In Nevada where 'odds' bolster the economy, what are the odds of capturing a rare mammal?
By Steve Leon, Reclamation Public Affairs

So you are a wildlife biologist out trapping small mammals for documentation. You return to check your traps and Wow! You find a species of concern that has not been trapped in Nevada since 1961! That pretty much describes the discovery made by Biologists Allen Calvert and Chris Dodge, while they were trapping small mammals at Big Bend at Laughlin on March 22 and 23, as part of their work for the Lower Colorado River Multi‐Species Conservation Program (LCR MSCP), Wildlife Group.

The species they caught were adult Colorado River cotton rats, one male and one female. “We caught the same two individuals on both days,” said Dodge. “We pittagged one individual and let her go, the other individual was taken as a scientific specimen and will be placed in the Museum of Southwestern Biology at the University of New Mexico.  “The Colorado River cotton rat is a covered species under the LCR MSCP and is a sub‐species of the Arizona cotton rat,” he said. “This sub‐species is only found on the Colorado River. “This sub‐species is not found in many locations on the river due to a lack of suitable habitat.” Dodge added that the “. . . species has only been documented in the state of Nevada on two previous occasions, the last one being in 1961.  “The species was considered extirpated, or completely absent in the state. Southern Nevada is the northernmost extent of its range.” While on this assignment, Calvert and Dodge were accompanied on the first afternoon, when the traps were set, by Jed Blake, Restoration Group Lead for the Big Bend Conservation Area.

Additionally, student employees in the Wildlife Group – Jeff Hill, Mary Ellen Given and Jenny Smith – assisted with setting up and collecting traps on the last survey, Calvert said. Nick Rice, a biologist with the Southern Nevada Water Authority (SNWA), was also part of the team on those two days.  “He is the person who works at Big Bend Conservation Area for SNWA, which manages the site in cooperation with the LCR MSCP,” said Dodge. “The site is a restoration area developed by both agencies. The find doesn’t alter our operations exactly.” “We will monitor the site much more closely for small mammals, now that we know that this covered species is present,” he added. “This site, as well as other restoration sites with this species present, will serve as a model for future habitat restoration efforts directed towards this species.” Dodge added that they will try to publish this information as a note in a scientific journal.

According to the Discover Life website, all cotton rats have a strong connection with grass. It’s where which they feed upon, and in which they construct their runways. Within their range in southeast and central Arizona and western Mexico, Arizona cotton rats inhabit only grassy areas where there is enough water to support grasses, weeds, or brush.  They are common around ponds and in irrigated fields. They give birth to fully furred young who can run around within a few hours after they are born. Population booms sometimes occur shortly after periods of rain.

“The Arizona cotton rat does use habitats as described by Discover Life, and in this case the habitat was a grassy secondary marsh,” said Dodge. “It is an area just a bit higher than typical cattail marshes where a more grassy habitat grows instead of reeds. “This type of habitat is often adjacent to cattail marshes, and is used quite often by Colorado River cotton rats,” he added.

Updated March 30, 2012