Distracted by non-frog signs of summer

It is easy to get distracted by the non-amphibian phenology, such as the flowers blooming around Duluth.  The lilacs in my yard are just starting to open:

In addition to these signs of spring (and summer!), frog activity continues.  The early spring breeders have growing tadpoles that will begin to develop hind limbs soon, while the late season species have not yet started to breed.  Mid-season breeders, such as the gray treefrog, are just finishing up calling. Gray treefrogs generally call from trees over and around wetlands (and thus are often mistaken for birds), and lay their eggs in seasonal and temporary wetlands.

gray treefrog in a wetland - notice the large toe pads

Gray treefrogs change in color from bright green to mottled gray in seconds to aid with camouflage. The below frog does not match it's surrounding in color, but is still hard to detect!

just grass

is that a frog?

gray treefrog in grass clump in wetland

A few years ago, I was fortunate to find many gray treefrogs while sampling a wetland with students.  Check out the variation in color.

gray treefrogs can change from bright green to dark mottled gray

The Eastern gray tree frog (Hyla versicolor) and the Cope's gray tree frog (Hyla chrysoscelis) are both found in this region and there is not a reliable way to tell these species apart in the hand.  The only way to distinguish these species is the number of chromosomes (Eastern gray treefrog is tetraploid while Cope's gray treefrog is diploid) or the males' calls (see below videos).  Additionally, there are may be habitat preferences and behavior that distinguish these species - I look forward to future research revealing the similarities and differences between the Eastern gray treefrog and Cope's gray treefrog.