Impacts of the herbicide glyphosate on moose browse and moose use of four paired treated-control cutovers near Thunder Bay, Ontario

Abstract

Re-assessment of the aerial and ground observations on four paired, glyphosate treated and control, cutovers near Thunder Bay, Ontario, indicated that aerial tending with glyphosate altered the use of these cutovers by moose. The number of pellet groups favoured the control areas (p < 0.05) by 1.5 times. Additionally, the number of moose tracks and moose track aggregates were more prevalent (p < 0.05) on the controls for 2 to 3 years after treatment. Pre spray data on 2 areas suggested use shifted away from glyphosate treated areas. Browse availability was significantly greater (p < 0.05) on the control plots by 18 times in the highest height class measured (201 - 350 cm) , 5 times in the next highest (101 - 200 cm) but not statistically significant (p > 0.05) in the lowest (51 - 100 cm), 2 years after treatment. Due to too few replications, differences in availability 1 year after treatment were not statistically significant. Biomass of browse removed by moose was 3 to 7 times greater on controls but again these differences were not statistically significant. The average length of moose trails observed in the snow was shorter (p < 0.05) on the controls suggesting less travel time. The size (area) of moose track aggregates was the same (p > 0.05) between treatments indicating equal search time while browsing. A carrying capacity model indicated that if all cutovers were sprayed, the treatment would have a negative impact on moose densities. Glyphosate treatments should be dispersed to create a mosaic of glyphosate treated areas next to non-treated areas. Similarily, areas of seasonal importance such as aquatics, salt licks, and calving areas should have at least a non-sprayed buffer beside them if the adjacent cut area must be treated with glyphosate.