The 25th annual Michigan DNR-Natural Heritage Program Frog and Toad Survey begins April 1 and ends about July 10. Designed to estimate the numbers of Michigan’s thirteen species of frogs and toads, the survey is carried out by volunteers. In 2019 there were 98 volunteers and you could easily become one. It’s a lot of fun going out in the middle of a crisp, star-filled night and listening to the frogs calling.
If you want to go beyond just listening and counting, frog hunting season opens on May 30 and runs through November 15. A fishing license is required, and possession is limited to ten in any combination per day. There is no size limit; that is best determined by how much meat is on those legs, but bullfrogs and leopard frogs seem to be the favorites of frog hunters.
I’ve been surrounded by frog calls every spring and summer of my life, but I never gave them much thought, except as signs of winter’s end. The only other frog sound that has stuck in my mind was made when we “pithed” a frog in college biology. We took a live frog, stuck a needle through the base of its skull, and scrambled its brains. The purpose was to show that the legs still move even after the brain is destroyed—they do, frogs’ bodies will twitch and jerk long after the brain itself is dead. I didn’t have the nerve to do it, so the lab assistant did it for me. This may sound silly, but that frog let out a loud shriek so un-froglike, so unearthly, so horrible—and this was almost fifty years ago—that I will never forget it.
Amphibians (which include frogs, toads and salamanders) were the first creatures to venture out of the water and onto the land, and therefore are our extremely remote ancestors. They have thrived for over 300 million years, but in recent decades many have declined in numbers or even disappeared altogether, mostly due to habitat loss. A 2004 study of the 7,000 known species revealed that a third are threatened or endangered, at least 168 have gone extinct and 43% more are in decline. Most of this is occurring in the tropics: Brazil has over 1,000 described species and the destruction of the rain forest means the elimination of frog habitat. Given this context, biologists here in Michigan realized we had no idea how many frogs and toads live in the state and we need to know so we can determine whether they are thriving here or not.
State Frog/Toad Survey
For the past couple of weeks, I’ve been listening to a tape of frog calls, preparing to be a volunteer in the 25th annual Michigan Frog and Toad Survey.
The DNR’s Natural Heritage Program is establishing a baseline population of amphibians for the state. Frogs aren’t deer or wild turkeys or cohos, all of which we do have a pretty decent count of.
Only lately have we come to appreciate the humble frog, that eats millions of insects—like mosquito larvae—every year. In turn, frogs and toads are eaten by waterfowl, sport-fish like pike, and mammals quick enough to catch them. They are an important part of the ecosystem, and sensitive indicators of water quality.
Happily, now I have a chance to learn the natural calls of our state’s frogs. Michigan has a dozen species of frogs, and two species of toads; only a few types of frogs and one kind of toad live as far north as my home in the U.P. Compared to learning hundreds of bird songs, learning twelve amphibian calls is, or at least should be, a cinch.
Students of the anurans—the family of frogs and toads—have come up with good sound-alikes as memory aids. Using these along with the time of year and type of habitat from which the sound is coming makes identification easy. The program uses a very clever method of roughly estimating frog numbers by establishing three categories:
1) 1-5 individuals with space between calls;
2) calls of individuals can be distinguished but there is some overlapping of calls (6-12 individuals);
3) full chorus where calls are constant, continuous, overlapping, and uncountable.
The earliest frogs to emerge and begin breeding (frogs call to attract mates and mark territories), are the wood frog, the Western chorus frog, and the spring peeper. These three species are small, and likely to be found in temporary (or “vernal”) ponds that don’t support predatory fish. Even with fewer predators, it’s risky—they have to mate early and the young have to develop quickly before the ponds dry up.
The first, the wood frog, may begin calling in March even with snow on the ground. It lives along forest edges, breeds in temporary ponds, and sounds like a duck quacking. The tiny, hard-to-see chorus frog breeds for only two weeks in the spring, and sounds like a fingernail running across the teeth of a comb. Spring peepers, in contrast, numerous and loud with their high-pitched, trilling peeps, can be heard for a quarter-mile. A group calling resembles jingling sleigh bells. Spring peepers sing sporadically right up until autumn.
Michigan’s other frogs and toads breed in permanent bodies of water. They breed later in the year (mid-April to mid-June), are larger, and take much longer—as much as two years—to reach maturity.
The northern leopard frog, two to four-and-a-half-inches long and green or brown with rounded black spots, likes marshy habitats and weedy lakes. Its call is a deep, low “snore” alternating with a chuckle. Leopard frogs were very common, but seem to be declining in numbers. They are by no means endangered or threatened.
The pickerel frog’s call is similar to the leopard’s, but harsher. It’s easier to identify by sight: the pickerel frog’s spots are square, not rounded, and the inside of its hind legs is bright orange-yellow. Pickerel frogs like spring-fed ponds.
The green frog is a common, medium-sized species that thrives even where water quality is low. They range from green through yellow to brown, and have a distinctive ridge of skin running from the eardrums along both sides of the back. The call, heard from May-September, is one repeated note like someone plucking a loose banjo string.
Michigan is also home to two nearly identical species of gray tree frogs: the eastern gray tree frog and Cope’s gray tree frog. You can’t tell them apart visually, but their calls are very different. The eastern sounds like a chattering squirrel, while the Cope’s call is a harsh squawk. Both species breed in May, but call throughout the summer. By autumn, the froglets develop a chameleon-like ability to change color to match their background.
The last (June-July) frog to breed, in the north at least, is the bullfrog. Yellowish-green to brown, and as large as eight inches, this is our biggest frog, with a voice to match. Loud and low, it sounds like a foghorn, or a bull bellowing.
You’ll have to cross the Straits to hear our other northern frog. Mink frogs, which sound like horses trotting over a cobblestone street, are (in Michigan) strictly U.P. residents. They give off a nasty, musky odor when handled, reminiscent of mink secretions (or something rotten).
But we mustn’t forget the gardeners’ friend, the Eastern American toad, whose high-pitched trill lasts 30 seconds or more. Each toad sings a slightly different note, creating a passable harmony with its neighbors. I’ve long mistaken the toad song for that of crickets, cicadas, or some other insect, which it strongly resembles. Do not eat toads, they are toxic.
Anyone who wants to participate in the Michigan Frog and Toad Survey should contact the MDNR. They have all the information you need. Happy listening.
FROGS AS FOOD
Frog legs are a specialty of French and Chinese cuisine. They are also eaten in Albania, Cambodia, Greece, Indonesia, Portugal, Romania, Slovenia, Spain, Thailand and the southern United States. The world’s largest exporter of frog meat is Indonesia (China is second), shipping more than 5,000 tons each year to France, Belgium and Luxembourg. Most Asian frogs come from frog farms where rice cultivation creates a perfect habitat while the fields are flooded.
The French consume 160 million frog legs every year. Worldwide, people eat up to 3.2 billion annually. They are rich in protein, omega-3 fatty acids, vitamin A, and potassium. Fried frog eggs and frog skin, which resembles a cracker, are also eaten. In the U.S. frog legs are occasionally available as expensive appetizers in ritzy restaurants, but they are free (with a fishing license) for the taking here in our Michigan ponds.
Hunting For Frog Legs
Nighttime is best for frog hunting. Frogs feel the vibrations you make walking on the bank, so the best way to approach them is to silently glide up in a canoe. A spotlight fascinates them and keeps them frozen in place. A light also reveals the size of the eyes, which is a good indicator of the size of the frog. Three of Michigan’s more uncommon frogs, the boreal chorus frog, Blanchard’s cricket frog and the pickerel frog are off limits to hunters, but they are so rare you probably wouldn’t come across them anyway.
The most challenging way of catching frogs—fun but inefficient because they are so slippery—is to grab them by hand, though “gigging” (using a special spear or gig) and netting are probably the most common frog hunting methods. Note that a 1929 law still in effect, though admittedly rarely enforced, forbids spearing frogs while using artificial light, though you can still use a light to catch them by hand or with a net.
You can even catch bullfrogs during the day with a fishing pole. Make sure you have a bucket with a tight-fitting top or your catch, even if you thought it was dead, will quickly hop away.
PREPARING COOKING FROG LEGS
Frogs are easy to dress. Cut the legs off above the “waist.” Grab the skin with pliers and peel downward; it’ll come off like a pair of pants. Cut off the feet, and separate (or not) the legs at the hips. I prefer single legs, otherwise the animal oddly resembles a person cut off at the waist.
Frog legs can be pan-fried, deep-fried, grilled or baked, usually dipped in a light flour and egg batter. One online chef suggests treating them like chicken wings.
When you’re out hunting frogs, you may, though very unlikely, run into some with deformities. These, and the location where they were found, should be reported to the DNR.
Reports of malformed frogs first broke in the mid-’90s, when school children studying a pond in Minnesota noticed a high number of frogs with extra, missing or strangely developed legs and eyes. Not long after, frogs with similar defects were discovered along the St. Lawrence River valley in Ontario, and in Vermont. Here in Michigan, 17 counties reported missing eyes and missing or extra legs in at least 6 of the 14 species of frogs and toads found in the state. The problem is probably more widespread, but many counties have not been studied.
The deformed frogs made the national news; heck, there’s even a horror movie, Strange Nature, based on them. It appears, yet again, that the problem may be caused, at least in part, by pesticides.
Chemicals that produce multiple limbs are well known by scientists who hope to someday enable people to re-grow severed arms and legs. They are called “retinoids,” and produce multiple limbs in frogs and lab mice. One pesticide, methoprene, is widely used to control mosquitoes and acts like a retinoid. This chemical, though, is not used everywhere deformed frogs are found, so if methoprene is implicated, it’s probably not the sole culprit. A Canadian study found that ponds in unfarmed areas produce deformities in about 2% of the population, whereas in ponds in areas where various insecticides and fungicides are used, 20% or more of frogs show deformities. Any number of chemicals or combinations of chemicals may play a role.
Researchers have also discovered that a common parasitic trematode, or flatworm, can cause developmental defects in frogs. But not all problem frogs have the parasites, and many frogs carry parasites and have no abnormal limbs. When frog eggs were hatched in the lab in parasite-free water from ponds in Minnesota that had produced frog deformities, they grew into frogs with the same deformities. Something in the water other than, or in addition to, a parasite is causing the problem.
Actually, if you are pursuing frogs for legs, an extra one or two legs may actually be a literal plus, depending upon how you look at it.