Effects of Winter Ticks and Internal Parasites on Moose Survival in Vermont, USA

Abstract

Moose (Alces alces) have experienced considerable declines along the periphery of their range in the northeastern United States. In Vermont, the population declined 45% from 2010 to 2017 despite minimal hunter harvest and adequate habitat. Similarly, nearby populations recently experienced epizootics characterized by >50% mortality. Declines have largely been associated with the effects of winter ticks (Dermacentor albipictus), but uncertainty exists about the effects of environmental and other parasite‐related conditions on moose survival. We examined patterns of moose survival among a radio‐collared population (n = 127) in Vermont from 2017 to 2019. Our objectives were to estimate causes of mortality and model survival probability as a function of individual and landscape variables for calves (<1 yr) and adults (≥1 yr). Observed adult survival was 90% in 2017, 84% in 2018, and 86% in 2019, and winter calf survival was 60% in 2017, 50% in 2018, and 37% in 2019. Winter tick infestation was the primary cause of mortality (91% of calves, 25% of adults), and 32% of all mortalities had evidence of meningeal worm (Parelaphostrongylus tenuis). Other sources of mortality such as vehicles, harvest, predation, deep snow, and other parasitic infections were negligible. The best supported calf model included sex differences and negative effects of tick engorgement (%/week) and parasite level (roundworm and lungworm). The best supported adult model included the effect of cumulative tick engorgement (cumulative %/week), which negatively affected survival. Our results indicate that winter tick engorgement strongly affects survival, and is probably compounded by the presence of meningeal worm and other parasites. Reduced tick effects may be achieved by decreasing moose density through harvest and managing late winter habitat to minimize tick density. Management of white‐tailed deer (Odocoileus virginianus) density may also affect the transmission of meningeal worm. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.

A Review of Commercial Metarhizium- and Beauveria-Based Biopesticides for the Biological Control of Ticks in the USA

“…Product tests in the laboratory on other tick species— Dermacentor albipictus (Packard), Dermacentor reticulatus (Fabricius), Ixodes ricinus (L.), Rhipicephalus sanguineus sensu lato, and Rhipicephalus ( Boophilus ) microplus (Canestrini)—also demonstrated high mortality under high temperature and humidity conditions (>80%RH) ( Table 4 ). Dermacentor albipictus larvae, a one-host tick that parasitizes ungulates like cattle, horses, and moose [ 35 , 36 , 37 ] has received the most attention. Although 100% mortality is achievable in vitro after three weeks when immersed or sprayed, broadcast applications of a granular formulation achieved a reduced level of mortality (89%).…”

Changes to Health Parameters of White-Tailed Deer during a Drought in the US Virgin Islands

“…These factors are influenced by both current and past food availability, and can therefore indicate health in both the present and recent past. Prolonged nutritional challenges such as drought can cause individuals to exhaust stored fat reserves which can result in a deterioration in body condition [6]. In contrast, coat condition demonstrated a Low-High-Low pattern during the drought.…”

“…Changing landscape conditions, including more frequent drought, can exert stressors on wildlife populations that have the potential to be detrimental to the health and fitness of individuals [4,5] and populations over time [6]. For wildlife populations, drought presents multiple simultaneous environmental challenges such as high temperatures, low food availability, and low water availability [1].…”

“…Our goal was to provide quantitative evidence for these changes for a protected island population at three distinct time periods of a drought. The monitoring of stress and nutrition in wildlife populations can provide researchers with valuable insight into the baseline stability and physiological impacts of environmental change on wildlife populations [6]. The deer of St. John represent a unique and intriguing case study for understanding a population facing highly altered future conditions due to climate change.…”

The Role of Wolves in Regulating a Chronic Non-communicable Disease, Osteoarthritis, in Prey Populations

“…This research adds significant evidence for how selective predation may regulate the health of prey populations (Packer et al, 2003;Barber-Meyer et al, 2007;Wild et al, 2011;Tanner et al, 2019), which has implications for two management issues. First, the management of population health for ungulates has typically focused on the use of culls or recreational hunting to reduce the incidence of disease or parasites of concern (Mysterud et al, 2019;Debow et al, 2021). However, culls and harvests tend to be less selective for old and diseased individuals than predation (Wright et al, 2006;Krumm et al, 2010).…”