Sand Wasps

I was introduced to sand wasps (Bembix sp) by Mike Arduser when he came to visit the Platte River Prairies back in 2012.  As we stood together in a sand prairie, a bee-like creature was zipping around us with incredible speed.  Mike explained that it was a sand wasp, and that it wasn’t interested in us, but rather was looking for flies that might be hanging around us.  Since that day, I’ve paid much more attention to sand wasps and have seen them all over the place in sandy places.

Sand wasp (Bembix americana spinolae) burrowing in sand in a blowout. The Nature Conservancy's Niobrara Valley Preserve.

Sand wasp (Bembix americana spinolae) burrowing in sand in a blowout. The Nature Conservancy’s Niobrara Valley Preserve.  This wasp was about 1/2 inch long.

While we were exploring a big sand blowout last week at the Niobrara Valley Preserve, there were lots of sand wasps buzzing around, and we found some of their nest burrows.  I took a little time to sit near a couple nests and photograph the females as they worked to excavate them.  The wind appeared to be blowing just as much sand back into the holes as the bees were digging out…

Here's the same wasp as above as it digs sand out of its burrow.

Here’s the same wasp as above as it digs sand out of its burrow.

The video below shows both the blowing sand and the valiant effort of the wasp to excavate its burrow despite the wind.  If the video doesn’t appear correctly, try clicking on the title of this post to view it through an internet browser.

Mike tells me these sand wasps and their relatives catch and paralyze flies for their young.  They lay eggs in their burrows and provide the flies as food for the larvae.  Females, of course, do all the work to create the burrows, catch the flies and lay the eggs.  The males are just around for mating purposes.  While the wasp larvae eat flies, both the adult males and females feed on nectar and pollen.

Here are a few more images of the sand wasps we saw last week, along with the blowout they were living in.

A big blowout where wind keeps sand moving and open.

A big blowout where wind keeps sand moving and open.

The sand wasp shown earlier takes off and twists its body to zip away.

The sand wasp shown earlier takes off and twists its body to zip away.

This was a little smaller wasp from a different species that was nesting in a different part of the blowout from the first wasp.

This was a smaller wasp from a different Bembix species that was nesting in the same blowout as the first wasp.

...and that wasp was also digging its burrow.

…and that wasp was also digging its burrow.

As often happens with invertebrates, once I’ve been introduced to a creature, I start seeing it everywhere.  Even better, I’ve yet to meet an invertebrate that doesn’t have a fascinating background story.  It’s an awesome world we live in, and we share it with some pretty great neighbors.

Thanks, as always, to Mike Arduser for his help with identification and ecology.

In Defense of Erosion

The Nebraska Sandhills region consists of about 12 million acres of sand dunes with a thin layer of vegetation draped across them.  That vegetation has come and gone over the last several thousand years, as long-term climatic patterns have shifted from wet to dry and back.  We are in a relatively wet period (geologically speaking) today, and grassland is clinging to the hills.  For now.

Except where it can’t.  Here and there, throughout the sandhills, particularly on steep hills, sand breaks through.  Most of the time, blowouts are triggered by a combination of topography and some kind of physical disturbance.  A two track road or cattle trail up a steep slope, for example, or a favorite hangout of livestock.  Just as with frayed fabric, once a small hole in the vegetation starts, it tends to spread.  Most Sandhills ranchers see blowouts as a great risk to their livelihood and work hard to prevent them, or to heal them once they start.  Those ranchers are encouraged in that view by watchful neighbors and a long history of agencies and university extension staff warning of the dire impacts of wind-induced soil erosion.

Sandh

Small blowouts dot the steeper hills in the background and a couple larger ones appear in the foreground.  Overall, these make up a tiny percentage of the landscape, but many ranchers see them almost as badges of shame.

big

A very large blowout like this can cause not only a loss of forage for a rancher’s livestock, but also a huge challenge for fence maintenance.

The Sandhills is ranch country, and all but a tiny fraction is privately-owned and managed for livestock production.  Most ranchers are conservative with livestock numbers and grazing strategies, trying to preserve that thin fabric of grass that feeds their livestock, and thus their families.

While there are certainly places that are prone to wind erosion and practices that can accelerate it, the risk of blowout creation and spread has also become a kind of mythology.  In much of the Sandhills, blowouts are actually difficult to create (we’ve tried) and the percentage of a ranch that could potentially be covered by blowouts is very small.

wet

Sometimes, wind erosion digs a blowout deep enough that it intersects groundwater, creating wetlands.

While conservative grazing has helped maintain healthy prairies in the Sandhills, it has also led to a loss of open sand habitat for a group of plant and animal species that depend upon blowouts and similar areas.  Those species are important, but asking a rancher to allow, let alone encourage a blowout, is much like asking a business man to go to work wearing Bermuda shorts with his sport coat.  The peer pressure and social norms associated with blowouts can be more influential than any potential loss of livestock forage they might cause.  Just as farmers judge their neighbors by the weeds in their fields, Sandhills ranchers judge their neighbors by the blowouts in their pastures.

blow

Blowout grass (Redfieldia flexuosa) is one of a select group of plants that can colonize a blowout and begin to stabilize the sand.

penstemon

Blowout penstemon (Penstemon haydenii) is a federally listed endangered plant that is found exclusively in blowout habitats.  This one is in a blowout that is healing and might not support penstemon populations much longer.

tiger beetle

Many species of tiger beetles can be found in Sandhills blowouts, including several of conservation concern.  These impressive predators hunt small insects in patches of open sand.

lesser earless lizard

Lizards, including this lesser earless lizard and other species, are often seen in and around blowouts, where they can forage in open areas but retreat quickly to cover to escape predation.

Regardless of the social or economic ramifications of blowouts for ranchers, bare sand patches really are important habitats for many prairie species.  The discussions I’ve had with ranchers about the ecological values of blowouts have always been polite, but I can’t say they’ve been met with great enthusiasm.  I understand that, but that doesn’t change the need to continue having those discussions.

spider

Spiderwort (Tradescantia occidentalis) grows on the edge of a large blowout, surrounded by bare sand and a cast of other plants struggling to survive in the shifting substrate.

It may be that changing climate will render moot our discussions about whether or not to allow or encourage blowouts in the Sandhills.  Eventually, we will experience enough consecutive years of hot dry weather that even the most conservative grazing won’t prevent widespread blowing sand once again.  We can’t predict whether those conditions will arrive in the next few years, or not for many decades.  When they do arrive, both the ecological and human communities of the Sandhills will be glad to have species that are well adapted to open sand.  Plants like blowout penstemon and blowout grass, for example, can help restabilize areas of bare sand, and they also provide food for both livestock and wildlife.

For now, the Sandhills provides a vibrant grassland that supports both humans and wildlife.  That will likely change at some point in the future.  Hopefully, blowout-dependent species will find enough habitat to maintain their populations until we really need them.

…and hopefully no one will feel like they have to wear Bermuda shorts in order to make that happen.