One of the classic national park experiences is a Colorado River float trip through the Grand Canyon. As one group discovered, however, memorable moments on such trips aren't limited to running the rapids, and some surprising adventures can also occur when you tie up for the night.

I had the opportunity some years ago to serve as "chief cook and bottle washer" for a ten-day river trip by a small group of researchers. Good scientific data is important if any park is to make sound decisions about managing its natural resources, and these experts from several universities were conducting a variety of projects in the depths of the canyon.

In this case, almost everyone on the trip also acquired some unexpected, useful and rather unsettling "scientific" information.

Camp was made each night on a sandbar along the riverbank. Depending upon their preferences for accommodations, members of the group either rolled out a sleeping bag, inflated an air mattress, pitched a small tent, or all of the above. Due to the warm weather, tents didn't see much use, and sleeping was on top of rather than inside sleeping bags.

One morning about halfway through the trip, everyone was starting to stir from his bed and look for that first cup of campfire coffee. As one of the researchers started to roll up his sleeping bag, he alertly spotted an unusual pattern in the sand.

Upon closer examination, he noticed that these markings appeared to be tiny tracks which ran across the soft sand to the edge of his sleeping spot, disappeared, and then reappeared on the opposite side of the place where he had spent the night.

A great thing about this group was that no matter how obscure the question, if it involved the natural world someone in the party probably knew the answer. Scientists are by nature curious individuals, and when our alert observer commented about this interesting phenomenon, a crowd gathered around to see what could be learned.

One among our number was by trade an entomologist—an insect expert—and he immediately solved the mystery.

“Hey, look at that,” he exclaimed. “That’s really amazing!” Turning to the man who had spent the night in that spot, he commented, “Good thing you’re a sound sleeper.”

“Why’s that?” asked his companion.

“Know what those tracks are?”

“Well, no.” The first man’s specialty was fish, which don’t leave many footprints in the sand.

“Scorpion,” replied the bug guy in a matter-of-fact tone. “They’re nocturnal, so they’re only active after dark. Looks like that little rascal took a stroll across the beach during the night, marched right across your body, back down the other side and kept on going.”

A somber silence descended upon the group, and all eyes swung in unison back to the tracks in the sand as everyone pondered his own nearby sleeping spot. Our resident expert in things that roam silently in the night sensed the discomfort and sought to reassure his comrades.

“Scorpions rarely bother people unless they’re stepped on or feel threatened, and besides, only one species in this area has venom that’s really dangerous to humans. Otherwise, a sting isn’t much worse than a wasp’s—unless you happen to be allergic to the venom.”

Glancing over at the man who’d had an unknown close encounter of the creepy kind, he concluded cheerfully, “It’s good you didn’t swat at him in your sleep, though.”

Thus supposedly reassured, the crew went back to the business of breaking camp. There must have been some further review of sleeping arrangements by the group, however, since I noticed the next evening that a couple of members who had previously opted for sleeping under the stars decided there were advantages to pitching their small tents after all—along with keeping those screened doors zipped tightly shut all night.

A good rule of thumb on any outdoor trip is to always shake out your shoes, boots and other items of clothing before putting them on. The same advice applies to a sleeping bag or other bedding before crawling in for a snooze. The purpose of that shaking is to dislodge any non-human life forms that may have taken up residence before you insert one of your body parts into that same space.

I couldn’t help but observe that there seemed to be a renewed vigor in such precautionary measures for the balance of the trip. It was a bit like the situation at times in parts of California and other earthquake territory—there was a whole lot of shakin’ going on.

This story is adapted from the book Hey Ranger 2: More True Tales of Humor and Misadventure from the Great Outdoors © Jim Burnett and Taylor Trade Publishing, used by permission