This browser does not support the Video element.
SAN FRANCISCO - The National Park Service posted "coyote alert" signs at Crissy Field in San Francisco to warn dog-walkers about recent coyote sightings and attacks.
"Three reports have come in from people indicating their off-leash dogs were killed by coyotes at that location this month," a Golden Gate National Recreation Area spokesperson said in a statement.
Dog-walker Janet Bran said she was surprised to see a coyote for the first time on Tuesday on the beach at Crissy Field.
"It was here Tuesday morning over on the beach over there, and when I pulled in I heard shouting, so I knew there was a coyote over there," Bran said.
The encounter prompted her and other dog-walkers to purchase collars and vests with metal spikes for dogs to wear.
"It's to deter a coyote when they put their mouth on it," said Bran.
"At night, you see them at the Safeway down the street. And they're just trying to survive and humans are taking over their land," said Angelo Miller, a San Francisco dog owner.
Wildlife biologists believe one or more coyotes in the area have become more aggressive when in the presence of off-leash dogs.
Staff were seen at Crissy Field keeping an eye on things and signs say rangers will be on site.
Owners should be aware of their surroundings and use a short leash instead of a long one, officials said.
In July, a young girl was bitten by a coyote while attending a camp in The City's botanical garden.
The signs remind people that coyotes are most active in the early morning and evening.
Professor Schell says if you see a coyote, do not feed or interact with it. He says most coyotes are afraid of humans but will protect their territory or den. Park officials say you should pick up your dog, make yourself big and make noise, and leave the area.
Park rangers say if you have an encounter you should report it to park dispatch at (415) 561-5505.
Professor Chris Schell, who runs a UC Berkeley lab researching urban wildlife, says co-existing with coyotes means taking precautions, and he says coyotes play an important role, even in an urban area.
"We should see coyotes as beacons of biodiverse systems, as helpers in us maintaining coexistence with all types of organisms in this city rather than seeing them as a villain," Schell said.
Jana Katsuyama is a reporter for KTVU. Email Jana at jana.katsuyama@fox.com. Call her at 510-326-5529. Or follow her on Twitter @JanaKTVU and read her other reports on her bio page.