AQUATIC AREAS PROVIDE HIGH NITROGEN FORAGE FOR MOOSE (ALCES ALCES) IN ISLE ROYALE NATIONAL PARK, MICHIGAN, USA

Abstract

The distribution of ungulates reflects spatial and temporal heterogeneity in forage quality and quantity across the landscape. Aquatic habitats have a patchy spatial distribution and are readily used by moose (Alces alces) and other ecotone specialists. However, the importance of aquatic feeding to moose has largely been attributed to acquisition of sodium, with little consideration given to the relative and comparative quality of aquatic and terrestrial forage types. We show differences in forage quality as measured by crude protein content and carbon:nitrogen (C:N) ratios between aquatic and terrestrial summer forage in Isle Royale National Park, Michigan, USA. Aquatic macrophytes had higher crude protein content and lower C:N ratio than preferred terrestrial plant species of moose. Consequently, measurable consumption of aquatic forage may provide high quality forage in less than optimal habitats. Because the distribution of aquatic habitats on Isle Royale exhibits strong spatial trends, the benefits of aquatic feeding may have spatial influence on the population dynamics of Isle Royale moose.