Refuge Notebook
Peninsula Clarion Article
Dated
05 May 2000
 Wood
Frogs Calling - A Sure Sign of Spring
by Ted Bailey
If you live near a small pond or bog surrounded by forest on the Kenai Peninsula,
you may have been hearing some mysterious sounds in the late evenings this past
week. Some say these sounds remind them of birds, others compare them to a group
of noisy ducks. The makers of these "clacking" spring sounds are difficult
to see unless you are intent on discovering their source. Usually the calls stop
before you can get close to the edge of the pond. However, if you are patient
a small creature will pop to the water's surface and you will be rewarded to see
the Kenai Peninsula's only amphibian - the wood frog.
Wood frogs began
calling in a pond near our home last weekend, and breeding should reach a peak
during the first two weeks of May. The snow and ice has barely melted from the
pond and some snow remains around the pond's margin. It is not unusual for wood
frogs to begin breeding before ponds are entirely ice-free. At the peak of their
breeding season, the calls of wood frogs can be heard during the middle of the
day. Male frogs, which are smaller than females, make the "clacking"
calls to attract females to the breeding ponds. Egg laying begins soon after the
females arrive.
Eggs from each female are laid in a gelatinous mass about
the diameter of a quarter. This egg mass soon expands by absorbing water to reach
the diameter of a tennis ball or baseball. Wood frogs are communal breeders. Pairs
of breeding wood frogs do not disperse their egg masses randomly around a pond's
margin. Instead, many frogs congregate together, and often nearly all the eggs
in a pond will be deposited in only one or two small areas. They may place more
than a hundred egg masses together within an area of only several square feet.
Each egg mass is typically attached to a stem of grass or a small shrub. Within
this egg mass are hundreds of separate eggs, each surrounded by its own protective
membrane.
Hatching time is dependent on water temperature. In time the
eggs develop into tiny tadpoles which break through the surrounding membrane and
enter the pond to feed on microscopic food. If they are lucky and the pond does
not dry up, they will grow into tiny frogs before the pond freezes over.
The
calls of wood frogs can be also be heard throughout May on larger lakes, as these
lakes become ice-free and their water temperatures rise. The larger lakes are
often the last places to be used by breeding wood frogs and may be avoided if
smaller nearby ponds are available. Although large lakes provide stable water
levels, they are dangerous places for wood frogs to deposit eggs. Large lakes
are more subject to wind action, and waves can tear the egg masses from the shoreline
vegetation and destroy them. Many large lakes also support fish that prey on frog
eggs or tadpoles. That is why small, shallow ponds whose margins are lined with
aquatic plants are preferred breeding sites. Water temperatures in small ponds
rise quickly in the spring, and the tadpoles are safer from predators.
This
should be a good breeding year for wood frogs because of last winter's high snowfall;
abundant meltwater has filled many small ponds and muskegs. Small shallow ponds
have been shrinking and many have dried up completely on the Kenai Peninsula over
the past five years. Thus there have been fewer breeding ponds, and many of these
ponds have gone dry before the tadpoles could hatch into frogs.
Among northern
animals, adult wood frogs have developed a unique way to survive our harsh northern
winters. They have the remarkable ability to thaw out and resume normal activity
after being frozen solid deep under the forest litter all winter. When you hear
these small northern creatures calling during the next few weeks, remember you
are not alone in celebrating the arrival of spring on the Kenai Peninsula.
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Ted Bailey, a supervisory wildlife biologist, has been responsible for the
Kenai National Wildlife Refuge's biological programs for over 20 years. He and
his staff monitor and conduct studies on a variety of refuge wildlife populations.
Previous Refuge Notebook columns can be viewed on the Web at http://kenai.fws.gov.
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