causes of mortality of cougars are not well understood. We investigated survival and documented causes of mortality of radiocollared cougars at 3 study areas in Oregon from 1989 to 2011 under contrasting management strategies. The Catherine Creek (1989–1996) and Jackson Creek (1993–2002) studies overlapped the prohibition of hunting cougars with dogs, and the Wenaha, Sled Springs, and Mt. Emily (WSM) study was conducted from 2002 to 2011 when hunting cougars with dogs was illegal. Hunting mortality was the most common cause of death for sub-adult and adult cougars in Catherine Creek pre- (18 of 23 mortalities) and post-Measure 18 (1 of 2 mortalities) and WSM (24 of 53 mortalities) study areas in northeast Oregon. In contrast, natural mortality was the most common cause of death of sub-adults and adults at the Jackson Creek (25 of 38 mortalities) study area in southwest Oregon, but hunting mortality was most common prior to the passage of Measure 18 (3 of 3 mortalities). We estimated annual survival rates of cougars using known fate models in Program MARK. Annual survival rates of adult males were lowest at Catherine Creek prior to the passage of Measure 18 ( = 0.57; 95% CI = 0.39–0.73) and increased after Measure 18 ( = 0.86; 95% CI = 0.79–0.92), which were similar to those rates observed at Jackson Creek pre- and post-Measure 18 ( = 0.78; 95% CI = 0.65–0.88) and WSM ( = 0.82; 95% CI = 0.69–0.91). Regardless of hunting regulations, annual survival rates of adult females was similar among study areas (Catherine Creek pre- and post-Measure 18 [ = 0.86; 95% CI = 0.79–0.92]; Jackson Creek pre- and post-Measure 18 [ = 0.85; 95% CI = 0.77–0.91]; WSM [ = 0.85; 95% CI = 0.76–0.90]). At Jackson Creek pre- and post-Measure 18 and WSM, sub-adult males (1–3 years) had significantly lower survival than sub-adult females, but survival rates of males and females were similar by age 4 or 5 years. At WSM, survival declined for both sexes at older ages (8–13 years), but this decline was not observed at Jackson Creek pre- or post-Measure 18. The effect of increasing age on cougar survival should be considered when using survival rates to estimate population growth rates. We did not detect an effect of age on cougar survival at the Catherine Creek study area pre- or post-Measure 18, which we attributed to selective harvest of prime-aged, male cougars prior to the passage of Measure 18 and lack of mortality post-Measure 18. Managers should understand local sources of mortality when setting harvest regulations because sources of mortality may vary widely within and among jurisdictions, even if management practices are similar. Because of low hunter success rates when hunting cougars without dogs, survival rates of cougars managed under this hunting regime should be substantially higher than areas where use of dogs is legal. This suggests the ability of managers to effectively manipulate survival rates of cougars to meet population management objectives will be dependent on available hunting methods. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.