CEH Editor Finds Evidence for Rare Rock-Nesting Bees

On a hike in Arizona, he documented
a rare bee’s nest site in sandstone

 

— We know about beehives of wax, but can bees really dig into sandstone? —

Photo story by David Coppedge, CEH Editor

It was April 23, 2023. I had just hiked over 4 miles in the morning around a rarely-visited portion of the Paria Plateau in Arizona. After a lunch break, I drove to another remote place nearby called Little Valley. A mesa to the west looked interesting, so I flew my drone over for a look, and found my interest to be confirmed: it was a colorful mesa that looked like a banana split with yellow and red colors.

This required more investigation, so I packed my day pack for a closer look. It would be another three-mile excursion into a  wilderness where few have walked.

Near the end of my hike, I found something strange: a wall of yellow sandstone pockmarked with tiny holes.

I was very familiar with tafoni—air pockets in rocks formed by dissolution of soft minerals—but these were different. They were much smaller. There were thousands of them, all on a particular vertical wall of Navajo sandstone and nowhere else. I photographed them but did not understand how the holes were made, and why they were found only at this one spot. Having viewed numerous outcrops of Navajo sandstone for many years, this phenomenon was a mystery.

Seven months later, I posted the above photo on my Flickr page. I whimsically teased that it might be a “woodpecker beak sharpening rock” or something, and invited viewers to explain it.

The Answer Comes

The photo caught the attention of a Flickr friend named Jeff Mitton, a naturalist in Colorado and a fine photographer. Dr Mitton is a professor emeritus in the Department of Ecology and Evolutionary Biology at the University of Colorado Boulder. He immediately suspected it might be a nesting site for a recently-identified species of bee named Anthophora pueblo, a type of digger bee. He checked with a scientist he knew, Dr Adrian Carper, who agreed with the identification, and offered the explanation as a comment under the photo. Both were excited to see it, because only a few nesting rocks were known up till now. Dr Carper said,

They look like digger bee nests. Anthophora peublo is a fairly recently described species that nests in sandstone. If so, this is an enormous nesting aggregation.

Under the other photo, he commented, “An awesome find!” With permission, Jeff included my photo for an article in the Colorado Arts and Sciences Magazine on December 20, a week ago. He tells about this rare species of stone-gnawing bee.

A few years ago, Adrian Carper, who is in my department and also the Museum of Natural History at the University of Colorado Boulder, told me about a species of bee that could chew nest holes into stone. It was fascinating, and it stuck with me.

Several weeks ago, David Coppedge posted photos in Flickr of sandstone cliffs riddled with small holes, and he asked if anyone had an explanation for the holes. These threads can be tied together, but we have to go back in time.

Jeff proceeded to tell about a bee expert named Frank Parker who 50 years ago had found a species of bee that gnaws into sandstone to lay its eggs. Samples of the rock were collected, but they idled in a museum drawer for decades.

Quite recently, Parker and Michael Orr, at Utah State University, were working in the University Museum in search of bees that had not yet been named. The blocks of stone and the bees that emerged from the stone were properly saved and accessible decades after Parker deposited them.

Before announcing their discovery of a new species, Orr and Parker felt that they needed to buttress their paper by discovering more bee populations. They soon found five additional sites, one of them in the Long House Ancestral Puebloan Cliff Dwelling in Mesa Verde. They published their discoveries in 2015 and named the new species Anthophora pueblo.

Only a few nesting sites had been discovered to this point, so my find, far away from Mesa Verde, was significant. For me, it was the only place like it on the Paria Plateau, where I had made many hikes for over 10 years. (I had developed a bit of a reputation as an explorer out there finding little-known wonders.) Jeff ends with this idea:

A. pueblo‘s story was released relatively recently, and it is not yet known in the general public. I am sure that many nest sites remain undiscovered and I think it would be fun to search for unknown nest sites while hiking on the Colorado Plateau.

The Biology of the Bee

Jeff’s article tells how the bees gnaw into sandstone even though it degrades their mandibles. The bees are able to soften the stone a little by wetting it with water they carry up from nearby water sources. He offers suggestions for why the sandstone works for the species: it is more permanent, it is free of pathogens, and it shelters the nests from sun and rain if below an overhang. Plus, the holes can be re-used by the next generation.

There were some differences at my site from what the article says. The holes in my photos look smaller than the ones in the other photos, and Navajo sandstone could be harder than the rock found at Mesa Verde, which looks crumbly in the photos (see end of his article for two more photos from Mesa Verde).

A nest site of A. pueblo is often an expanse of vertical sandstone, facing east, with an overhang above and a reliable source of water nearby. 

I did not see a source of water nearby, and my site faced west instead of east. And I did not see any bees. The similarities, though, and the lack of any other explanation, make the identification of the rock-gnawing bee the best explanation. The bees might only use the rock during particular breeding seasons.

If this is the work of the same species of bee, I have no idea how they got there. Mesa Verde is a good 175 miles to the east. If there are populations of A. pueblo between the two locations, one might expect that more nest sites would have been discovered by now. Maybe people have not been looking for them.

But that’s biology: some species are plentiful, and some are rare. How amazing is it to think of a bee that builds its nests in the rock? I hope this story inspires more outdoors types to keep an eye out for this fascinating phenomenon!

My experiences and photos in the southwest have provided creation scientists with material for geological research, but this was the first time I had a chance to contribute to biological discovery. I’m glad that Dr Mitton and his colleague, though evolutionary biologists, did not appeal to Darwinism to explain these amazing stone-nesting digger bees. They have all the parts that other digger bees have (mandibles, wings, brains, muscles, digestive tracts, reproductive organs and all the other sophisticated systems that make bees so amazing), so nothing evolved—nor could any of these interconnected systems have “emerged” through blind material processes. We believe, instead, that the Creator of life has equipped each family of organisms with the ability to adapt to new environments. This is one particularly interesting example. I learned something and hope you did, too.