Produced by The Wild Side LLC
Home | The reporters | Sample reports | Subscribe | About us | Contact us | FAQs/Help
Email:   Password:

Return home
Printer-friendly version

Bison Babies!

by Rick Lamplugh
May 10, 2016

We round the curve and see brake lights ahead. “What’s going on here?” Mary asks, anticipation and excitement warming her voice. 

“Do you think it could be…?” I let the question dangle. We both know what we have come into the park looking for this afternoon. 

I stop our car behind the one parked on the road between the Yellowstone River bridge and Tower Junction. The first adult bison comes into sight, climbing the bank, stepping among roadside sage. Another adult follows. 

“Oh,” I say, turning to face Mary, “This looks like just more adults. I don’t see any…” 

“Babies!” Mary exclaims, pointing and cutting off my lament. 

I look to the side of the road and like magic, here they come. First, one behind its mother. Its back barely reaches as high as the mom’s belly. Then, more moms, more babies. When the bison gather in the road, I count 14 adults and seven calves. I pull to the side of the road, shut off the engine, roll down the window, and listen to the light clicking of their hooves on blacktop. Mary and I point and laugh and smile. For us, these babies—the earliest of Yellowstone’s newborns—signal Spring’s arrival and much more.  

These beauties with their curly red-orange hair, with their long legs, with their black eyes seeing the world anew are the next generation of our country’s just-designated national mammal. These bison are genetically pure; they have no cattle in their DNA. They have not been bred to be sluggish or docile. Their clear lineage goes back before our earliest ancestors hunted here, before the last glaciers formed here, before mastodons and mammoths grazed here, before the land bridge arose and connected Asia with Alaska.  

And bison were everywhere: before the mid-1800s, 25 to 30 million bison roamed from the Pacific Ocean to the Appalachian Mountains. But today, the only place left in the US where bison have lived continuously since prehistoric times is Yellowstone. And we almost lost them here; by 1900 just 23 bison remained, hiding in Pelican Valley, probably to escape the pressure of hunting outside the park.  

As the newest descendants of those early survivors stand in the road, each calf only inches from its mother, it’s easy to see how they differ from adults. The calves don’t yet have the prominent shoulder hump that adults do. That crane of muscle and bone will come later and enable them to swing their big adult heads and clear up to 18 inches of snow from life-sustaining dried grasses. The calves don’t yet have the bouffant hairdo adults sport. The calves are not the same color; they won’t begin turning brown until July.  

When born, each of these calves weighed between 33 and 66 pounds. And they weren’t born very long ago: we can see the dried remains of a shriveled umbilical cord hanging from the bellies of several. Things happen quickly once a calf slides out of mom and onto Yellowstone’s soil. Within thirty minutes the calf can stand and nurse. Within one week the calf can eat grass and drink water, and will begin learning which plants to eat by watching mom. Within seven to twelve months, it will be weaned. The calf will have developed the large digestive tract with multiple stomachs that enable bison to be better than cattle, deer, or elk at digesting lower-quality foods. Their ability to subsist all winter on dried grass is just one of the reasons that bison survived while other species of large mammals went extinct. 

I smile at the sight of one of the calves nestling its black tipped nose into the mom’s pantaloons, the long hair on her legs. It’s hard to imagine that an animal as tiny and helpless looking as this one will grow to 2,000 pounds if a male and 1,100 pounds if a female. It’s also hard to imagine, as we watch these calves wobble along with their mothers across the road, that one day they will be able to run at 35 miles an hour, turn on a dime, and jump a five-foot high fence. 

Most of these female calves will become mothers. They may conceive their first calf when they are two to three years old. They will then produce, according to P.J. White, Rick Wallen, and David Hallac in their book, Yellowstone Bison, a single calf every one or two years for the rest of their lives. That means that each of these female calves could produce nine or ten offspring before they die. Their prodigious reproduction is another reason the species survived while others vanished.  

These calves that are male will not all succeed in becoming fathers. They have a number of years of frustration to live through, since breeding bulls are usually five to six years old, though they are biologically able to breed well before that. Once old enough, they will still have to battle to breed. And that comes at a cost. Harold Picton, in his book, Buffalo Natural History and Conservation, writes of one research paper which found that 50 percent of bulls studied showed previously fractured ribs that most likely occurred during the rut.

As the mothers reach the other side of the road, Mary and I notice that a couple are starting to shed their winter coat. Like all bison, they will rub away excess hair on any surface handy, but rough-barked trees are a favorite. The rubbing actually removes some of the bark. The other day as Mary and I walked in Hayden Valley, home to another bison herd, I counted 30 trees in a row with large bison rubs on them.  

We also notice that some of these adults have ribs showing, have barely won the race between starvation and spring. Now, as Yellowstone greens, they must graze and rebuild their fat and strength. While adults have the stamina to graze ten hours a day, their calves need to rest. Recently, on our way back from the Old Faithful Area, we had to maneuver our car around a single calf that was sleeping, laid out flat, on the warm road surface, surrounded by a small group of adults. Formidable protection for a youngster’s nap. 

The bison’s instinct to protect their young and other members of their group is another reason for the species survival. Bison are very social animals and while only half the females in this group have calves, the other females will watch over the group’s growing members.  They surely would have come by to lick and sniff the newborns.  

In a few weeks, we will smile and laugh as we watch these calves play with one another, running and jumping and kicking up their little hooves. That play helps them develop physically and teaches them the rules of the herd. One rule they had better learn quickly is to not stray too far from the protection of the group. Hungry grizzly bears and wolves may take stragglers. A mother, writes Picton, will fight to defend her calf. But only to a point: Under the commonsense rules of nature, it’s better for the mother to withdraw and save her own life so that she can produce more calves later on.  

But bison, with their large size, incredible speed and agility, sharp horns, and the willingness to defend each other, lose few members to predators. As they age, some of these calves will die from the trauma of a hard winter, from falling through thin ice of a lake, after colliding with a vehicle, or while giving birth to the next generation. 

There is one predator that bison have to fear. Since 1985 we have killed more than 6,000 Yellowstone bison, say White, Wallen, and Hallac. Almost all these bison were either captured at the Stephens Creek Facility and sent to slaughter or killed by hunters just outside the park. (I wrote a four-part series about both the capture and the hunt. Here’s the link to Part One)

The 14 adults and seven calves are heading away from the road and silhouetted against a clear blue Yellowstone sky. In a moment they will drop out of our sight behind a sage-covered rise. I hate to see them go, but a busy social spring and summer awaits them. By early summer, their group of 21, which is about average size for this time of year, will join other bison and form a group of about 200. By the time of the rut, mid-July to mid-August, that group will merge with others and form a group of about 1,000 in nearby Lamar Valley. There, older, one-ton, males will grunt, bellow, and roar challenges to each other for the right to breed as many females as possible. Last summer, while Mary and I hiked in Hayden Valley, we watched a bull chase a female and her three-month old calf. The bull hazed the calf away so that he would have the female to himself. 

Once the breeding ritual is complete, the bulls will go off to spend winter alone or in small groups. The females, some pregnant, will merge back into smaller groups, each led by a matriarch. The pregnant females will carry their calf through the ravages of winter, through below-zero temperatures and wind and snow and sleet. Then after nine to nine-and-a-half months, the babies will appear, once again heralding Spring and the preservation of this incredible species of survivors. 

Comments? Questions? I welcome your feedback. Email me at

Rick Lamplugh lives near Yellowstone’s north gate and is the author of the Amazon Bestseller In the Temple of Wolves: A Winter’s Immersion in Wild Yellowstone. Available as eBook or paperback. Or as a signed copy from the author.


View slide show

© 2009-2023 Yellowstone Reports. All Rights Reserved.

Yellowstone Wolf Tracker