Thursday, June 30, 2016

Coexisting with cottontails [from the archive]

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.

Thursday, June 23, 2016

Appreciating turkey vultures [from the archive]

Appreciating turkey vultures

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If you watch the sky as you travel by car in warm weather, you’re likely to see soaring birds from time to time, even if you don’t count yourself a birder.In our part of the country, most of the large soaring birds you’ll see are turkey vultures, which you can recognize from a long way off without binoculars or a field guide.

Turkey vultures in flight are identified by their large size—they have a six-foot wingspan—their blackish color above and below, and their manner of flight. Turkey vultures hold their wings in a shallow dihedral, or “v” shape, and constantly tilt back and forth. They are so skilled at using rising currents of warm air for lift that you’ll rarely see a turkey vulture flap its wings, even if you watch and wait for it to do so.

A group of turkey vultures circling together is called a kettle. A kettle may form as vultures come together to take advantage of an updraft for gaining altitude, or as they scan the countryside looking for food. It is not, by any means, a sure sign that something below has died.

Turkey vultures are very well equipped to search for food on the wing. They have excellent vision, which is not uncommon in birds, as well as an extraordinary sense of smell, which is. A turkey vulture’s sense of smell allows it to locate carrion even when it is concealed from above by a forest canopy.

Turkey vultures are not at all picky about which animals they eat, as long as they are dead. A turkey vulture’s diet may include anything from dead domestic livestock to roadkilled animals like skunks, raccoons and deer, or even turtles and snakes. This is not to say that turkey vultures have no preferences, as they have been shown to select recently dead animals over more decayed food when given a choice. Turkey vultures also eat varying amounts plant material, presumably more when carrion is scarce.

If you happen to see a turkey vulture close up, you’re likely to notice its red, featherless head. In this feature, as well as its bulky, brownish-black profile, the turkey vulture resembles the wild turkey, which is where it gets its name. Being bald allows the turkey vulture to poke its head right into a carcass and not wind up capturing little bits of its meal in hard-to-clean feathers.

Couple the turkey vulture’s bald head with its cast-iron digestive system, and you’ve got a very effective processor of carrion.

Now, I realize that you might be inclined to leave off contemplating turkey vultures as they soar in the sky, half a mile away. But I think looking at them more closely really can foster a deeper appreciation for the diversity and complexity of life. After all, without turkey vultures and other decomposers, life as we know it simply wouldn’t be possible.

Thursday, June 16, 2016

Mystery of the tiny bouncing spheres [from the archive]

Mystery of the tiny bouncing spheres

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What’s shaped like a ball and white, less than a millimeter in diameter, and bounces like a Mexican jumping bean?

This odd question occurred to my wife, Karen, last week as she locked her bicycle to the rack near her office on the University of Illinois campus in Urbana. She’s not the sort of person who conjures up such questions hypothetically. It occurred to her because the concrete at her feet was alive with such spheres—thousands upon thousands of them—and she had never seen anything of the sort.

Initially, she speculated the bouncing spheres were associated with the many ants that were also present—eggs, maybe, or larvae, and that their movement was caused by the adult ants shifting them from one place to another. Needing to get on with her day, she snapped a photo to share later with others who might be able to shed light on the question.

As it turned out, however, the photo didn’t contain enough evidence to produce a good answer, so she and I returned to the scene for further investigation together a few days later at lunch. And what a scene it was—thousands of white balls bouncing around on the concrete, tiny enough to go unnoticed by most people walking by, but large enough to be seen with the naked eye by anyone curious enough to stop for a look.

We noticed almost immediately that the spheres moved without any help from ants. And by shielding them with our hands, we ascertained they weren’t being propelled by breezes, or just bouncing up from the ground after falling. But they did originate from above. The leaves of the massive bur oak tree standing over the bike lot were covered in them, and they popped off the leaves at a touch.

Thanks to internet access, the solution to our mystery was just a few keystrokes away. We searched “oak tiny white Mexican jumping beans” and that took us to—drumroll—jumping oak galls!

Jumping oak galls form around the larvae of tiny, stingless wasps as they feed on the leaves of certain species of trees in the white oak group. As the larvae mature, the galls fall to the ground, where they overwinter and then emerge as adults the following spring.

Although jumping oak galls have been observed in the U.S. since at least the 1870s, the questions of why and how they jump have yet to be investigated very fully. In a paper published just last summer, researchers from the University of California at Santa Cruz suggest that the jumping behavior protects the gall-wasp larvae from getting too hot and drying out, which can kill them. By jumping repeatedly, they settle down into the leaf litter, where conditions are cooler and moister than above. That’s the “why.”

As for “how,” the researchers observed that the larvae are packed into their galls so tightly it’s impossible for them to cause movement by thrashing around. As an alternative, they propose the larvae move by means of snap-like abdominal contractions, which transfer momentum to the gall shell through the fluid that surrounds them. As far as the researchers know, this mechanism for producing motion is unique to jumping oak gall wasps.

Whatever conclusions scientists eventually come to about how jumping oak galls jump, I am delighted to have found something so new to me and so weird in a spot that’s been part of my everyday experience for nearly 30 years (thanks to my observant spouse, of course). Who knows what we have yet to learn about the 1300 or so other species of gall wasps that occur around the world?

Thursday, June 09, 2016

Appreciating common snapping turtles

Appreciating common snapping turtles

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Two kinds of snapping turtles occur in North America, and both of them can be found in Illinois. Alligator snappers, which most people will never see, are listed as endangered, and they inhabit only larger rivers and streams in the southern part of the state, the Mississippi, Ohio and Wabash Rivers, and tributaries directly connected to them. In fact, no wild alligator snapping turtle was documented in Illinois for the thirty years between 1984 and 2014, when scientists from the Illinois Natural History Survey discovered one.

(Ironically, as I reported in a commentary last year, they discovered a wild alligator snapper as they sought to relocate individuals they had translocated from other states as part of a multi-year program to reestablish alligator snapping turtles in Illinois. More on that project here in future.)

It’s only common snapping turtles, scientific name Chelydra serpentina, that residents of Illinois are likely to see, and it’s them I’d like to call attention to here. Common snappers can be found throughout the state, and their overall range includes the entire eastern two-thirds of the U.S. and corresponding parts of southern Canada.

The “common” part of Chelydra serpentina’s name is entirely appropriate. They can be numerous in suitable habitat, and suitable habitat for them includes lakes, ponds, and marshes, as well as rivers and smaller streams—just about any permanent body of water. And while we’re on the topic of names, “serpentina” fits well, too, given the common snapping turtle’s long, snake-like neck and it’s ability to strike in a flash.

[Photos of common snapping turtles by author.]

Humans who wade or swim in waters where snapping turtles live have little reason to fear being bitten by them, because they strongly prefer to avoid us and they move with ease in water.

What do common snapping turtles really want to bite? Fish, of course. Or frogs, or snakes, or crayfish, or snails, or small mammals and waterfowl—really, they’re not picky, and they eat carrion as well as prey they dispatch themselves. Snapping turtles even include a fair amount of plant material in their diet.

On land, snapping turtles respond to humans and other threats more aggressively, since they possess neither speed to escape nor the ability to retreat fully into their shell. But their strength to bite through objects people provoke them with is greater in stories than in reality.

You’re most likely to see snapping turtles on land in June, when females leave the water to find a site with loose soil or sand in which to lay eggs, up to 30 of them. Digging a hole and covering their eggs with soil is the extent of care female snappers provide, so few nests escape predation, and even hatchlings from successful nests face long odds of surviving.

When I see other kinds of turtles on a road I stop to pick them up and move them across in the direction they are headed, but it’s not a good idea to do that with large snappers. Better to give them space and just direct oncoming traffic around them, as long as it’s safe to do so.

Given the right vantage point, it’s also possible during summer to observe snapping turtles as they bask, usually by floating near the surface of the water with just their snout sticking out. In Champaign we’ve got a perfect spot for that, the overlook on the east side of the Second Street Basin. There are no guarantees in wildlife watching, but if you approach the railing there slowly and quietly on a sunny afternoon, you’ve got a good chance of spotting a basking snapper for yourself.

Thursday, June 02, 2016

Cultivating an appreciation for toads in Illinois

Cultivating an appreciation for toads in Illinois

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Two species of toads inhabit Illinois, and neither one of them is threatened or endangered. It seems the factors that are contributing to the decline of other amphibians in the state and around the world—habitat loss, fungal infection, chemical contamination, etc.—pose no insurmountable obstacles to the continued health of toad populations here.

So, why give toads a second thought? They are common and approachable. [Pictured is a Fowler's toad I came across on a gravel bar along the Middle Fork of the Vermilion River.] For me, encounters with such creatures hold their own pleasures, and they reinforce the natural inclination to value other forms of life, even animals I’ll probably never see for myself.

At a glance, most people would not notice a difference between adult American toads and Fowler’s toads. Both are about two to three inches long, and they are similarly marked. Their skin is a light shade of gray or brown, dotted with darker spots. One way to distinguish between the two toad species found in Illinois is to observe the number of warts per dark spot on the back: the dark spots on American toads contain only one or two large warts, while the dark spots on Fowler’s toads have three or more smaller warts.

Toads have thicker skin than frogs, which enables them to inhabit drier environments. They thrive in forests, prairies, and wetlands, along the margins of lakes and streams, and even at the edges of highways. Toads can live in the midst agricultural fields and in urban settings, too, as long as they have access to bodies of water for reproduction.

Even when it comes to the choice of where to breed, toads are not very discriminating. If the nearby body of water is a pristine vernal pool, toads will get together there. If it’s a ditch or a flooded field, toads will use that as well (although toad offspring will survive only if the water persists for at least the 40 days it takes them to develop from tadpoles into terrestrial creatures). My family once received a gift of toad tadpoles from the water that had collected on top of a friend’s swimming pool cover.

You might well recognize the mating call of American toads even if you don’t realize you have heard it before. It is a sustained, high pitched trill that carries a very long way. Near ponds and other places where they breed, it is the background sound of evening in April and May.

Do I need to say people don’t get warts from handling toads? People don’t get warts from handling toads.

Under extreme stress toads secrete a toxin from the oblong glands behind their eyes, which irritates the mucous membranes of other animals that would eat them. (For this reason it’s a good idea to wash your hands thoroughly after handling a toad.) This defense works well in many cases, as you know if you’ve ever seen the reaction of a dog that picked up a toad in its mouth, but not all. Some snakes are not bothered by the toxins toads release, and other animals, including skunks and raccoons, get around the problem by eating them from the underside.

If you’re interested in a wildlife experience close to home this summer, you might start by looking for toads in nearby window wells, since they have a knack for falling into them. You can then increase the odds of survival for toads you find in window wells by releasing them a little ways off.