Moose antler type polymorphism: age and weight dependent phenotypes and phenotype frequencies in space and time

We provide the first detailed description of the phenotypic polymorphism of the European moose (Alces alces) bulls with three different antler types: cervina, intermediate and palmated. We assess how the frequencies of bulls with different antler types as well as antler spread and tine numbers are related to age, body weight, region and time. Our results indicate that antler type phenotypes are linked to other body and antler size characteristics. The cervina type had the smallest and the palmated the largest carcass weight, antler spread and tine numbers. The youngest age groups were predominantly of cervina type. At the prime age of 6.5-10.5 years, the prevalent types were intermediate and palmated. At an older age, the cervina type increased and the other types decreased. We propose that the penetrance of inherited antler type is best at prime age when it is important for a bull to be successful in mating competition. The cervina type was most prevalent in the southern zone and the palmated type in the northern zone. The mean age, mean carcass weight, antler spread and tine numbers all decreased from 1976-1986 to 1996-1999. The results were similar in the age-standardized prime age bulls. We hypothesize that intensive selective hunting as well as possible fitness differences between antler types in managed forests may have been involved in the decrease of the palmated antler type.