Throwing the Frogs Out With the Bath Water

Columbia spotted frog

Young Columbia spotted frog in the Endangered Species Lab, WSU Arboretum & Wildlife Conservation Center.

Say hello to our new Columbia spotted frog friend, Fred, or Fredricka, as the case may be.  We don’t know which it is yet, but we were quite surprised recently to discover this little frog sitting in our amphibian breeding pond at the Endangered Species Lab in the Wildlife Conservation Center at Washington State University.  

We hadn’t expected to hear the pitter patter of little frog feet this year, because we had thought that our adult Columbia spotted frogs had failed to breed this spring.  Sometimes it’s really nice to be wrong!

Several days ago while checking on the amphibians in our breeding ponds, I noticed this little frog emerge from underneath the floating duckweed.  At first I doubted what I saw, thinking it must be a tree frog.  Adult tree frogs are about the same size as young spotted frogs.  But the coloring and patterning on its back, along with the distinctive facial pattern, told me it was a young Columbia spotted frog.

Columbia Spotted Frog

Top view of young Columbia spotted frog sitting in shallow water.

I quickly grabbed a net and captured the tiny frog for verification, but also to prevent it from being eaten by the much larger adults in the pond.  Many different frogs will eat almost any prey that fits into their mouths, so tiny young frogs that have recently changed from tadpoles to young adults sometimes are vulnerable to predation by other large adult frogs.

Fred or Fredricka, represents the first time that we’ve had Columbia spotted frogs breed in our outdoor ponds at the Endangered Species Lab.  While Columbia spotted frogs aren’t endangered, they are a species of some conservation concern and an important component of amphibian diversity in Palouse Prairie.

Normally, Columbia spotted frogs breed quite early in spring, so here in the heat of September, I’ve long ago dropped any expectation of seeing these frogs breed this year.  However, I have seen evidence of extremely tiny spotted frogs in the wild in early fall, so I’ve always suspected that there might be some late breeding in some years.

Columbia spotted frogs often are communal breeders, which means that males select calling sites in shallow water areas of wetlands in early spring, and attempt to attract females for mating.  However, where one spotted frog female lays an egg mass in shallow water, you’ll often find other females coming in and laying eggs nearby.

That’s another reason why I didn’t expect our Columbia spotted frogs to breed this year.  The few spotted frog adults we had this spring were placed in a relatively small, 8 x 8 foot, mesocosm – or small artificial wetland habitat that we have fenced to keep the frogs inside and secure from predators, such as birds, raccoons, or snakes.

We did not have a large artificial pond available to put the spotted frogs in this spring, so I didn’t really expect that they’d find our small holding pond suitable for breeding.  But the fact that they did surprise us and lay eggs and hatch tadpoles in this pond isn’t the whole story.

The Rest of the Story…

We check our amphibian ponds multiple times every day to make sure all is well in frog land, and that everyone is safe and healthy.  But in early spring, we noticed that a male tree frog had climbed into the Columbia spotted frog pond and set up a calling station.  And not surprisingly, we soon found three or four golf ball size egg masses that appeared to be from Pacific tree frogs.  We have had wild tree frogs climb in and lay egg masses in our ponds before.  So, there was no surprise there.

Pacific tree frog

Adult Pacific tree frog. Photo source: Wikipedia.

The density of tree frog tadpoles was soon so high that it was obvious they would all starve, because our small holding pond doesn’t have the shallow water habitat and productivity for algae and other tadpole foods that a larger natural pond would have.  So we instituted a feeding program by adding “tadpole pellets.”  

Yes, they make commercial food pellets for tadpoles, which look much like small goldfish food pellets.  And we also added algae in the form of large dried flakes of cultured algae, sold in pet stores as food for algae eating fish.

With the addition of these supplemental foods, the tree frog tadpoles grew quickly, but soon threatened to over run the small pond.  And we knew that they would be in danger of being eaten by the adult Columbia spotted frogs as soon as they started to emerge from the water as adults.

The solution was to trap the tadpoles and release them into an adjacent pond where they could finish undergoing metamorphosis (changing from a tadpole into a young frog) and leave to resume life in the wild in the surrounding natural habitats in the WSU Arboretum & Wildlife Conservation Cener. And there you have “the rest of the story.”

We now wonder whether it is possible that we “threw the frogs out with the bath water” – meaning, we wonder if it is possible that a few spotted frog tadpoles were in the mix of tree frog tadpoles that were allowed to emerge from the adjacent rearing pond and disperse into the wild.

We’ll never know, of course, but we don’t think so.  Columbia spotted frog tadpoles have a larger, more robust head than tree frog tadpoles, so we’re pretty sure that Fred or Fredricka is a result of a later breeding event in the pond, after all the tree frog tadpoles already were gone.  Perhaps Fred or Fredricka is the lone surviver of a late-season egg mass in the spotted frog pond.

We’ll never know for sure exactly what happened, but it’s always fun when Mother Nature throws you a few surprises.  And now you know….  the rest of the story!

Columbia spotted frog female

Large adult Columbia spotted frog female floating in duckweed in a breeding pond at the Endangered Species Lab at the WSU Arboretum & Wildlife Conservation Center.

Oh, but one more thing.  When will we know whether our young frog is a Fred or a Fredricka?  It may take a while. Perhaps a year or more.  When young, the sexes look alike in Columbia spotted frogs.  But females soon begin to grow much larger than males, especially when they are healthy and fed well, as is our captive population.  If this little frog continues to eat well and grow rapidly, we might know its sex by next summer.  In nature, patience is a virtue.

[Note: All amphibians at the Endangered Species Lab are managed under appropriate state, federal, and university permits and regulations and our facilities and animals are regularly inspected and tended by WSU veterinarians.  The basic purpose of this project is to support the conservation and restoration of declining amphibian populations in the wild through collaborative projects with state and federal agencies.]

Comments
4 Responses to “Throwing the Frogs Out With the Bath Water”
  1. Lane Alexander says:

    Great story for us frog lovers, keep us posted on Fred/Fredericka. I have observed both tree and Columbia frogs in my garden (which is close to a creek).

    • Rod Sayler says:

      Yes, in our amphibian studies, we’ve also tended to find Columbia spotted frogs near small streams or wetlands in watercourses. They’re definitely much more aquatic than tree frogs, so I’m not surprised that they associate more closely with water sources.

      We’ll keep you posted about Fred or Fredricka! So far so good. It’s eating well and lively.

  2. Tyler Hicks says:

    I am curious do Pacific Tree and Columbia Spotted Frog tadpoles compete for the same resources? Or do tadpoles have niches too?

    • Rod Sayler says:

      Good question. Various studies of tadpoles of different species have sometimes found evidence for both interspecific and intraspecific competition among tadpoles. However, the predator community (e.g., salamanders, fish, bullfrogs, etc.) also greatly influence the survivorship and ecological relationships that are observed among tadpole communities. I can’t say that I know for sure whether Pacific Tree frog tadpoles compete with those of Columbia Spotted Frogs, but we have some data from 800+ tadpole trapping sessions that we are examining to see if we can detect any statistical relationships between the two species. However, it is quite likely that a variety of controlled experiments are needed to tease apart what might be happening among tadpole communities in Palouse Prairie. Simple ecological questions are often difficult to answer, but then, that’s what makes science and research so much fun!

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