Historic and Current Distributions of River Otters (Lontra canadensis) and (Lontra longicaudis) in the Río Grande or Río Bravo del Norte Drainage of Colorado and New Mexico, USA and of Chihuahua, Mexico and Adjacent Areas
The Río Grande drainage is an important and imperiled wetland of the US/Mexican border arid lands. There is a desire to restore otter populations in this river by interested parties. In order to follow IUCN guidelines for restoration, biologists need learn more fully the situation prior to implementation of restoration management. A prerequisite for proper restoration conservation is to know the organism’s taxonomy (i.e., what taxa or species and subspecies one is dealing with), distribution, and relative abundance. The historic and current distribution of the Nearctic otter (Lontra canadensis) and Neotropical otter (L. longicaudis) in the borderlands of US and Mexico are reviewed in this paper. The evidence indicates that otters were native to the Río Grande valley and has been recorded in the languages and customs of Native Americans such as the Pueblo people prior to European settlement of the area. The first Spanish documents we were able to find whereby otters were recorded, date to the middle 16th century. Otters during historical times were probably more numerous than previously thought and one of the first wildlife laws in the borderlands revolved around a moratorium on trapping the otter and beaver. Presently, populations of otters occur in 1) the Río San Pedro of Chihuahua, a tributary of the Río Conchos entering the Río Grande from the southeast, 2) the upper Río Grande near the Colorado/New Mexico border, and 3) the middle Pecos River in southeastern New Mexico entering the Río Grande from the west. These observations are corroborated by multiple observations by competent observers and in the case of the first population, otter photos and sign. These populations are centered on areas with macro-habitats characterized by a river flowing through 1) deep canyons, or 2) ancillary wetlands. Considerable more detailed survey work is needed to determine the full extent of the distribution of otters in the Río Grande drainage. A genetic study is critically needed to determine the true taxonomic affiliation of these recently discovered populations. A moratorium on translocations should be put in place for the Río Grande to conserve the native populations already existing.