Enter humankind. We domesticated and bred wild cats and dogs (wolves) to be smaller and cute, but they are still predators.
In the case of cats, in addition to owned cats, which kill between four and 18 birds and between eight and 21 small mammals each, each year, there are 30 million to 80 million feral cats in the USA alone, which pose an even greater threat to small mammals and birds.
"According to the research, published today (Jan. 29) in the journal Nature Communications, cats kill between 1.4 billion and 3.7 billion birds and between 6.9 billion and 20.7 billion small mammals, such as meadow voles and chipmunks."Dogs are also a big threat to wildlife:
"Free-roaming dogs can especially cause harm on islands, where ecosystems tend to be vulnerable in the face of non-native predators like dogs. For instance, in the late 1980s, researchers found that a single German shepherd on the loose in New Zealand's Waitangi State Forest was responsible for killing up to 500 kiwis. The dog had a collar, but was unregistered, and its owner was not found.
In another example from 2006, 12 ownerless dogs were thought to be wiping out populations of the endangered Fijian ground frog on the tiny Viwa Island. The Fijian villagers' solution was to "befriend" the dogs by feeding them scraps of food. Ten of the canines were eventually tamed and shipped off the island and the remaining two were killed.