Image of the Day: A Frog's-Eye View

By Bruce G. Marcot, Ecology Picture of the Week:

Crawling along the forest floor in the rainy Pacific Northwest, U.S., is this Pacific Treefrog, eyeing potential insect prey and the approaching quick hand of this wildlife biologist.  

What does a frog see?  Some classic studies had suggested that a frog's vision is blurry from myopia (nearsightedness) beyond about 6 inches, but is sensitive to movement, such as of prey or potential predators.  Frogs can see somewhat into the ultraviolet range.  The Pacific Treefrog has a horizontal pupil which is common in diurnal frogs, so it can tolerate the bright light of day.  

Although frogs cannot move their eyes within their sockets, the protruding eyeballs allow them to peek above the waterline while hiding much of their body beneath, such as with the bullfrog in the photo at right.  When they shut their eyes, a frog retracts the eyeball into the socket and a lower eyelid closes over it.  

Frog and toad eyes have been the stuff of macabre witches' plots for centuries (and of a tasty salad, at least in name), but this frog seemed content to only cast a watchful gaze, and was none the worse for wear when I soon released her back into her forest floor world.  

--Bruce G. Marcot

Image and text © Bruce G. Marcot, Ph.D. Research Wildlife Ecologist,
who produces the Ecology Picture of the Week website.