Monday, April 25, 2011

Spring Peepers

Spring peepers (Pseudacris crucifer) started calling today in Duluth.  Although spring peepers have a loud voice, these frogs are pretty small at full size.  
adult spring peeper in hand for size reference

adult spring peeper in wetland
 spring peeper - identifying marks: X on back, toe pads, small size, light color
These frogs are great at hiding - I rarely spot them in wetlands, but there are a lot of videos up on UTube.
 It is exciting to hear a full chorus of spring peepers - I haven't heard this large a group calling in the city since I first moved to Duluth. About 10 years ago the spring peeper population seemed to be greatly reduced (based on calling activity), likely due to a cold winter with little snow cover. Spring peeper overwinter in leaf litter or bark, but are not as freeze-tolerant as wood frogs.

I heard spring peepers in northern Wisconsin as well, but today was my first visit to that area.

Friday, April 22, 2011

Wood Frogs!

The wood frogs are calling in Duluth - Yesterday, I heard wood frogs calling in small wetlands in and near Hartley Park.  Most of the wood frog activity was in ponds that are shallow and have solar exposure.  These ponds are likely warmer than deeper or completely shaded wetlands. 

I even found wood frog eggs in two ponds.  Wood frogs are probably still in the midst of breeding as many of the ponds I visited yesterday did not have eggs. 

Wood frogs are explosive communal breeders, meaning that breeding occurs over just a few days and all (or most) of the eggs are laid in one location in a pond.  Eggs are generally attached to submerged vegetation near the water surface in open areas of a pond that are fairly shallow (1-2 feet).  When first laid, wood frog eggs are very easy to spot.

30+ wood frog egg masses (each female lays one egg mass consisting of hundreds of eggs)
Up close, it is easy to see the embryos through the clear protective gelatin-like layers.  This allows us to track development before the eggs hatch, which occurs in 4 to 28 days depending on conditions.
recently laid wood frog eggs masses
  ***Note: If you find wood frog eggs, please leave them undisturbed in the water. 

Sunday, April 17, 2011

Still waiting for spring

I have not received any new reports of frogs calling in the Duluth area since Thursday, when the temperatures dropped and then a snowstorm blew in.  The birds have continued to sing, so I don't doubt that spring is truly here.  However, this weather has probably slowed the frogs down.  I don't expect any more frog activity until it warms up again, probably Thursday based on the current weather predictions.

Wood frogs (Rana sylvatica) are the first to start calling around Duluth.  The wood frog call is usually described as 'quark-quark-quark' or duck-like. Wood frogs are easily recognizable by a dark mask and white lip line.  In overall color they range from light to dark brown and sometimes are pink or reddish. 
wood frog
Within a few days, wood frogs are joined by Western Chorus Frogs (Pseudacris triseriata) and Spring Peepers (Psedacris crucifer). Both of these frogs are very small, reaching only 1 inch or 1.5 inches as adults, but make very LOUD calls. Chorus frogs sound like running your thumb over a comb and spring peepers make a really loud 'peep' over and over. Chorus frogs range in color from tan to brown to green and can be recognized by the strips on their back. Spring peepers are generally light tan with a slightly darker brown X on their back. 
chorus frog

spring peeper

To see when frogs begin to call across North America see the map at Journey North Spring 2011 - First Frogs

Next week I'll give some tips on identifying wood frog eggs (along with photos).

Wednesday, April 13, 2011

Waiting for Wood Frog Calls.....

Reports have come in of wood frogs (Rana sylvatica) calling south of Duluth (around Solon Springs, WI) AND north of Duluth.  So now I am waiting for them to start calling here!

One wood frog sounds like 'quark-quark-quark' and a full chorus of wood frogs make a huge racket.

Listen to this chorus of wood frogs heard about this time two years ago:

Wood frogs will call during the day as well as evening and night.  Listen for them on your next walk through the woods or local parks- pretty much anywhere that there are small to medium wetlands.

Monday, April 11, 2011

Spring is Finally Here!

That was the talk of the neighborhood this morning as we left for work in 50 degree temperatures.  Looks like tomorrow will be spring again, but the following few days may take us back to late winter.

It has only been 4 days since I visited the frozen wetlands, but I will head out again tomorrow to see if they have opened up yet.  If the vernal pools are open, we can expect the wood frogs to be calling and laying eggs in about a week!

In case you were wondering what these amazing northern frogs might be up to right now - they are probably in the process of thawing out.  Yes, wood frogs are the famous frozen frogs!  Most amphibians find more suitable habitat for winter hibernation, such as a sandy hole below frostline or the muddy bottom of a larger lake, but wood frogs spend the winter frozen in the leaf litter.

This NOVA segment is a great intro to frozen frogs

You can learn more at: Frozen Frog: Expert Q & A (Jon Costanzo)

Thursday, April 7, 2011

Is it spring yet?

Spring comes slow to northern Minnesota - this year it seems exceptionally slow, perhaps due to the super early spring of 2010.  Although the robins and cardinals are singing in my yard, we will be waiting a few more weeks before the frogs start to call.

I visited some ponds located within city limits today - still frozen and snow covered (see below).

Quite a difference from this time last year, when the ponds were open and the wood frogs had already laid their eggs! On April 7, 2010 this same location looked something like this:

While we wait for the ponds and lakes to open up, all we can do is practice our amphibian ID skills.  The first frog to call and breed in this region is the wood frog (Rana sylvatica). I recommend the Online ID Guide from Northern Prairie Wildlife Research Center for great pictures and maps, and the Amphibians of Reptiles of Minnesota for detailed descriptions and calls.