Tuesday, February 28, 2012

Busy, Busy Beavers (and Frog)

I've posted before, about Minthorn Springs Wetland in Milwaukie.  It's a great little wetland habitat, surprisingly close to commercial, light industrial, and residential development along the Milwaukie Expressway (HWY 224, connecting I-205 and HWY 99E).

My office is on the edge of this wetland, so I drive by frequently.   On one recent trip, I looked in to the woods around the wetland as I was driving by, and noticed the bright, exposed wood of fresh beaver chews on several large trees.  One was pretty far along, and I was hoping to get back there with a camera before the tree came down.  Turns out I was too slow.  But I think the one felled tree with the three or four soon-to-be-felled trees actually made for a more interesting picture.


That's the Milwaukie Marketplace shopping center in the background.  Doesn't seem to bother the beavers.  In fact, it looks like they're trying to clear a better view!

I'm always amazed by the size of the wood chips made by the beavers.  They look like something from a commercial chipper.
A Beaver's "To-Do" List

The Wetlands Conservancy manages this area along with the City of Milwaukie.  Someone has protected some of the larger trees with wire fencing, but others have been left to their own defenses. It won't be too long before the trees pictured here give way.

Beaver Teeth Marks in Detail
A beaver's gotta do what a beaver's gotta do!

A beaver's teeth have a high iron content, making them very strong - and orange.  And they never stop growing either, so they don't get worn down.  Pretty handy if you like to chew on wood.

I recently saw a beautifully-filmed documentary about beavers, called Beavers - The Biggest Dam Movie You Ever Saw.  That film had me thinking that beavers were diurnal, because it has lots of great footage of beavers doing their thing in broad daylight.  One website I read said that beavers can be seen during the day (especially early or late), but it said they are mostly nocturnal.  Maybe the beavers in that film just felt safe because their pond was so pristine and remote.  (Or maybe they were paid actors - I don't know.)  Actually, the remote habitat might be precisely the reason those beavers were day-workers.  According to the Oregon Zoo, "beavers are active during the day... but become nocturnal with human encroachment."  I'm guessing the beavers at Minthorn Springs are nocturnal.

Beavers are one of the largest rodents - weighing up to 65 pounds - and they can be found in many places around the Portland Metro area, across Oregon, the Northwest, and beyond.  Beavers, in fact, can be found across most of North America and throughout a large part of Eurasia as well.  Where have you seen them?  Any surprising places around Portland?  (Remember - nutria can do a pretty good beaver impression if you don't get a look at the tail.)

Can you spot the native amphibian in this image?
OK, enough about beavers.

Somewhere in the picture above is a small, native amphibian.  Hint: It jumped out of my way as I was leaving the wetland.

Did you find it?

There it is!  It's Pseudacris regilla, a Pacific Tree Frog! (Or Pacific Chorus Frog.)

Here's a closer (if a bit blurry) look at the little jumper (it's in the upper right portion of the first photo).  I believe it's a Pacific Tree Frog, also known as the Pacific Chorus Frog.  Apparently the species is not technically a tree frog, so Pacific Chorus Frog may be a more accurate name, but it seems like there is some disagreement out there about exactly what to call these native frogs. 

Pseudacris belongs to the genus Hyla.  And according to Wikipedia, because of some geographic-turned-genetic separation, "...the genus Hyla has been split into three separate genera: Aris, Limnaoedus, and Pseudacris. This is where the current confusion has taken place. Although the Pacific Tree Frog has carried the scientific name of Hyla regilla for many years, the most current consensus among scientists is that they should actually be Pseudacris regilla. This is still not agreed upon completely, and in the future we will see what becomes of these names."

When I saw this frog, I wasn't sure what kind it was.  But I had heard about the Pacific Chorus Frog, and thought that might be it.  Looking through pictures of Chorus Frogs online, I couldn't find one with the exact same markings.  Then I learned that, not only can these frogs change color from brown to green, they can actually change between distinctive markings and solid colors.  (Although the dark stripe from the nose, through the eye, and back to the shoulder - which is just visible on the frog's right side in my photo - is a more permanent field mark along with the presence of rounded toepads.)  From what I've read, these color changes are not fast like a chameleon, but slower changes in response to changes in their environment, or to seasonal color changes in their surroundings.  

I wanted to get a closer, clearer picture of this frog, but he jumped down into one of the many sinkholes that dot the dry ground in this wetland.

Minthorn Springs may be small in size, but it never fails to present something interesting.

Read my older post about Minthorn Springs, which includes maps and more info, here.

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