Often not legally. It depends on your city, so here is how to check the rule and where to post if poles are off limits.
The short answer
It depends on where you live, and in many US cities the answer is no. Utility poles are often covered by local sign rules, and the US Supreme Court has upheld a city ban on posting signs on public property, including utility poles. Plenty of lost pet posters go up on poles anyway and many stay up, but that does not make it allowed, and a crew may remove them. Spend ten minutes checking your local rule. If poles are banned, use private fences and business windows with permission, which often reach the same drivers.
What the Supreme Court decided
In Members of City Council v. Taxpayers for Vincent, decided in 1984, the Court considered a Los Angeles ordinance that prohibited signs on public property. Campaign supporters had attached signs to utility poles, and city workers took them down. The Court upheld the ordinance and said utility poles are not a traditional public forum for communication, noting that other channels such as leaflets and signs on private property were still available. That ruling does not ban posters everywhere. It means a city can ban them. Whether yours has done so is a local question, and a lost pet notice gets no automatic exemption unless your local rule gives it one.
How to check your local rule
Search your city or county name with the words municipal code and signs on utility poles. Most codes are online and searchable. Look for sections on signs, handbills, posting or public right of way. If you cannot find an answer quickly, call the city’s non-emergency code enforcement number or ask animal control, who deal with this question often. Say that you are posting about a lost pet and ask where notices are allowed and how long they can stay up. Some places have a time limit or allow temporary notices in certain places, and you will not know unless you ask.
Who owns the pole
Even when a city has no sign rule, the pole usually belongs to someone. It may be the electric company, a phone or cable company, or the city itself. Their rules can differ from the city’s, and the same street can have poles owned by different companies. A metal tag or stamp on the pole often names the owner. In practice, if the city prohibits posting or the owner removes it, your poster is simply gone, and you have used up a copy on a spot you will now have to replace.
Why poles are not the best spot anyway
A poster on a pole faces one direction, is often narrow compared with the paper and sits among staples from old notices. Tape tends to fail on wood, and paper wrapped around a curve cannot be read in full from a car. A flat surface near the same corner often works better. The goal is a driver stopped at the light reading your phone number. A fence, a shop window or a sign in someone’s yard gives you a flat, stable face toward traffic.
Legal places that work just as well
Ask the homeowner on the corner if you can fix a poster to their fence or put a sign in their yard. Many people will say yes when they see a photo of a missing pet. Ask gas stations and convenience stores on the corner to use a window that faces the street. Try real estate or yard signs: a plain corrugated plastic sign with a big LOST DOG and your number, staked with permission, survives weather far better than paper. Vets, pet stores and grocery store boards are the next ring. See our post on where to put lost pet flyers for a full list.
If poles are allowed where you live
If your local rule allows it, keep the impact small. Do not cover anyone else’s notice, especially another lost pet. Use tape or a zip tie rather than a dozen staples. Keep the poster at a height a driver can read, and keep it clear of any signs and signals. Write the date on it so people know it is current. Most of all, write down the location and take it down yourself the day your pet is found. An old poster left behind gives neighbors a reason to object to the next one.
Sources
Members of City Council v. Taxpayers for Vincent, 466 U.S. 789 (1984): law.justia.com/cases/federal/us/466/789. This is general information, not legal advice. Check your own city or county code.