Your kittycat might be cuddly, but he’s also been shaped by millions of years of evolution into an efficient killing machine.

While in recent years, cats have become household fixtures, they used to be mostly viewed as pest control -- and for good reason. Just about every part of a cat’s anatomy enhances its predatory skills.

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Start with the eyes. Cats see as well as humans in daylight, and six times better than people in poor light. This is because they can open up their pupils much larger than humans can, enhancing their eyes’ ability to collect light. Cats have the highest developed binocular vision of all carnivores, meaning they have great depth perception. And they can see in color – in contrast to dogs, which have limited color vision.

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The cat’s jaw and teeth are also specially adapted for killing. Their shorter muzzles mean they can deliver a stronger and wider bite, and their canine teeth are exceptionally strong. One of their premolars also has an interesting add-on – a special spur of bone, called an anterior cusp, which allows it to crush bones.

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The sharp ridges on a cat’s tongue that make it feel rough and sandpapery are called papillae. These little spines are made of keratin, the same stuff that’s in hair and fingernails, and come in handy whether a cat is grooming itself or stripping flesh off of the bones of a bird or mouse.

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A cat’s ears are particularly good at catching the high-pitched frequencies made by rodents. The rounded shape of the ear funnels even the softest or highest of sounds inward, allowing it to pick up minute traces of prey.

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Its whiskers can also pick up tiny vibrations that help them zero in on an unsuspecting meal. When it has captured a small animal, a cat will usually extend its whiskers in front of its mouth to sense where best to deliver a lethal bite.

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The cat’s hunting prowess also owes much to its nature as both a sprinter and acrobat. Cat spines are very flexible, allowing them to put more muscles in gear when running and attain faster speeds.  They can rotate half of their spine about 180 degrees, and jump many times their own height. Because cats’s collar bones are not attached to the shoulder joint, and their shoulderblades swing along with their legs, they have a broader range of movement and can also slip through small spaces.

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Because a cat’s claws are retractable and kept sheathed while walking, they maintain their sharpness. The pads and fur on a cat’s feet also muffle its steps, helping it stalk prey silently. Cats can also rotate their wrists, unlike dogs, giving their paws a greater dexterity and allowing for a broad range of movements like grasping, climbing, and swiping.

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All of these adaptations added together make for a fearsome hunting machine – one that scientists say might be decimating animals, including migratory birds and native wildlife, across the U.S.

In an article published in the journal Nature Communications on Tuesday, researchers from the Smithsonian Conservation Biology Institute and the U.S. Fish and Wildlife Service estimated that “free-ranging” domestic cats – a group that includes both feral cats and pet cats that are allowed to roam outside – kill between 1.4 and 3.7 billion birds each year.

They also wagered that cats are responsible for the deaths of between 6.9 and 20.7 billion mammal deaths.

“Our findings suggest that free-ranging cats cause substantially greater wildlife mortality than previously thought and are likely the single greatest source of anthropogenic mortality for US birds and mammals,” the authors wrote.

One New Zealand businessman, faced with its own national catastrophe, has taken the bold step of calling for his countrymen to stop keeping cats.

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