March 8, 2010

The Mysteries of Cave Ecology

I’d been crawling through water for five minutes. My gloves were full of grit, my boots grating across the cobblestones in the streambed. My kneepads were not doing their job and I could feel tiny rocks digging into my knees and my shins. I stopped to readjust the padding. I moved to the side of the stream, sat down in the mud, and tossed my backpack onto the wet and glistening cobblestones. My hardhat glanced across the ceiling of the cave passage I was exploring, making a funny grating sound as the acrylic met limestone. My headlight nicely illuminated this rather short (only three feet tall!), but wide cave passage deep underneath the Cumberland Plateau in north Alabama. The passage looked like a symmetrical tube. The ceiling was nice and flat. Beads of condensation clung to the limestone, glittering like glass. Flowing down the center of the passage was a shallow stream, less than a foot deep. When I sat still, I could hear the water flowing across countless thousands of small rocks; I was sure I could hear voices calling to me, but it was only the sound of flowing water.

After moving my kneepads around a bit and cursing their ineffectiveness, I got ready to continue down the water crawl. As my headlight glanced to the mud slope, a glistening black pebble caught my eye. I looked closer. It wasn’t a pebble, it was a slimy salamander (Plethodon glutinosus).

The next person moving down the water crawl sloshed by, and I pointed to the salamander. We both stopped to marvel at the tiny creature, living in total darkness in an environment almost totally devoid of life.

I’ve been exploring caves almost my entire life and I’ve never stopped being amazed at the delicate ecology found deep under the earth’s surface. Many creatures live in this extremely harsh environment; many not only live, they thrive. Slimy salamanders are one of the animals I frequently see underground. According to the Animal Diversity Web:

The slimy salamander is commonly found beneath stones and decaying logs in wooded areas and alongside streams, as well as in the crevices of shale banks and along the sides of gullies and ravines (Davidson 1956; Grobman 1944). It generally moves about underground using animal and insect burrows (Cowley 1999). Mean home-range area is 3.01 +/- .613 sq. meters for adults and 3.46 +/- 1.851 sq. meters for juveniles (Marvin 1998).

I’ve often wondered if the salamanders I see in caves live near a small crack or crevice that allows them easy access to the surface. Usually I see them very far back into a cave, not just around the entrance as most literature states (the salamander I saw on Saturday was at least 1,000 feet into the cave). From what I’ve read, slimy salamanders feed mainly on ants, which are never found inside caves, but they also prey on beetles and sowbugs. Cave adapted beetles do live in caves, as well as cave-adapted insects and crustaceans, so perhaps slimy salamanders can find plenty of food inside caves. Or, maybe they can easily move between the world of light and the world of dark when food or temperature conditions warrant a change.

I’ve been trying to uncover more information about the natural history of animals living far inside caves, but it’s pretty hard! I get the impression that many researchers choose to study more easily accessible animals (maybe crawling through streams, mud, and rappelling down deep pits isn't appealing to most biologists). One journal, the Southeastern Naturalist, published an article discussing the lack of information about cave-dwelling salamanders.

Recent publications have addressed the need for information regarding the natural history and monitoring of plethodontid salamanders using caves and the rock-face habitats adjacent to cave openings (Dodd et al. 2001, Himes et al, 2004, Jensen and Whiles 2000, Jensen et al, 2002, Salvidio 2001). Due to the threat of local and worldwide amphibian declines, there is a need for accurate natural history data and knowledge of population dynamics. Cave habitats are complex and present sampling challenges when attempting to detect and quantify cave inhabitants.

The lack of substantial natural history information affects not only our understanding of cave-dwelling amphibians, but other animals like bats that play key roles in not only cave ecosystems, but overall ecosystems (you'll hear lots about bats from me as I get back into the blogging groove!).

I’ll continue to look for information about the cave life I find interesting. If you have any hot tips, let me know! In the meantime, here’s a great video showing one of my favorite cave dwellers.

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