Thursday, July 30, 2015

Nighttime is the right time to count frogs and toads

A nighttime outing to count frogs and toads

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If you were to base a movie character on Dave Stone, you’d probably have to tone down his enthusiasm for science and teaching—and that’s saying something, given that he’ll begin his thirty-second year in the classroom at Uni High this fall. This was my thought, anyway, as we headed out of Urbana in his Prius one early July evening, on our way to the Middle Fork River Forest Preserve in the northeast corner of Champaign County. This will be so cool,” he kept saying. “We’re going to get you set up for some great frog pictures.”

Although Stone and I were both excited about the frog pictures we might get, our primary mission that evening was to gather data about the numbers and kinds of frogs present at two of the Preserve’s wetlands.

These are Stone’s designated sites in a frog and toad monitoring program coordinated by the Champaign County Forest Preserve District. The program relies on citizen-scientists to gather information about which species of frogs and toads inhabit its five preserves, and in what numbers, along with information about how they are distributed across the landscape.

[Photo: A southern leopard frog at the Middle Fork River Forest Preserve, by author.]

Why? As wildlife, amphibians are of interest for their own sake, and around the world many of them have been declining for decades. Locally, they play important roles in food webs, as they eat (insects and other small invertebrates, mostly) and are eaten (by a wide variety of other animals, from herons to raccoons to largemouth bass).

Amphibians also serve as indicators of environmental health, since they tolerate varying degrees of degradation in their habitat. Some highly tolerant species can breed in ditches along roadsides and railroad tracks, while others require better preserved or restored natural settings to thrive.

If you’re with unfamiliar frog and toad surveys, you may wonder why we were headed out in the evening, rather than earlier in the day; it’s because to count frogs and toads you use your ears rather than your eyes. Think about it—these critters are generally small and very well camouflaged, and they often occupy habitats that are inaccessible to people. To count all of the frogs and toads you see in a walk around a marsh is normally to count very few of either.

But in spring and summer, frogs and toads gather at bodies of water to breed. And there, males advertise themselves with calls distinct to their species, in a chorus of peeps, boinks, chirps, and trills that really heats up only after darkness has fallen.

So we surveyed by standing still and listening for about a minute, once at each spot while there was still some light to see by, just to get a sense of what was out there, and once about half an hour after it was fully dark to make our official count. Stone also made an audio recording of our official observations so he could confirm what we were hearing later, at home. What we heard were four species of frogs: grey treefrogs, cricket frogs, green frogs, and bullfrogs, pretty much what would be expected, given the setting and time of year.

The month of July marks the end of the frog and toad survey season, and the species we heard represent the tail end of a procession that began in March, with spring peepers and western chorus frogs, and continued in April, May and June with the addition of three more species.

Oh, and we got some frog pictures, too, although I felt like the results of my efforts didn’t do justice to the trouble Stone took to get me set up. I definitely need to get out for more practice at this in the future.

Thursday, July 23, 2015

Annual cicadas enliven dog days with love song

Annual cicadas enliven dog days with love song

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Even if the heat and humidity of recent weeks have limited your time outdoors, I bet you’ve been hearing a familiar insect song. It’s the mating call of dog day cicadas, loud enough to rise above the drone of air conditioners and so persistent and widespread that people who hear can hardly miss it.

I say, “dog day cicada” I mean the insect (pictured right) that goes by the two-part scientific name, “Tibicen canicularis,” which is the most common species of forest dwelling cicada that occurs in the eastern U.S. and Canada, one that has also adapted well to life in urban and suburban settings where enough trees grow to support it. These cicadas have bulky, bodies about an inch and a half long that are dark on top with green and white markings, and entirely white below. At rest their clear, heavily veined wings close over the back like a pitched roof and add another half inch to their length.

Some people call these and other cicadas locusts, a name that was first applied to them by settlers of European extraction for whom the emergence of large broods called to mind the plagues of the Bible. But the name locust is more properly applied to certain grasshoppers. Other people know cicadas by the name “harvestfly,” which derives from the fact that they emerge as adults at the same time crops are maturing.

The singing of dog day cicadas is one of the loudest insect noises on earth, sometimes exceeding 110 decibels up close. This means the song of a cicada perched your shoulder would be plenty loud to damage your hearing. The song is often compared to the whirring of a circular saw, although I think that comparison ought to be reversed, since cicadas have been around far longer than power tools. The earliest fossil record of a cicada dates back 65 million years.

[Photos by author: above, cicada "singing" on a tree trunk; below, newly captured and paralyzed cicada in the grip of a cicada killer wasp.]

The fact that dog day cicadas are also called annual cicadas sometimes generates confusion about their life cycle, but do they live for more than a year. They start out as tiny nymphs, which hatch from eggs laid in tree branches. These nymphs drop to the ground and burrow down to find a root they can latch onto for nourishment, and there they remain, probably for something like two to five years. (Scientists aren’t sure exactly how long, and the span probably varies according to conditions affecting the cicada’s development.) Some annual cicadas emerge as adults each year because their generations are staggered, which sets them apart from periodical cicadas, generations of which mature in synch, on 13- and 17-year cycles.

It is a common misperception that adult cicadas do not feed, but the fact is they have all the mouthparts needed to extract liquid from plants, and they’re not afraid to use them. Dog day cicadas do no damage to trees as they feed, and no measures to control them are warranted.

The only warm-blooded predators that pose a significant threat to cicadas are birds, but there’s another insect that specializes in them, the cicada killer wasp. A female cicada killer stings a cicada to paralyze it, then carries it back to her burrow still alive. There she seals the unlucky creature in a chamber with one of her eggs, to become nourishment for the grub that hatches.

But that’s not where I want to leave you. Let’s get back to cicadas singing their love song in trees, and appreciate how that enriches our summer.

Thursday, July 02, 2015

Coexisting with cottontails

Coexisting with cottontails

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Some people love rabbits. “Soooo cute!!! More bunnies please,” was the response from one friend when I posted a rabbit picture online recently. More people, perhaps, have mixed feelings about them. “Love bunnies, but baby just ate a large butterfly milkweed I bought a few days ago,” added another friend. There are also among us plenty of people who look at rabbits pretty much the same way Elmer Fudd looks at Bugs Bunny; some 60,000 Illinois residents hunt rabbits.

Whether you value them as food, objects of affection, or something in between, rabbits are fascinating creatures, and they’re among the wild mammals most of us are likely to encounter on a regular basis.  That’s because they thrive in the sorts of habitat we create for ourselves—lawns of any sort, old fields, roadsides, railroad embankments, forest edges, etc.

When I say rabbits here, I’m referring to eastern cottontails, which occur statewide in Illinois; some southern counties where suitable habitat remains also support populations of swamp rabbits, which are a separate species.

Eastern cottontails are full size and sexually mature at just six months of age, and they really do breed like . . . well, you know. Female cottontails give birth to litters of four to six young as often as three times in a year. It’s a good thing for them, too, because the average lifespan of cottontails is only about a year.

[An eastern cottontail stands up to assess the threat posed by a photographer, i.e., the author.]

In the words of the Field Manual of Illinois Mammals, “A rabbit’s life is full of danger.” The list of other animals that eats them includes coyotes, foxes, weasels, dogs and cats, as well as hawks, owls, crows and snakes. In addition, many rabbits are killed by cars, mowing and other human activity.

Some children, as well as adults of a certain sensibility, may be interested to learn that rabbits eat their own poop. That’s right, after consuming your beloved garden plants they scamper off to a sheltered spot where they excrete lightly digested fecal pellets, which they then re-ingest for more thorough processing the second time around.

A fact about rabbits that everyone should know is that mothers leave their young alone in the nest on purpose, so as to not attract the attention of predators. That means if you happen to find unattended baby rabbits it is important to leave them where they are and resist the urge to rescue them.

How does a person prevent rabbits from damaging plants? There are no easy, surefire answers to the question, but a website maintained by University of Illinois Extension called “Living with Wildlife” offers a number of possibilities. You can cut down on the amount of cover in your yard to make rabbits less comfortable there. And you can favor plants they don’t normally eat, although in tough circumstances they will eat just about anything. Or you can protect special plants with commercial repellents or wire mesh.

Most of the time wire mesh does the trick for me; I haven’t lost a butterfly milkweed since I started putting fence up on the same day I install new plants. But even fencing isn’t foolproof. Last summer, an enterprising mother rabbit in our yard leapt up to where she could wriggle through the wire and gave birth to a litter on the inside of the fence around our vegetable garden. So that struggle continues.