Reptiles
Sonoran Desert Tortoise
Gopherus morafkai · also called Sonoran desert tortoises
For decades, a Sonoran desert tortoise resting among the rocky slopes of Arizona was assumed to be simply another Mojave desert tortoise, until genetic studies revealed the two had been quietly evolving apart for long enough to be recognised as entirely separate species.
Overview
The Sonoran desert tortoise, Gopherus morafkai, is a long-lived herbivore native to rocky desert slopes and mountain habitat across the Sonoran Desert region of Arizona and northwestern Mexico. Its relatively recent 2011 species split from the Mojave desert tortoise, preference for rugged rocky terrain and natural shelters, and monsoon-timed activity pattern make it one of the more taxonomically and ecologically distinctive desert tortoises in North America.
A species hiding in plain sight for decades
What field biologists long assumed was simply a regional variant of one well-known desert tortoise turned out, under closer genetic scrutiny, to be a genuinely separate species that had been evolving its own path for a very long time.
Status
Vulnerable, facing ongoing pressure from habitat loss, road mortality, and disease across the Sonoran Desert region, with slow maturation limiting how quickly populations can recover.
Sonoran Desert Tortoise: common questions
Why was the Sonoran desert tortoise only recently recognised as its own species?
For a long time this population was considered part of the same species as the Mojave desert tortoise, since the two look broadly similar, but genetic and physical studies conducted in the years leading up to 2011 revealed enough long-term evolutionary separation between the two populations to justify formally splitting them into two distinct species.
How is the Sonoran desert tortoise different from the Mojave desert tortoise?
This species favours rockier, more rugged desert terrain and relies more heavily on natural rock shelters for protection, while the Mojave desert tortoise typically occupies flatter desert basins and digs its own extensive burrows, differences in both habitat and shelter behaviour that likely reflect their long separate evolutionary histories.
When is the Sonoran desert tortoise most active?
This species is often most active during the summer monsoon season, when seasonal rains bring a temporary flush of the desert plant growth it depends on for both food and water, a pattern distinct from some other desert tortoise populations that are more active during cooler spring conditions.
Why is the Sonoran desert tortoise considered vulnerable?
This species faces ongoing pressure from habitat loss and fragmentation due to urban and agricultural development across the Sonoran Desert region, along with road mortality and disease, and because it matures slowly and lives for many decades, its populations recover only slowly from these kinds of disturbance.