CAN HUMAN PREDATION OF MOOSE CAUSE POPULATION CYCLES?

Abstract

The demography of a moose population in central Newfoundland was investigated using hunter statistics and cohort analysis to estimate moose density. The moose population occurs in a forested area of relatively high primary productivity for which trophic dynamics theory predicts regulation of herbivores by predation. No natural predators capable of density dependent regulation of moose live in Newfoundland. Therefore, we assessed the regulatory effects of human hunting on moose density. We used phase plots rather than time series to help describe nonlinear system dynamics. This approach characterized the behaviour of the human-moose system as a stable limit cycle with a period of about 11 years. Fluctuations in the prey population were tracked overtime by fluctuations in the numbers of predators (number of hunters), predator searching time (hunter effort), and predator kills (harvest). The functional response of hunters reached an asymptote at densities greater than 1.4 moose·km^-2. Although the total response indicated a stable equilibrium due to density dependent hunting, we argue that cyclical behaviour in the numerical response leads to instability and population cycles. The regulatory effect was caused by delayed density dependence due to the time lag in the management response (number of licenses) to changes in moose numbers. However, changes in food may have also had a delayed response and should be considered as a possible influence on synchronizing population cycles.