The year of the frog

by Marshall Jones, Spring 2008

Fossils tell us that amphibians were the first animals with backbones to emerge from the primeval swamps and venture on to the land, nearly 400 million years ago. At the start, they were just unusual fish with muscular fins, wriggling out on mud banks to feed on worms and insects. Later, those fins gave rise to bony legs, allowing them to crawl from one pond to another. Some ultimately became fierce predators, growing up to six feet long. Others remained relatively small and gave rise to today's salamanders and newts.

But one group of amphibians developed in a different way, their hind legs becoming magnificent jumping appendages. These first frogs were able to search for food at the edge of the pond, but then hop quickly back into the water at the first sign of danger. Over time, they ventured farther into adjacent grassy or forested habitats, relying on their legs to leap their way to safety.

Like their salamander relatives, these early frogs and toads still depended on their original aquatic habitats to breed. How did they find each other at the right season of the year? That problem was solved by another amazing advance – the ability of males to vibrate the skin of their throats and make sounds, calling their lady loves to the water. Long before the first bird, it was frogs and toads that filled the air with their romantic calls.

A banner year for wood frogs

	Floating wood frog. Photo by Marshall Jones.

At our home in Keyser Hollow, the burbling voice of the wood frog is the harbinger of spring. With the first warm spells in February, we scrutinize every thaw of the small pond beside our house, at once eager to see them and yet also afraid that they'll emerge too early.

But even if an Alberta clipper brings us a late snowstorm and a hard freeze, the wood frogs are well prepared. They can survive being frozen solid, as Sara and Jim Lawrey documented in their RappNature column in this newspaper in March 2005. Their natural antifreeze mechanisms minimize damage from the jagged edges of ice crystals that cause frostbite within the cells of humans and most other animals.

Wood frogs have lost many former breeding sites, but this was a banner year for them in our pond. The dark brown males emerged in early March and continued serenading the larger, reddish-brown females for nearly two weeks. As the weather warmed, their eggs hatched and our pond was taken over by perhaps 10,000 tadpoles, who quickly consumed all available algae and other natural food.

As I write this, at the end of April, my wife Clay and I are now supplementing their diet with boiled lettuce, tropical fish food, and rabbit chow. Last year's northern water snake just emerged from hibernation to find this tadpole bonanza and is now eating many each day, but with no visible dent in the population.

No banner years for threatened frogs

American toad. Photo by Jason Gibson.

Unfortunately, there are no banner breeding years for far too many of the world's 5,000 species of frogs. At least one-third of them are threatened with extinction, according to the World Conservation Union (known for short by its old acronym, IUCN). To publicize the plight of the world's disappearing frogs and toads, 2008 has been designated as the "Year of the Frog" by the IUCN, the American Zoo and Aquarium Association, and individual zoos like the National Zoo in Washington D.C. and its Conservation and Research Center in Front Royal. Displays, events, and activities throughout the year will help people understand what's happening to our frogs and toads (as well as salamanders) and what's being done to try to save them.

Of course, animals of all kinds are suffering from degradation and loss of natural habitats, but frogs and toads are especially vulnerable. Mammals have hair, birds have feathers, and reptiles have scales, protecting them from drying out or absorbing toxins. Amphibians, on the other hand, are protected only by their smooth, moist skin. This allows them to breathe under water – a real advantage for animals that still must live part of their lives in their original aquatic home – but that moist skin also absorbs everything else in their environment. Amphibian eggs, laid in the water, also lack shells. Every pollutant which goes into our wetlands eventually makes its way into their bodies or eggs.

Frogs and toads are also especially susceptible to the effects of climate change, since their breeding seasons are closely aligned with the weather. Another threat is a fungus first identified by scientists at the National Zoo in the 1990s. This chytrid ("kit-rid") fungus has now been identified in wild frogs in five continents. Its rapid spread, probably accelerated by global climate change, makes it one of the worst wildlife disease outbreaks ever identified.

Conservationists from around the world are now working to increase our understanding of these threats and develop ways to counter them. In extreme cases, some species may need to be brought into "protective custody" in zoos to ensure they do not disappear, with the hope that future breakthroughs will enable them to be reintroduced back into their native habitat.

Why frogs are important

The loss of amphibians can tell us important things about the quality of our environment. They are among the earliest indicators of habitat degradation which may ultimately threaten us, too.

Frogs and toads are also key parts of the natural food web. They eat copious quantities of insects and in turn provide food for reptiles, like the water snake in our pond, wading birds, and raccoons, among many other animals. The ability of wood frogs to survive being totally frozen may yield clues about how to prevent frostbite, and many other frogs harbor equally fascinating mysteries.

And frogs can bring us delight. Before the wood frogs in our pond had finished their subtle singing, shrubby wetlands all over the Virginia Piedmont were filled with the piercing whistles of spring peepers, which will continue well into May. The melodious trills of American toads also joined the peepers, though for me their breeding finished all too soon.

As summer comes on, wetlands will be filled with raucous trills of the gray treefrog, plunking notes of the green frog, and the deep bass resonance of the bullfrog's "jug-o-rum" call. Altogether, there are thirteen species native to this part of Virginia, each with its own distinctive song, habitat needs, and life history.

Conserving our frogs

So far, none of the frogs and toads in this part of Virginia is known to be threatened, but many species have declined with the loss of natural wetlands. Others may soon be in trouble. We can all help maintain them as part of our landscape by learning about their conservation needs through "Year of the Frog" activities.

Some measures that will benefit native amphibians and other wetland species include maintaining or planting native vegetation and avoiding the spray of pesticides and herbicides in and around wetlands; fencing cows out of streams; and developing ponds with gently sloping sides, lots of vegetation, and no fish.

You can also learn to identify their calls and then monitor their arrival every spring. Hopefully every year will be a banner year for the frogs and toads of your favorite wetland.

For further information

The National Wildlife Federation maintains Frogwatch USA, a volunteer frog monitoring program (www.nwf.org/frogwatchUSA). The RLEP's Biodiversity Task Force provides training and is organizing participation in Rappahannock County and adjacent areas, in cooperation with the Virginia Master Naturalist Program; contact marshall.jones@mindspring.com.

The National Zoo has many "Year of the Frog" activities and links (nationalzoo.si.edu/Animals/ReptilesAmphibians/YearoftheFrog).

The Virginia Herpetological Society has an excellent website (http://fwie.fw.vt.edu/VHS) with descriptions, photos, calls, and conservation information about of all 26 Virginia species of frogs and toads, as well as salamanders, turtles, snakes, and lizards. The Virginia Department of Game and Inland Fisheries also has extensive information about Virginia's amphibians (www.dgif.state.va.us/wildlife).