Tag Archives: species diversity

The Diversity, Beauty, and Secret Lives of Grasshoppers

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I know I say this about a lot of different insects, but grasshoppers are truly amazing creatures.  Grasshoppers have a reputation as voracious consumers of crops and forage grasses, and that reputation is well-earned.  However, the pest tag is far too often and broadly applied.  There are something like 400 species of grasshoppers in the western United States, and only about 20 species are categorized pests.  In Nebraska, we have 108 grasshopper species, with only a handful that ever cause economic damage, and that damage occurs sporadically – mainly in years when those species have population booms.

The differential grasshopper is one of only a few grasshopper species that can cause economic damage to farmers, ranchers, and gardeners. It’s a native species that has adapted very well to the way we’ve altered its world.

Unfortunately, the “Grasshoppers Destroy Crops” headline tends to swamp the many and much more interesting grasshoppers stories we should be talking about.  Let’s start with the numbers I’ve already presented.  THERE ARE 400 SPECIES OF GRASSHOPPERS IN THE WESTERN UNITED STATES AND 108 SPECIES IN NEBRASKA ALONE!  That doesn’t include katydids or crickets, by the way, just grasshoppers.  I’m guessing most of you had no idea there were that many kinds of grasshoppers.  Am I right?

I’m including a half dozen grasshopper photos in this post to show off just a taste of the beauty and diversity of grasshoppers in prairies.  If you want to read more about this, you can read an article I wrote for the August/September issue of NEBRASKAland Magazine.  While you could be forgiven for thinking there are two kinds of grasshoppers in the world – green and brown – you would be very wrong.  There are grasshoppers with much more color and pattern variation than many species of birds, but nobody makes movies about people circling the globe to see more grasshopper species than anyone else, do they?  Many band-winged grasshoppers show off gorgeous red or yellow wings as they fly, wings that rival those of butterflies, but you don’t hear about historically-prominent British Prime Ministers collecting grasshoppers, do you?

The painted grasshopper (Dactylotum bicolor) rivals any bird for beauty in color and pattern.

Now let’s discuss grasshoppers’ diet, which can include far more than just grasses.  Some grasshopper species feed high up in the canopy of prairie vegetation, while others stay on the ground.  Many have a very wide diet, including both grasses and wildflowers, but others are much more specialized, including grasshoppers that feed almost completely on one or a few wildflower species.  Grasshoppers are often seen feeding on the pollen of flowers, especially sunflowers, providing further evidence that they are much more than just grass eaters.  Most grasshopper species prefer the newest, most tender leaves of plants, but some – especially those that live mostly on the ground – make their living off of older leaves, including some dropped by their brethren living above them.  Regardless of what they like to eat, grasshoppers have very sensitive organs on the tips of their antennae that help them determine the forage quality of a leaf before they eat it.

The cudweed grasshopper (Hypochlora alba) is named for its favorite food plant – cudweed sagewort, aka white sage (Ambrosia ludoviciana), on which it is supremely well camouflaged.

When you think about animals that have sophisticated communication systems, you probably think about creatures like apes, whales, and even prairie dogs, right?  You might be surprised to learn that grasshoppers have their own complex methods of communication as well.  Every grasshopper species produces its own unique set of sounds, most of them created by rubbing their hind legs against their abdomen.  In addition, some employ what’s called “crepitation” – a loud clacking sound made by snapping their hind wings while flying.

The huge and flightless plains lubber (Brachystola magna) is as gorgeous as it is large.

Grasshoppers can also communicate visually.  They can do this by rubbing their legs against their wings, flashing their wings, and making a variety of motions with their legs.  Those visual signals can help them attract mates, defend breeding territories and feeding areas, and ward off unwanted suitors.  I’m not saying we should make documentaries about people trying to teach grasshoppers how to communicate with American Sign Language, but I’m not NOT saying it either…

This bandwing grasshopper (Oedepodinae) is about as well camouflaged as you could hope for against its sandy background.  When it flies, though, it displays very colorful wings (color and pattern varies by species).

If you’re someone who doesn’t care about the beauty, diversity, or communication abilities of grasshoppers, maybe their utilitarian value will make an impression.  As a major consumer of vegetation in prairies, grasshoppers play a huge role in nutrient cycling, a role that becomes even more important in prairies without large vertebrate grazers.  Perhaps most importantly, though, grasshoppers are a crucial food source for many other animals, including birds and other wildlife species you (hopefully?) enjoy having around.  They are large and packed with nutrients, as well as abundant and fairly easy to catch.  In addition, while they aren’t a particularly popular food item among people here in North America, grasshoppers are an important source of protein for humans in other parts of the globe.

When grasshoppers start to emerge next spring, please take a little extra time to notice and appreciate them.  See how many different colors and shapes of grasshoppers you can find in your neighborhood prairies (remembering that if their antennae are as long as their body or more, they are katydids, not grasshoppers.)  Look for the grasshoppers with big colorful wings as they clatter noisily away from your feet.  And if you’re a person of financial means, and are interested in making a movie about grasshopper watchers or people trying to teach grasshoppers how to talk to humans, call me.  I know people who know people.

How can you not like and admire the green fool grasshopper (Acrolophitus hertipes), with its raised back ridge, bright red antennae and charming face?

Trying to Figure Out What We Did Right

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When converting crop land to restored prairie, it’s always hard to predict what you’re going to get.  Numerous examples prove that even when you control as many variables as possible – including soil conditions and the rate, timing, and technique of planting – no two seedings turn out alike.  Sometimes, you can use hindsight to explain what happened (weather conditions, herbicide carryover, etc.) but most of the time it’s clear that we just don’t understand much of what’s happening out there.

I’ve been analyzing some data from one particular restored prairie lately, and trying to puzzle out what’s going on.  In this case, the results are good – which is nice.  It’d be nicer, of course, if I could explain WHY things worked so well and then replicate whatever happened…

The Dahms 2000 prairie restoration has turned into one of the most aesthetically pleasing prairies we manage along the Platte. It has tremendous diversity and abundance of wildflowers. Most importantly, its plant diversity is still increasing fairly rapidly after twelve field seasons.

The prairie in question was seeded with a mixture of about 200 plant species onto 69 acres of disked cropland that had been in corn the previous season.  The seed was planted sporadically between December 1999 and April 2000.  Wetlands were added to the site by excavating down close to groundwater and recreating the kind of swale/ridge topography that is typical of nearby Platte River meadows.  Those wetlands and sandy spoil piles (ridges) were seeded with appropriate seed as well. 

All of the seed was broadcast onto the site – some by fertilizer spreader and some by hand (I was experimenting) and no harrowing or packing of the soil was done.  Unfortunately, this was the last year BEFORE I started keeping good records of the amount of seed from each plant species I included in the mixture, so I only have a list of the species we harvested seed from that year.  What I know is that my seeding rate per acre was about 15 gallons of grass seed (mostly big warm-season natives) that was harvested by combine from nearby prairies, and about 1/2 gallon of hand-harvested forbs, grasses, and sedges.  That’s roughly 12 bulk pounds of grass seed and 1/2 pound of forb (wildflower) seed per acre.  I have no idea what germination rates were that year, but it was a pretty light seeding rate compared to what many others around the country use.  Today, our typical mix is a little lighter on grass and includes about twice the forbs.

To cut to the results, this prairie has turned into our most diverse and showy restoration we’ve ever done.  You’d never know we’d used such a light seeding rate of forbs by looking at the site now – its appearance is dominated by big showy wildflowers.  By every measure I use to look at the plant communities of our restored prairies, it comes out high.  I’ve found 178 plant species in the site so far, which is excellent.  The mean Floristic Quality (combination of species number and “conservatism values”) is high, and still climbing rapidly.  It averages twelve plant species per square meter, which is higher than most other restored or remnant prairies in the area.  (Yes, I know that seems like a very low number to you eastern tallgrass prairie folks, but it’s good for out here.  Don’t rain on my parade, ok?)  Twelve years after it was planted, tall warm-season grass species are still not very dominant.  The species found at the highest frequency is big bluestem, and it was only in about 80% of 1m2  plots stratified across the site last June.  In short, it’s a beautiful prairie.  And I don’t know why.

I know most of you are ITCHING to see the actual data tables and graphs, but because there are a few who aren’t, I’m including them as a PDF file, which you see by clicking here.  The PDF also includes a cumulative list of plant species found in the restored prairie.

Flower species such as black-eyed Susan (foreground) and bee balm (pink flowers in the background) are still dominating the plant community in this photo from 2009 (the 10th growing season of this seeding). The lasting abundance of those species is, I think, tied to the lack of dominance by major grass species.

It’s particularly impressive that this seeding turned out so well, because the odds seemed stacked against it early on.  It was seeded right at the beginning of a 7 year drought.  The first several years were dominated (as usual) by weedy species and a few colonizing native species such as Canada wild rye and common evening primrose, but in this prairie those species remained dominant for several more years than is typical.  Once other plant species started breaking through, there were few legumes present – and we don’t typically have problems establishing legumes in our prairies.  Those legumes are still more scarce than in other nearby sites, but they’re increasing over time.  Finally, in about its eighth season, the site stopped looking like a weed patch and matured into something that most people would recognize as a prairie.

As I’ve discussed in other blog posts, I’m still struggling to define success in our overall prairie restoration efforts, but at the scale of individual seedings, there are a couple things I look for.  First, I want to see a good diversity of plant species, and I want to see that diversity sustain itself over time.  Second, I don’t want to see invasive species increasing at the expense of that overall plant diversity, even as the prairie is exposed to disturbances such as drought, fire, and grazing.  So far, this restored prairie passes those tests with flying colors.  We’re moving toward implementing some measures of invertebrate use as well, but aren’t there yet.  Initial data and observations, however, show higher butterfly abundance and diversity in this site than in other nearby restored prairies – for whatever that’s worth.

The prairie has been managed with some periodic fire and grazing, which should be helping to suppress dominant grasses. However, this site has gotten much less of that kind of management than nearby restored prairies, and those other prairies have stronger populations of major grasses, so management can't explain the whole phenomenon. In this photo, cattle are grazing in the burned portion of this site - within a patch-burn grazing system. The grasses are primarily grazed short, helping to showcase the abundance of the forbs.

So why did this restoration turn out so well?  I really have no idea.  It caught a couple nice rains during its first spring, but the rest of the summer was awfully dry.  The overall seeding rate for forbs was considerably lower than we use now, but I don’t know how much seed we had of individual species.  I wish I understood why it has taken the big grasses so long to fill in, but I don’t.  I think the delayed grass dominance probably plays a role in encouraging the abundance and diversity of wildflowers at the site, but I don’t know how to replicate it.  The soils at the site are a little sandier than some of our other sites, but we’ve worked on sandier soils and had very quick grass establishment, so it seems unlikely that the sand is the key.

Besides its aesthetic appeal, the prairie is also a great seed harvest site because of its wildflower abundance. Nanette Whitten (left) and Mardell Jasnowski (right) are harvesting seeds in this photo.

The vast majority of our prairie restorations turn out pretty well, but this one is extraordinary, and I can’t explain it.  Was it something about our technique?  Something about the weather or soil conditions?  I know I should probably just be happy with the results, but I want to know WHY! 

Success is sure frustrating.