A Ponder of Western toads

[John]

Refreshingly interesting questions that I believe I can answer:

The main large pool was formed from the largest rainstorm we’ve had in ten years, yet it dried up before any of the tadpoles could fully develop. How can they continue to propagate with that survival rate?

This is the survival game that explosive breeders play. Really dry ground that receives a downpour often won't hold the water for long due to cracking and overall huge porosity (the degree to which it will absorb water or let it pass through). It varies with soil type and consistency, but often with dry soils like what you've probably seen there, they need a gentle or mild rain a few days before the heavy rain falls, in order to reach the right consistency to hold a lot of water. The amphibians don't know that though and they often have to take what chances come their way. In many species of toad that breed like this, not all of the females will lay during the first storm, particularly if it's early in the year. They're the ones that help ensure there are successful "crops" of toadlets even when most of the other toads made a bad laying decision. Still, most amphibian populations can go a year or two without recruitment of juveniles, so all is not lost.

I also observed that most of the tadpoles (for lack of a better word) were the typical blackish-brown color while about 2% of them were stark white with gold dust. They all have exactly the same body structure and mouth parts. What is the difference here between the two drastic color morphs? Will they keep that color into adulthood?

It's unlikely they'll keep that into adulthood. I've seen colour variety in the tadpoles of some US toad species in the wild. Unless it's a true colour mutation, it's likely a way for the toads to hedge their bets regarding light versus water temperature - a dark tadpole will absorb a lot of heat from the sun, which will speed its metabolism and likely lead to metamorphosis sooner (perhaps at a bigger or smaller size). The lighter tadpoles may have a slower rate of metabolism but that might present advantages in the event of a lower abundance of food. This is educated speculation. Presence or lack of predators may also be factors.

What’s more, I found another pool about a mile away (far enough away with hills and thick bushes which would prevent toads from pool-hopping) which might last long enough for the tadpoles in it to finish their metamorphosis, but all I could find in that one were the stark white tadpoles.

Assuming they're not a different species, that might speak to my hypothesis in the last answer. It's quite normal for toads to prefer very temporary pools over those that last longer - fewer predators to eat the tadpoles, but they risk the pool not lasting so long. Also, some toads prefer certain types of temporary pool - I've seen this quite a bit where Great Plains Toads and Woodhouse's Toads overlap in Oklahoma - they'll breed at the same time after a storm, but rarely share the same breeding pool - Woodhouse's prefer ditches and GPTs prefer shallow pans in fields (which are often relict buffalo wallows).

Lastly, at the large pool I also found pacific chorus frogs! This place in in the middle of chaparral for miles with no lasting water source. I thought that chorus frogs needed a continual water source. Can they hibernate like the western toads?

I would imagine that Pacific Chorus Frogs can find refuges, perhaps not in the same manner as toads (digging down), but the fact that you're seeing them breed means that they have found some moist refuge to survive the drought.