Mayslake Marsh Update: Amphibian Traps

by Carl Strang

I set out some amphibian traps in Mayslake Forest Preserve’s stream corridor marsh to assess how the marsh has recovered from the drought of 2012 and another drying out in 2013.

This leopard frog still is dark from its recent emergence.

This leopard frog still is dark from its recent emergence.

I have caught and released several of the large predaceous diving beetles, Dytiscus hybridus.

I have caught and released several of the large predaceous diving beetles, Dytiscus hybridus.

Similar in size, this water scavenger beetle, Hydrophilus triangularis, was an addition to the preserve species list.

Similar in size, this water scavenger beetle, Hydrophilus triangularis, was an addition to the preserve species list.

The club-like end of the antenna separates the water scavenger beetles from the predaceous diving beetles, whose antennae are thread-like.

The club-like end of the antenna separates the water scavenger beetles from the predaceous diving beetles, whose antennae are thread-like.

The identification of this juvenile crayfish is uncertain, but the slender pincers have me thinking White River crayfish, in the past the most common species in that marsh.

The identification of this juvenile crayfish is uncertain, but the slender pincers have me thinking White River crayfish, in the past the most common species in that marsh.

I caught only one magnificent adult White River crayfish against 10 or so juveniles, sign of a recovering population.

I caught only one magnificent adult White River crayfish against 10 or so juveniles, sign of a recovering population.

Meanwhile, the grassland crayfish have been opening up their tunnels around the peripheries of the wet areas.

Meanwhile, the grassland crayfish have been opening up their tunnels around the peripheries of the wet areas.

Grassland crayfish mainly come out at night to forage on land. Sometimes these foragers become foragees.

Grassland crayfish mainly come out at night to forage on land. Sometimes these foragers become foragees.

The marsh’s muskrats regard the amphibian traps as suitable platforms for their territorial markings.

The marsh’s muskrats regard the amphibian traps as suitable platforms for their territorial markings.

Through all of this, the marsh’s sounds have been dominated by the songs of western chorus frogs. They are so small that they can squeeze their way out of the traps.

Through all of this, the marsh’s sounds have been dominated by the songs of western chorus frogs. They are so small that they can squeeze their way out of the traps.

 

Advertisements

Measuring Marsh Recovery

by Carl Strang

Now that Mayslake Forest Preserve’s stream corridor marsh is full of water again after several months’ drying out, I am curious as to how fast its animal community will recover. Apart from simply observing what I can on the surface (waterfowl have been back, and last week there were a muskrat and a few singing western chorus frogs), my best tool is the amphibian trap.

Each end is capped by an inward-angling funnel with a 1-inch hole in the end. Animals that enter through the hole have a hard time finding their way back out. The top of the trap is out of the water so they can breathe if they need to.

Each end is capped by an inward-angling funnel with a 1-inch hole in the end. Animals that enter through the hole have a hard time finding their way back out. The top of the trap is out of the water so they can breathe if they need to.

Five traps placed around the marsh produced nothing for two days, and were absolutely clean, suggesting little or no activity around them. The third day brought the first capture.

One of the traps had a medium-sized White River crayfish.

One of the traps had a medium-sized White River crayfish.

I don’t believe this species could survive the marsh drying out, so this individual probably was a recent immigrant from the nearby stream.

Friday was the big day, however. The first three traps I checked were empty, but in the fourth I found these:

Five tiger salamanders.

Five tiger salamanders.

Prior to that moment, in two springs of trapping I had caught a grand total of one salamander. But that wasn’t all.

The final trap held two more.

The final trap held two more.

Most of these appeared to be males, but at least one appeared to be a female (proportionately shorter tail, with less tail fin, and much less swelling around the genital area). Furthermore, none of them had spot patterns matching the one I caught last year. With predatory insects diminished, this would seem to be a promising year for tadpole survival. A final observation as I released them was that they swim by folding their limbs against their bodies and propelling themselves entirely with their tails. This is interesting, given that they move about their terrestrial tunnels all the rest of the year with their legs.

Why this sudden success? Looking back, I suspect that in previous years I may have put the traps out too late, and the salamanders were done and gone. This year I got the traps out within days of the last ice melting away.

Going, Going, Gone

by Carl Strang

The drought we have been experiencing this summer in Illinois has taken its toll on the marshes at Mayslake Forest Preserve. On Monday of last week I took a panorama series of the stream corridor marsh to show how small the pool had become.

The west end

The center

The east end

At that point the pool was perhaps 30 feet wide and 50 feet long, but only inches deep. By Friday it was nearly gone.

At this point a single photo was sufficient to show perhaps 50 square feet of a pool only an inch or two deep.

Monday of this week, but a puddle remained.

Perhaps 5 square feet by less than an inch of depth.

On Tuesday it was gone.

Damp soil only marked the center of the marsh.

The basin was punctuated by the whitened shells of crayfish.

When will this marsh again see white river crayfish?

Some residents could emigrate easily, some could bury themselves and become dormant, but others could not, and when the water eventually returns the community will need to reconstruct itself.

Graphic Assessments

by Carl Strang

The amphibian trapping season at Mayslake Forest Preserve is done for the year. A painful back strain stopped me a week early (I mention this so you’ll know why blog postings may be thin for a time). The main purpose of the trapping effort is to determine which amphibian species occur on the preserve, particularly salamanders which, unlike frogs and toads, are silent and hidden most of the year. As I posted earlier, in this second year the traps did indeed reveal the presence of tiger salamanders. In addition, though, the traps have caught a variety of larger invertebrates.

One example is the predaceous diving beetle Dytiscus verticalis. I photographed this one on its back to show the brown color on the underside of the abdomen, a species identification feature.

As time goes on, the traps continue to catch animals, but new species appear less and less often. This can be rendered graphically.

This graph combines the two years’ data. I keep records of all individuals caught, which allows me to see how new species have appeared as the total catch has grown.

As you can see, there appears to be a leveling off at the current total of 11 species. Keep in mind that this is not the total number of animal species in the stream corridor marsh, just those that can be caught in the traps. Such data usually are converted to logarithms in ecological analyses.

The same data as in the previous graph, converted to their logarithms.

Again there seems to be a leveling-off, but not so dramatic. Another approach to species richness is to consider the accumulation of species according to sampling effort.

Here the same species are shown being added as the trap-days accumulate.

This graph reveals something significant. Can you see how there appear to be two episodes of the species count leveling, at 4 and at 11 species? That first leveling represents the latter part of last year’s trapping. If I had been content with those results, I would have drawn the conclusion that the marsh contains around 4 species susceptible to these traps. But this year’s results were different, adding not only the tiger salamander but a few new invertebrates as well as two frog species. Also, I did not catch two of the species I caught last year. Here is the same data set converted to logs.

This graph gives a hint of why the logarithmic conversion is done. It takes out some of the misleading tendencies that appeared in the unconverted data.

From this final graph I conclude that I need to continue trapping at least another year. I will sense that I have an idea of the marsh’s species richness when the log-log graph of trapping effort levels off. Even without this graphical analysis I would have wanted to continue trapping, however. Something the graphs don’t show is the dramatic difference in the kinds of animals caught each year. Where last year the sampling was dominated by predaceous diving beetles, this year there were few of them but a lot of white river crayfish. Clearly there are some dynamic changes occurring between years, and I want to see what future years hold.

White River Crayfish Young

by Carl Strang

This week brings the end to another year’s running of amphibian traps in the stream corridor marsh at Mayslake Forest Preserve. As was the case last year, I have caught relatively few amphibians compared to the number of invertebrates. This year the majority of captures have been, specifically, white river crayfish (a species of marshes and other still waters in flood plains adjacent to streams).

A mature white river crayfish is impressive in its red coloration.

Last year I caught only adults. This year brought all sizes, and I was able to get a sense of how they change with age (my reference gave only verbal descriptions). Young ones have small pincers, and are an olive color with distinctive black spots on the sides.

Immature white river crayfish, around 1.5 inches long.

As they get bigger the spots fade, the pincers get a little bigger, but the color remains olive.

This one is around 3 inches long.

I keep watching for some variation that might hint at a young grassland crayfish among the white river ones, but so far none have turned up.

Marsh Invertebrates

by Carl Strang

They are called “amphibian traps,” but the little cage-like contraptions I have been running at Mayslake Forest Preserve’s stream corridor marsh have revealed more about the wetland’s invertebrates than its amphibians, though last week’s tiger salamander was a major coup. The salamander was not alone in its trap, as there also was one of the predaceous diving beetles, Dytiscus verticalis, one of only two I’ve caught so far this year. That low number makes me wonder if predators such as the bufflehead pair and the hooded mergansers that frequented the marsh last year might have made inroads on the Dytiscus population. On the other hand, a few representatives of a new insect turned up in the traps last week. At first I thought they were water boatmen, as they preferred to sit on their bellies in the trap.

The pale backs made me suspicious, however, as this seemed likely to be the countershading one would expect in a backswimmer.

Sure enough, when placed in the water, the half-inch-long true bug flipped over.

The dark underside blends with the marsh bottom, while the pale back is better camo against the sky.

As best I can tell from the BugGuide website, these belong to the common species Notonecta undulata. I also found some amphipods.

Also known as scuds or sideswimmers, these tiny invertebrates are not identifiable to species from photos. There seem to be a lot of them, though, in the marsh.

A final, more familiar invertebrate in the traps has been the white river crayfish.

Two of the red-hued crustaceans turned up last Friday.

They are one of Mayslake’s two known crayfish species. I found a tragic example of the other while leaving the marsh on Tuesday.

It was a large, dead grassland crayfish.

Grassland crayfish live in tunnels they dig on land, away from open water, though the tunnels go deep enough to reach the water table. Sometimes these odd crustaceans climb up on land to wander on warm, humid nights. Now is the time of year when mothers leave their tunnels to carry their young to water and release them. The young grow to the point where they are big enough and strong enough to go out on land and dig their own tunnels. After letting the babies go the mothers remain in the water for some undetermined time, and then return to their homes. The dead crayfish was pointed toward the marsh. I turned her over.

Sure enough, the ground beneath her abdomen was littered with little dead crayfish. Others still were stuck to the mother.

She nearly had made it.

The dead crayfish is at the center of the bottom edge of this photo. She is only 15 feet from the water’s edge.

I’m inclined to attribute this tragedy to the unseasonably warm, dry weather we have enjoyed in recent days. In most years the mother crayfish can come out in March, day or night, with no danger of dehydration. Not so in this case.

Marsh Survey Update

 

by Carl Strang

The marshes at Mayslake Forest Preserve continue to warm into the season. Less than a month ago, in late March, there still were mornings when skim ice formed around the edges.

The ice was thin and crunchy when I waded out to check amphibian traps.
In addition, there was plenty of humidity in the air for producing ice crystals.

One of the more remarkable events at the stream corridor marsh was the prolonged visit by a pair of bufflehead ducks.

Here the female takes a break from swimming.

The buffleheads stayed for more than two weeks, finding plenty of food while they waited for the weather to moderate.

Plants have begun to grow. Here a muskrat gnawed off some tips for its dinner.

The rodent’s incisors clip the leaves cleanly.

Over in the parking lot marsh, the traps have been producing some bullfrog tadpoles.

These have been around 3 inches long.

Last week in the stream corridor marsh I caught what appeared to be a second species of large predaceous diving beetle.

I was alerted by the filled zone of yellow at the back tips of the elytra.

Several characters pointed to Dytiscus hybridus. It was lucky to be alive. Overnight rain had elevated the marsh so that the trap was completely under water and the beetle could not reach the surface for fresh air.

It floated at the surface for a long time after I released it. The cold water, and some diffusion of oxygen into the bubble held beneath the wings, apparently allowed the insect to survive.

Now I have to look at all these beetles more closely. Later I caught one that seemed in some ways to be between the two known species.

For instance, there were thin yellow lines at both front and back edges of the pronotum.

Underneath, though, the brown color with some black placed it in the more common species, Dytiscus verticalis.

Now I’ll need to look at tops and bottoms of all of these I catch.

I thought for a time that I had caught a second crayfish species. Unlike the white river crayfish I caught earlier, this one did not have a dominant burgundy color.

It was mainly greenish.

It proved to be the same species, though, when I carefully went through all the physical features. Little experiences like this give one a concrete sense of the variability within species, which also is an aspect of biodiversity in the broad sense.

White River Crayfish

by Carl Strang

The stream corridor marsh at Mayslake Forest Preserve continues to dole out little lessons in diversity. The newest addition to its species list appeared in one of the amphibian traps late last week.

How to hold a crayfish so it can’t pinch you.

I was struck by the general reddish color, but otherwise I am not familiar with crayfish and so took a number of photos from various angles. Details of the dorsal view of head and carapace proved to be especially helpful.

For example, the broad convex sides of the top of the head leading to a point, the slightly dished in top of the head, and the separation between the grooves defining the sides of the carapace all are important features.

The broad black stripe on the dorsal abdomen or tail also was an important characteristic.

I released the crayfish after photographing it.

This is a white river crayfish, Procambarus acutus. The name is somewhat ironic, as this species lives in marshes, ponds and other still waters, albeit in flood plains of streams, throughout the Mississippi River drainage. Though they do not live in streams, presumably they use them to disperse among suitable bodies of water. I was pleased to find that this is a native species.

The reference I used was The Crayfishes of Missouri by William L. Pflieger, published by the Missouri Department of Conservation. I was intrigued by the caption to a photo in that book which showed a pond resembling the stream corridor marsh. It said that 5 crayfish species occur in that pond, and I am hopeful that others will turn up here as well. Thanks also are due to Don LaBrose, Forest Preserve District aquatic ecologist, who suggested some possibilities which included the white river crayfish.

%d bloggers like this: