THE IMPACT OF WINTER TICK ON MOOSE IN MAINE AND TESTING POSSIBLE SOLUTIONS, USA.
Lee E. Kantar1
Maine Department of Inland Fisheries and Wildlife , 106 Hogan Rd. Suite 1, US
Abstract Background and Methods:
During a seven-year study on adult cow and calf moose (Alces americana) survival in Maine, USA (2014-2020), 417 calves (~8 months of age) and 128 adult cows were fitted with Global Positioning System (GPS) collars and sampled for winter ticks (Dermacentor albipictus), blood parameters and internal parasites. The study was implemented in Wildlife Management Districts (WMD) 8 (2014-2020) and 2 (2016-2020) to investigate winter tick impacts on annual survival of adult cows and calves.
In phase 2 (2020-2025; Adaptive Hunt) we increased the harvest of antlerless moose (adult cow or calves) within WMD 4 (half unit control/half experimental) to assess whether decreasing moose population through a general hunting framework could reduce winter tick abundance and increase overwinter survival of calves. We GPS fitted overwintering calves to compare overwinter mortality rates to prior study and cause of mortality.
Results and Conclusions:
Annual survival rates of adult cows were high (90-92%) except in 2014, when an abnormally high loss of adult cows (48%) was observed. Mean overwintering survival of calves in WMD 8 was 38% compared to 63% survival in WMD 2. Winter tick abundance was higher on moose in WMD 8 and was associated with higher over-winter calf mortality and depressed reproduction; we recorded reduced ovulation rates and low rates of twinning.
Initial results (4 years) from the Adaptive Hunt phase revealed the social angst of substantial permit allocation increases as well as the challenges of increasing hunter success rates to meet population reduction goals. In support of this phase 420, 8-month-old calves were fitted with GPS collars to compare overwinter survival rates with initial study phase results. Overwinter mortality rates ranged from 87% - 8%, demonstrating that climatic conditions remain the most significant driver of winter tick abundance and hence overwinter mortality.
A third phase of research is proposed to delineate fine scale spring/fall adult cow home ranges using high fix rate GPS collars to determine where the acquisition of winter tick larvae is highest with the potential of mitigating high winter tick loads through forest management practices and dispersal of moose on the landscape.