Monday, May 11, 2009

Size Doesn't Matter

As the end of the semester is right around the corner, most students likely spent their Friday night tying one on at the bar. I on the other hand, was more concerned with tying my shoes on, tightly, so they wouldn’t get sucked off my feet as walked through the muck on the bottom of a farm pond.

We were back in Henry County, Alabama, for another attempt to gather some greater sirens for a study back in Auburn. The goal was to arrive after dark to seine, trap, or otherwise get our hands on one of the slippery, slimy amphibians. Once captured, the animals would be safely transported back to campus and held in aquariums to take place in a respiration study. The research aims to determine how sirens best absorb oxygen through the water. It’s always difficult to conduct a study on animals other than lab mice, because you can never count on having an easy time finding your subjects. This is particularly true when they live in the weeds and mud of swamp bottoms.

After we exited the van and prepared to enter the pond, a sharp exhalation of breath caught my attention. I slowly turned around and illuminated about two dozen cows with my headlamp. Their eyes glowed white as they staring inquisitively at me. So as to not alarm the giant, lumbering animals, I quietly turned around and crept into the water. I hoped the curious beasts would choose not to investigate beyond giving me more unsettling looks.

For the first time this year, I could hear barking tree frogs (below) calling.

Off in the distance, there was a full chorus of this species singing to one another. We consider these congregations a full chorus when there are so many calling frogs that we cannot distinguish individuals, just a lot of singing frogs. Periodically, one of a few bullfrogs would catch our attention with their long, deep, resonating bellow. There were also green tree frogs, bird-voiced tree frogs, and cricket frogs calling. Not a bad complement of species for a pond in the middle of a cow pasture.

My ankles submerged in the water, I waited a few seconds and let the mud seep through my sneakers. I always find it necessary to adjust to walking through the mud. There’s something that feels inherently wrong about striding right into swamp muck when you were sitting in a van listening to music and minding your own business just minutes before.

As I stood in the water I took in the swamp. In contrast to my visit in March, I could see several pairs of orange eyes looking back at me, illuminated in the beam of my headlamp. As the weather warmed in the last few weeks, the alligators emerged. There were a couple alligators zooming around the main pool of the swamp, perhaps hot on the trail of prey. I could also see the eyes of a smaller, solitary and motionless alligator about 20 feet away. Instinctively, I scanned the water around my legs and watched my step, although I knew there was unlikely to be any danger.

Alligator eyes, and those of the curious cows, reflect light because of a layer of tissue in the back of their eyes called the tapetum lucidum (which would be an awesome band name). The tapetum lucidum reflects available light onto an animal’s retina. This allows the animal to see better in the dark by making the most of the little light that’s available. As you might expect, tapetum lucidums are most often found in nocturnal animals. One side-effect of this tissue is bright and glowing eyes when illuminated by a flashlight. It’s a lifesaver too; the bright eyeshine of a deer in the road has likely averted many car accidents.

Putting the cruising alligators out of mind, I began to help seine through the waters of the swamp. Sirens spend most of their time within dense aquatic vegetation or within packs of leaves that settle at the bottom. In these hidden areas, they wait to ambush prey, such as small fish or tadpoles. They’re also safer here from predators, like the patrolling alligators. There wasn’t a lot of cover in this pond, however, and we struggled to find areas that looked promising.

By the time 11:00 had rolled around, we had yet to match the total catch of our previous attempt, a single siren. We were, however, hauling in plenty of small bluegill, largemouth bass, and crayfish. We held a few of the latter to feed the captive siren at Auburn. It was apparently a picky eater, and would only accept the clawed crustaceans. Resigned and tired, we decided to give the seine one last try.

As we hauled the net out of the water, we noticed a larger than usual mass of weeds. It was a promising pile that we set upon with an enthusiasm that defied the late hour. A brown squiggling form caught our attention, but it was revealed to be a small bullhead, a type of catfish. It was carefully grabbed and thrown unceremoniously back into the swamp. Following the catfish were numerous dragonfly larvae, more bluegill, but no giant writhing form that would give away the two-foot long amphibians we were after. Resigned, we started to toss back the clumps of vegetation into the water, just in case there was a fish stuck inside that we missed, and rolled up the seine in preparation for the drive home. When the last clump of swamp weeds was removed, a slight movement caught my eye.

A tiny, eel-like animal wriggled within a slight puddle in the mud. It was with great excitement that I scooped up the beast and exclaimed that the expedition was a success after all; we had captured a siren barely an inch long. It was a larval siren. When greater sirens are babies, they’re miniscule and incredibly difficult to find or trap. In fact, it was the first one ever recorded from the state of Alabama.

Saturday, May 2, 2009

Auburn University, A River Runs Through It

Ten pound turtles, serpent-eating kingsnakes, three-feet long fish, and many other animals roam through the heart of Auburn University, and most people have no idea they’re even there. Inconspicuous and unassuming, Parkerson Mill Creek meanders through Auburn, providing habitat for numerous plant and animal species that are often more likely to be seen residing within natural marshes and wetlands than in the midst of parking lots, dormitories and the 80,000 people that cram into Jordan-Hare stadium during football season (War Eagle!).

But Parkerson Mill Creek has seen better days. The surrounding pavement does not absorb water like soil would; resulting in a greater amount of runoff into the creek, carrying with it increased pollution. Due to construction and culverts, natural flow patterns have been disrupted. When a creek is stuffed into a culvert the water pressure increases considerably. After a rain, when water levels are high, the creek blasts out of culverts and erodes the banks. Walking along the stream today will reveal many trees with their roots exposed, the water has washed away all the dirt beneath it. Occasionally, these trees are so undercut that they simply fall over.

A heavily degraded section of creek, with barren, eroded banks and litter strewn about.

Every Thursday this semester I’ve worked to help supervise a volunteer effort restoring and revitalizing Parkerson Mill Creek. One of the primary goals is to address perhaps the most insidious threat to stream health, invasive species. An invasive species is any organism introduced into an area other than where it belongs and that has a negative influence on native species. In our region, perhaps the most well-known example is the kudzu that blankets the natural vegetation in central Georgia. This plant is native to Japan and it smothers other plants, out-competing them for sunlight and nutrients in the soil. Over time, the kudzu eliminates other life in the area.

As is often the case with the most damaging invasive species, kudzu was introduced deliberately. It was once thought to be an excellent form of erosion control, and farmers in the Southeast were urged to plant it on their property. Now, we can’t get rid of it. Chinese privet, another Asian species, was introduced to the Southeast as an ornamental plant. Today, Chinese privet and kudzu dominate Parkerson Mill Creek.

The volunteers and I work along the banks of the creek, clipping kudzu, chopping down privet shrubs, and hauling it all to a nearby dumpster. These species have become so abundant and overbearing that the creek becomes almost entirely shaded, resembling a dark tunnel enveloped by kudzu vines and the overhanging branches of the larger privet branches. Our hope is to clear the area of the invasive species and plant native vegetation, like sapling willow trees, instead. Ideally, the willow trees will take advantage of the lack of competitors and thrive. This leaves less nutrients and light for the invasive species to use and discourages them from taking over, although it is likely that they will never be completely eliminated. Hopefully, the willow roots will also help hold the soil in place, reducing the amount of erosion.

A section of creek that we helped restore. Note the willow trees dominating the bank.

I’ve only been involved in the project for a few months but it has been running for several years, coordinated by Eve Brantley. There are already signs of progress; I found two-lined salamanders hiding alongside the stream and a school of small fish darting back and forth within the creek bed. Perhaps most exciting (to me, at least) were numerous water snakes and a single kingsnake, a three foot long gar hovering in one of the deeper pools, and a large snapping turtle moseying along the stream. All of these animals can indicate a healing habitat, but there is still a lot of work to do.

On my last day, a larger than usual number of volunteers showed up to help. Some eagerly grabbed trash bags and filled them with the broken bottles and plastic bags that are typical of your standard litter crop within our natural areas. Others helped remove vines or some of the larger privet shrubs.

I introduce the volunteers to the Parkerson Mill Creek project

Towards the end of the afternoon and after the volunteers had left, I stood along a bridge that spanned the creek where we had spent most of our time and reflected on the semester. After months of work, we had removed the invasive vegetation from only a short stretch of creek, but the difference was striking. Hopefully this will be a prime spot for willow saplings next spring and their limbs will provide natural cover for wildlife.

As I watched the water cascade over the rocks in the creek bed, I began to hear an eastern towhee sing in the neighboring woods as it investigated the leaves for something to eat. A tufted titmouse suddenly arrived and began hopping from rock to rock over the stream, illuminated by the sunlight that now reached the water. Although we have done considerable damage to so much of our natural areas, we can sometimes restore them through hard work, sweat, and perseverance. The wildlife may be waiting to return.

The stretch of creek where we spent most of our time this spring. Note the dense invasive species in the background and the open foreground, where it has all been removed.

If you're an Auburn University student and interested in helping out on the creek next semester, click here

To get involved in stream restoration in general,
Click here for Alabama opportunities
Or here for Georgia opportunities