Photos of the Week – June 10, 2022

False gromwell, aka marbleseed (Onosmodium molle) is blooming in our local prairies right now and I’ve been out photographing its unique flowers and the invertebrates visiting them. It’s a plant that is pretty widespread and common around Nebraska, especially in the east and north, though not so much in the Sandhills. Cattle don’t tend to graze the plants, so they can be found even in native prairies with a history of overgrazing.

False gromwell (Onosmodium molle). Gjerloff Prairie. Nikon 10.5mm fisheye lens. ISO 500, f/8, 1/800 sec.

Marbleseed is a very distinctive looking plant. Its flowers are particularly interesting looking, and describing them can be tricky. In a way, they look like white flowers that haven’t opened yet. Or maybe like little white sock puppets sticking their tongues out?

The Flora of Nebraska has a much more technical and precise description for those of you fluent in botanical terminology:

“Flowers well developed but not showy; sepals lanceolate, strigose, united at the very base; corolla tubular, 7-15 mm, with 5 erect, acute, greenish to yellowish-white lobes, without fornices; stamens inserted in the upper 1/3 of the tube, the anthers longer than the filaments, included; style long-exserted, persistent; gynobase flat.” – The Flora of Nebraska

I expect that clears things up for you? If not, here are a couple photos that show the flowers up close.

Helzer family prairie. Nikon 105mm macro lens. ISO 320, f/7, 1/800 sec.
Gjerloff Prairie. Nikon 105mm macro lens. ISO 500, f/14, 1/640 sec.

Given the unique shape of the flowers, you’d probably think pollination might be difficult for some species. You’d be right. I mainly see them visited by bumble bees, though I’ve read that honey bees and even some smaller bees can sometimes gain access as well (I’ve never seen that) as well as other insects like true bugs and ants.

Earlier this week, I had the chance to photograph several bumblebees demonstrating their technique for obtaining pollen and nectar from the flowers. All of them were basically just pushing their faces into the flowers and forcing them open. That’s a perfectly reasonable approach if you’re big and strong enough to do that, but it helps explain why many smaller bees don’t seem interested or able to follow suit.

An eastern bumblebee (Bombus impatiens) forcing its way into a flower. Gjerloff Prairie. Nikon 105mm macro lens. ISO 500, f/16, 1/500 sec.
Black and gold bumble bee (Bombus auricomus). Gjerloff Prairie. Nikon 105mm macro lens. ISO 500, f/10, 1/1250 sec.
Eastern bumblebee (Bombus impatiens) pausing to clean off its tongue. Gjerloff Prairie. Nikon 105mm macro lens. ISO 500, f/16, 1/500 sec.

As the ‘marbleseed’ nickname implies, the seeds are hard and round. They’re very similar to those of puccoons, which isn’t surprising since they’re fairly closely related. I don’t know what eats them but I’ve found little caches of them stored in prairie (often exposed by a prescribed burn) that I assume were collected by mice.

According to John Hilty’s excellent Illinois Wildflowers website, there are several insects that are specialist feeders on the leaves, stems, and/or roots of the plant. The abundant stiff hairs, though, make them unattractive to many larger animals, and that avoidance is further enhanced by the fact that the foliage contains toxins (alkaloids). That’s not a bad combination of defense mechanisms.

It’s rare to see thick patches of false gromwell in the prairies I know. It seems to occur as scattered plants, though some prairies do have quite a few of them. I don’t think it enjoys strong competition from other plants or really productive soils (two factors that are correlated). Instead, it’s usually in drier soils or hillsides where growth conditions, aided by large grazers, help limit competition.

We’ve had great luck getting marbleseed to grow in our cropland restorations at the Platte River Prairies and it is spreading in our family prairie too. Apparently, the bumble bees are good at their job and facilitating the development of lots of seeds. I’m glad – it’s a fun species to have around.

Crab spider on the flowers, probably hoping for something a little smaller than a bumble bee to stop by. Helzer Family Prairie. Nikon 105mm macro lens. ISO 320, f/16, 1/125 sec.

Disappearing Act

I was driving out to the Platte River Prairies last week when Cody (our Preserve Manager) called. Emma had been doing some mowing and Cody had seen what looked like a toad hopping away from the mower. Being the kind person (and good biologist) he is, he flagged Emma down and grabbed the toad before it got chopped up.

To his surprise, it wasn’t a Woodhouse’s toad, which is what we almost always see. Instead, it was a plains spadefoot, which isn’t actually a true toad (its non-warty skin and other features align it more with frogs than toads). Cody was calling to let me know he was going to hold on to it until I arrived.

A plains spadefoot (Spea bombifrons).

I’ve worked along the Platte River for more than 25 years and this is the first spadefoot I’ve ever seen here (I’ve seen one at the Niobrara Valley Preserve). I guess that’s not surprising since they spend most of their lives underground. If you’re not familiar with the habits of spadefoots (spadefeet?), they’re usually only seen aboveground during or after rainstorms. They emerge from the ground to quickly mate and lay eggs in puddles. Their tadpoles can turn into little froglets within a couple weeks, which sometimes is faster than the puddles disappear.

Once they’re finished with their reproductive activities, spadefoots dig themselves back underground. They have special projections on their rear feet (for which they’re named) that aid in that excavation work. I’d heard they were pretty good diggers, but I’d never seen them in action. Until last week.

When I arrived, Cody handed me the spadefoot and then watched while I put it on the ground and tried photograph it. For the first several minutes, Cody had a front row seat to a sketch comedy show as the little critter repeatedly hopped away from me just as I got it in focus. I was lying on my belly to get the angle I wanted, so I ended up sliding around in the recently-mowed grass after the frog – wary of the little cacti (Opuntia fragilis) that I knew were in the area. I eventually managed a couple reasonable shots, including the one above, but wanted a few more since I figured it might be a while before I got another opportunity.

As the spadefoot hopped away from the camera yet again, I finally grabbed it and set it down on a pocket gopher mound Emma’s mower had flattened. This time, instead of hopping away, the little frog immediately started shuffling its rear feet in the loose soil. As I took advantage of its stationary position to photograph it, it continued moving its legs and Cody and I quickly realized it was starting to sink.

The spadefoot started wriggling its rear legs in the loose sand…
… and started lowering itself into the earth.

As it conducted the subtle excavation with its rear legs, it slowly rotated and began sinking lower and lower into the loose sandy soil. It was hard to understand exactly how it was happening, but it was a smooth and efficient process.

Getting lower…
…and lower…
…until it finally disappeared altogether.

Later, Cody and I compared our memories and agreed it had taken about a minute and a half to disappear. Based on the time stamps from my photos, it was probably more like three minutes, but even so, it was impressively fast. I don’t know how long it would take me to completely bury myself in sandy soil – even with a shovel – but I bet it would be hours, not minutes. After it was gone, I toyed with the idea of digging it back up and trying to get video of it repeating the process but I couldn’t bring myself to do it.

Here’s the only evidence the spadefoot had been there.

As Cody and marveled in the experience, we also wondered what the little spadefoot was doing aboveground. It hadn’t rained for a few days, so it seemed weird for it not to be belowground. Our best hypothesis was that it had been buried in a pocket gopher mound and that Emma’s mower had knocked the top off of the mound and either exposed the toad or made it feel like it needed to change locations. Whatever the reason for its appearance, we were sure grateful for it!

Don’t forget to sign up for one of our two events coming up next month! Our public field day on July 9 will be a great way to see the Platte River Prairies and learn about plants, birds, wetlands, small mammals, insects, and much more. Our two day workshop on Conserving Fragmented Prairies (hosted in conjunction with Prairie Plains Resource Institute) will be a terrific opportunity to explore prairie stewardship strategies with other land managers. Read more about both events here.