Vanishing Prairies, Part 2

Today’s prairies are home to a dazzling array of wildflowers, as well as birds, butterflies, and mammals. Endangered prairie species, besides the golden paintbrush, are the Mazama pocket gopher, streaked horned lark, and Taylor’s checkerspot butterfly. They all depend on the prairie plants. Some critters that I’ve seen at the prairies include the osprey, northern harrier, and Puget blue butterfly. Bats and owls are also common, but I haven't seen them because I haven't gone there at night.

Golden paintbrush

Mazama pocket gopher (from US Fish and Wildlife Service)

Puget blue butterfly

The gopher is endangered because it eats the plants that inhabit the prairie. No prairie, no plants, no gopher. The butterflies use the prairie plants as host plants for their caterpillars. No prairie, not plants, no butterflies. Streaked horned larks nest on bare ground. In western Washington, pretty much anything that is not forested is either oceanfront or developed, with the exception of the prairies (US Fish and Wildlife Service).

Northern harrier (from New York Department of Environmental Conservation)

Streaked horned lark (from US Fish and Wildlife Service)

Taylor's checkerspot butterfly (from US Fish and Wildlife Service)

How did a region known for its forests wind up with this little-known prairie? The geology is fascinating and mystifying all at once. The prairies formed on glacial outwash, but the origins of the mounds remains a mystery to this day. The soil around them is dry and gravelly. The mounds, however, are made of black sandy loam mixed with gravel. There are several theories as to how they formed.

Mounded prairie

Cross section of a mound (from Washington Landscape blog)

One theory is that the mound soils collected on top of glaciers in pits, then settled as mounds after the glaciers melted. Another is that they are wave peaks caused by soil that liquefied during earthquakes. Another theory is that following floods caused by a glacially dammed lake, sediment deposits collected when water flowed around vegetation, forming the mounds. There is a theory that the mounds were formed by erosion. My favorite theory is that pocket gophers built the mounds (Washington Department of Natural Resources). A lot of very industrious pocket gophers.

There are some prairies that are open to public access for hiking and wildlife viewing. Glacial Heritage Natural Area, where I took last week’s pictures, I owned by Thurston County and open only on Prairie Appreciation Day in May. Others owned by the State of Washington, such as Mima Mounds Natural Area and Scatter Creek Wildlife Area (also in Thurston County) are open year-round.

This week's references:

US Fish and Wildlife Service: https://ecos.fws.gov/ecp0/profile/speciesProfile?spcode=B0B3

Washington Department of Natural Resources:  http://file.dnr.wa.gov/publications/amp_mima_mounds_mistery.pdf

Gopher: https://www.fws.gov/wafwo/articles.cfm?id=149489588

Harrier: http://www.dec.ny.gov/animals/7090.html

Horned lark: https://www.fws.gov/oregonfwo/articles.cfm?id=149489450

Checkerspot: https://www.fws.gov/oregonfwo/articles.cfm?id=149489449

Mound cross section: https://washingtonlandscape.blogspot.com/2012/05/mima-mound-cross-sections.html