It all started with the tadpoles. For the third year in a row, most of the stream at Placerita is dry. There is some water in the waterfall, but it comes down as a fast trickle that disappears quickly in the stream bed.

Tadpoles have a few requirements to be able to grow into a frog: They need warm and tranquil water with plenty of nutrients – so the water should not run too quickly.

Pacific tree frogs are the common frogs found in Placerita and in the wash in Santa Clarita. They are the most common frog on the West Coast of North America, so you have certainly heard their voices.

They are nocturnal, very small – as small as a fingernail. They are green or brown and can change their color to match their environment, so they are hard to see. They reproduce in a riparian environment but can live in woodland, chaparral, pasture and your garden, too, if they have access to a small body of water to reproduce.

They are also known as the Pacific chorus frog, and if you take a walk along the wash right now, you will know why.

However, many parts of the wash are dry now. Lyons Avenue is one good spot, in Old Orchard Park, close to the bridge (across the way from Boxes Etc.). We have been in a drought for three years, and I have heard a few frogs a Placerita calling for a female – only the males do the calling – but there are no places to lay the eggs. The stream is dry.

I’ve also heard, “We have lost three generations of frogs because they could not lay eggs for the past three years.” I had a vision of geriatric frogs trying to reproduce when and if water ever comes back in the stream. I could not find exactly how long a male frog reproduces well, but as usual, it is the strong stud that reproduces the best and calls the loudest to attract the females.

I was hoping the tadpoles could become frogs quickly to use to their advantage a pool of water left over in a shady corner. No such luck: The embryos hatch into tadpoles in one to three weeks and become frogs only two and a half months later. They need to eat vegetation from the rocks, so they need more water than a small puddle.

I was running out of answers as to how those tadpoles could survive. How do frogs manage in a dry climate such as Australia? Do they have frogs in their deserts? They do have the Spencers burrowing frog, which makes a hole and has eggs after a big rain storm … but that would not work in our climate where the big rain storms are supposed to happen when it is winter, and too cold for any tadpoles to develop.

I guess we are not going to have too many tadpoles this year; a few will make it and will carry on the population.

All of this worrying about the tadpoles had me thinking about evolution.

You know the story about Darwin’s finches showing up with different beak shapes on the Galapagos Islands? It seems that the finches came from South America and landed on various islands, having been pushed in slightly different directions by a strong storm. The islands were too far away from each other, so they could not breed with each other. They had to survive, and so they did, but after many generations of eating different foods, their beaks started to change and adapt. The finches with the thin, fine beaks were insect eaters, and the ones with the large, sturdy beaks were eating nuts. However, this evolution took many, many generations and a long time.

To be able to observe evolution, you need a strong genetic variation and diversity, and you need many babies very fast. Another experiment was done by Prof. David Reznick on guppies. They could be found in a special setup in Trinidad, with two little lakes and one river leading to each lake. In one river, the guppies have a predator lurking to eat them; it is a fish like a pike. In this river the guppies grow up fast, maturing when they are smaller; they need to breed quickly because they could be eaten by the pike, and they look plain to avoid attracting attention.

In the river without the pike, the guppies have more colors and stripes and have offspring later in life.

Those were interesting spots to do some experiments. Reznick took some of the brightly colored guppies that did not have to grow up escaping from the pike and put them in the pond where they had to deal with a predator.

He did the same with the smaller, duller-colored guppies and put them in the warm, peaceful water from the lake without predators.

Then they all went home and came back 10 years later. The experiment worked like a charm. The evolution was replicated, and the fish had a larger body size and delayed maturation in the quiet waters without the predator and had the smaller body size and earlier maturation if they had to deal with a predator trying to eat them.

There are not many animals that can achieve such a change in 10 years. The Pacific tree frog does not have much genetic diversity; the tadpoles won’t be able to survive in a dry stream bed. But I know they will find special niches and they will make it.

We won’t see as many as we usually do, that is certain. So listen carefully for them this year, and we will just wait patiently for more rain … next winter.

Evelyne Vandersande has been a docent at the Placerita Canyon Nature Center for 28 years. She lives in Newhall.