25 May 2009

Making Up Time

Southeast Nebraska was much easier than I thought. It took a few false starts at areas that apparently only have Plains Leopard Frogs, but after only a day I found a population of Northern Leopard Frogs that was heavenly. There were frogs everywhere, more than I've ever seen at one place. This will be an interesting population genetically, because Plains Leopard Frogs were also present and hybridization has been reported in the past based on morphology. No one really knows whether these hybrids are fertile, but my genetic work should be able to tell us whether they are.

I saw something here that I'd only read about: I saw a bullfrog catch and eat a leopard frog! It all happened so fast. I scared a leopard frog that took two quick hops. As it landed the second hop, a large bullfrog that was waiting nearby lunged forward and grabbed the easy meal. Whoops! Bullfrogs have been so widely introduced that we don't really know whether they are native or introduced in some parts of their range. This is one of those parts. I felt bad for the leopard frog, of course, but this was fascinating to see. I got a distant photo, below, of the bullfrog with leopard frog legs hanging out of its mouth. You should be able to enlarge the photo by clicking on it.

It only took two days to catch the frogs I needed from this location. Even when they're abundant, they're not easy for me to catch! So, now I'm in Iowa, back on schedule. The weather has turned rainy for a day or two and I still have a couple of reports I need to finish, so now I'm working in a coffee shop. It's nice to just sit inside for a while after spending so much time chasing after frogs.

19 May 2009

A Slow Start to the Field Season

This blog has been quiet for a while, but it's only because I had nothing good to say. (Oh, and it’s hard to find time to be online while I’m looking for frogs.) My field season started three weeks ago in northeast Nebraska, where I need three more populations to finish off the project I was doing last year. I was afraid I was getting too late a start, hitting the road on April 26th, but in fact I think it was the opposite. The northern leopard frogs just weren’t active yet. At first I thought I might just be looking in the wrong spots, but I think it kind of hit home on May 1st, after I had been looking for almost a week, when I woke up to snow.

I gradually worked my way south as I hoped for better weather. About mid-way through my second week, I heard frogs calling at night. What a relief – I had found them! I spent three more days looking for them at that spot, day and night, but I never saw a single frog there. I know they spend their winters underwater, and I wonder if they were still spending their days at the bottom of the ponds and only coming up at night to mate. The odd thing is that I never found any egg masses or tadpoles, either. I still haven’t. This is the big mystery of the year so far. Even when I know frogs are breeding, I can’t find their egg masses. This is a big disappointment, too, because it is much easier to catch an egg mass than a frog!

After a few days at that location, I tried Crescent Lake National Wildlife Refuge. This was a nice change of pace because the refuge manager kindly allowed me to stay in their researcher housing – a bed and a shower for free! Again I spent several nights hearing northern leopard frogs, and several days not finding them. I decided I needed a positive control to figure out what was happening, so I went back to a place where I had found frogs to be abundant last year. They were still abundant. It was a nice change to finally be catching frogs again! But I still didn’t know why I couldn’t find them elsewhere. A few things I noticed were that it was warmer here than the other places I had been looking, and warmer on that day than on any day so far on my trip. Also, although I could hear frogs calling at night here, I couldn’t find them in the lake where they were calling, and conversely I never heard any calling from the ditch where I was finding frogs. So, I think they’re just too hard to find when they’re breeding, and just then, in the first week of May, they were finishing their breeding and heading to their summer hunting grounds.

I decided to travel further southeast in search of frogs that were already active. (In spring in Nebraska, it is usually warmest in the southeast and coldest in the northwest.) What I found were lots of leopard frogs. Of the wrong species! It was exciting to find my first plains leopard frogs, Rana blairi (photo below), but the excitement soon turned into frustration when I couldn’t find any northern leopard frogs, Rana pipiens.

I gradually worked my way north again until I found a good population of northern leopard frogs. Once I found the right place, I was able to collect all 24 that I need in three days, but now I was two and a half weeks behind schedule. I cruised back west toward Crescent Lake NWR, and found another population of leopard frogs on the way. I was able to collect all I need there in three days, putting me only one week behind schedule instead of two and a half. Now I’m on my way to southeast Nebraska for my last stop in the state. This might be tricky because I need this to be an edge population, and in this part of the state northern leopard frogs and plains leopard frogs occur together. They are very similar, so I usually need to catch them to tell them apart. So, instead of just catching 24 frogs, I might need to catch 50 or so and throw half of them back! Wish me luck. . . .