MINNEAPOLIS — The federal government is considering adding the Blanding’s turtle to the endangered species list, as the yellow-throated reptile that once thrived throughout the Upper Midwest can now only be found in large numbers in parts of Minnesota and Nebraska.

The sand dunes, marshes and backwaters of the upper Mississippi River, including the Weaver Dunes of southeastern Minnesota, hold one of the largest remaining populations of the Blanding’s turtle, which the Minnesota Department of Natural Resources already classifies as threatened. A population in Valentine National Wildlife Refuge in northern Nebraska, where the species is classified as at-risk, is more secure but still vulnerable.

In response to a petition from the Center for Biological Diversity, an environmental advocacy group, the U.S. Fish and Wildlife Service last week began a formal assessment of whether 20 amphibians or reptiles found in various parts of the country, including the Blanding’s turtle, and one plant species should be listed as endangered or threatened under the Endangered Species Act. Such listings would give them greater protection.

The center said the fragmented, remnant populations of Blanding’s turtles across their historic range aren’t enough to sustain what’s left of the species.

“They have these bright yellow chins, these beautiful domed shells, but their beauty is part of their problem,” said Collette Adkins, a biologist and lawyer with the center. Blanding’s are collected illegally for the pet trade, she said, but the loss of the distinct habitat they need is the main driver of their decline.

Rich Baker, the state endangered species coordinator with the Minnesota Department of Natural Resources, said it’s safe to say that Minnesota is home to thousands of Blanding’s turtles, perhaps as many as 10,000 or more. Besides the Weaver Dunes, he said, there are also populations on the Anoka Sand Plain north of the Twin Cities and another in southwestern Minnesota.

The DNR hasn’t taken a position on whether the Blanding’s turtle should get federal protection. But Baker said they definitely deserve their threatened status within Minnesota. The species spends much of the year in wetlands but needs to have sandy uplands nearby for nesting. While Blanding’s normally are long-lived, he said they don’t begin to reproduce until they’re 12 or older and don’t lay a lot of eggs even when they do. And the odds are against them in other ways, too.

When people move into turtle habitat, scavengers such as raccoons and skunks that are adept at finding turtle eggs tend to follow. That’s happened on the Anoka Sand Plain, Baker said. Another problem there, he said, is that there are places where adults Blanding’s still live but have nowhere to nest, so they’re not reproducing and will die out eventually. Road kill is probably the main cause of mortality in the Weaver Dunes because there’s a highway between the sandy uplands and the wetlands, he said.

The Fish and Wildlife Service will field public comment about the species assessments through Aug. 31, and spokeswoman Georgia Parham said the federal agency will gather information from many sources over the next two years. The agency could then launch the process of putting the Blanding’s turtle on the endangered list, or it could put it on a list of candidate species that might eventually get federal protection behind species that are in more trouble — an outcome Adkins said is the most likely.

“This is the very beginning of a process that we’re undertaking to find out as much as we can about this species,” Parham said. “Our decisions are always based on the best available science, which is why this public comment period is important.”