Age and sex-specific variation in detectability of moose (Alces alces) during the hunting season: implications for population monitoring

Abstract

The sustainability of wild ungulate harvests can be greatly enhanced if monitoring data are available to permit an adaptive management approach. Utilising data provided by hunters is potentially the most cost-effective approach. In Scandinavia, observations recorded by moose (Alces alces) hunters provide a range of indices of population density, composition and reproductive performance. These are routinely used in practical management, but there are still many questions about their accuracy and precision. In this study, we availed of the fact that virtually all individual moose on the island of Vega in central Norway were marked during the period 1992-2005. Thus, we were able to compare the observation indices provided by hunters to the known size and composition of the population. The results indicate that the hunter observation indices provided accurate estimates of variation in moose cow recruitment and twinning rates. The estimates of sex ratio closely followed the pattern of annual variation but showed a consistent pattern of over-estimating the proportion of males. Thus, males seem to visually expose themselves more often for hunters than do females. The density index, measured as number of moose seen per hunter day did not to the same extent follow the variation in population density, possibly because moose were more naive in the first years after hunting was introduced or because of reduced detection conditions due to increasing scrub and tree encroachment during the study period. The results are discussed in light of their application to management and the evolutionary pressures in moose anti-predator behaviour.

Harvest-induced phenotypic selection in an island population of moose,Alces alces

“…Probably hunters have less opportunities to selectively shoot females than males, because they expose themselves less often to hunters (Solberg et al. ; Ericsson and Wallin ) and are followed by one or more calves (see also Table and Fig. ).…”

“…; Solberg et al. , ). Furthermore, with tissue samples from all marked and hunted individuals, a genetic pedigree with a total of 499 individuals born in the period 1984–2012 was constructed (for details see Haanes et al.…”

Population properties affect inbreeding avoidance in moose

“…Finally, we predicted increased inbreeding in years with low variation in relatedness and high mean relatedness, which provide fewer opportunities for inbreeding avoidance [4]. 0 N, 11855 0 E) provides excellent moose habitat [16]. The island was colonized by three moose in 1985 and immigration has been relatively low (figure 1a).…”

“…Moose are a long-lived species that can start reproduction as yearlings, and later often give birth to twins [16]. Moose is sexually size-dimorphic and polygamous, and sexual selection on morphology and mating is likely influenced both by female mate choice and male-male competition [17].…”

“…Harvesting started in 1989 and has kept the number of breeding moose between 20 and 40. Variation in the proportion of adult males in the harvesting quotas [16] has caused large fluctuations in the age and sex-structure (figure 1a-c).…”