FrogWatch 2005 Report

Bullfrog (Rana catesbeiana) seen at foot of Crosby,
near site #8, 3/30/05
Summary by Frog Species
Summary by Site Location and Month

Five Frog Species Observed in Sligo in 2005

Five frog species were heard calling in Sligo this spring and summer (2005) by a team of twenty-one volunteer monitors organized by Sligo Friends to participate in FrogWatch, a program of the U. S. Geological Survey and the National Wildlife Federation. The team made at least 76 nighttime visits to seventeen sites along the creek to listen for calling frogs.

The most abundant species, both heard in large choruses, were the American Toad and Gray Tree Frog, the latter of which had not previously been confirmed for Sligo. American Toads were the only frogs heard calling downstream from the Beltway (at the Dallas Avenue boardwalk), although a male Bullfrog was seen nearby. Several calling Bullfrogs were heard at two locations. We heard only one each of the Pickerel Frog and Spring Peeper, even though the Peeper is so numerous elsewhere in the county.

A disappointing result was the complete lack of frogs at the Wheaton Branch vernal pools, even though 27 visits were made to the site by four volunteers. John Galli of the Council of Governments suggests we consider an egg capture and transfer from Northwest Branch to Wheaton Branch next spring, working with Park and Planning.

Even though Gray Tree Frogs were heard only at the University Blvd stormwater ponds, their presence is significant because a 1998 list of Sligo amphibians, prepared by the Council of Governments, indicates that this frog had not been confirmed for Sligo. COG listed it only as "expected," based on observations first published in 1970 and 1975 for comparable, nearby habitats.

The Gray Tree Frog (which makes a short, high, monotone trill lasting a half-second) was heard in large choruses on two occasions separated by more than ten weeks. Field guides tell us these frogs stake out perches 30 inches apart on tree limbs, and they can brighten or darken their color to match background vegetation. Females arrive at the site throughout their long breeding season.

Our monitors heard American Toads calling at four locations. (They make a long, high monotone trill lasting up to 30 seconds; each frog sings at a slighty different pitch, giving the chorus a distinctly modern-music sound.) They were heard in large choruses at the Dallas Ave. boardwalk (near the golf course) and at the University Blvd stormwater ponds, and in smaller groups in two headwaters sites. The frogs at Dallas Ave. were the only ones heard downstream of the Beltway. Singing by the American Toads was heard only between April 4 and 8, when mating presumably occurred.

According to field guides, American Toad females lay up to 20,000 eggs, and the tadpoles, which are distasteful to predators, hunt in schools. In 5-10 weeks, they transform into frogs, who join the adults in the woodlands for summer, fall, and winter. American Toads are known to migrate between 75 and 1500 feet from their birth place into surrounding forest for the winter. Bullfrogs migrate an average of 1300 feet. Overall, frogs in North America migrate between 600 and 1200 feet from their breeding ponds and back each year, meanining that habitat must include significant! forest around breeding water in order to be suitable.

In July, several Bullfrogs were heard at the University Blvd. stormwater ponds, while one was singing at the Godwin Drive marsh, where a tentative sighting was also made. In March, at the foot of Crosby during daytime, a male Bullfrog was captured, photographed by a FOSC member, and released (see photo this page).

The only Spring Peeper heard in Sligo this year was an individual singing at this site. The individual Pickerel Frog (which sounds just like a snoring human) was heard at University Blvd stormwater ponds.

In addition to the nighttime FrogWatch monitoring for calls, a daytime visual sighting was reported of possible Wood Frog egg masses at our vernal pool in the headwaters. And a photograph (shown at the top of this web page) was submitted of a large Bullfrog captured (and later released) by a young boy using a net in the creek near Crosby Road (across from the golf course).

Overall, our twenty-one volunteers made 76 nighttime visits to seventeen sites between the headwaters at Blueridge and lower Sligo at East West Highway. Thirty visits were made in March, 31 in April, 10 in May, none in June, and four in July. Earning the record for most site visits were Susan and G. T. Hunt, who stopped by the Wheaton Branch vernal pools no less than 17 times, without hearing a single frog. Karen Nelson invested considerable time preparing materials for our two orientation sessions in February, and entered all of the sites into the USGS FrogWatch system.

According to FrogWatch protocol, sight visits are made any time at least thirty minutes after sunset or later and last three minutes. Identification is by song only, which is easier and more reliable than visual ID and indicates mating behavior.

If you are interested in participating in the 2006 FrogWatch, e-mail Michael Wilpers.


All twenty-one of the FrogWatch volunteers deserve thanks and credit for contributing to this year's survey. Special note must be made of the effort put in by G. T. and Susan Hunt, who made no fewer than seventeen visits to the Wheaton Branch vernal pools, even though they did not hear a single frog. (John Galli suggests we look into a capture and transfer of frogs eggs from Northwest Branch next spring to repopulate those pools and surrounding upland.) Among all the volunteers, no fewer than 58 site visits were made, mostly in March and April. This kind of enthusiasm is not uncommon in Maryland, which ranks second only to Indiana in the number of FrogWatch volunteers! Following are the FrogWatch volunteers for 2005. If you voluntered and are not listed, please contact the webmaster.
  • Ian and Ross Campbell
  • Bob Ford and Adelaide Flanagan
  • Margaret Herbers
  • Ann Hoffnar
  • G. T. and Susan Hunt
  • Dorothy Jachim
  • Beth Knox
  • Chris Kosnik
  • Lewis/Ying Family
  • Kathleen Michels
  • Ed Murtagh
  • Karen Nelson
  • Winnie Neunzig
  • Barbara Schroeder and Tom Bigford
  • Gretchen Schwartz and Charlie Dorian
  • Michael Wilpers

Michael Wilpers, Chair
Natural History Committee
Friends of Sligo Creek