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.

 

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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.

Finding Changes

by Carl Strang

My back and leg had healed enough for me to retrieve the amphibian traps from the stream corridor marsh at Mayslake Forest Preserve.

The marsh had dried around the edges, making the approach easier.

As I went, I noticed some changes. The shelf of wood that had supported the ill-fated Canada goose nest collapsed.

Traces of the nest remained, but the eggs were long gone.

I also found two new plants. One was abundant enough that I should have seen it before.

Nodding bur marigold, blooming early for a Bidens, like everything else this year.

There was only one individual of the other plant, so I took photos and a single tiny flower.

It proved to be marsh cress, a member of the mustard family.

There always is something new to be found in preserve monitoring.

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.

Spring Time

by Carl Strang

It’s spring, and it’s time, time to shift into the new season. There are signs in abundance.

Downy woodpeckers have been getting feisty.

On Tuesday I saw Mayslake Forest Preserve’s first butterfly of the season.

An eastern comma, one of the butterflies that hibernate in the adult form.

Yesterday I set out the amphibian traps in the stream corridor marsh. It seems doubtful there are any salamanders to catch, but other interesting things turned up last season, and I’m willing to try again.

It’s important to make sure part of the trap is out of the water, for the benefit of air breathers that may get caught.

I also have begun to break out of my routine preserve monitoring routes. I am sure that after 3 years I am getting diminishing returns from them. Yesterday provided a case in point.

I have walked the trail past this big cottonwood (40 inches in diameter) many times, but yesterday I made my way through the brush on its backside, and saw this scar.

A close look revealed an interesting story.

Years ago, beavers had the ambition of chewing down the big tree. Their gnawing girdled it half way around before they gave up, or left.

In the first of the two photos you can see how large the area is where the tree has grown back over the scar. This is the largest such overgrowth I have seen, apart from lightning scars. Those are not as deep as this, however. This is a good example of how much of this preserve’s story I still have to learn.

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