The Sonoran Desert gets some rain in the winter, and monsoon storms in the summer. The native Tohono O’odham call the gentle winter rain female, and the intense summer thunderstorms male rain. Global warming seems to have made for smaller and more intense storm cells. It has flooded less than a half-mile away while our place – we call it Wild Heart Ranch – remains completely dry. By late July 2016, this season’s official total rainfall at the Tucson Airport measuring station was 2.67 inches, with much more in some areas. At Wild Heart we recorded just 6/10th of an inch, with a long spell of 105-110-degree days.
That has noticeably affected our toad population. When we accumulated that meagre total on June 30th and July 1st we were glad to hear the distinctive Spadefoot mating call, a loud, grating quaaaackkk, and to find a male and two females in our little artificial pond on July 2nd.
Spadefoots have adapted to the desert by digging deep into the sand, using the ‘spade’ on their rear feet, and waiting for the vibrations of rainfall to waken them. They find puddles, call for mates, and get together quickly, the male hugging the female and spraying sperm over her eggs as she excretes them. The process moves incredibly fast.
On July 3rd there were strings of jelly-like eggs, thousands of them, in the pond. On July 4th there were hundreds of tiny tadpoles. I boiled romaine lettuce to simulate algae for their food, and they were voracious eaters. In two days, by July 5th, they had doubled in size. I took about 50 over to the Picture Rocks Community Center for their kids’ programmes to observe, with coordinator Adam Bernal taking on the lettuce-cooking chores at his end.
By July 13th a number of the tadpoles had sprouted hind legs and a few even had tiny front legs as well. I divided them into five groups with containers and set them out in shaded garden areas with rocks for an escape route and latticed covers to keep predators out. Pollywog predators in this neighbourhood could include some birds and insects, and that big gluttonous Sonoran Desert Toad, of which there were a couple around. Fortunately our dog, Gus, avoids them, even when they occupy his water dish. They can be toxic to dogs.
By July 18th virtually all of the 60 or 70 tadpoles were metamorphosing and had four legs. They still had tails which propelled them to the lettuce, and they seemed quite happy. Metamorphoses as short as nine days have been recorded, with an average of two weeks, so we were right on schedule. Other frogs and toads outside of the desert take up to twelve weeks to make the transition.
On July 19th most of the Spadefoots now appeared to have four legs and to have absorbed most of their tails. They still swam, but also hopped, covering an amazing distance for their still-tiny size, no larger than a short fingernail. It was just about time for liberation.
On July 20 I went to release the toadlets but the Pollywog Liberation Front had beat me to it. A light rain overnight had sent all but a few of the tiny Spadefoots out into the world. They were all in shaded and well-watered gardens where they could find tiny bugs to feed on. They would gorge themselves and dig down to grow and wait for the next storm, whether it came this year or next.
At the community centre Adam directed the release of his toadlets into protected park areas with the kids all participating. For some reason, perhaps related to sun and shade, those tadpoles took about a week longer to morph.
Maybe we had taken a small step to combat the ravages of climate change, to repopulate our little piece of our world. We had no idea how many would survive, but I’m looking forward to monsoon season 2017 to find out. At age 78, it gives me something more to live for.