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Refuge Notebook: Bison in our back yard?

Posted: December 6, 2012 - 3:26pm

Three years ago, Ted Bailey, a retired biologist at the Kenai National Wildlife Refuge, posed the question of whether Woolly mammoths had once roamed the Kenai Peninsula to our Refuge Notebook readers. At the time, a scattered assortment of mammoth bones and tusks had been found, but the reports were not verified. Since then, Janet Klein, a local historian, and Dick Reger, a geologist, have given residents a mission and a search image. The results are stunning: both Woolly mammoth and Steppe bison remains have been uncovered.

Continental glaciers repeatedly expanded and contracted during the Pleistocene, a geologic time-period about 2.5 million to 12,000 years ago. The last glacial advance, named the Wisconsin glaciation, occurred 110,000 to 10,000 years ago. At its peak 18,000 years ago, ice extended all the way into Missouri. Strangely, Interior and Northern Alaska were ice free because it was too dry to accumulate snow.

The Mammoth Steppe, an arid grassland ecosystem, extended from Eastern Siberia to Alaska. The Bering land bridge periodically connected the continents when enough sea water was frozen in the ice sheets to expose the shallow sea-floor, allowing humans and other mammals to disperse from Asia into North America. These grasslands supported a rich array of megafauna like American lions, Saiga antelope, mammoths, and Steppe bison. 

During a warm period 60,000 to 30,000 years ago, when ice was low, the Kenai Peninsula sat on the southern extent of the steppe. In contrast, during the glacial maximum, only a few islands would have remained in a sea of ice. On the Kenai, these ice-free islands were nunataks in the Harding Icefield and the Caribou Hills.

Carbon dating of the partial skull and horn of the steppe bison found on the Kenai place that particular individual here 43,000 years ago during the warmer period. Steppe bison (Bison priscus) migrated across the Bering land bridge 200,000 years ago and moved south into central North America about 80,000 years ago. A genetic study published in 2004 in the journal Science indicates that Steppe bison were abundant but declined dramatically 37,000 years ago when steppe habitat was being replaced by expanding forests. Steppe bison became extinct near the end of the Pleistocene, either due to changing ecological conditions or overhunting by humans.

Steppe bison were slightly larger than wood bison (Bison bison athebascae) with long hindlegs. They had long, curved horns that spanned up to four feet. The University of Alaska Museum of the North displays a mummified bison carcass named Blue Babe due to a mineral coating that covered the animal and turned blue when exposed to air. Discovered in 1979 by gold miners near Fairbanks, Blue Babe was excavated and preserved by Dale Guthrie, a UAF paleontologist. Claw marks suggest Blue Babe was killed by lions and then scavenged by other carnivores. Agropyron and Danthonia grasses were found in Blue Babe’s tooth jam. Similarly, scientists studying the stomach contents of a Siberian Steppe bison carcass found it full of grass and grass pollen.

We don’t know much about habitats on the Kenai Peninsula 60,000 years ago because the glaciers scoured away any pollen that could have been examined. However, Ed Berg, a retired Refuge ecologist, and Scott Anderson from Northern Arizona University, have examined pollen in peat cores and can say with some certainty that our peat bogs began forming about 14,000 years ago, with willows and alders establishing 11,000 years ago. Spruce trees more recently colonized the Kenai 8,000 years ago. The UAF Scenarios Network for Alaska and Arctic Planning research group has modeled how the climates associated with current biomes might change in the future. Interestingly, the climate in western Kenai Peninsula is forecasted to become more similar to Saskatchewan prairies than to our current boreal forest.

Since the spruce bark beetle outbreak that killed white, Lutz and Sitka spruce on the Kenai beginning in the 1980s, the grass Calamagrostis canadensis has expanded around Caribou Hills while white spruce seedlings have become scarce. This may be a short-term outcome due to the loss of seed trees and nurse logs after salvage operations. 

However, these empirical observations coupled with climate data makes me wonder if white spruce will recover. The Caribou Hills fire, which burned over 55,000 acres in 2007, was unusual because it occurred early in the season and spread quickly through grass as opposed to being carried through forest canopy. Grassland ecosystems are maintained by hot fires that burn quickly through dead grass from the previous growing season because these fires tend to kill seedlings. Again, there is not enough evidence to say whether the Caribou Hills fire was a freak occurrence or a harbinger of a changing ecosystem.

The Pleistocene has recently become a hot topic for conservation biologists. A few prominent ecologists have proposed reintroducing to North America species related to the large mammals that went extinct 13,000 years ago. This approach, called Pleistocene rewilding, argues that these extinctions were largely driven by humans and therefore, North American fauna is depauperate. Introducing species like wood bison would restore lost ecological functions and evolutionary potential. In Interior Alaska, the introduction of wood bison has been considered in areas where both archeological evidence and oral history indicates they were present within the past 500 years. 

However, this wood bison introduction has been delayed for a decade because there is a lack of agreement amongst people regarding whether they still belong in the ecosystem. Reintroducing a species missing for over 13,000 years would be even more contentious, but I still find it incredibly fun to imagine bison in our backyard.

 

Dr. Dawn Robin Magness is a landscape ecologist and GIS Manager at the Kenai National Wildlife Refuge. You can find more information about the Refuge at http://kenai.fws.gov or http://www.facebook.com/kenainationalwildliferefuge.

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