American Dog Tick

Dermacentor variabilis


Primarily found east of the Rocky Mountains, but also found in limited areas along the Pacific coast, American Dog ticks (Dermacentor variabilis) are found predominantly in areas with little to no tree cover, such as grassy fields and along walkways and trails. They feed on a variety of hosts, ranging in size from mice to deer, and can survive for up to 2 years at any given stage if no host is found. Females can be identified by their large off-white scutum against a dark brown body.

Adult Male Adult Female Engorged Female

Disease Transmission

The American dog tick is the species of tick most commonly responsible for transmitting Rocky Mountain spotted fever in humans, and may also transmit tularemia.


The American dog tick exhibits a three-host tick life cycle. In warmer regions of its southern range all three stages may be active on hosts throughout the year with a pronounced increase of occurrence during spring. In northern regions, larvae and nymphs are active spring to autumn while adult questing appears to be highest in spring. Gravid females may lay from 4,000–6,500 eggs.

Range Distribution

Widely distributed east of the Rocky Mountains. Also occurs in limited areas on the Pacific Coast.

Range Map - American Dog Tick