Thursday, June 28, 2007

Appreciating Illinois Crayfish

Appreciating Illinois Crayfish

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Crawdad. Mudbug. Crawfish. Crayfish. Whatever name you know them by, you probably don’t associate these lobster-like, freshwater crustaceans with the traits that give other wildlife their appeal. Crayfish are not warm and fuzzy, and they don’t sing or sport much color. (They do make great eating, but that’s another story.)

I checked in recently with Chris Taylor at the Illinois Natural History Survey to get the scoop on crayfish in our state. Taylor is a crayfish biologist and Curator of Crustaceans there, and he’s eager to help people understand the important role crayfish play in aquatic ecosystems. [Photo: Chris Taylor celebrates the unexpected discovery of a Rusty Gravedigger crayfish outside Mobile, Alabama. This species was formerly thought to be on the verge of extinction, but Taylor and others have found enough additional populations of it to ease that concern.]

Although to most people a crayfish is a crayfish, there are actually 360 species of them in the U.S., 24 of which occur in Illinois. Crayfish inhabit every aquatic environment in the state, from the smallest creeks and ponds to the largest rivers and lakes.

Crayfish that live in permanent water bodies typically spend the daylight hours concealed under rocks or woody debris. Other crayfish, known as burrowers, spend much of their time in tunnels and chambers they excavate in the ground. Some burrowers inhabit the margins of water bodies, but others live in habitats where there is no surface water for much of the year. You’ve likely seen the entrances to crayfish burrows even if you didn’t know what you were looking at. They are recognizable by the mud chimneys that rise several inches above them, which are formed from material that crayfish excavate with their claws.

All Illinois crayfish are most active from dusk to dawn, when they come out from under cover to forage for food and seek out mates. Depending on circumstances, crayfish may eat just about anything they can get their claws on, including plant material and carrion. But recent studies suggest they prefer live animal food--insects, snails, and even small fish. Crayfish in turn serve as a critical food source for sunfish and bass, but also show up on the menu for any number of wading birds, small mammals, reptiles, and amphibians.

Aside from biologists and environmental writers, I suppose few adults bother to ever catch crayfish. But if you get children into shallow, clear water, and show them how to find crayfish by turning over rocks, you may have trouble getting them to stop. Crayfish flee danger by a powerful flip of the tail that propels them backward. They are just fast enough to be difficult to catch, but not so fast as to be impossible.

There are two important things people can do to help promote the health of crayfish populations in Illinois. The first is to support efforts to conserve and restore aquatic environments. The second is to never release crayfish into a body of water they weren’t taken from. Many species of crayfish occur in very limited ranges, and so can be lost altogether when aggressive outsiders are introduced. One invader, the rusty crayfish, which was probably introduced by anglers dumping out unused live bait, has already displaced native crayfish from many waters in the northern half of Illinois.

Although the role of crayfish in aquatic ecosystems has been sometimes neglected in the past, scientists like Chris Taylor are working hard to further our understanding of them today. That understanding benefits all of us who love the outdoors and value the health of natural resources.

Article "The Rusty Crayfish in Illinois" from Illinois Natural History Survey Reports.

Sea-Grant fact sheet on Rusty Crayfish

Thursday, June 21, 2007

Biofuel Crops as Invasives? The Importance of Weighing the Risks and Benefits

Biofuel Crops as Invasives? The Importance of Weighing the Risks and Benefits

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You’ve probably heard of kudzu, a.k.a. “the vine that ate the South.” And if you’ve traveled in the South, you’ve likely seen how this monster overwhelms the landscape. But did you know that kudzu, which is native to Asia, was initially introduced on purpose, touted as a forage crop and a means of erosion control? If southerners knew then what they know now about kudzu, they would never have bought it.

The same can be said of landowners and stewards of natural areas in Illinois who bought the idea that exotic plants such as autumn olive, bush honeysuckle and multiflora rose could be safely introduced to improve the landscape of the Midwest. If we knew then what we know now, we wouldn’t have put entire ecosystems at risk by planting these exotic invaders. And we wouldn’t be spending millions of dollars at the state level each year—and billions nationally—to combat the problems associated with invasive plants.

Or would we?

In hindsight, we can see that our willingness to adopt exotic plants in attempts to solve ecological problems in the past was based on slipshod decision making. Policy makers and the public alike accepted claims about the supposed benefits of establishing nonnative plants without solid support. And we asked far too few questions about the potential costs—both economic and ecological—of such introductions.

Knowing what we know now about the catastrophic consequences of introducing the wrong plants, you would think we’d have adopted a rigorous process governing all large-scale plant introductions.

But that doesn’t seem to be the case when it comes to some of the plants now being investigated as potential biofuels, especially the perennial grasses, such as miscanthus. And in the current social and political climate, there’s so much pressure to develop biofuels that some scientists who study the ecology and management of invasive plant species are concerned we may be headed down the kudzu path all over again.

In a paper published last September [If you're logged into a computer on the UIUC campus or elsewhere with a subscription to Science online you can click here to open the paper in a new window], S. Raghu of the Illinois Natural History Survey and six colleagues from around the country call attention to how little serious analysis is being devoted to the potential consequences of cultivating nonnative grasses for biofuel. Indeed, they point out that six of the eight ecological traits identified as ideal for biomass energy crops are also traits that contribute to the potential for an introduced plant to become invasive. They further explain that it is nearly impossible to eradicate or even control invading grasses once they are established.

Raghu and colleagues acknowledge the potential benefits of introducing some plant species as sources of biofuel. But they call for a policy of first establishing the safety of such introductions by means of stringent agronomic and ecological analysis, the sort of up-front studies that are already required for other beneficial introductions, such as biological control agents and transgenic plants.

Perhaps the best way to think about whether the large-scale introduction of a given plant species makes sense would be to ask whether, or at what price, a person could buy insurance that would compensate for the damage that species might cause were it to become invasive. Without the answer to that question we don’t have enough information to develop sound policy.

Thursday, June 14, 2007

Appreciating Turkey Vultures

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.

Turkey Vultures on the Web:

The Turkey Vulture Society

Turkey Vulture entry on Cornell Lab of Ornithology's "All About Birds"

Thursday, June 07, 2007

Introducing University of Illinois Extension’s Big Tree Program

Introducing University of Illinois Extension’s Big Tree Program

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Picture a sycamore tree that’s 119 feet tall, as tall as 13-story building. Now make the trunk of your tall tree wide, 31 feet around at chest height, so you would need five friends with you in order to touch your hands together in a circle around it. Then give your giant sycamore a crown that spreads out to an average width of 134 feet, 15 feet wider than the tree is tall (and more than wide enough to cover the lots many of us live on). As you might have guessed, such a tree does exist. It stands on private property in Christian County, and it is the champion of champions on the Illinois Big Tree Register.

The register is one component of the Illinois Big Tree Program, which is based in the U of I’s Department of Natural Resources and Environmental Sciences and coordinated by extension forester, Jay Hayek. [Photo: Volunteer Big Tree Inspectors measure the girth of the state--and national--champion Shumard Oak (Quercus Shumardii) in Union County, Illinois. Photo by Larry Mahan.] The goal of the Big Tree Program is to identify the biggest individual of every species of tree native to Illinois, using a scoring system that takes into account height, girth, and crown spread. At the same time, however, the Big Tree Program is also very much about people—promoting a greater awareness of trees as a natural resource in Illinois, and encouraging people to get out and enjoy them.

To help people get connected with the Big Tree Program, Hayek has established a web site for it. There you can read how big tree measurements are taken, obtain a form to nominate a tree, and view the list of 125 current state champions. Entries on the list include measurements, of course, along with information about where each tree is located, who nominated it, and when it was certified.

The tallest tree on the list reaches a height of 165 feet, which is 46 feet taller than the overall champion. It’s a red oak found in Dixon Springs State Park, near the far southern tip of the state. The champion listed with the thickest trunk is a baldcypress tree that measures 34 feet around, which grows in the Cache River State Natural Area, also in the far south.

Residents of central Illinois may be interested to know that Sangamon County is home to eight champion trees, more than any other county in the state. These include a 98-foot-tall American elm and an 88-foot tall silver maple. The state champion trees closest to Champaign-Urbana are a shingle oak and a yellow buckeye located in Danville. Both of these trees grow on private property, but they can be seen from the street at the addresses listed for them on the Big Tree Register.

If big trees interest you, you might consider joining the network of certified Big Tree inspectors that extension forester Jay Hayek is working to develop throughout Illinois. Volunteer inspectors participate in a one-day workshop where they learn to measure and certify Big Tree Champions using fairly simple equipment and straightforward math. Hayek envisions training enough inspectors to check out reports of potential champions anywhere in the state, and to help make sure champion trees are recertified every 10 years.

The next Big Tree inspector workshop will be conducted at the Sugar Grove Nature Center in Funks Grove, Illinois, southwest of Bloomington, on Saturday, June 16. For more information about that workshop call the Sugar Grove Nature Center at (309) 874-2174, or click here for a PDF version of the registration form.