Rocky Mountain Wood Tick Identification Guide
Dermacentor andersoni
The Rocky Mountain wood tick is a hard tick found throughout the western United States and Canada. It is the primary vector for Colorado tick fever and Rocky Mountain spotted fever in western regions, and can cause tick paralysis in humans and pets.
Taxonomy
Rocky Mountain Wood Tick Coloration
Common color patterns to help identify rocky mountain wood tick
Rocky Mountain Wood Tick
Seasonal Activity
When rocky mountain wood tick are most active throughout the year
Where Rocky Mountain Wood Tick Are Found
Hover over states to see their names. Green regions indicate where rocky mountain wood tick have been reported.
Rocky Mountain Wood Tick Identification Guide
Physical Characteristics
The Rocky Mountain wood tick (Dermacentor andersoni) is a medium to large hard tick with clear markings. Unfed adults are 3 to 5 millimeters long. After a blood meal, females can swell to 16 millimeters or more. The body is oval and shaped like a teardrop. Its reddish-brown color sets it apart from other ticks.
The best way to spot this tick is by looking at its scutum. This is the hard shield on its back. Females have a light silver-gray or cream scutum behind the head. Males have gray and white spotted markings on their whole back. Both have reddish-brown legs. Under a magnifying glass, you can see small pits in the scutum.
Like all adult ticks, Rocky Mountain wood ticks have eight legs. You will often see them with front legs stretched forward. This is called “questing.” It helps them grab onto passing hosts. Their mouthparts have barbs that point backward. These barbs hold them in place while they feed.
Similar Species
Rocky Mountain wood ticks belong to the Dermacentor genus. This group includes several ticks that can spread disease:
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American dog tick (Dermacentor variabilis): Found in the eastern United States. It looks very similar but is darker brown. The two species rarely share the same area.
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Pacific Coast tick (Dermacentor occidentalis): Found along the Pacific Coast from Oregon to Baja California. Its range overlaps with the Rocky Mountain wood tick in some areas.
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Winter tick (Dermacentor albipictus): Affects moose and other large mammals. It rarely bites humans.
Rocky Mountain Wood Tick Behavior and Biology
Rocky Mountain wood ticks are three-host ticks. They feed on a different animal at each life stage. The full life cycle usually takes two to three years in the wild but can stretch longer in harsh conditions.
Life Cycle
Female ticks drop from their final host after mating and feeding. They lay 2,500 to 4,000 eggs in leaf litter or soil over a period of 10 to 33 days. Eggs hatch in early summer, producing tiny six-legged larvae.
Larvae climb onto low plants and search for small mammal hosts. They prefer mice, voles, ground squirrels, and other rodents. After feeding for several days, they drop off and molt into nymphs with eight legs. Nymphs seek out similar hosts such as hares, rabbits, and weasels. After another blood meal and molt, they become adults.
Adult ticks target larger mammals. They prefer deer, elk, cattle, horses, dogs, and humans. Adults wait on vegetation tips about knee high. They sense hosts through body heat, movement, and carbon dioxide from breathing.
Habitat Preferences
Rocky Mountain wood ticks live in the mountain and foothill regions of western North America. They prefer:
- Shrubby areas with sagebrush or bitterbrush
- Lightly wooded slopes and forest edges
- Mountain meadows and grasslands
- Transition zones between habitats
- Elevations between 4,000 and 10,500 feet
These ticks can tolerate dry conditions better than many other tick species. They are most common in areas where their wild mammal hosts are abundant. Unlike the brown dog tick, they do not infest homes.
Seasonal Activity
Adult Rocky Mountain wood ticks are most active in spring and early summer. Activity peaks in May and June in most areas. They slow down during hot, dry mid-summer months. They pick up again briefly in fall. Some activity can happen from January through November based on local weather.
Nymphs and larvae are active in summer, feeding primarily on small rodents. These immature stages rarely bite humans. The adult stage poses the greatest risk to people and pets.
Treatment Methods for Rocky Mountain Wood Ticks
Good tick control in areas with Rocky Mountain wood ticks uses both habitat changes and targeted treatments. These ticks live in wild, mountainous terrain, so complete removal is rarely possible. The goal is to lower tick numbers in areas where people and pets spend time.
Environmental Management
Reducing tick habitat around homes and recreational areas can lower encounter rates:
- Clear brush and tall grass from frequently used areas
- Create gravel or wood chip barriers between lawns and wild areas
- Remove leaf litter where ticks shelter
- Discourage rodents by eliminating food sources and harborage
- Keep vegetation trimmed along trails and walkways
Chemical Control Options
Tick sprays can cut tick numbers in targeted areas. Spring treatments before peak tick season work best. Focus treatments on:
- Property edges where landscaping meets natural areas
- Along trails and paths
- Shaded areas with dense vegetation
- Areas where wildlife commonly travel
Personal Protection
When spending time in tick habitat, take precautions:
- Wear long pants tucked into socks
- Use EPA-approved tick repellents with DEET, picaridin, or permethrin
- Stay on cleared trails when possible
- Check yourself, children, and pets for ticks every few hours outdoors
- Shower within two hours of coming indoors
Health Risks and Disease Transmission
Rocky Mountain wood ticks can pass on several serious diseases. Removing ticks quickly and knowing the warning signs can help you avoid problems.
Colorado Tick Fever
Colorado tick fever is a viral illness spread mainly by Rocky Mountain wood ticks. It is the most common disease from this tick. Symptoms start 1 to 14 days after a bite.
Symptoms include fever, chills, headache, body aches, and fatigue. About half of patients get a “saddle-back” fever pattern. This means several days of fever, a brief recovery, then another round of fever. Some people develop sore throat, vomiting, or stomach pain.
There is no specific treatment for Colorado tick fever. Most people recover with rest and supportive care. Severe cases may need hospitalization. Patients should not donate blood for six months after illness because the virus persists in red blood cells.
Rocky Mountain Spotted Fever
Despite its name, Rocky Mountain spotted fever (RMSF) occurs across North America. The Rocky Mountain wood tick is a major carrier in western states. The disease comes from the bacterium Rickettsia rickettsii.
Symptoms usually show up 2 to 14 days after a tick bite. They include sudden fever, bad headache, muscle pain, nausea, and vomiting. A spotted rash often starts on the wrists and ankles, then spreads. Without quick treatment, RMSF can be deadly.
Early treatment with the antibiotic doxycycline is critical. If you develop fever and other symptoms after a tick bite, seek medical attention immediately. Do not wait for a rash to appear.
Tick Paralysis
Female Rocky Mountain wood ticks can cause tick paralysis through a toxin in their saliva. Symptoms begin 5 to 7 days after a tick attaches. The paralysis starts in the legs and moves upward. It affects walking and balance. If the tick stays attached, it can spread to the breathing muscles.
The good news is that tick paralysis reverses rapidly once the tick is removed. Symptoms typically resolve within hours to a day. Finding and removing the tick is the key treatment.
Tularemia
Rocky Mountain wood ticks can also spread Francisella tularensis, the germ that causes tularemia. Symptoms may include fever, skin sores at the bite site, and swollen lymph nodes. Doctors treat tularemia with antibiotics.
Medical Disclaimer: This information is for educational purposes only and is not medical advice. If you experience symptoms after a tick bite, seek medical attention immediately.
References and Further Reading
Other Ticks
Explore other species in the ticks family
Commonly Confused With
Rocky Mountain Wood Tick are often mistaken for these similar pests
Where Rocky Mountain Wood Tick Are Found
Hover over states to see their names. Green regions indicate where rocky mountain wood tick have been reported.
Common Questions about Rocky Mountain Wood Tick
How do I identify a Rocky Mountain wood tick?
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Rocky Mountain wood ticks are reddish-brown with distinctive silver-gray or white markings on their backs. Females have a prominent light-colored shield behind the head, while males have gray and white spots across their entire back. They are similar in size to American dog ticks, measuring 3-5mm unfed and up to 16mm when engorged.
Where are Rocky Mountain wood ticks found?
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These ticks live primarily in the Rocky Mountain region of the United States and southwestern Canada. They prefer shrubby areas, lightly wooded terrain, and grasslands at elevations between 4,000 and 10,500 feet. They are most common in transitional zones where meadows meet forests.
What diseases do Rocky Mountain wood ticks carry?
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Rocky Mountain wood ticks are the primary vector for Colorado tick fever, a viral illness. They can also transmit Rocky Mountain spotted fever and tularemia. Their saliva contains a neurotoxin that can cause tick paralysis in humans and animals.
When are Rocky Mountain wood ticks most active?
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Adults are most active from late spring through early summer, typically March through July. Activity peaks in May and June, then drops off during hot, dry mid-summer months. They can be active from January through November in some areas but are rare during winter.
How long can Rocky Mountain wood ticks survive without feeding?
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Adult Rocky Mountain wood ticks can survive up to two years without a blood meal. This makes them remarkably persistent in outdoor environments. Their full life cycle typically takes two to three years to complete.
Can Rocky Mountain wood ticks cause paralysis?
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Yes. Female Rocky Mountain wood ticks produce a neurotoxin in their saliva that can cause ascending paralysis. Symptoms begin in the legs and move upward. The paralysis typically reverses within hours to a day after the tick is removed. Quick tick removal is critical.
How do Rocky Mountain wood ticks differ from American dog ticks?
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The two species look very similar but live in different regions. Rocky Mountain wood ticks are found in the western U.S. and Canada, while American dog ticks dominate the eastern U.S. Rocky Mountain wood ticks tend to have a more reddish, teardrop-shaped body compared to the darker brown American dog tick.
With five years of hands-on experience in the pest control industry, George Schulz is a registered technician with the Virginia Pest Management Association and a proud third-generation professional in a family business that's been protecting homes for over 57 years. He manages and trains a team of service pros while also leading internal research efforts—recently spearheading a deep-dive review of thousands of documents on pest control materials to hand-pick the most kid and pet friendly, most effective solutions tailored specifically for homes in the DC metro area.