Mystery of the Missing Frogs

I’m writing for the first time from home today.  My last night of fieldwork and data collection was officially carried out last Tuesday.  Jonathan says the hard part is over.  It’s true that fieldwork is draining and puts your sleep cycles on crack, but I still think that the ‘fun part’ is also over.  From now on my time will be spent pushing around a massive data set, organizing and analyzing, and better yet, writing a scientific paper. Fun fun…

Then again, it may not turn out to be so bad.  I have already begun to write the methods section of the paper.  We also have a great deal of very interesting data, especially when it is taken together with Jonathan’s North Carolina data from 2004-2008.  Essentially, we have an extensive data set that covers most of North Carolina and Southern Virginia, including Cricket Frog incidence, relative abundance, and recordings for every site.  Of course, you can never have enough data, and the set may be expanded with incidental trips to North Carolina.  I probably won’t be able to accompany Jonathan on most of these trips, but the data will hopefully be collected.  We are still missing sites from two large chunks of the Chowan River watershed on the very southern border of VA. W

When you look at the big picture, you see some very interesting things indeed.  Our original hypothesis was that Southern Cricket frogs may be disappearing from their historical ranges in Virginia.  This was based on the fact that the 2004-2008 data showed complete disappearance of the species from most of Northeastern North Carolina, where they used to be found in abundance.  We assumed that the decline extended geographically farther upward into Virginia.  Now, looking at our data, it’s clear that this is not true.  We did not find Southern Cricket frogs within about 30 km of the border, but then again, that area is very lacking in sufficient sites to draw a concrete conclusion about their absence.  And once you get about 3o km North of the border, Acris gryllus starts calling with gusto. We found decently large choruses, most of them mixed, with varying relative abundance of species.  Near the end of our field season, we also found a few sites on the peninsula between Richmond and Hampton that contained a few Southerns; surprising since we never expected to find them that far north at all.  But there they were, all over the Southeastern corner of Virginia that we covered.  Basically, the only disappearance of the Southern Cricket frogs occurs in a large chunk of Northeastern North Carolina that spills over slightly into Southern Virginia.

The question now is, why?  This is the question we hope to address during the coming school year using GIS analysis.  As i mentioned in a previous post, the incidence of Northern Cricket frogs was very consistent with the dominance of hardwood vegetation, and the incidence of the Southern Cricket frog was very consistent with the dominance of pines.  A mix of hardwood and pine often surrounded a mixed chorus.  One night we were finding all big choruses of Northern Cricket Frogs, when we came upon a gigantic Southern chorus….in the middle of a pine plantation.  How’s that for a hint?

The vegetation parallel suggests a possible difference in the land use between North Carolina and Virginia.   That is one of many possibilities that we hope to explore using sophisticated GIS analysis and data layers.  For now, we are looking for ways to organize the data, especially distinction between chorus strength and relative abundance.  We are also separating the data into sites for which we have historical data and for which we don’t.  This will give us a stronger base for the eventual work we will do, extending into next semester and possibly next summer.

The current paper will address our findings on the current ranges of the Northern and Southern Cricket frogs.  Jonathan says that I will probably be getting this paper published eventually, and he also hopes that I may present it at the next meeting of the Virginia Herpetological Society.  I’m excited because it will mean added experience and some bonus points for my resume, not to mention the fact that I may make a real difference in the future of these frogs, which, though common and plain, are an excellent test subject for amphibian decline, and, of course, are super adorable.

Wish me luck!