In summer, rattlesnakes tend to do most of their moving around after dark.

And it's in the dark that the heat-sensitive pits located just behind each nostril come into their own.

The body heat given off by this pack rat is enough to alert the rattlesnake, even though the animal is still several feet away.

The closer the pack rat gets, the more accurate the heat-sensing pits become.

Accurate enough to make a perfect strike.

The rattlesnake does not want to get into a fight.

He might get damaged by sharp teeth or claws.

But the venom it has injected is already starting to digest the rat.

By combining its heat-sensing ability with its keen sense of smell, a rattlesnake has no trouble tracking its victim down.

Normally this pack rat would be enough food to last the snake 2 or 3 weeks.