Song of the Magpie: September 2009

Wednesday, September 23, 2009

Prehistoric Bison

Paleo Bison / Bison latifrons is an extinct species of bison that lived in North America during the Pleistocene. Also known as the giant bison, or ice age bison it reached a shoulder height of 8.5 feet, and a horn spread that spanned over 6.5 feet. The species was much larger than today's species of bison and it is estimated that it would have weighed well over a ton, standing as much as 8 1/2 feet at the shoulder. They would have been very similar to modern bison in appearance, only larger, with their most distinct feature being the long set of horns protruding outward from the skull. It was perhaps America's earliest bison species.

Several times during the Pleistocene epoch the first bison made the journey from Asia to North America by migrating across the existing land bridge between Siberia and Alaska. Such species include the modern bison, Bison bison; the small bison, Bison antiquus; the Eurasian steppe bison, Bison priscus; and the large broad-horned bison, Bison latifrons.

Nearly 75 percent of all the megafauna that existed in North America disappeared from the face of the continent by the close of the last ice age. The bison species managed to hold on during this last mass extinction, eventually to thrive in vast herds as North America's largest extant land mammal.

Bison latifrons appeared by 500,000 years ago in North American and lived alongside these other bison species until going extinct some 20,000 years ago according to scientists. Their fossils are scarce, found only in late Pleistocene layers.

The first appearance of Bison antiquus in North America was around 250,000 years ago.
This line may have led to modern American Plains Bison, with this speciation occurring around 5,000 years ago. European bison may be descendants of Pleistocene bison that returned to Europe from North America.

2,000 years ago American Plains bison / Bison bison reached its maximum range. An estimated 50 million bison inhabited the continent when Europeans arrived on the continent.

It wasn't until the 1830s, when European settlers started to expand westward, that the modern American bison's range shrank and it's existence became seriously threatened. By the mid 1800's, bison became the target of large-scale extermination and were nearly extinct by the turn of the century. Only an estimated 300 wild bison remained.

Today, thanks to the foresight of a very few enlightened individuals, the modern American bison was pulled back from the brink, surviving in two subspecies: Bison bison bison (American Plains Bison) and Bison bison athabascae (American Wood Bison).

Today, the largest free-ranging populations occur at Mackenzie Sanctuary, Wood Buffalo National Park and Slave River lowlands in Canada and at Yellowstone National Park in the United States.

There is also one surviving European bison species, genetically very close to the American bison: Bison bonasus (European Bison), until recently made up of three subspecies: Bison bonasus bonasus (Lowland Bison), Bison bonasus caucasicus (extinct in 1925) and Bison bonasus hungarorum (extinct Hungarian Bison).

Thursday, September 17, 2009

Woodhouse's Toad

This little guy is from the the Nebraska Sandhills where he blends in well into the light-colored landscape. Woodhouses Toads like him come out around dusk in droves, and especially attracted to any brightly lit spots where insects may congregate, such as under porchlights. During daytime, they'll burrow deep into the sand to escape the heat of the harsh summer sun.

Our little toad is barely the size of a thumbnail, but on average they grow up to around 4" in size. Judging from the voracious appetite he's got, I wonder what's holding him back!

I say he's got a face like Jabba the Hutt ;D