Snapshots of several rare Minnesota species under watch

Piping plover Endangered

Federally threatened, this small shorebird once existed in Duluth Harbor, in extreme west-central Minnesota and on beaches in Lake of the Woods County. Today, its appearance is rare in Minnesota. No birds have nested in the state the past two years. The plover population declined because of a variety of factors, including predation, fluctuating water levels, habitat loss, human disturbance and competition with gulls for nesting areas.

Uncommonly known: The beach on which piping plovers last nested has been shrinking in size, likely owing to to the Rainy River channel changing its course. Beach size matters. The bigger the beach, the harder it is for predators to see this sandy-colored bird and find its sandy-colored eggs.

Wood turtles exist along swift streams and rivers that flow through forests, which they use for foraging and basking. They are found only in Minnesota's eastern counties. Their low population is due to predation, road construction, timber harvest, nest flooding, edge of national range and other factors. Wood turtles have a low reproductive rate.

Uncommonly known: Wood turtles seek sandy and sunlit road edges to lay their eggs because heat from the sun incubates eggs. Increasing nesting habitat closer to water is a conservation strategy.

Monarch Butterfly Federal Candidate for Threatened or Endangered

The monarch is struggling largely because of the loss of habitat for breeding, migrating and overwintering. In 2010, the World Wildlife Fund included monarchs on its top 10 list of species thought to be in need of close monitoring and protection. In 2014, the Center for Biological Diversity and others filed a legal petition with the U.S. Fish and Wildlife Service seeking "threatened" protection status for the monarch under the endangered species act. National and international organizations are working to conserve the monarch.

Uncommonly known: The University of Minnesota Monarch Lab is a leader in monarch conservation, as is the university's professor Karen Oberhauser. She chairs the national Monarch Joint Venture project and is director of the Monarch Larva Monitoring Project. What can you do for the monarch? Said Oberhauser: Provide butterfly habitat in your own yard, participate in monarch citizen science, be a local monarch advocate and support national monarch conservation efforts.

Purple martins historically nested in natural cavities such as woodpecker holes. However, thousands of years ago people began to make houses for martins out of dried, hollowed gourds. Over time, these nesting sites, along with a decline in natural cavities, led to a rare shift. Today, virtually all martins east of the Rocky Mountains depend on human-made homes for their existence.

Uncommonly known: Minnesota scientists use geolocators to track purple martin migration routes. This technology has determined that martins that begin their 7,000-mile migration from Minnesota in August arrive at their wintering grounds in Brazil in October, and will stay there for five months before returning to Minnesota.

Higgins eye mussel State and Federally Endangered

Before settlement, mussels were so thick in the Mississippi River they virtually armored the bottom. That changed in the 1800s when they were excavated by the boxcar load as a source of pearls and button material. Mussels had little chance to recover during the next century because of water pollution and sedimentation. The 1972 Federal Clean Water Act and improvements to Twin Cities' waste treatment plants set the stage for mussel recoveries that are underway.

Uncommonly known: Mussels, which cleanse water by filtering oxygen and particles, need a host to exist. In a DNR laboratory at Lake City, fish in aquariums are inoculated with mussel larvae that fall off when they reach juvenile stage. These mussels are collected, reared and released into rivers to enhance or start new populations. Some mussel species can live for 100 years.

The timber rattlesnake exists in southeast Minnesota, roughly from Goodhue County southward through bluff country to the Iowa border. Though it's secretive and nonaggressive, its decline can be traced to human fear. From 1909 until 1989 it could be killed for a bounty. Houston County paid nearly 5,000 bounties in 1970. The county paid only 191 bounties in 1987. The rattlesnake bounty was repealed in 1989.

Uncommonly known: The timber rattlesnake prefers to hibernate and bask on south-facing bluff prairies. This habitat is in decline because of encroachment from red cedar, buckthorn and shrub species. Some private landowners graze their bluffs with goats to sustain rattlesnake habitat.