REPRODUCTION, SURVIVAL, AND OCCUPIED RANGES OF SHIRAS MOOSE TRANSPLANTED TO SOUTHWESTERN COLORADO

Abstract

Moose (Alces alces shirasi) were released into previously unoccupied habitat in southwestern Colorado in 1991, 1992, and 1993. Nine radiocollared males and 32 radiocollared females were tracked and relocated approximately monthly until they died or the study terminated on December 31, 1996. Females were observed each year in July, August, or September to determine if calves were present. The females had 97 opportunities to produce calves. Fifty calves were observed resulting in an average calf to cow ratio of 52 calves per 100 cows. All radiocollars were equipped with mortality sensors and each dead animal was examined to determine cause of death. Illegal kill was the primary known cause of death followed by birth complications, winter loss, and impacted rumen. We were unable to determine the cause of death for 9 animals. Average annual survival rates were 0.94 for males and 0.83 for females. Locations of each animal were recorded and mapped. An adaptive kernel analysis was used to create seasonal polygons of occupied habitat. By December 31, 1997 more than 5,500 km² were occupied by moose in the fall. The mean area occupied, over multiple years, by individual moose during all seasons was 624 km² for males and 772 km² for females. Moose numbers are increasing in the release area and we believe that range expansion will occur to favorable adjacent habitats.