What the Frog!
I’ve been waking up in a dreamlike state every day for almost a month now. In the perma-dry climate of Southern California it’s rare to have heavy rains at all. These last few months have been filled with storms up and down the coast, filling our thirsty creeks and saving our strained cracking oaks.
Not only were there a few weeks of beautiful strong rains, but every night there has been a light sprinkle even up in the notoriously dry Topanga canyon. The ground has been wet and the soil remains damp. It’s been so dry for decades I’ve been truly stunned by this constant moisture.
There is a small creek that runs along my street and even up by my home. Even on big rains that creek rarely ever flows, and now it still has water. It’s pooled up and inviting insects and amphibians to breed. The sounds of buzzing and croaking becomes deafening as these frogs and insects pile into the creeks.
Since these creeks in Southern California are often dry for 350 days, if not more, out of the year, these creatures need to be adaptive and ready at the first sign of rain. These animals associated with the Santa Monica Mountains that breed in water, Pacific and California tree frogs, Red legged frogs, California, boreal, and spadefoot toads, arboreal salamanders, and a whole slew of insects, all head to the creeks as soon as it rains heavily.
California Toad or Anaxyrus boreas halophilus
The reason these creatures need to be so vigilant to these rains is the quickness of the drying. These insects and amphibians can only successfully reproduce in freshwater. Not only do they need to lay their eggs in the water but their offspring need to undergo an aquatic larval phase and live in the water for multiple weeks. This means that they need to time their egg laying to perfection within the few weeks the creeks have water.
Very well camouflaged California treefrog or Pseudacris cadaverina
If these amphibians and insects don’t lay their eggs as soon as the creeks fill up, the water will all flow down to the sea, evaporate, or be sucked into the ground before their offspring fully metamorphosize into adults. These creatures have offspring that can only live in the water. Frogs and toads offspring are tadpoles and have gills so they can only breathe underwater. Part of their metamorphosis is growing lungs that allow them to breathe air and live outside of the water. On top of that change, they grow arms and legs, and lose their long swimming tail. So finally they can breathe, and venture into the world outside of the water.
Either Bullfrog or Red-Legged Frog Tadpole
Although I have not found a peer reviewed publication on this subject, I have observed an incredible adaptation present in pacific treefrog tadpoles. These treefrogs are used to laying their eggs in pools of water that will dry out quickly. They can live in highlands where water is extremely rare. When I was younger I was hiking through one of my favorite creeks.
Another very well camouflaged California treefrog or Pseudacris cadaverina
On this hike I found a rock next to a small pool of water. In the pool squirmed some black dots with tails. I identified them as little pacific treefrog tadpoles. On the rock next to the pool where some interesting black spots. On closer inspection and with grief, I realized that the rock was covered in dried out tadpoles. They had clearly been out of the water for a few days, and appeared to be long dead, as they cannot survive out of water.
I observed this sad sight for a few moments, and when I stood up to move on, I accidentally spilled some water on the rock. It landed on the dried bodies of the tadpoles, and to my astonishment, it seemed that they moved. I thought I might have been seeing things, so I poured a little more water. Suddenly the tadpoles seemed to swell up, being filled again to their round state by the water I was pouring. They then began to wiggle and revive from the dead with the water sloshing onto them.
California treefrogs or Pseudacris cadaverina and one (green) Pacific Treefrog or Pseudacris regilla sharing a hiding place
I was shocked as I poured water on the rock and watched as almost all of the tadpoles wriggled back to life and slid into the pool below. They swam around as if nothing had happened prior. To this day I remember that as an astonishing adaptation to survive the harsh drought like conditions of this region. To be able to dry out and lay dormant waiting for maybe another rain to revive you, would be a fantastic tactic to survive drought and continue one's population.
I am sure more fascinating adaptations like this exist, and ones we haven't even discovered yet, or even imagined. That is what makes science and the exploration of the natural world so fascinating to me. One can make strange and wonderful discoveries just by taking a walk and looking closely at what is around. I encourage you to head to your local creek, while it is still wet, and learn about what critters you might have living there!
Let us know in the comments what you find, and if you know any other interesting adaptations that allow creatures to survive the drought.
Isaac Yelchin is foremost a herpetologist. He studies lizards, frogs, newts, and the like. Specifically, he spends all day and night thinking about what it is like to be an animal. What are the animals thinking about? What is their perspective? When he should be working, he sits and stares at his pet lizard asking himself these questions.