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Posts Tagged ‘Rana catesbeiana’

bigbullfrog

It’s been interesting to observe the changes to the frog community in our little pond. Just a few weeks old, the pond already looks quite settled, with water plants and duckweek created interesting patterns on the water surface. Within a few days of set up, frogs were already moving in, little Green Frogs (Rana clamitans melanota). Then I noticed that some of the Green Frogs were, in fact, Bullfrogs (Rana catesbeiana). The two species are rather similar, but Bullfrogs are bigger, the largest frog species in North America. Knowing this isn’t too helpful, though, when you are looking at two juveniles of similar size, and a big Green Frog can attain impressive proportions too.

twofrogs

When I looked carefully at this pair, sitting together on a log, I could see that the individual on the right is a Bullfrog, while the leaper on the left is a Green Frog. The green on the Bullfrog’s face is more broad and shades into his body colour, while the bright green on the Green Frog’s face more closely resembles a moustache. Also, you can easily see the distinctive line formed by the dorsolateral fold running along the upper side of the Green Frog.

For a while, the little frogs all shared the pond. On one day, I counted 15 of them. Then, a very large, mature Bullfrog moved in. That’s him in the opening photo. That cleared the pond! It’s a big frog eat little frog world, and the juveniles decided it was time to seek out new living quarters. I heard the Bullfrog singing last night, but this morning when I looked in the pond, I couldn’t see any frogs. Not one. It will be interesting to see how the population changes over the remainder of the season. Below is a photograph of one of the smaller frogs resting in duckweed. I like the way his pattern camophlages him so well in the vegetation.

pond1

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pondreflection

Reflection

The other day, I walked down to the pond to see what the inhabitants were up to. As soon as I got there, I turned around and walked back to the house, because I was greeted by a horde of deer flies. I put on a sweatshirt, even though it was a warm day, to save swatting at my arms. Back at the pond, I took stock of who was out and about.

bluetpairs

Along the shore, dozens of bluets were zipping back and forth and perching on vegetation along the edge of the water. Many pairs were flying in tandem, or were forming a copulation wheel, the position in which the male transfers a packet of sperm to the female.

bluetpair2

You know that “I’m being watched” feeling? Down by the pond, you don’t have to be paranoid to believe that many eyes are watching you. A lot of those eyes belong to frogs. As I walked along the shore, every few yards a large frog would leap into the pond before my advance. Many more simply rested in the water and watched from a safe distance. The pond is home to a sizable population of Bullfrogs (Rana catesbeiana) and a fewer number of Green frogs (Rana clamitans). One charismatic character seemed to have a Mona Lisa smile:

pondsmilingfrog

Another was floating in a relaxed posture as if enjoying a day at the beach…which I guess he was!

pondfloatingfrog

This big fellow sang a few bars of his throbbing love song for me. Well, maybe I wasn’t the female he had in mind…

pondbullfrog

Along the shore, schools of tiny fish fry and minnows swam by.

pondfish

The vegetation, both in the water and along the edges is full and luxuriant. There is plentiful pondweed (Potamogeton sp.) to provide cover for floating frogs and little fish. Along the shore, Swamp Milkweed (Asclepias incarnata) adds a touch of colour.

pondswampmilkweed

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bullfrogpond

Although the man-made pond is growing increasingly naturalized each year, with assorted willow shrubs and small trees growing up on the south bank, you can still walk all the way around its perimeter. Just a few weeks ago, this was a quiet walk, but as the weather has warmed up, that has changed. As you stroll along the shore, 10 or 15 feet ahead of you squawks of alarm, followed by a splash, precede your approach. It seems the pond is excellent habitat for Bullfrogs (Rana catesbeiana). Their distinctive “yelp” is quite startling when you’re not expecting it. You can listen to the yelp-splash at CaliforniaHerps.com.

bullfrog

Bullfrogs are the largest North American frog species and adults may reach 10 to 20 cm (3.7 to 8 inches) in length. The individual above was close to the larger end of that scale. As females are generally larger than males, I assume it is a female, close to 8 inches long. Other signs to check for to differentiate males and females are the tympanum (eardrum), the round patch behind the eye, and the throat. In males, the tympanum is larger than the eye, while it is about the same size as the eye in females. Males have yellow throats while females have white.

secondbullfrog

Bullfrogs will eat almost any small animal that they can capture and swallow, including fish, snakes and young waterfowl, but most of their diet is made up of invertebrates such as dragonflies, beetles, spiders, snails and crayfish. They, in turn, are dinner for fish, turtles, herons, raccoons, otters and mink, and yes, people. Because of their large size, Bullfrogs are hunted for their legs. But not here at Willow House. Their legs are safe.

bullfrog in water

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