Game and non-game animals are beginning the most vulnerable time of their lives — birthing season.

The killers are domestic dogs and cats, usually well-fed animals that do not kill to survive as wild predators do. It’s because they don’t know any better and, apparently, neither do their owners.

Now is the time that domestic dogs begin to run in packs, attacking snow- and ice-bound deer. Pregnant does and newly born fawns are the easiest targets. Even the gentlest shepherding dogs will return to the hunting instincts of their wolf ancestors now.

Unlike wolves, however, dogs have lost the instinct to go for the throat and kill quickly. They often attack from the rear and mangle their prey, leaving it to die slowly.

When they’re not mauling wild animals, dogs allowed to run free will kill chickens and other livestock without eating the kill. They’ve already eaten at home.

Domestic cats are worse.

A study at the University of Wisconsin found that a rural cat’s diet may contain 35 percent songbirds. It was estimated that rural cats in Wisconsin killed an estimated 39 million birds each year.

“Free-roaming cats kill hundreds of millions of birds and probably more than a billion other small wildlife in the U.S. each year,” according to the Bird Conservancy.

“Even when well-fed, cats will continue to hunt and kill birds and other wildlife,” according to the Montana Department of Fish and Wildlife. “Domestic cats don’t kill to eat; they pursue their natural instincts as hunters and predators for entertainment.”

Ground-nesting birds such as wild turkeys, grouse and piping plovers are the most vulnerable to free-roaming cats. So are young birds that leave their above-ground nests for a few days before they perfect flying.

Putting bells on cats doesn’t work. Watch a cat wait to ambush a field mouse or a bird in a bush, and you won’t see a muscle move until the explosive and deadly ambush. There is no time for the bird to escape when it does hear the bell — if it hears the bell. Besides, birds and other wildlife do not associate bells with being stalked.

Even in states where it’s legal for citizens to kill stray dogs and cats, doing so can become a legal nightmare in our litigious society.

You can call the environmental police, but game wardens generally have more important things to do than catching stray cats.

Animal control officers? When a stray dog nailed one of my chickens this autumn, the animal control officer didn’t even return my phone call.

You can catch a cat in a live trap and turn the animal over to your animal-control officer, humane society or animal shelter. Tuna and sardines are effective baits, but may attract wildlife, too.

Montana wildlife officials recommend baiting with catnip. Dogs can be trapped, too, but they’re more difficult and dangerous to handle.

The best bet is to confine your own cats and dogs and to urge everyone in your neighborhood to do the same.