Canis familiaris
The most common 'mystery' track on trails. Dog prints are rounder and messier than a coyote's, and the trail wanders.
1–4 in, hugely variable by breed. Four toes with blunt claw marks. Round overall shape, toes splayed. Large heel pad relative to toes. Meandering trail, often with human boot prints nearby.
Anywhere people go. Worldwide.
Daytime, whenever a walk is offered
Omnivore
A dog's nose print is as unique as a human fingerprint.
Should I be concerned?
Ask before petting — a leashed dog is someone's family member.