Thursday, September 9, 2010

The problem with caves

Caves pose specific problems to many forms of life. Caves are dark, and animals must develop their non-optic senses to survive. Many cave organisms have no pigment - what's the point of a pretty color pattern if no one can see it? On the right is a photo of a blind cave fish from the National Park Service's Ozark Riverways page. As you can see, it has no pigment and no eyes. Over time this group of fish has evolved inside caves and lost many of the features that would be beneficial in a normal stream habitat.

Now, you may be wondering why I'm talking about living things. I just felt it was a nice lead-in to my cave discussion. Here's my cave discussion: Caves are really hard to georeference. The Best Practices for Georeferencing tell us to georeference the mouth of a cave for a specimen that was collected within the cave system. But what do you do when a cave system has multiple entrances? Take Mammoth Cave in Kentucky for instance. There are presently over 30 entrances (not all natural) known for this cave system. If we had a fossil collected from within Mammoth Cave, we may be able to pick an appropriate entrance based on locality data.
Historical entrance to Mammoth Cave (photo)
If the specimen was collected prior to 1921, then the most logical choice would be the "Historical Entrance." This was the only entrance known until 1921.

The cave was initially one among many caves in the area. If locality data named one of the other caves which has since been connected to the Mammoth Cave system, it would be logical to georeference an entrance to that portion of the cave system.
As for determining the extent of error on that point, the Best Practices suggest using the surface extent of the cave. For Mammoth Cave, there are over 365 miles of the system that have been explored. Could historical data be helpful here as well? If the specimen was collected early in the cave's explored history, could a map of the cave system at that time be used to determine a lesser extent of error?
Mammoth Cave provides an extreme example of potential problems one encounters when trying to georeference cave specimens. And, until GPS units can get signals underground, these problems will continue to pester us. The Best Practices guide provides a method to consistently georeference caves even when they are very extensive.

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