Where are the Frogs?

An adult Green Treefrog “hides” on a blackberry stalk.

I’ve been meeting nearly every week with Summer Campers at the Museum as part of a behind the scenes program where the campers get a glimpse of what the staff here at the Museum does as part of their normal routine. When they meet with me we conduct a survey of the Green Treefrogs around the Wetlands.

Each week I have the campers fill out a data sheet with information such as the current weather conditions (temp, humidity, pressure, and sky cover), the area that they will cover in their survey, how many frogs were seen and whether they were adult frogs or juveniles (newly morphed). They also record whether or not there were frogs calling at the time of the survey.

The objectives of the survey are to find out how many adult treefrogs are present, where we see them, the weather conditions that are conducive to their breeding, and when the juveniles climb up out of the water to take up life on the land, trees, and shrubs.

With well over a dozen young eyes searching the vegetation, we’re bound to find frogs, right? So far, we’ve turned up very few of the little green amphibians.

Same frog as above, and one of only a handful seen so far in the Wetlands.

We began the survey in mid June and many of our frogs had already bred by then, but the season is a long one and as long as there are thunderstorms rolling through our area, and water in the Wetlands, the frogs should be here.

I expected to have seen at least a few juvenile treefrogs by now. The product of early breeders in May and June should be showing themselves on the leaves and stalks of the plants surrounding the Wetlands. Where are they?

An adult Green Treefrog earlier this year on Equisetum along the Dinosaur Trail.

I hate to sound like a broken record (or scratched CD) but could this absence of treefrogs be related to the red swamp crayfish in our Wetlands? I posed the same question last year when I noticed fewer treefrogs in the Wetlands but attributed some of the paucity of frogs to the low water level. It was a dry summer. The water level is a bit low this summer as well but not to the level as it was last summer at this time. And, the early part of the treefrog breeding season was fairly wet, so I would expect at least some juvenile frogs.

There didn’t seem to be a shortage of treefrogs along the Dinosaur Trail earlier this spring and summer, whenever the rain rolled in treefrogs were there and easy to find, mostly on equisetum. It’s here in the Wetlands that they seem to be missing. What’s the difference between the Wetlands and the Dino Trail? For one thing, there are no crayfish on the Dino Trail.

Even the pool in the Black Bear Enclosure has treefrogs. There are hundreds of tadpoles swimming around in the lower bear pool. Most look to be cricket frogs, but I haven’t seen many of them in the Wetlands either.

There’s no shortage of tadpoles in the Black Bear pool.

Yesterday morning while I stood at the edge of the Wetlands I saw three adult crayfish crawl out of the muddy ooze that is the north side of the water. It may have been a coincidence, but all three followed the same path and were all in view at the same time.

One of three crayfish seen leaving the water within minutes of each other.

Our little survey is not over yet and more data will be collected in the coming weeks. I’m anxiously waiting to see what that data shows but my feeling is that most of the data will be on the negative side.

It’s important to note that the surveys are conducted only one day per week and this particular camp is not in session every week. However, I still run the course on weeks that the camp is not scheduled, so the data is consistent. Additionally, I do see and hear Green Treefrogs on days when the survey is not being conducted but it’s usually one or two individuals that are seen.

4 responses to Where are the Frogs?

  1. Sarah says:

    The keepers’ enrichment/mulch storage bins at bears and lemurs typically hold a half dozen or more Green Treefrogs during the summer and fall. I haven’t been out there much this season to look for them, but in the past, there’s always been a few to find just under the lids. In the farmyard, it’s Grey Treefrogs we hear a lot of…and they are LOUD!

  2. dj says:

    Do the crayfish eat the Green Tree Frogs (tadpoles, eggs, etc) or take over their habitat like kudzu has taken over a lot of vegetation?

    • Greg Dodge says:

      While I do think that the crayfish eat the tadpoles, and probably eggs too, I think the biggest problem with the crayfish is the fact that they destroy the submergent vegetation of the bodies of water that they inhabit. Many species of aquatic invertebrates, fish, and tadpoles depend on that vegetation for both food and shelter.
      The presence of the crayfish also increases the blue-green algal blooms which may have an adverse effect on the eggs and decrease the oxygen levels in the pond.
      But the truth of the matter is that I don’t know what the real effect is on the treefrogs. I can’t prove one way or the other how or even if the crayfish are impacting the frogs of our Wetlands. I just know that there are fewer of them (frogs) since the crayfish have become so numerous. Perhaps our little survey will be the start of another larger study documenting the frogs and toads of our wetland.
      By the way, I noticed fewer American Toads this spring as well as fewer of several other species of frogs and toads here in our wetlands, but I have no data to back it up.

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