DELMARVA ALMANAC

Delmarva’s Amphibians

by Dave Wilson

Naturalist Dave Wilson has a conversation about Delmarva's amphibians with Jim White of the Delaware Nature Society.

Dave:
When people think of frogs, they normally think of spring and summer, but a lot of folks don't realize that there are a lot of species here on Delmarva that begin breeding while overnight temperatures are still well below freezing. We're going to talk about some of those species today. In the studio we have Jim White from The Delaware Nature Society and co-author with his wife, Amy, of "The Amphibians and Reptiles of Delmarva". Jim is a native Delawarean who has worked for The Delaware Nature Society for 33 years where he is currently serving as a Senior Fellow for Land and Biodiversity Management. He teaches Herpetology at the University of Delaware. Jim, welcome.

Jim:
Thanks, Dave. It's great to be here.

Dave:
I wanted to start out by getting into some of these frog species a little bit. Some people don't realize that some species of frogs may breed all winter long even though they may, more typically start in January or February. Can you tell us about some of these species; where they might be breeding and how they can cope with the cold.

Jim:
Sure. There are several species that breed in late winter. Some you may have heard of, the New Jersey chorus frog, spring peeper, the Atlantic Coast leopard frog, but probably the most interesting is the wood frog. It is the one species that is well adapted for cold and freezing weather. Most of the species actually just sink below the ice level down in the mud where temperatures are relatively moderate, sometimes as low 30°, maybe a little bit lower. The wood frog, however, is a species that can actually deal with the freezing. The animal itself can freeze solid, actually, and still come back to life as soon as it defrosts.

Dave:
What kind of habitat do wood frogs normally need to survive?

Jim:
Wood frogs need woodlands, a healthy woodlands, but they also need ephemeral pools, large basically fishless bodies of water that fill up in the winter and dry down in late summer.

Dave:
And is there an issue with the protection of some of these pools in Delaware or Maryland?

Jim:
Oh, yes. Most of these pools are relatively small, no more than large puddles and very few of them actually have any kind of protection by the law. So they are often filled and used for housing or whatever type of development they may want to put into that area.

Dave:
Is the type of tree species important when you are dealing with this. I know there's been a lot of conversion to pine multiculture in Maryland and I am wondering about the leaf litter and the needs of some of these frog species.

Jim:
All these frogs really like either a deciduous or a mixed coniferous deciduous wilderness. Pine plantations are probably not the best habitat for any of these species of frogs you have on Delmarva.

Dave:
How big are some of these frogs? Sometimes I think people hear peepers or chorus frogs. They don't think about the size of some of these species and how tiny they are and how they can make so much racket for their tiny size.

Jim:
Yeah. The spring peeper and New Jersey chorus frog are very closely related. They're about an inch in total length. So that makes them very small and their voices are extremely loud if you've ever been in the middle of this, as I'm sure you have Dave, these choruses can be deafening.

Dave:
How do the species get started in the Winter. Sometimes we'll hear them when it is 35° and sunny. Is there any kind of trigger that you're aware of that makes these frogs decide, "okay, we're going to start breeding now" and is there a progression of certain frogs that start, for example, do chorus frogs start first and then peepers and then Southern leopard frogs, etc.

Jim:
Well, I think the trigger...here on Delmarva we often have warm days, sometimes spanning a three day period and the temperatures get up into the high 50's in the day time, even the 60's. So as soon as these temperatures rise they are often accompanied by rain and on rainy warm nights, that's when these frogs come out. The first frogs I usually hear are the New Jersey chorus frog and the Spring peeper. But very closely after, especially after a hard rain, we'll get the wood frogs.

Dave:
Can you talk about maybe the status of some of these species?

Jim:
Yes. Well, the wood frog in particular seems to be suffering from a pretty strong decline lately and it is twofold reasoning: One is habitat loss and the other is actually a virus they're getting. It's called a rana virus. It seems to be fairly common here on Delmarva. We're not really sure what it's going to do to the wood frog populations.

Dave:
Does this rana virus affect any other frogs?

Jim:
Yes, it does, but right now the only data we have is the decline of the wood frog. It probably will affect some of the other species.

Dave:
What ecosystem niches do frogs fill? We certainly know that they eat insects; other species eat them. Can you maybe elaborate on that a little bit.

Jim:
Yes. Most of the species are wetland species. They are all coniferous so they all eat small insects and other invertebrates. That makes them very good food sources for other animals like snakes, birds, even mammals.

Dave:
Is there a sense of some of the change in diversity of frogs since we arrived here and converted a lot to agriculture? Is there a sense that there were probably more wood frogs or more peepers or more of everything and maybe fewer bullfrogs?

Jim:
Yes. That's very true. The species that are associated with woodlands and natural vernal wetlands were probably much more common prior to Europeans coming to this country and changing the landscape. Species like bullfrogs and green frogs, the pond species, were probably relatively uncommon in those days because the ponds, at least most of the ponds on Delmarva, if not all, were man-made for milling.

Dave:
Maybe you could talk a little bit about the need for a lot of these species to have fishless ponds. Some folks, they create wetlands. They want to put fish in them. Certainly, I love fishing as much as the other guy, but there is, I think, sometimes a lack of understanding of what reptiles and amphibians needs are; particularly amphibians when they are breeding in water.

Jim:
Yeah. That's a good point, Dave. Fishless bodies of water, or at least bodies of water that only have native fish. When I say native fish, that excludes the bass and the sunfish. Most of our amphibians require that to be the type of habitat except for maybe bullfrogs.

Dave:
And why is that?

Jim:
That's mainly because the fish eat the eggs and the adults of the frog species and the salamanders, too.

Dave:
Can you talk about those for a second?

Jim:
Yeah. Well, we do have three species of what we call mole salamanders here on Delmarva that breed in the very same habitats that the wood frog breeds: the marbled salamander, the spotted salamander and the eastern tiger salamander.

Dave:
Yeah, I know the tiger salamanders are facing some threats basically from just not having big populations and also from losing habitats. What other threats besides the rana virus and development are any of these species facing? Or if we can get those under control, is there a good chance for a lot of these species to survive in the long term?

Jim:
I think, well I'm hopeful there is a good chance of many these species of surviving. Probably with somewhat lower numbers than may be natural. However with good protection of wild areas, good wetland protection and creation, we might have these species for many years to come.

Find out more at:
delawarenaturesociety.org
The Amphibians and Reptiles of Delmarva - on Amazon.com