Rocky Mountain Wood Tick

Dermacentor andersoni

Appropriately named, the Rocky Mountain Wood tick (Dermacentor andersoni) is found predominantly in states with the Rocky Mountains, and is typically found in shrubs, lightly wooded areas, and grasslands. As with its very close cousin, the American Dog tick (Dermacentor variabilis), Rocky Mountain Wood ticks are a known vector of Rocky Mountain Spotted Fever, Tularemia, and Anaplasmosis; as well as Colorado Tick Fever and Tick Paralysis in both humans and pets.

Adult ticks feed primarily on large mammals, while larvae and nymphs feed on small rodents. Adult stage ticks are the ones primarily associated with pathogen transmission to humans. Wood ticks typically take two to three years to complete their life cycle.

Rocky Mountain Wood Tick

Quick Overview:

  • In the Pacific Northwest, Wood ticks are far more common than American Dog ticks.
  • Typically found at higher elevations; in shrubs, meadows, and lightly wooded areas.
  • Diseases transmitted: Rocky Mountain Spotted Fever, Colorado Tick Fever, Anaplasmosis, Tularemia, and Tick Paralysis.
  • Male ticks are not known for transmitting infections.
  • Adult Wood ticks can go up to 2 years without feeding on a host.
  • Female ticks lay an average of 6,000 eggs in a single clutch before dying.
Tick ID -- Rocky Mountain Wood Tick

The Rocky Mountain Wood tick (Dermacentor andersoni) has a similar appearance to the American Dog tick but can be distinguished by its bright reddish, tear drop shaped body (Dog ticks are more dark brown). Females will have a white colored shield and males will have gray and white spots on their body.

They are primarily located in the Rocky Mountain States of Nebraska, South Dakota, Arizona, New Mexico, and California. Lower elevations will typically lead to high population densities.

Mountain Rocky Wood Tick (Dermacentor andersoni)

In the Mountain region of the U.S., adult male and female wood ticks can be active from January through November, but are most common in the late spring/early summer and their activity diminishes during the hot and dry mid-summer period. Further west in the northern inter-mountain region, large numbers of adult wood ticks can occur in April and May.

Adult ticks prefer to feed on medium to large mammals and can be found questing about knee-high on the tips of vegetation. Males only blood feed for short periods of time to initiate spermatogenesis, after which they seek to attach to and mate with female ticks. Female wood ticks feed for 4-17 days before dropping off their host and laying up to 6,000 eggs.

The primary determinant of lifespan for Rocky Mountain Wood ticks is the availability of the blood meal required to reach each life stage. Larvae can survive up to a month without a blood meal; however, with a single meal they are able to molt into nymphs, which can then survive upwards of a year before needing another blood meal.

With yet another single feeding, nymphs are able to morph into adults, which can survive up to 2 years without feeding. Members of this species will typically live 1-3 years total in the wild. The longest recorded lifespan in captivity for this species is 4 years. Variation in life span may be influenced by external factors such as humidity, temperature, and host availability, which may cause these ticks to be dormant for longer periods of time between life stages.

Medical Importance

All life stages of the tick can transmit Colorado Tick Fever to humans, and Rocky Mountain Spotted Fever (Rickettsia rickettsii) to humans, cats, and dogs. Rocky Mountain wood tick saliva contains a neurotoxin that can occasionally cause Tick Paralysis in humans and pets.

A bite from an adult female can induce an ascending paralysis that should stop after just a few minutes after the tick being removed, however may persist for up to a day or more. Both nymphs and adults of this tick can transmit Tularemia to a variety of hosts, including humans, cats, and dogs.

Rocky Mountain Wood tick saliva contains a neurotoxin that can occasionally cause tick paralysis in humans and pets; usually a bite from an adult female induces an ascending paralysis that dissipates within 24-72 hrs after tick removal.

Both nymphs and adults of this tick can transmit the agent of tularemia (Francisella tularensis) to a variety of hosts, including humans, cats, and dogs. These ticks typically take two to three years to complete their life cycle.

Habitat Lone StarAs their name would suggest, Rocky Mountain Wood ticks  prefer wooded habitats with low-growing vegetation, around trails and grasslands where larger animals commonly pass by and thrive in areas that are also accessible to humans.

Appropriately named, the Rocky Mountain Wood tick is found predominantly in Rocky Mountain states and Southwestern Canada from elevations of 4,000 to 10,500 feet., and is typically found around shrub-lands, lightly wooded areas, open grasslands, and along trails, mainly at lower elevations.

Range Map - Rocky Mountain Wood Tick

The American Dog Tick occurs primarily in wooded, shrubby and long-grass areas. However, it is possible for residential areas to support populations of this tick. Shrubs, weeds, tall grass, clutter and debris on the property attracts the rodents that are hosts for immature ticks. By maintaining grass short, removing possible rodent harborage, and sealing cracks and crevices in and around the property one can directly reduce or prevent local tick populations.

Keeping grass and weeds cut short decreases humidity, which helps kill ticks or makes an area undesirable for ticks and rodents. Additionally, it makes it difficult for ticks to climb on the vegetation and wait for its host. If pesticides are applied, cutting the vegetation short increases effectiveness and allows for better coverage. Removing rodent harborage areas may reduce an infestation.

Because dogs can easily pick up ticks while walking on infested grass or roaming through wooded areas, it is necessary to treat the pet properly. There are many products that can be applied to prevent or treat a tick infestation on an animal including topical treatments and sprays. Regularly grooming, washing bedding, and examining the dog are strongly recommended to prevent tick infestations.