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. . . .


Mama bee said...

Good luck, Ryan! Hope this next batch of Northern Leopard Frogs makes collecting easy on you.

John Weiss said...

Hi Ryan
Love reading your blog and seeing where you are- keep up the frog hunting. We are heading up to the bush block this weekend - will hear some pobblebonk (banjo) frogs for you. Also doing some fishing - only 2 weeks before closed season. 30 birds on bird list so far - about 4 new spp each visit
Best wishes
John and Penny