From the February 2012 Conservationist
the northern cricket frog
By Jay Westerveld
Growing up in a family of sportsmen in New York's verdant Hudson River Valley, I quickly developed an intimate knowledge of the vast variety of organisms inhabiting our diverse patchwork quilt of forests, fens, hills and marshes. Indeed, the lower Hudson River Valley is a crossroads of biodiversity, hosting overlapping fringe populations of a multitude of species, while fostering unique interplay between these diverse organisms, like some ecological Grand Central Station.
Photo: Matthew D. Schlesinger
My older brother and I spent hours afield hiking, fishing, hunting and trapping in this ecological quilt located only an hour's drive from Manhattan. The species that most caught our attention was the northern cricket frog: a tiny, colorful frog that was unlike any other frog we came across. We imagined it was some accidental, exotic vagrant from the Amazon that was transplanted thousands of miles north by some odd wind.
We would see northern cricket frogs frequently: at lakes, marshes and swamps in summer, and in deep woods and dry ridge lines in spring and fall. Depending on the season, we'd find them in just about any habitat. Even during bowhunting season, we'd glimpse them darting across our path in their signature low-trajectory, four-foot-long leap. They captivated us with their different color morphs, tiny size and surprising twice-yearly migration; and thus began my lifelong study of this species' ecology in New York State.
Photo: Kelly McKean
Rarely exceeding one inch in length, northern cricket frogs are New York's smallest vertebrates and only endangered frog. Their coloration varies from dark brown to light gray, and they can have markings of stripes or spots in green or red, and occasionally bright blue. During the warmer months, they inhabit weedy areas of lakes, creeks and ponds. In the fall, winter and spring, however, they live upland of water bodies-sometimes as far as 2,000 feet away, as one researcher, Dr. Jonathan Micancin, discovered in North Carolina.
In New York, cricket frogs often call at wetlands near rocky outcrops. But over the years, their chorus has grown quieter as their numbers have declined. While habitat destruction may contribute to this decline, in my observations it doesn't appear to be the primary cause. For example, northern cricket frogs used to abound in Harriman State Park-I recorded robust populations there throughout the 1970s and '80s-and despite the fact that the ponds, marshes and creeks from which they once called appear virtually unchanged, cricket frogs are no longer heard anywhere within this large, undisturbed state park. In addition, other outwardly pristine habitat in the state has also fallen silent of their clicking call. Today, the species survives, and in a few cases, thrives, at only a handful of locations within New York. The largest and most robustly populated of these sites is the Glenmere Reservoir/Black Meadow Creek Reservoir lands in Orange County.
In 1983, DEC biologist Joel Hermes and I reviewed some of my cricket frog records, as observers were noting a decline in cricket frog numbers. We found that many sites had far fewer cricket frogs, both audibly and visually, than they held previously. By 2000, I confirmed cricket frogs only at five remaining sites in Orange County.
At that time I lived at the Glenmere Mansion, an enormous, Mediterranean-style structure overlooking the Glenmere Reservoir, and home to New York's largest population of cricket frogs. I discovered small masses of live cricket frogs overwintering in the vast, subterranean cellars of the mansion. These frogs arranged themselves in small clumps of six or more, all with eyes and nostrils exposed, at cutouts in the thick masonry that formed passageways.
Photo: Kelly McKean
I began to search for similar natural habitat in the reservoir's wild uplands and found cricket frogs assembling at comparable, sheltered crevices in the adjoining forests, often more than 1,500 feet from the nearest lake or creek known to have cricket frogs. On the coldest days, accompanied by other zoologists, I'd find the frogs collecting at the entrances to rock crevices among shale cliffs, and also near holes in rotted tree stumps. Within hours of falling temps, they'd no longer be present at the openings, suggesting there were tunnels that likely lead the tiny amphibians to well below the frost line. When temps would warm again, we'd find them back at the entrances to these tiny cracks and holes.
Locating these deep overwintering sites is important for the frogs' survival, as unlike many other frog species found in the state, cricket frogs produce very little "antifreeze" to prevent their bodies from freezing. Their nearest cousins, the gray treefrog and the spring peeper, both manufacture glycerol similar to the antifreeze that we use in our cars' radiators.
The fact that cricket frogs migrate such a long distance is incredible. In fact, in 2006, we conducted a study of the cricket frog's overwintering habits and discovered that New York's tiniest amphibian migrates farther than most other amphibians in the state. We photographed the unique, individual markings of each frog we found entering rock crevices and root holes in the fall, and compared them to photos of the frogs we found emerging from these same, often tiny cracks and crevices the following spring. It was a perfect match and indicated that cricket frogs were surviving winter freeze in hibernacula over 1,800 feet from their summer habitat.
The traveling frogs collect at ephemeral woodland pools (seasonal pools which occur in the spring, fall or winter), when the leaves are off the trees. Here, the sun warms the dark, shallow waters, increasing the frogs' metabolism and protecting them from freezing temperatures while en route to and from their summer breeding habitat.
Water-lily planthoppers (Photo: Stephen
P. L. Luk)
The pools also provide food for the little vagabonds; in fact, we've observed cricket frogs following migrations of tiny insects called water-lily planthoppers (Megamelus davisi) from these pools to the lakes and creeks. Cricket frogs will fatten up on these planthoppers prior to embarking on their long fall migration. A single cricket frog might spend several hours on one lily pad, devouring planthoppers as they move by the thousands over a lily pad.
These tiny planthoppers may shed light on the cricket frog's decline in New York. At locations where these frogs have disappeared, there were no water-lily planthoppers to be found, while at Glenmere, where the frogs are abundant, these insects virtually carpet the vast wetlands.
Photo: Linda Masi
In my opinion, aerial pesticides sprayed to control gypsy moth populations in the 1970s may have decimated water-lily planthopper populations, and hence be indirectly responsible for the decline in cricket frog numbers. Interestingly, Harriman State Park, where cricket frogs have disappeared, received continuous treatment just prior to the crash in cricket frog numbers, while Glenmere, where cricket frogs remain abundant, was spared any spraying because it is a public water supply. Also, since water-lily planthoppers lack full wing sets, they can't fly, so once extirpated, it could take them decades to repopulate an area.
Hopefully, as populations of the water-lily planthoppers rebound, cricket frogs will return to the wetlands they formerly inhabited, and places like Harriman State Park will once again resound with the rythmic clicking call of the northern cricket frog.
But for now, New Yorkers can visit the Glenmere Reservoir to hear the unique summer chorus of this tiny, colorful frog.
Jay Westerveld has spent more than 30 years studying the northern cricket frog in New York. He resides in Orange County and is founder of the New York Natural History Council.
Photo: Linda Masi