Amphibians
Black Toad
Anaxyrus exsul · also called Deep Springs black toad
The black toad’s entire species lives in one desert valley, dependent on a handful of springs that, between them, make up the whole of its natural range on Earth. Tens of thousands of years ago the surrounding desert dried out and left this small, dark population stranded, and it has stayed exactly there ever since.
Overview
The black toad, Anaxyrus exsul, is found only in Deep Springs Valley, an isolated desert basin in eastern California. Its notably dark colouration and extremely narrow natural range make it one of the most range-restricted amphibians in North America.
A species the size of a few springs
With its entire wild population tied to a small number of specific water sources in one valley, the black toad’s fate rests on careful, sustained management, a genuine case of an entire species’ survival depending on just a handful of specific places holding steady.
Status
Vulnerable, with a currently stable trend maintained through careful, cooperative management of its extremely limited spring-fed habitat.
Black Toad: common questions
How small is the black toad's entire natural range?
The black toad is found nowhere on Earth outside Deep Springs Valley, an isolated desert basin in eastern California, and within that valley its population depends on just a handful of specific springs, making its total natural range one of the smallest of any vertebrate species and considerably smaller even than several other narrow-range desert toads.
How did the black toad end up isolated in just one desert valley?
The black toad's ancestors are believed to have become isolated in Deep Springs Valley as the surrounding desert environment dried out over tens of thousands of years, cutting the population off from other toad populations and leaving it to develop independently into the genetically distinct species recognised today.
Why is the black toad so dark compared with other desert toads?
The black toad has a notably dark, almost black dorsal colouration, often marked with small pale or yellowish spots, a distinctive appearance that sets it apart from the generally lighter, sandier colouration seen in many related desert toad species, though the specific evolutionary advantage of this darker colouration within its habitat is not fully settled.
Who is responsible for protecting the black toad's habitat?
Deep Springs Valley is largely managed in cooperation with a small private educational institution located within the valley, and coordinated management involving that institution alongside conservation agencies has played an important role in maintaining the specific springs and wetland areas the black toad's entire population depends on.