It feels so gross to call this group of 20-something bison a "herd" but I didn't know what else to call it.
Before bison were wiped out (as a deliberate tactic to starve the Plains Indians), small bands like this would only exist in the non-breeding months, throughout fall/winter. But as spring approached, they would join other bands on their migration, eventually forming herds that could number up to 4 million heads.
So numerous were bison, that it's estimated a herd could lose 20,000 individuals in a single river crossing without making a dent in the population. For comparison, this is the Atka Bay emperor penguin colony, numbering 20,000. Imagine this many bison corpses, solely due to one river crossing, without impacting the population:
(Photo by Bertie Gregory)
Diary entries by colonizers describe in graphic details how dead bison would cover the river banks for miles upon miles:
(Excerpts from The North American Buffalo (Frank Gilbert Roe, 1972, 2nd edition), one of my favorite books)
With no exaggeration, the American prairie was covered in bison during the summer. There's no other migration today that can match its size. The closest thing we have are the wildebeest migrations of East Africa:
(Left photo stock, right photo by Gail Woloz)
But even that doesn't come close. The greatest wildebeest herds 'only' number a little over 1 million. A wildebeest herd of that size may live behind 4000 drowned bodies. Imagine the size of this bison herd that left behind over 7000 bodies:
They piled bison skulls three stories high, and turned the prairie white with death, but it should've made no difference. There were millions of bison.
But somehow it did. The bison population was brought down from possibly as much as 60 million to a mere 600. So today a gathering of 20-something heads might as well be called a herd.