Craig Ludwig displays samples of silky pocket mice from 1892, part of the collection managed by the Biological Survey Unit at the Smithsonian National Museum of Natural History. (Bill O’Leary/The Washington Post)

The 133-year-old Biological Survey Unit, slated to be closed this year, has gotten a short reprieve from the budget ax, according to documents obtained by The Washington Post.

The U.S. Geological Survey, which oversees the division, had planned to close it this spring. The unit, which boasts a $1.6 million annual budget and six employees, helps maintain nearly a million bird, reptile and mammal specimens and historic field notes housed at the Smithsonian National Museum of Natural ­History.

Interior Department officials sought to shutter it as a way to trim the department’s overall budget. Several academics and scientific societies protested the move, saying the unit’s staff provided access to key specimens that shed insight on critical scientific questions, including on how ecological conditions changed over more than a century out west and elsewhere in North America.

New USGS budget documents show that the agency will keep the division intact at least until Sept. 30, the end of the current fiscal year, as it devises a plan to transfer its responsibility to the Smithsonian. The Smithsonian serves as the official repository for the collection and jointly manages it.

“The Survey is directed to formulate a transition plan with the Smithsonian Institution regarding the curation of the Institution’s collection for which the Survey is currently responsible,” the documents state.

A USGS spokeswoman confirmed Thursday that the Biological Survey Unit will continue operating until the end of the fiscal year. “We value our long-term relationship with the Smithsonian and are in the process of developing a transition plan,” A.B. Wade said.

Researchers welcomed the temporary stay of execution but warned that it did not address larger questions about the future.

Robert S. Sikes, president of the American Society of Mammalogists, said in an email that the plan to close the division  “and transition its collections to the Smithsonian is shortsighted.”

“Such a move curtails core work by the unit’s scientists and will undoubtedly limit use of collection materials by researchers at a time when dwindling populations of so many species is headline news,” said Sikes, a biology professor at the University of Arkansas at Little Rock.

He noted that the society’s leaders had written the Smithsonian a year ago about its curatorial staff for mammals being underfunded and lacking the number of experts needed to provide researchers sufficient access to the collections.

“Now the size of those collections will double while staff shrinks,” he said. “These specimens are irreplaceable spatial and temporal records whose value continues to grow as science devises new ways to glean data from them.”

Portland State University biology professor Luis Ruedas, who regularly works with specimens and field notes from the unit’s collection, said only a long-term budget fix can address researchers’ dilemma.

“At the close of September, the same situation remains: No one is left to take care of the specimens,” Ruedas said.

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