There are several types of predators that are threats to domesticated dogs; two common ones are birds of prey and coyotes. Coyotes and birds or prey are excellent hunters and are easily able to take down dogs weighing less than 25 pounds.
When approaching prey, coyotes may lay a trap to ambush it or work in a pack to take it down. Preventative measures to help protect pets include leaving them in enclosed areas and using flashlights to scare the predators away.
Birds of prey, which include owls and hawks, are harder to control. They tend to stalk out the area where their prey resides and, given the opportunity, will swoop down to scoop them up. The best defense against these birds is to keep the smaller animals in an enclosed environment.