Tuesday, January 21, 2014

Catching Frogs in Green Pond

It's been quite a while since I have posted anything here, but now that I am back out in the field on a new adventure... I think an update is appropriate. I am currently living in Green Pond, South Carolina at the ACE Basin National Estuarine Reserve Research Station (NERR) and working for Dr. Emily Moriarty Lemmon (Assistant Professor - FSU) as a Field Technician. My job centers around her research on Chorus Frogs (Pseudacris) and the speciation process... which is quite fascinating. I'll explain more about that later.
Upland Chorus Frog (Pseudacris feriarum) - our focal species
A couple weeks before this job was scheduled to start (Jan. 15), I got an e-mail from Emily asking if I could head down early... since she heard the Chorus frogs in Florida "screaming" right after New Years and was concerned that if we didn't move quickly we may miss out on a major breeding event in South Carolina, where we were slated to be stationed. 

So I packed up my bags a bit early and drove down to Green Pond, SC to find myself in a gorgeous and largely undeveloped area of the southeast. We are stationed at the end of Bennett's Point Rd, a 14 mile road surrounded by huge live oaks covered in Spanish moss, and lined with ancient plantations. On the way in, I couldn't help but get excited as the buildings disappeared and I became surrounded by southern forest. 
Driving down Bennett's Point Rd
Along the way, I passed over the Ashepoo river and through a large area of untouched, pristine salt marsh. I would later learn that this area contains over a million acres of protected land. It's pretty cool to see so much conservation in action down here. As I passed by one section of wide open water I saw something I'd never encountered before... a huge flock of Tundra Swans, just paddling about and enjoying the warm weather.
Tundra Swans, sheltering in the south for the winter
Upon arriving at our home for the next few weeks, the ACE Basin NERR, I was blown away. The place is about as nice as it gets for a field station, complete with large dorms, a lab, full kitchen, and a gorgeous backdrop that can't be beat. 

A small part of our gorgeous backyard view
We are pretty isolated from the rest of the world, which is really quite refreshing. The stars at night are spectacular! To put things in perspective, the nearest grocery store is over 40 minutes away. The few people around us are largely a part of the fishing community, as there is a salt marsh in our backyard that is about 5 miles away from the ocean, as the crow flies.

The evening I arrived (Thurs, Jan. 9) I met everyone else on the crew, as they had all come from Tallahassee earlier that day. Hannah was there first. She is a graduate student at FSU and Emily is her adviser - so she is very familiar with the project and was able to fill me in a bit more while we waited for the others to arrive. 

After darkness fell, Emily arrived with Zack and Alyssa - the two other field technicians that will be working on this project alongside me. Zack is our crew leader, so he is in charge of delegating tasks and making sure things generally get done properly. Alyssa works in Emily's lab at FSU, so she is very familiar with the lab techniques that we will be using during the season.

As we would soon learn, we were all going to have to learn on our feet. The weather was blowing in for a perfect storm mixed with warm weather that Emily predicted (correctly) would bring the Chrous frogs out in force to breed. This particular species is an "explosive breeder" which means they all attempt to breed after a major storm event. The trick was making sure we were ready when that storm happened. 

Thursday evening we ate dinner while Emily filled us in a bit about what we would be doing over the next few days. We needed to set up the huge trailer she had hauled up from FL so that we could conduct most of the experiments inside of it. The set up process took most of the day on Friday. 

Our massive field truck, with trailer in tow
We set up the trailer so that we could conduct female call preference tests within two sound-proof chambers constructed inside. This involved all of us doing different tasks, to make sure things were ready for us to collect frogs that evening. We had to park and level the trailer, test and install speakers and cameras, clean baby pools, and gas up a generator...  to name a few tasks.

Cleaning out baby pools
We got a crash course on how to set up the experimental stations, and how to collect and input the data. Everything needed to be done according to a very specific protocol in order in insure that results are not influenced by alterations in our methods.

When everything seemed to be good to go for the most part, we geared up for heading out into the field with a few storm clouds moving in over head. All of us were very excited for our first time out into the field in this new habitat... and a little nervous about what to expect. 

As it turns out, we have to travel quite a long way in order to reach the locations where these frogs are known to breed... as the area around us is almost entirely brackish, which isn't ideal for frogs. We grabbed a quick dinner on the road, and stocked up on snacks and supplies in preparation for being awake all night.

We would be catching frogs and then testing the female's preferences for certain male calls in the sound-proof chambers in the trailer. Emily anticipated that we would be catching quite a few frogs, so she even set up two extra "ghetto" chambers in the bathrooms of both dorms, so that we could conduct extra tests there in order to speed up the process of data collection. Needless to say, for the first few days of work - we didn't get a shower.

A female preference test chamber in our bathroom
That evening, we headed out on rural roads with our heads out the window listening for loud choruses of our frog, (P. feriarum). These frogs only need a bit of water in order to breed, so roadside ditches work quite well for them. This makes our job finding them somewhat easy, but not too glorified. We did find a couple areas where vernal pools had formed in the forest, which resulted in us finding not only a bunch of frogs... but also this little guy! He's a Spotted Salamander (Ambystoma maculatum) Way cool.
Spotted Salamander we found in the forest
Our search was specifically geared towards finding amplexed pairs (frogs in "the act") since those females are the most responsive during the preference tests. After we had caught over 30 pairs, Emily sent Hannah, Alyssa and I back to the field station to start testing the frogs while she and Zack continued to look for more pairs in other locations. Not all of the places we searched were ditches, and we had to be careful to tread lightly when we ventured off of the road and deeper into the woods. A lot of the land is privately owned, or part of hunt clubs, and not everyone takes kindly to people looking for frogs 'round here. Needless to say we turned around pretty quickly when we saw this sign... 

Time to go...
Thankfully no one was shot. The work went on all night, separating the pairs, acclimating the females to an appropriate temperature (frog calls are highly dependent on temp) and then conducting the actual experiments to see which calls the females preferred. This involved placing the female in the middle of the baby pools and then playing two different frog calls on either side of the pool and recording which side she chose to head towards - if there was an obvious choice. 

At 7:30 or 8 am we finally stopped the tests, because at that time the frogs are no longer responsive since they are nocturnal. As a result, we became nocturnal. We slept until 3 pm, then woke up to eat and gear up for more work. This time only Emily and Zack went back out into the field while the rest of us continued to run tests on the frogs we didn't get to test the night before. Once again the work went on all night, while Zack and Emily eventually returned with over 50 more pairs around 2 am. We worked until dawn, but at least we got to catch a gorgeous sunrise as our shift came to a close. 

Watching the sun rise over mist covered water
That morning, Sunday, Emily left to head back to Florida - as she has lots of other responsibilities to take care of there. It was our job to continue the research with these two days of intense training, and with Hannah's help. Hannah was there for her own project though, so she would only be around to offer suggestions as needed... the majority of the work was on us. We continued to bust our butt for the next week, collecting frogs, and testing them all night long... only taking small breaks to sleep and eat. 
Our "command center" within the trailer
Finally, the frog catching began to subside as the temperatures dropped again, but we still had lots of work to do before we could rest. Each female frog needed to be reunited with her male counterpart and then both of them had to have a small tissue sample taken from them before they could be returned to the wild. This was a very time consuming process, and kept us awake for many more nights.

Eventually we released all the frogs back to their homes, and were able to breathe a large sigh of relief and actually sleep while it was dark outside. We are currently waiting for another breeding event, but in the time being we are able to relax and explore the surrounding area. This is why I actually have time to write this post! 

Yesterday we went into Charleston and walked around (such an awesome city), and the day before we went for a hike on a nearby Nature trail. Field work is always unpredictable, so for now we are enjoying this small break... since it is hard to say when we may be working nocturnally again. But no matter what happens, I'm happy to be here!

Our Field crew on a hike
OK be warned... going to get a bit nerdy here in an attempt to roughly explain a bit more on what the project is all about. Please stop here if you don't care! 

Essentially the project focuses on how female Upland Chorus frogs (Pseudacris feriarum) that live in close proximity (aka sympatry) with other Chorus frogs (P. nigrita & brimleyi) chose their mates based on the minor differences in male frog calls. The idea being, in order for the girls to continue to reproduce within their species - they should be able to tell their males' calls from the calls of males of another species. Kind of like us recognizing people's accents to determine where they are from (Know'm sayin', y'all...). This is an important decision for them, because hybrid offspring have been shown to have significantly less success at reproducing (Lemmon & Lemmon, 2010). This process of being picky about who you mate with in order to avoid hybridizing is also known as "reinforcement."  This gets interesting, because in this case the male Upland Chorus frogs that live near other species of Chorus frogs have actually modified their calls so that the females can distinguish them. 

Mixing two species doesn't work!
Now here's the cool part... these minor changes in the males calls, and as a result the female's choice, can actually lead to the creation of new species! Formally called speciation... this happens over the course of time as females fine tune their preference for a certain call that she knows won't lead her into hybridizing; thus making sure to give her babies a better chance of surviving to make tadpoles of their own. Since the calls of Upland Chorus frogs (P. feriarum) living in a neighborhood with other Chorus frog species have been modified from their original form, the females living in this multi-species neighborhood may become so picky over time that they won't even go for frogs of a different neighborhood (population) that use the original (P. feriarum) call - even though it is from the same species. This process of modifying what species look for in a mate is known as "Reproductive character isolation." This can potentially lead to the two populations becoming reproductively isolated from one another, and thus separating into two species. Our work involves testing female (P. feriarum) preferences for certain male calls to see if this happening. Cool stuff! 

Disclaimer: This is a very rough explanation of what the project is about, and should not be taken as anything more than an attempt to fill in my friends on what is going on here. I may have made mistakes or errors in explaining this process, as I have only recently become acquainted with this research. This information is not to be used for scientific purposes. If you are interested in learning more... please refer to Dr. Lemmon's website.

No comments:

Post a Comment