Often, but it is unproven for lost pets. Tracked village dogs covered more ground at night, and quiet hours suit a scared dog, so plan for dawn, dusk and dark.
Probably, but nobody has measured it in lost pets
Many lost dogs seem to move at night and around dawn and dusk, but no study has tracked lost pet dogs to prove it. What exists is a little GPS research on free-roaming village dogs, plus years of field reports from people who search for lost pets. Together they suggest a scared dog is likely to shift toward quiet hours, when there are fewer people and cars. They do not mean your dog sleeps all day or that it moves only after dark. Plan to look at both ends of the day, and put cameras on the hours you cannot cover in person.
What GPS studies show
Two studies are worth knowing, and they disagree a little. In a village in Cambodia, researchers put GPS collars on 13 free-roaming dogs and found they covered more ground at night: about 2.75 miles between 6 p.m. and 6 a.m., against about 2.1 miles in the daytime. In rural Chad, a much larger study tracked 174 dogs in the dry season and 151 in the wet season. Most showed daily rhythms, but the peaks were often at midday, and in the dry season some dogs peaked between 6 a.m. and noon and again between 6 p.m. and 10 p.m. Both groups were owned dogs living loose near home. They were not frightened American pets, so use these only as a sign that timing changes with place and season.
Why your sightings may mislead you
Your sighting log has a built-in bias. People report dogs when people are awake. If most of your calls come at 7 a.m. and 6 p.m., that may show when your dog moves, or only when commuters are driving past. A dog crossing a road at 3 a.m. is seen by almost nobody. Practitioner Kat Albrecht makes a related point: a dog that escapes in the middle of the night will travel farther before being seen than one that gets out at rush hour. So treat one report from a night-shift nurse or a bakery driver as worth more than five from the school run, and ask each witness what time they were out.
Put the dark hours on camera
You cannot watch all night, but a camera can. Place a trail camera or a borrowed security camera at the spot with the most recent sighting, or at a feeding station, and check it each morning. The time stamp is the valuable part. After three or four nights you may see a pattern, such as a visit at 4:30 a.m. Ask neighbors to scan their doorbell footage from midnight to dawn, not only the hours just after the dog left, and to look for a low shape crossing the edge of the frame. Then spend your own hours around whatever times the footage shows.
A night plan you can keep up
Do not stay up all night. A tired searcher misses things and drives badly. Use two short shifts instead: the last hour before dark and the first hour of light, walking or driving slowly with the windows down. Add a late check only if you have a recent sighting or camera visit. Use a headlamp, since light held near your eyes makes eyeshine easier to spot, and sweep low at the edges of yards and tree lines. Keep your voice down. If the dog is near, a flashlight and a shout may push it on. Our post on how to catch a scared lost dog covers what to do when you see it.
Stay safe and stay legal
A stranger with a flashlight in a backyard at 2 a.m. can frighten people. Ask permission during the day, and stay on sidewalks and public land until you have it. If you plan to be out on foot late at night, tell the police non-emergency line what you are doing and give a description of your car. Wear something reflective, because drivers will not expect you on a dark road. Walk with another adult if you can. Be wary of anyone offering a paid night search with a drone: Lost Dogs of Wisconsin warns about drone service scams, and says a real service has a phone number that reaches a real person and should be nearby.
Use daylight for what light is good for
If your dog is moving at night, it may be resting by day, so daylight searching should be calm and close to the ground. This is the time for checking culverts, loading docks and the gaps under decks, and for talking to people. It is also the time to look along roads at first light. Hang your posters where the night traffic goes as well as where the day traffic goes: truck stops, 24-hour gas stations, hospitals and bakeries. Ask the staff on the late shift, since the day staff will not have seen what you need to know.
Sources
Ladd et al., Activity range and patterns of free-roaming village dogs in a rural Cambodian village, Wildlife Research: connectsci.au/wr/article/41289/Activity-range-and-patterns-of-free-roaming. Wilson-Aggarwal et al., rural Chad dataset: datadryad.org/dataset/doi:10.5061/dryad.hhmgqnkfp. Missing Animal Response Network: missinganimalresponse.com/lost-dog-behavior. Lost Dogs of Wisconsin, drone scams: lostdogsofwisconsin.org/post/how-to-spot-a-drone-services-scam.