Science Corner - Pacific Chorus Frogs
What do you call an itty bitty frog with sticky toes and a high octane singing voice? Not sure? Biologists have the same problem. Inarguably, our subject is a frog so that part is pretty easy but it gets a little muddy after that. The Pacific Chorus Frog, aka Pacific Tree Frog, aka Northern Pacific Tree Frog are all seemingly appropriate common names for a teensy-weensy frog that can climb straight up a nearby tree trunk, dangle from nearby vegetation by the tip of a toe, or scale an interior shower wall like spiderman (ask me how I know) and, is a troubadour of the amphibian world. Not only are scientists not sure what to casually call it, they also wobble between various scientific names as well. They probably should have written in pencil because the species has had a taxonomic journey going from the genus Hyla (tree frogs) to Pseduadris (chorus frogs), then briefly to Hyliola, which resulted in taxonomic arguments, and then finally back to Pseudaris which is where the species is currently filed. Fun fact #1: Pseudaris translates to “false locust” which makes sense for such a wee frog.
Although biologists are still working out the taxonomy, generally three species are recognized - at least for the time being. P. regillla is the northern species and occurs in northwestern California, Oregon and Washington; P. sierra is the central species that occurs in our region south to Central California, and parts of Nevada, Idaho and Montana; and P. hypochondriaca is the southern species, sometimes called the Baja California Treefrog. Fun Fact #2 - all three used to be considered one species because they all look identical but have since been separated out based primarily on their ranges.
The Pacific Treefrog/Northern Pacific Tree Frog/Chorus Frog (I’m just going to call them “tree frogs”) is about two inches long from snout to the base of their spinal column (urostyle for folks that like technical terms). The male tree frogs are normally a bit smaller than the females and if you flip them over (which they largely disapprove of) you’ll see a dark “turtleneck” under their chin. This dark band is their vocal sac that stretches when filled with air out to create that glorious melody that lures the ladies. Tree frogs can be shades of brown and green with light colored bellies and usually yellow on the undersides of their hind legs. Their back and sides usually have a variety of darker spots and they always have a signature dark eye strip that extends across their nose and eyes to their shoulders.
Tree frogs can alter their coloration to match the seasons and their surroundings. Fun Fact #3 - Pacific Tree Frogs can not only change background colors but they can yo-yo between being spotted or not! Tree frogs are overall slender with long legs and relatively long toes that have partial webbing and are unique in that the tips of each toe is modified to include a sticky disk. It is this disk that allows them to cling to surfaces to climb and ambush prey which includes insects and other invertebrates.
The range of the three species complex combined includes British Columbia south to Baja California and from the Pacific coast east to Idaho and Montana. There is even a small population surviving in a pond on an island near Ketchikan, Alaska after an intentional introduction in the 60’s. Tree frogs can tolerate a vast variety of habitat types and climates from sea level to high altitudes. They commonly occupy naturally occurring and artificial wetlands such as lakes, ponds, streams and even neighborhood pools and storm drains. They need persistent water for breeding and to keep their skin moist but they also utilize surrounding upland habitat such as chaparral, grasslands, woodlands and even pastures, fields and parks. Because their range is so vast and varied, mating begins in early winter and lasts through early spring depending on their habitat and weather conditions. Male tree frogs sing to attract females but their serenading also attracts other males who join in the choir creating quite a cacophony that can be heard from over a mile away. Like salmon, tree frogs usually return to their own former nursery to breed. Ten to hundreds of eggs may be attached to or under submerged vegetation and hatch in about three weeks. Like their parents, tadpoles are also tiny and are dark brown-black from above with squishy whitish bellies (like orcas - camouflage from top and bottom). They nosh on algae, bacteria and organic matter until they fully metamorphosis into adults in about six to twelve weeks depending on habitat conditions.
Drought conditions, non-native species introduction, loss of habitat, pollution (this is a big one because all amphibians have thin skin that readily absorbs air, water and chemicals directly into their bodies) and other human-caused impacts have created a global decline in the amphibian population. Fortunately, our regional tree frog populations appear to be holding fairly steady.
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