Texas A&M Researchers Help Preserve History Through Equine Genetics Study
Posted August 07, 2018
From the stunning rock formations to the fields of wild flowers,
the Theodore Roosevelt National Park in North Dakota offers more
than 70,000 acres of adventure. The park is also home to some of
the most majestic and breathtaking animals in the United
“Legend has it that the Teddy Roosevelt horses are descendants
of the horses that were used by Sitting Bull and the Sioux tribe to
defeat Lt. Col. George Custer at the Battle of the Little Big
Horn,” said Gus Cothran, a clinical professor at the Texas A&M
College of Veterinary Medicine & Biomedical Sciences (CVM).
“But the known history of the herd suggests that only some of the
Sioux horses had been in the park area at one time. Probably
little, if any, genetics of the Sioux horses remain in the horses
of the Teddy Roosevelt Park today.”
Cothran, who works in the animal genetics laboratory at the CVM,
recently published a study in PLOS One that explored the Teddy
Roosevelt horses’ genetic history to determine the possible origins
of the herd.
“The genetics agreed that the herd was probably of diverse
origin,” Cothran said. “This happens through horses being removed
and other horses being introduced to the herd.”
Although their genes may have outgrown the legend, the Teddy
Roosevelt horses are still a piece of living history. In fact,
feral horses have existed in the park area since the mid-1800s.
However, efforts to preserve feral horses didn’t begin until the
1950s. These preservation efforts still continue today and
researchers at Texas A&M such as Cothran are proudly a part of
Genetic diversity: Going, going, gone?
In addition to exploring the genetic history of the Teddy
Roosevelt horses, Cothran’s study also analyzed the horses’ genetic
diversity. Genetic diversity refers to the amount of genetic
characteristics in a species’ genetic makeup that differs among
individuals. Species with more genetic characteristics, or genetic
diversity, tend to survive and thrive in their environment better
than species with less genetic diversity.
Unfortunately, Cothran and his team of researchers found that
the Teddy Roosevelt horses’ genetic diversity was limited.
“Limited genetic diversity means that all of the individuals
within the population are very similar to each other,” Cothran
said. “This can lead to inbreeding depression, which basically
means that a large proportion of the population is carrying
deleterious recessive variants of genes, or genes that will
decrease the animal’s ability to survive in its environment.”
Luckily, Cothran and his research team found no evidence that
the horses of the Theodore Roosevelt National Park are currently in
danger of inbreeding depression. However, Cothran said, “They’re at
a level of genetic variability that should raise concern. Their
genetic variability is low enough that the possibility of an
inbreeding effect is real.”
After publishing their study in 2018, Cothran and his research
team released a statement about adaptive management practices that
could help increase genetic diversity within the herd. These
practices would be carried out by the National Park Service and
potentially include introducing new horses to the herd while still
keeping the population low enough for the environment to sustain
It takes a herd to save one
The study was initiated by Blake McCann, a trained population
geneticist at the National Park Service. McCann and Cothran began
working together several years ago when McCann sent Cothran almost
200 hair samples from horses within the herd.
Cothran, who has been researching wild horse genetics since the
1990s, began collaborating with Igor Ovchinnikov, who had also done
genetic testing on this herd of horses through McCann.
Along with several other researchers at Texas A&M, Cothran
and Ovchinnikov analyzed the horse samples for both mitochondrial
genetic diversity (genes passed on to offspring from the mother
only) and nuclear genetic diversity (genes that are passed on to
offspring from both parents).
“This study was significant because it was the first time that a
feral horse population had been comprehensively analyzed for both
mitochondrial and nuclear genetic diversity,” Cothran said. “The
study confirmed that the herd has low genetic diversity, which
should be taken into consideration in future herd management.”
After all, who wouldn’t want to help preserve a piece of living
To learn more about the horses of Theodore Roosevelt National
Park, visit https://www.nps.gov/thro/learn/nature/feral-wild-horses.htm.
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