As this man learned the hard way, male deer can be very territorial, especially during mating season.
According to NBC News, the man strolled too close to a herd in a west London park, leading this deer to chase him. The man finally climbed up the tree to protect himself and witnesses called the police.
Breeding season begins as days get shorter, when bucks begin to leave signs that they are ready to mate. It is typical for bucks to be on edge during breeding season as they "spar" or challenge other bucks to "establish dominance" and gain female attention, according to the Noble Foundation.
This behavior, along with leaving scents around the wilderness by rubbing trees or scraping the ground, are a normal part of mating season, known as the rut.
Mating season for deer has begun in London, and park rangers are warning people to stay far away from the animals during this time.
Last month a deer was the one that became trapped in an unusual place, after falling into a Colorado swimming pool. Fortunately, a homemade ramp helped the animal escape.