SOUTHWESTERN RIVER OTTER RE-DISCOVERED IN NEW MEXICO

otterlandscapeResearchers at the University of New Mexico have discovered the first physical evidence of a river otter not seen in New Mexico in more than 50 years, according to a paper released recently by International Union for the Conservation of Nature Otter Special Group Bulletin.

The Southwestern river otter, once a thriving subspecies across the state of New Mexico and the Southwestern U.S., is considered one of the most endangered mammals in North America and arguably the world says UNM Research Associate Professor Paul Polechla. The last time a documented otter specimen was collected in New Mexico was in 1953 when a state wildlife officer captured one on the Gila River in southwestern New Mexico.

Polechla and a team of researchers, including New Mexico State Park Rangers Aubony Burns, a former UNM Research Technician, and Scott Rist discovered three presumptive river otter (Lontra canadensis) scats or feces. The scat samples, two new and one old, were found Nov. 3, 2004, at Navajo Lake State Park in northwest New Mexico.

They were on a small spit of dried and cold mud, in an area not conducive to receiving fresh tracks. The scats contained remnants of crayfish exoskeleton, fish bones and scales. A number of other indicators in and around the site area, including birds such as the great blue heron, merganser, Canada goose and gulls were also observed. These species are considered good indicators of quality otter habitat says Polechla.

Although river otters weren’t seen and no tracks were found due to the terrain of the area, the evidence is solid. Kristin Moore, a UNM undergrad, and Jerry Dragoo, a research assistant professor in UNM’s biology department, performed a DNA analysis to confirm or refute the field identification. DNA was extracted from the three samples and one negative control was performed following established standards. Two of the three scats provided enough quantity and quality of DNA for positive identification as that of river otter. Additional research is underway for subspecies identification.

“This study was an innovative way of combining the time honored art of reading signs with the new science of DNA analysis,” said Polechla, the lead author in a paper recently released on the discovery. “What’s more is we didn’t kill an otter to make the determination. The question now is where else might they occur?

“Until you do a thorough survey of available habitat, you really don’t know what’s out there. Similarly, an Ivory billed woodpecker, was discovered in Arkansas recently. Both are wetland dwellers that were thought to be extinct until thorough studies were performed and they were documented. We need to survey the state’s waterways thoroughly for otters.”

Polechla says that only about five percent of the river miles and adjacent waterways have been properly surveyed in New Mexico. He added that very little of the waters in adjacent states have been surveyed as well.

The paper adds that recent plans to translocate otters may be premature in New Mexico and the Southwestern U.S. and northern Mexico until the majority of river miles, including shoreline of habitat is surveyed, by biologists experienced in tracking otters and other New Mexican fauna during seasonal peaks.

In addition, the potential habitat should also be surveyed prior to any otter restoration plans in a particular watershed, which would involve a field assessment of current suitability of habitat and the removal of factors that contributed to the decline of the population.

Decline of otters in other areas of North America have been attributed to water pollution, excessive wetland development, over trapping, and intensive water use. Reasons for the previous decline of otters in New Mexico in particular is speculative.

“Just like for humans, a healthy riparian and watershed environment is essential for survival,” said Polechla, who has studied river otters for more than 20 years with a concentration in the Southwest United States the past 10 years. “Perennial streams and rivers are required. The bottom line is otters need to have clean water, a minimum or steady stream flow, and adequate food supply and cover.”

There are six other different river otter subspecies in North America, some of which have been indiscriminately stocked into the wild in the Southwest. Otters vary in size, but generally grow to about four feet long weighing approximately 25 pounds. River otters spend part of the time on land and part in the water. Otters use the river to hunt and travel. Unlike land animals, otters follow drainages, which is one of the reasons why Polechla feels waterways hold the clues of otter presence.

 

This article was originally published in "UNM Today: Campus News and Information" (http://www.unm.edu/~market/cgi-bin/) on May 11, 2005 by Steve Carr (505/277-1821).