No abstract

With the decline of many lekking species, the need to develop a rigorous population estimation technique is critical for successful conservation and management. We employed mark—resight methods to estimate population size for 2 lekking species: greater sage‐grouse (Centrocercus urophasianus) and Gunnison sage‐grouse (Centrocercus minimus). We evaluated 2 different estimators: Bowden's estimator and the mixed logit‐normal mark—resight model. We captured and marked 75 greater sage‐grouse. We counted marked and unmarked birds as they attended 15 known leks. We used 36 and 37 marked Gunnison sage‐grouse to estimate population size in 2003 and 2004, respectively. We observed marked and unmarked Gunnison sage‐grouse daily as they attended 6 leks in 2003 and 3 leks in 2004. Based on our examination of the assumptions of each mark—resight estimator, relative to behavior and biology of these species, we concluded the mixed logit‐normal mark—resight model is preferred. We recommend wildlife managers employ mark—resight approaches when statistically rigorous population estimates are required for management and conservation of lekking species.

Low lamb recruitment is a major challenge facing managers attempting to mitigate the decline of bighorn sheep (Ovis canadensis), and investigations into the underlying mechanisms are limited because of the inability to readily capture and monitor bighorn sheep lambs. We evaluated 4 capture techniques for bighorn sheep lambs: 1) hand‐capture of lambs from radiocollared adult females fitted with vaginal implant transmitters (VITs), 2) hand‐capture of lambs of intensively monitored radiocollared adult females, 3) helicopter net‐gunning, and 4) hand‐capture of lambs from helicopters. During 2010–2012, we successfully captured 90% of lambs from females that retained VITs to ≤1 day of parturition, although we noted differences in capture rates between an area of high road density in the Black Hills (92–100%) of South Dakota, USA, and less accessible areas of New Mexico (71%), USA. Retention of VITs was 78% with pre‐partum expulsion the main cause of failure. We were less likely to capture lambs from females that expelled VITs ≥1 day of parturition (range = 80–83%) or females that were collared without VITs (range = 60–78%). We used helicopter net‐gunning at several sites in 1999, 2001–2002, and 2011, and it proved a useful technique; however, at one site, attempts to capture lambs led to lamb predation by golden eagles (Aquila chrysaetos). We attempted helicopter hand‐captures at one site in 1999, and they also were successful in certain circumstances and avoided risk of physical trauma from net‐gunning; however, application was limited. In areas of low accessibility or if personnel lack the ability to monitor females and/or VITs for extended periods, helicopter capture may provide a viable option for lamb capture. © 2013 The Wildlife Society.

With the decline of many lekking species, the need to develop a rigorous population estimation technique is critical for successful conservation and management. We employed mark-resight methods to estimate population size for 2 lekking species: greater sagegrouse (Centrocercus urophasianus) and Gunnison sage-grouse (Centrocercus minimus). We evaluated 2 different estimators: Bowden's estimator and the mixed logit-normal mark-resight model. We captured and marked 75 greater sage-grouse. We counted marked and unmarked birds as they attended 15 known leks. We used 36 and 37 marked Gunnison sage-grouse to estimate population size in 2003 and 2004, respectively. We observed marked and unmarked Gunnison sage-grouse daily as they attended 6 leks in 2003 and 3 leks in 2004. Based on our examination of the assumptions of each mark-resight estimator, relative to behavior and biology of these species, we concluded the mixed logit-normal markresight model is preferred. We recommend wildlife managers employ mark-resight approaches when statistically rigorous population estimates are required for management and conservation of lekking species.