“There’s way too many issues and animals — there’s always something waiting,” said Mr. Ibanez, who has held the job for more than five years. “It can be dangerous. I’ve never been bitten, and I don’t want to get bit.”

Across Guam, which is home to about 170,000 people, packs of these “boonie dogs,” as they are known, can be seen everywhere — crossing highways and chasing cars, roving the parking lots of luxury hotels, lounging in cul-de-sacs fringed with coconut trees.

On social media, residents frequently post stories and photos of dangerous encounters, like one that left a tuxedo cat with bloodied eyes and a ring of red around its neck, and another in which a feral stray climbed three stories of an apartment building to attack a pet.

In the animal control office, Mr. Ibanez looked through photos of pet dogs with bloodied legs and one that showed a stray baring its teeth at a toddler as she stood on her doorstep.

“I can say like 80 percent are vicious,” he said. “We get hospital reports about stray dogs biting kids, even elderly people.”