Heart of the stone

Lichens are a classic example of symbiosis -- the close association of two or more species.   In fact, the word "symbiosis" (literally, "together living") was coined in order to describe lichens.  The structure of a lichen is formed by a fungus.  Meanwhile, cells of algae and/or cyanobacteria are embedded within the fungus and perform photosynthesis to capture energy.  Although symbioses are not always harmonious relationships, the lichens pictured below appear to be the symbol of affection.

Lichens on a rock.

Explore some more: The lichen symbiosis - what is so spectacular about it?

Too much ground to hog

I can't think about Groundhog Day without recalling our backyard groundhogs, and today I have been imagining them snug in their burrows deep under the snow.

A surprise encounter with a groundhog when I went to photograph its burrow entrance.

Last summer we had two frequent groundhog visitors -- or rather, at least two, since I'm not very confident in my ability to distinguish between individual groundhogs.  However, I was sure it had to be at least two.  Though we only ever saw one groundhog at a time, the conspicuous difference and rapid alternation between big...

The big groundhog.

 ...and small groundhogs was enough to convince me that there was more than one.

The little groundhog.

I was especially worried that the small groundhog would make a tempting target for the red foxes, but it grew steadily larger over the course of the summer, while the squirrel population steadily declined.

Here is a video of the smaller and larger groundhogs for comparison: