Emergence of the Turtles

Along the lower Susquehanna, an unseasonably mild day in early spring can provide an observer with the opportunity to witness an annual spectacle seldom seen by the average visitor to the river—concentrations of dozens, sometimes hundreds, of turtles as they emerge from their winter slumber to bathe in the year’s first surge of warm air and sunshine.

Reptiles of the Lower Susquehanna River Watershed: Snapping Turtle
Snapping Turtles (Chelydra serpentina) spend the winter buried in mud along the river shoreline and in nearby Alluvial Terrace Wetlands.  We photographed this one just as it was digging its way out.
Reptiles of the Lower Susquehanna River Watershed: Snapping Turtle
A cold and stiff Snapping Turtle crawls away from the shade toward sun-drenched shallows where it will have a chance to limber up.
Reptiles of the Lower Susquehanna River Watershed: Snapping Turtle
A cruise in open water loosens up the muscles and gets rid of some of the accumulations of sticky mud and muck.
Reptiles of the Lower Susquehanna River Watershed: Painted Turtles
Freshly emerged Painted Turtles clamber onto a log to bask in the cloud-filtered sun.
Reptiles of the Lower Susquehanna River Watershed: Painted Turtle atop a Snapping Turtle
A Painted Turtle looking for a place to get out of the chilly water soon discovered the obvious solution.
It’s catching on, more Painted Turtles atop a Snapping Turtle in an Alluvial Terrace Wetland.
Reptiles of the Lower Susquehanna River Watershed: Red-eared Slider and Common Map Turtle
The Common Map Turtle (right) is the turtle most frequently observed basking on rocks and logs along the main stem of the Susquehanna.  To the left is a Red-eared Slider (Trachemys scripta elegans), an increasingly numerous invasive species.  The first Red-eared Sliders arrived in the river as, you guessed it, unwanted pets.  Editor’s Note: Special thanks to the local Beaver (Castor canadensis) for trimming the trees and providing a clear shot for this photograph!
Reptiles of the Lower Susquehanna River Watershed: Red-eared Slider and Painted Turtles
And now, a quick quiz.  Name the things that don’t belong in this picture?  Here’s a hint: a non-native Red-eared Slider (left) joins indigenous Painted Turtles atop a discarded tire in an Alluvial Terrace Wetland in Dauphin County, Pennsylvania.

State of Confusion

The humid rainy remains of Hurricane Nate have long since passed by Pennsylvania, yet mild wet weather lingers to confuse one’s sense of the seasons.  This gloomy misty day was less than spectacular for watching migrating birds and insects, but some did pass by.  Many resident animals of the falls are availing themselves of the opportunity to continue active behavior before the cold winds of autumn and winter force a change of lifestyle.

Warm drizzle at daybreak prompted several Northern Spring Peepers (Pseudacris crucifer crucifer) to begin calling from the wetlands in the Riparian Woodlands of Conewago Falls.  An enormous chorus of these calls normally begins with the first warm rains of early spring to usher in this tiny frog’s mating season.  Today, it was just a few “peeps” among anxious friends.

The tiny Northern Spring Peeper is recognized by the dark “X” across its back.  Soon, shelter must be found among loose bark and fallen logs to commence hibernation.  Emergence, often prompted by warm spring rains, will quickly be followed by a growing chorus of breeding calls as sometimes hundreds of these frogs assemble in vernal pools where mating will then occur.

Any additional river flow that resulted from the rains of the previous week is scarcely noticeable among the Pothole Rocks.  The water level remains low, the water column is fairly clear, and the water temperatures are in the 60s Fahrenheit.

It’s no real surprise then to see aquatic turtles climbing onto the boulders in the falls to enjoy a little warmth, if not from the sun, then from the stored heat in the rocks.  As usual, they’re quick to slide into the depths soon after sensing someone approaching or moving nearby.  Seldom found anywhere but on the river, these skilled divers are Common Map Turtles (Graptemys geographica), also known as Northern Map Turtles.  Their paddle-like feet are well adapted to swimming in strong current.  They are benthic feeders, feasting upon a wide variety of invertebrates found among the stone and substrate of the river bottom.

Adult Common Map Turtles hibernate communally on the river bottom in a location protected from ice scour and turbulent flow, often using boulders, logs, or other structures as shelter from strong current.  The oxygenation of waters tumbling through Conewago Falls may be critical to the survival of the turtles overwintering downstream.  Dissolved oxygen in the water is absorbed by the nearly inactive turtles as they remain submerged at their hideout through the winter.  Though Common Map Turtles, particularly males, may occasionally move about in their hibernation location, they are not seen coming to the surface to breathe.

The Common Map Turtles in the Susquehanna River basin are a population disconnected from that found in the main range of the species in the Great Lakes and upper Mississippi basin.  Another isolated population exists in the Delaware River.

Common Map Turtles, including this recently hatched young seen in August, are often observed climbing onto rocks in the river.
Note the oversize swimming fin adaptations of the feet on this adult Common Map Turtle found among the Pothole Rocks in Conewago Falls.  Young and adults are capable of navigating some strong current to feed and escape danger.
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SOURCES

Committee on the Status of Endangered Wildlife in Canada.  2002.  Status Report of the Northern Map Turtle.  Canadian Wildlife Service.  Ottawa, Ontario.