Critter Corner No. 7 – The Bullfrog by George Sly

As all of us know, a visit to Goose Pond FWA can present us with an extraordinary visual banquet. The sight of thousands of Sandhill Cranes descending into their evening roost, the stately soaring of a group of American White Pelicans, or the blizzard of Snow Geese departing on a feeding foray are the kinds of visual images which tend to remain imprinted in the minds of we who love wild things. But the Goose Pond can offer another kind of feast as well; this one is an auditory treat. For many, the melodic trill of the Red-winged Blackbird is all that is needed to conjure images of a wetland in the mind’s eye. Others would say much the same in regards to the unk-a-chunk pump handle call of the American Bittern or the whinnying call of the Sora. Here I would like to nominate one additional candidate as a distinctive voice of the Goose Pond wetlands – the Bullfrog (Rana catesbeiana).

The deep, bass “brr-rum” of this frog is unmistakable among the frog fauna of GPFWA. If one wants to be immersed in the natural loveliness that is GPFWA I suggest this exercise. Find yourself a secluded spot overlooking the wetlands. The parking spot near the old bridge on the south end of CR 1200 W is one of my favorites. Situate yourself there along about sunset and prepare to be enthralled. While one gazes out over the main pools, their emergent vegetation glowing golden in the light of the setting sun, there will come from a dozen directions the sonorous “brr-rumming” of the bullfrogs. Their little cousins, the Cricket Frogs, will add a chorus sounding much like the striking together of two large rocks. The last, evening trills of the redwings and a final verbal squabble among the geese will add to the atmosphere. Sitting, listening, contemplating one can be carried back to a time when Indiana was truly wild. It is not a bad way to spend an evening.

The volume and tone of their call immediately suggests size and the Bullfrog is indeed our largest Indiana frog. In fact the Bullfrog is the largest frog in North America and one of the largest in the world. The average body length of the Bullfrog is about five inches (record eight inches according to Minton2001). Their enormous legs can add another eight to ten inches to the total length. Average weight is around a pound.

I once saw a Bullfrog leap from the water in an attempt to snag a meal of Red-winged Blackbird. I also seem to remember running across a newspaper article years ago which had a photo of a Bullfrog which had a rattlesnake in its mouth. Such dietary endeavors obviously suggest an anuran of extraordinary size and strength. Bullfrogs will apparently eat about anything they can stuff into their mouths. Minton lists among their prey animals such as crayfish, insects, insect larvae, other frogs, minnows, tadpoles, and small mammals. They really are quite voracious. This gastronomic quality has a downside. Bullfrogs are native primarily to the Midwestern and eastern United States. However they have been introduced into many western states and even some foreign countries (such as Canada and Taiwan). These introduced frogs, as is typical of invasive species, invariably cause ecological damage among native faunas.

Incidentally, we have another frog which is somewhat easy to confuse with the Bullfrog. The Green Frog is also large and has a coloration and general body form quite similar to those of the Bullfrog. A distinguishing feature is that the Green Frog has a ridge of skin (called the dorsolateral fold) which runs along the outer edges of its back. The bullfrog’s skin in this area is smooth, not raised into a fold. The call of the Green Frog has often been likened to the twanging sound of a plucked banjo string. It has neither the bass nor volume of the Bullfrog’s call.

Like most other frogs, Bullfrogs reproduce in the water. They practice external (though direct) fertilization of the eggs therefore the water is necessary as a medium for the sperm to swim into contact with the eggs. Eggs are laid in tremendous numbers and hatch within a few days. May through July seems to be the primary period for egg laying. Bullfrog tadpoles typically take one to two years to metamorphose depending on latitude and thus water temperature. Like other anurans (frogs and toads), Bullfrogs hibernate during the winter by burying themselves in the bottom mud, or under submergent debris, in their aquatic habitats – marshes, ponds, streams, strip-pits.

Bullfrogs are prized by many for the edible quality of their legs. To hunt Bullfrogs in Indiana, once must have a hunting license and the season is regulated. Hunting Bullfrogs (and Green Frogs) is permitted from June until April of the following year. This season the specific dates are June 15, 2014 – April 30, 2015. There are certain restrictions on how these species may be taken. Hunters may use a gig or spear with a head not more than three inches in width and a single row of tines. It is also permissible to use a long bow and arrow. A person may use their hands, a club, or a fishing pole (or hand line). Not more than one hook or artificial lure may be attached to the line. The only type of gun allowed for frog hunting is a .22-caliber firearm and it must be loaded with bird shot.

Reference:
Minton, Sherman A. Jr. 2001. Amphibians and Reptiles of Indiana. Indiana Academy of Sciences. Indianapolis.