“Deer tick” is an East Coast term for Ixodes scapularis, and that species doesn’t live in California at all. If you’re searching “deer tick vs dog tick” after pulling something off yourself or your dog in San Diego, you’re almost certainly comparing our region’s actual western black-legged tick to the brown dog tick, two ticks with very different habits and very different risks.
Why “deer tick” is the wrong search term here
National pest and health sites default to Ixodes scapularis, the deer tick, because it’s the primary Lyme disease vector across most of the country. San Diego’s climate and geography don’t support that species. What we have instead is its close West Coast relative, the western black-legged tick (Ixodes pacificus), which does carry Lyme disease but behaves differently and shows up in different places than what national articles describe.
That mismatch matters because the advice changes. Deer-tick content assumes eastern woods and a fall spike. CDPH: in California, western blacklegged nymphs are more active in spring and early summer, and adults are more active from fall through early spring. County Vector Control: ticks here are common in grassy, brushy trail edges, not as an indoor dog-tick problem.
The two ticks you’re actually comparing
Once you set “deer tick” aside, the real comparison in San Diego is between two species with almost nothing in common except that people find both of them on themselves or their pets.
Western black-legged tick (Ixodes pacificus) is easy to miss, especially as a nymph. County Vector Control: tick nymphs may be about the size of a poppy seed. CDPH: this is the California Lyme vector. It lives outdoors on trail edges, leaf litter, and oak woodland understory. Named parks on this page are examples of that habitat type, not a field survey we ran. This page does not map an adult color recipe for this species.
Brown dog tick (Rhipicephalus sanguineus) is uniformly reddish-brown and built for a different life. UF/IFAS: it can complete its entire life cycle indoors and outdoors, and dogs are the preferred U.S. host. Infestations can explode in carpet, baseboard cracks, and dog bedding even if the dog never leaves the yard. UF/IFAS: it is a vector of canine ehrlichiosis and canine babesiosis; it has not been shown to transmit the bacterium that causes Lyme disease.
| Trait | Western black-legged tick | Brown dog tick |
|---|---|---|
| Color | No mapped adult color recipe on this page | Reddish-brown, elongated, no ornamentation (UF/IFAS) |
| Where it lives | Trail edges, chaparral, oak woodland (CDPH, County) | Indoors, kennels, dog bedding, yards with dogs (UF/IFAS) |
| Peak activity | Nymphs: spring and early summer; adults: fall through early spring (CDPH) | Can complete the life cycle indoors (UF/IFAS). Year-round indoor cycles are documented for Florida, not as a San Diego peak |
| Bites people | Yes | Uncommon in the U.S.; this species will bite humans (UF/IFAS) |
| Main disease risk | Lyme disease (CDPH) | Canine ehrlichiosis, canine babesiosis (UF/IFAS) |
| How it gets inside | Hikers, pets returning from trails | Dogs from groomers, kennels, infested homes (UF/IFAS) |
How to tell them apart on sight
Habitat and mapped color notes are the useful clues we can source. UF/IFAS: brown dog nymphs and adults are reddish-brown, elongated, and have no ornamentation on the back. CDPH and County Vector Control: western blacklegged nymphs are about the size of a poppy seed. This page does not rank unfed adult sizes against each other, and it does not map a western black-legged adult color recipe.
Location is the second clue, and often the more useful one. If you found the tick on a hiking trail, in tall grass, or brushing against chaparral, it’s almost certainly the western black-legged tick. If your dog just got back from a dog park or boarding stay and you’re finding ticks crawling across your kitchen floor days later, that’s the signature of a brown dog tick infestation establishing itself indoors.
Why the difference changes what you do next
A single western black-legged tick picked up on a trail is mostly a “remove it correctly and watch the site” situation. CDPH: an infected western blacklegged tick must be attached and feed for at least 24 hours before it can transmit Lyme bacteria, so prompt removal matters. We do not have a sourced 36-hour cutoff on this job. A brown dog tick problem is different. UF/IFAS: finding ticks crawling on walls or curtains is often how owners first notice an indoor population. That source does not evaluate vacuuming as an indoor method.
If your dog is the source, treating the dog through your veterinarian handles one side. The indoor population still needs a separate look. Our flea and tick treatment page explains how a Branch 2 match works. For the full rundown on ticks San Diego County lists, see ticks in San Diego.
Frequently asked questions
Does San Diego have deer ticks?
No. CDPH: the blacklegged tick that carries Lyme in the eastern United States is Ixodes scapularis. California’s Lyme vector is the western blacklegged tick (Ixodes pacificus), which is active on a different seasonal schedule.
Can a dog bring ticks into the house even without going to the woods?
Yes, if the tick is a brown dog tick. Unlike the western black-legged tick, the brown dog tick doesn’t need outdoor habitat at all. A dog can pick one up at a dog park, groomer, or boarding facility, and once inside, the species can complete its entire life cycle indoors without ever going back outside.
Which tick actually carries Lyme disease in San Diego?
The western black-legged tick is the confirmed Lyme disease vector in California, not the brown dog tick. UF/IFAS: Rhipicephalus sanguineus has not been shown to transmit the bacterium that causes Lyme disease. County Vector Control: Lyme and other tick-borne diseases are rare in San Diego County.
How do I know if I have a brown dog tick problem inside my house?
UF/IFAS: the early indoor stages are often missed, and the first sign is often ticks crawling on walls or curtains. A single tick on the dog is not unusual. Multiple ticks loose indoors, especially after a kennel or groomer visit, usually means the population is already using carpet or baseboard cracks.
If you’re finding ticks indoors and aren’t sure whether it’s a one-off or an established problem, call (858) 400-6561 to request a match. The matched company inspects. Pest Pros San Diego does not.