One of the interesting aspects of a park ranger's job is the knowledge that every day brings the possibility of a new—and frequently unusual—experience. That was definitely the case for me one day at Willow Beach, Arizona, a popular fishing spot in Lake Mead National Recreation Area.

If I had learned there was trouble lurking in the depths of Black Canyon and decided to round up the usual suspects, it's unlikely my list would have included … a beaver. After all, this was the Mohave Desert.

Here's a little background to set the stage: Willow Beach is 13 miles downstream from Hoover Dam, which was constructed within a deep, narrow canyon on the Colorado River. The dam impounds Lake Mead and discharges water into the upper end of a second reservoir, Lake Mohave. For the first twenty miles below Hoover Dam, the water is confined within the steep, narrow walls of Black Canyon, and the water level is determined primarily by discharge of water through the dam.

The water can get pretty shallow at times in the upper reaches of the canyon, and the rocky river bottom is downright unforgiving to propellers on boat motors. Two fishermen learned this the hard way one day, and I found myself squarely in the middle of their mishap.

Early in the afternoon I heard a boat approaching the Willow Beach launch ramp. The outboard motor seemed to be running pretty rough, so I watched to make sure the craft got in safely. The two occupants spotted me as soon as they reached shore, and I could tell right away they were not happy campers.

Hoping a preemptive friendly greeting would help defuse the problem, I headed over to see what was amiss. Nice try. The men wasted no time informing me it was a disgrace the government didn't do something to control those awful beavers in the river, and suggested I get right to work on that problem!

This was a classic case of "just when you think you've heard it all…." Although there were a few beavers in the area, I wasn't aware that they had caused any problems.

"Yeah, come look at this!" one of the boaters commanded. As he talked, he tilted the outboard motor so the propeller was out of the water. I walked out on the dock and noted a familiar sight: a metal prop with its blades badly chipped and bent from hitting the rocks on the bottom of the shallow river. This particular prop was in especially bad shape, but I was still having a hard time making any connection to beavers.

"We couldn't figure out what was going on until we talked to the other ranger up the river," the man said. "That's when he explained to us about the beavers."

Now I was really stumped, because I was the only ranger on duty within at least forty miles, and the mystery of the beavers was no closer to being solved.

Boater #2 quickly jumped in. "Yeah, you guys need to put up signs warning boaters to take this seriously, until you can trap those little *#@* and get them off the river! Who'd ever imagine that they could do this kind of damage to a prop?"

All eyes swung back to solemnly study the piece of mangled metal and the conversation faltered. I realized this was a chance for a non-committal comment to help pry out a little more information.

"Yes, it is hard to imagine, isn't it?" It was easy for me to agree, since I still had absolutely no clue what they were talking about.

#1 rose to the occasion.

"Yeah, when the ranger explained it to us, it made sense. I've heard that beavers have to keep gnawing on something almost all the time. Since there aren't enough trees around here for them to gnaw on, they'll even chew on boat props out of pure desperation." His glare in my direction clearly suggested it was my fault that suitable trees were in such short supply here in the desert.

It was #2's turn to hammer the point home. "It makes sense when you think about it. Metal props are kinda shiny, and that's sure to attract the attention of the poor beavers. If you're just drifting along fishing with your motor off, that prop hanging down in the water is bound to be too much for them beavers to resist. Besides, these new props are made out of that soft aluminum or somethin' - not like the good un's we used to get. You don't realize the damage has been done until you crank up your motor again, and by then it's too late."

I read once that you should never consider a day to be a success unless you've learned something new. On that basis, this day was certainly a winner–but I'll refrain from commenting about what I had just learned from this conversation.

Fortunately, I was saved from further discussion by the arrival of another boater who was waiting his turn at the dock. My new acquaintances prepared to depart, with a parting admonition that I should check into this situation "right away." I assured them that I would do just that, and I intended to start by heading upriver to see if I could locate their mysterious "ranger."

It didn't take long. Less than two miles upstream, I spotted a familiar boat headed back downriver. It was the local state game warden, who had launched his craft about twenty miles downstream, so I didn't realize he was in the area.

I eased my outboard down to idle and waited for the warden's boat to come alongside. We had a great working relationship, and I could tell he was working hard to suppress a grin. We exchanged greetings and there was a brief silence.

"So," I asked, "seen any beavers today?"

The warden burst out laughing, and I couldn't help but join in. "I can't believe you gave those guys such a wild tale! What in the world were you thinking?"

My friend at least had the grace to look a little sheepish. "Well, that pair wouldn't listen to any advice when I tried to warn them about the shallow water. Said they'd been boating before I was even born and all that stuff. When I saw them later, they couldn't figure out why their motor was vibrating so much.

"When I took a look at the prop, I knew right away what had happened. I can't believe they didn't feel the prop hitting the rocks! I offered to make sure they got back okay, but they said didn't need any help. I figured I'd catch up with them before long if they had any trouble."

After a brief pause, he continued. "Sorry, but they were so determined not to take any suggestions that I just couldn't resist. I gather you talked to them."

"Well, actually, they did most of the talking. And if I were you, I'd give them a few more minutes to make sure they're gone before you show your face down there. On second thought, why don't you run on down and give them your phone number in case they need any follow-up on our 'beaver problem.'"

After I included this story in my first book, I received a humorous e-mail from a reader who had designed an "official NPS beaver lure." Proving that American ingenuity is still alive and well, the man included a sketch of his invention.

It bore an uncanny resemblance to an outboard motor propeller.

This story is adapted from the book Hey Ranger! True Tales of Humor and Misadventure from America’s National Parks © Jim Burnett and Taylor Trade Publishing, used by permission.