A remarkable scene near Yellowstone National Park has given wildlife researchers a rare look at just how cooperative bison mothers can be.
Beside Hebgen Lake in Montana, two female bison gave birth less than an hour apart. Normally, each mother would be expected to focus primarily on her own newborn. But these two females did something very different.
They stayed together—and began caring for both calves as a pair.
Observers watched as both mothers cleaned and tended to the newborns. Then the behavior became even more extraordinary: each calf began nursing from both females, and both mothers appeared to accept it.
In biological terms, nursing another female’s offspring is known as allonursing. Researchers described the observation as the first documented case in wild bison in which cooperative birthing behavior and allonursing were seen together.
Scientists observed the small family group for more than five hours, documenting the mothers remaining close to one another while the calves moved between them.
The reason for the unusual partnership remains unclear.
The females may have been related, which could make cooperation more advantageous. Another possibility is that remaining together simply made life easier during the vulnerable hours after giving birth.
With two adult bison nearby, the calves potentially had more protection from danger, while the mothers could share some of the demands associated with guarding and feeding newborns.
Still, researchers cannot know from a single observation exactly what motivated the behavior.
What makes the encounter important is not just its rarity, but what it suggests about animals often viewed mainly through the lens of herd movement, competition and survival.
Bison may have more flexible and cooperative maternal relationships than scientists previously understood.
For generations, these massive animals have been one of the most recognizable symbols of the American West. Yet even after centuries of observation, they can still surprise us.
Near a Montana lake, two mothers gave birth almost simultaneously.
Instead of going their separate ways, they remained together, cared for both newborns and allowed both calves to nurse.
Two mothers. Two calves. One extraordinary partnership—and a behavior researchers had never formally documented in wild bison before.