I dug out a fish-free backyard pond last year, attempting to create habitat for Oregon's native tree frogs.
This year I saw native Treefrog/Chorus tadpoles (Pseudacris regilla) in my 6 x 8 x 1.5' backyard pond (I call it the Frog Mitigation Area (FMA) on June 4, 2015. I counted over 40 at rest on flat stones in a couple inches of water on top of the pumphouse, and another 40 or more reposing at various locations and depths. According to Wiki, the terms tree frogs and chorus frogs refer to the same critter.
The tadpoles metamorphized rapidly into tiny frogs than are smaller than a bumblebee.
My FERC (Frog Environmental Regulatory Commission) permit originally required me to watch the tadpoles for an hour a day. I appealed that condition and had it changed to two hours of daily perusal. Almost all tadpoles have changed into frogs now. Here is my FERC-required report. (The picture above shows a hydrenga at the FMA headwaters.)
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Primordial feelings swept over me when I watched the tadpoles, who seemed ancient and timeless. Frogs have occupied the Earth for about 200 million years.
The younger, large-headed tadpoles stayed near the pond bottom, and occasionally rose like a balloon riding on a breeze. The tadpoles gulped air, although they had gills, and sank back to the bottom.
The older, larger tadpoles sought out shallow, warmer water at the surface. Many preferred to rest on flat rocks under an inch or two of water.
The tadpoles metamorphized quickly. Within 5 days of my first tadpole sighting, I could spot several tadpoles sporting hind legs.
The tadpoles utilized their new legs, clinging to underwater plants. They also began eating duckweed, a floating plant of small leaves.
After growing front legs, they crawled out of the water, preferring to stay in the droplets of water cradled by the lily pads. Watching them, I thought about eons ago, when the Earth witnessed the first critters creeping onto land from the sea, probably wriggling on mutated fins that had developed leg-like qualities.
The tadpoles' seemed to replicate a sped-up version of that primeval event, as their tails shrank, they sprouted legs, left water, and sought drier habitat.
Morphing must consume enormous energy. The tadpole sheds a tail and grows legs, but also grows lungs, a skeleton, and converts their intestines to handle protein.
Tadpoles morphed to legged tadpoles and into frogs every day after the first week. Each morning I could spot about 2 to 5 newly minted, tiny frogs on the lilies. After morphing, the frogs seemed tired and would sit in one spot on the lily pads for several hours. The pictured frog remained in one spot for almost 4 hours.
After resting, they abandoned the pond. I began finding the tree frogs in the gardens and the strawberry patches within 30 feet of the pond. They also hid under the flat rocks that lined the pond, where it remained moist and shady.
I built up the pond sides a few inches, and added water. About half of the remaining tadpoles began swimming upstream from the pond into the newly accessible creek, which is now 2-4 inches deep.
Luckily, I was too lazy to clean out the sequoia needles, maple leaves, and other accumulated materials in the creek bottom of sand and pea gravel. The tadpoles nibbled at these materials and also sought shelter in it. A school of 10 moved upstream but fled back to the pond's depths when spooked. Here is a picture of the detritus. There are also weeds growing in the creek.
This week, there are only about 5 legged tadpoles left in the FMA who haven't completed morphing.
I feel responsible for the fate of these tiny native frogs whose habitat I cultivated. I wish I'd picked a tougher or larger critter to advocate for; any sparrow could pick off these bug-sized frogs.
The fish-free FMA allowed tadpoles to develop without much predation, and the dragonflies flourished also. Here is a picture of a couple of nymph shells left behind. Duckweed is in the background.
My suspicious eyes watch the nymphs and the dragonflies; they could easily prey on the tadpoles and frogs, who are smaller.
The 10 bullfrogs (Lithobates catesbeianus) in two nearby ponds represent a graver threat. One study discovered that every bullfrog dissected had been eating other frogs. (Stewart, M.M. and P.Sandison. 1972. Comparative food habits of sympatric mink frogs, bullfrogs, and green frogs. Journal of Herpetology 6: 241-244.)
Bullfrogs also lay 20-25,000 eggs annually and can overwhelm the tree frogs, who only lay 500-750 eggs annually.
This morning I watched a small bullfrog (body length of 3 inches) on a lily pad in one of my ponds.
Suddenly something much larger reared out of the water and grabbed it so fast than I couldn't positively identify it. It could only have been a larger bullfrog striking with efficient, merciless vehemence and swallowing the smaller bullfrog whole. Either that, or there's a gator in my pond.
One study claimed that bullfrogs do almost all their hunting in the water. My suburban bullfrogs did not read this study. http://www.uri.edu/...
At dusk I watch the bullfrogs leave their ponds and follow their routes to patches of vegetation. One bullfrog heads 20 feet to the grape and lavender bed,leaping over a wall. Another bullfrog hops from the pond to a small apple tree, 3 feet away.
They move cautiously, perhaps because I am watching. I had hoped they were only hunting and eating bugs, but bullfrogs eat everything that fits into their mouths.
I fear that heron, raccoon, and cat predation will not control the bullfrogs. Additional bullfrog control measures will require another amendment to my FERC Plan of Operation and Permit. I need to deal with FERC anyway. I got kind of an odd phone message from FERC this afternoon, also. Something about a pipeline?
Now It's Your Turn What's interesting to you? Please post your own observations and your general location in the comments. I'll respond after lunchtime because I work tomorrow morning.
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