Invasive Burros

 
A group brown-hued burros stand in the foreground of the desert spotted with bushes, while desert mountains loom in the distance.
A group of invasive burros in Butte Valley, where a lot of resource damage has been found.

NPS photo/W.Sloan

What do they look like?
If you have never seen one before, they look like horses with large heads, long ears and a cow-like tail. There can be a lot of variety in their color, which can range from black, white, brown, grey and paint and can be striped, spotted or speckled. They are smaller than a typical horse, and can range in size from 400 to 500 pounds. They typically will be seen together, as mothers and their offspring will form long-term social bonds. Dominate male burros are territorial and will either be with the females passing through, or on their own.
Where do they live?
Though Death Valley has sparse vegetation and few permanent water sources, this is a great habitat for invasive burros to thrive in. They are typically spotted in Saline Valley, Butte Valley and along the Emigrant Canyon road, near Wildrose campground. Though they do travel around, they will stay near springs for water and food.
What do they eat?
In Death Valley, they primarily eat grass, shrubs, and desert plants for an average of 6,000 pounds of forage eaten per burro per year! They will often over-browse the vegetation, especially near springs. This has a significant negative impact on spring ecosystems, especially since some of these plant species only exist in these small, fragile habitats.

 
Moist soil with background vegetation that is trampled with countless hoof prints.
A spring is trampled and damaged by invasive burros.

NPS/W.Sloan

How long do they live for?
Invasive burros give birth to one colt each year. There is no natural predator, competitor or common disease that will affect the burros’ longevity. They will typically live up to 25 years.
Where did they come from?
Originally E. asinus came from the rolling desert hills and sparse vegetation of northern Africa and the Arabian Peninsula. They were utilized for their ability to be great desert pack animals- helping people carry goods across Egypt. Eventually they were domesticated in Europe and brought to North America by Christopher Columbus in 1495. During the Gold Rush, burros were brought by Mexican explorers, and either escaped or were abandoned. The descendent of these burros are many of the invasive burros we see today.

 
Stems void of vegetation are in the foreground.
Native vegetation with damage caused by invasive burro browsing.

NPS/W.Sloan

Who do they affect?
Invasive burros eat a lot! The desert ecosystem is already sparse with vegetation and forage eaten by burros can have a big effect on what is available to native animals. In Death Valley, this has a large impact on native Bighorn Sheep. Bighorn Sheep also need to eat and drink water. Invasive burros are aggressive animals that defend their territory and young. They will often prevent other animals from using springs, keeping these vital few water sources from the native animals that need them too. They don’t just out compete native plant-eaters, but their forage reduces the amount of seeds available, affecting seed-eating birds as well.

Last updated: May 19, 2018

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