Coyote attacks on small pets in So. Cal are very common..if you have small pets, do not let them outdoors unattended, espcecially at night. Day attacks can happen but are not as common. Coyotes can easily jump over a fence as tall as 6 feet. Mountain lion attacks on pets are much less common, but can still be possible. Mountain lions disperse in the winter months..so now would be a time that they may be in neighborhoods that they do not regularly inhabit, so this would be an especially dangerous time to let your pets outside alone. Coyotes are out and about year round. If you are out in the yard with your pet, coyotes are not going to bother you. They will usually not bother large dogs either, as they are actually not very large themselves. I see coyotes often, daily during the spring season and have never been threatened by one. I am much more worried about running across stray dogs while out working...much more unpredictable and dangerous. Moutain lions will avoid humans whenever possible, attacks on humans ALWAYS turn out to be an injured or sick animal that was not able to hunt it's normal prey. As long as you accompany your pets outside..they will be safe.
me: wildlife biologist who lives and works in So. Cal and who has treated many pets attacked by coyotes during a 12 year veterinary career.