For many people, hearing coyotes howl in the distance is a beautiful experience. But a face-to-face encounter with the predators can leave a different impression.

Scientists say these adaptable animals could be becoming more aggressive and less fearful of humans—to the detriment of both species.

Wildlife specialist Robert Timm, of the University of California's Hopland Research and Extension Center, has documented some 160 coyote attacks and dangerous incidents over the past 30 years in California alone.

"There is an increasing problem with coyotes losing their fear of humans and becoming aggressive," Timm said.

"We've seen any number of instances where they came into a fenced yard and killed a small dog or cat," he added. "And we've documented pets taken from a