IUCN/SCC Otter Specialist Group Bulletin ©IUCN/SCC Otter Specialist Group Volume 25 Issue 1 Pages 1 - 74 (April 2008) Citation: Polechla, P.J. and Walker, S. (2008). Range Extension And A Case For A Persistent Population Of River Otters (Lontra canadensis) In New Mexico. IUCN Otter Spec. Group Bull. 25 (1): 13 – 22 Previous | Contents | Next Range Extension And A Case For A Persistent Population Of River Otters (Lontra canadensis) In New Mexico Paul J. Polechla Jr1 and Sam Walker2 1Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA e-mail: ppolechl@sevilleta.unm.edu 2#15 County Road 3151, Aztec, NM 87410 USA

INTRODUCTION

Ethnozoological data provide evidence that Ute, Navajo, and Jicarilla Apache people knew of river otters (Lontra canadensis) in their homelands in present-day southwestern U.S. using them for clothing, adornment, and ceremonial purposes prior to the advent of scientists (Polechla 2000, 2002a,b). In 1844, Lieutenant John C. Fremont and scout Christopher “Kit” Carson trapped and traded with the Utes of the upper Colorado River drainage collecting “18 packs” of beavers (Castor canadensis), otters, and pine martens (Martes americana) (Sabin, 1912).

Authors of previous writings about otters in New Mexico (Findley et al., 1975; Jones and Schmitt, 1997; New Mexico Friends of the Otter 2005-2007 http://www.amigosbravos.org/river_otter.php, BISON-M 2005 http://fwie.fw.vt.edu/states/nmex_main/species/050555.htm) declared that otters are extirpated from the entire state. Polechla et al. (2004) reported on finds of river otter scats, confirmed by DNA analysis, near Grassy and Albino Canyons of the Los Pinos River arm of Navajo Reservoir, San Juan County, New Mexico, USA. The Los Pinos or “The Pines” River is a tributary of the San Juan River and a branch of the Colorado River drainage at large. Navajo Reservoir is the second largest artificial lake in New Mexico (the 5th largest state in the USA) with a capacity of over 1.85 billion cubic meters of water (http://www.usbr.gov/uc/wcao/water/rsvrs/ds/navajo.html). The upper reaches of the reservoir are in the state of Colorado.

The 2004 discovery (Polechla et al., 2004) constituted the 1st time in over 50 years that anyone had collected physical evidence of river otters in the state (McClellan, 1954; Findley et al., 1975; Polechla et al., 2004). No information had been published documenting otters at other localities in New Mexico and it was virtually unknown whether or not this constituted a transient otter or a member of a resident population. The purpose of this paper is to address the following questions. Does the river otter occur elsewhere in New Mexico? If so, how abundant are they?

MATERIALS AND METHODS

On 9 June 2007 at 0800 M.S.T., the second author was fishing in La Jara Canyon of the San Juan River branch of Navajo Reservoir, Rio Arriba County, New Mexico when he heard a commotion and observed an active dark-colored, wet animal on the bank about 15.2 m away. The long-necked animal periscoped out of the water as he noticed the two-toned face darker above and lighter below. It “wolfed” and “barked” repeatedly and swam to a range of 22.8 m. It had a long, tapering tail.  Just as his daughter was readying a camera, the animal dove. They were certain the animal they saw was a river otter and they notified park officials who then notified the first author. The two authors arranged a rendezvous to search for physical evidence. We used Murie (1974) and Polechla (1987, 2001) as guides for tracking and trailing riparian mammals, Ivey (2000) for tree and shrub identification, and a Field Guide to the Birds of North America (National Geographic, 2002) as an aide in bird identification. A reconnaissance trip to that same locality by both authors on 7 July 2007 revealed bona fide sign of river otters beneath the shelter of overhanging rocks.

RESULTS

Evidence

Sign consisted of tracks (seals in British English) and scat (or spraint in British English) and was only 10 m from the last sighting of the river otter in the previous calendar month. This constitutes only the 2nd time physical evidence of river otters has been collected in the state. Preliminary examination of the nine or more scats of different ages (shown by different colors, including white, dark brown, and black) revealed both fish scales and bones and crayfish exoskeleton. The five-toed, 1-3-1 patterned tracks lead to a rocky sandstone crevice amongst sandstone boulders.

We found abundant sticks cut by beaver placed onto the base of the rocky nook created by the rocks. This crevice, about 2.44-3.05 m high, was about 25.4-30.5 vertical cm above the water and 1.52 m horizontally from the lake margin. It served as a beaver feeding/den site and then was subsequently used by one or more river otters. Local fishermen had seen a beaver swimming in the area the day before our visit.

We also found recent white gnawing grooves of beaver incisors on five Rio Grande cottonwood (Populus deltoides wislizenii) 2.5-6 cm in diameter and eight salt cedar (Tamarix ramosissima chinensis) 1-2 cm in diameter. These shrubs were prevalent since the U.S. Bureau of Reclamation dammed the San Juan and Los Pinos Rivers and their tributaries in 1962, raising the water level to the cusp of the cliff face (elevation 1,854 m) overlooking the river canyon. One-seed juniper (Juniperus monosperma), cliff rose (Purshia stansburiana), and serviceberry (Amelanchier creophila), three typical shrubs of cliff faces, grew in the rocky outcropping undoubtedly established before the dam flooded the canyon.

We observed other animals in the vicinity. Exotic bluegill (Lepomis macrochirus) and crayfish (Orconectes virilis) were observed swimming amongst the jumble of rocks. Carp (Cyprinus carpio) and white crappie (Poxomis annularis) were seen or caught in the area. River otters prey on all these animal species (Melquist et al., 2003). Sign of mule deer (Odocoileus hemionus) and deer mice (Peromyscus maniculatus) were also observed. We also saw American robins (Turdus migratorius) and rock wrens (Salpinctes obsoletus) along the water/soil/rock interface. The margin of the reservoir was exceedingly difficult to traverse due to a combination of a jumble of various-sized boulders, thickets of dense shrubs, and the current water level, making access difficult for surveying.

We collected seven of the nine otter scats for later analysis. Two were left to encourage revisiting by otters. We cast the tracks with plaster-of-Paris and took photos of the habitat (Figure 1 and 2). Figure 3 is a map of the distribution of recent observations of otters in the San Juan River drainages in context with key past observations.

Figure 1. Site where a river otter (Lontra canadensis) den was found (to the left of the large boulder), La Jara Canyon, San Juan River branch, Navajo Reservoir, Rio Arriba County, New Mexico, on 7 July 2007. Note the light green Rio Grande cottonwood at waters edge and the dark green one-seed juniper higher in the rocky escarpment (click for larger version)

Figure 2. A closer view of the area where a river otter (Lontra canadensis) den was found in La Jara Canyon, San Juan River branch of Navajo Reservoir, Rio Arriba County, New Mexico on 7 July 2007. The den is located beneath the lower right hand corner of the large rock in the foreground. Note the dead snags in the water in the foreground caused by rising waters behind Navajo Dam, and the feather light green foliage of the tamarisk just above the water (click for larger version)

Distribution

Otters were observed on the San Juan, Piedra, and Los Pinos Rivers prior to translocation of otters of other subspecies into the waters inhabited by the southwestern river otter (L. c. sonora) from 1973 to 1975 on the upper Piedra River. In 2002, otter sign was found during an intensive walking survey extending a total of 178.2 km in length (i.e., 64 km on the Los Pinos, 56.3 km on the Piedra, and 57.9 km on the San Juan) at 29 different localities in the Piedra River and its tributary, Stollsteimer Creek (Polechla, 2002a). Polechla (2002b) also collected observations of otters by other people (Figure 3, small solid stars) in the Piedra, San Juan, and Los Pinos Rivers. The senior author necropsied and prepared specimens (PJP 2966 and 2967) of salvaged river otters of both sexes (Figure 3, open stars) from beaver control trappers via the Colorado Division of Wildlife. The specimens were derived from the upper Los Pinos River. The most recent sites (Polechla et al., 2004 and this study) (Figure 3, solid circles) occur in the lower reaches of the Los Pinos River and now the San Juan River where the water backs upstream of Navajo Dam in New Mexico. These observations occurred at side canyons where smaller tributaries (Figure 3, dash and three dots) now join Navajo Reservoir. There are many intermittent tributaries flowing from the south into the San Juan River in New Mexico that only flow periodically after torrential thunderstorms. No otters or their sign have been observed in these tributaries to date.

Figure 3. River otter (Lontra canadensis) localities of the San Juan drainage of the states of Colorado (CO) and New Mexico (NM), USA, at approximately 37° North Latitude and 107° West Longitude. County boundaries of this area are displayed. The corners of the states of Utah (UT) and Arizona (AZ) are also shown. Map from U.S. Geological Survey (1971, 1973, 1983) with river otter data from Polechla, 2002a, b; Polechla et al. 2004, and this study. Locations of pre-translocation (1973-75) river otter observation sites were positioned using the Colorado Division of Wildlife web site (http://wildlife.state.co.us/Hunting/GMUnitMaps.htm). The remainder is otter localities from the 21st century, signified by small solid stars. Observations of native river otters from 1973 to 1975 are signified by solid triangles. Open stars, inside a solid circle, represent release sites of exotic trans-located otters from 1979-1983. Survey point starts and stops (performed in 2002) are indicated with arrows.  Large solid circles represent points where otter sign was located in the present study (click for larger version)

DISCUSSION

Apparently the river otter(s) had overtaken a beaver feeding /den site, consisting of a rocky crevice or lair (holt in British English) modified with sticks. Along the entire escarpment of this large reservoir were innumerable crevices in the jumble of rocks along the escarpment, affording numerous potential den sites. Neither typical beaver bank dens nor stick lodges were observed in Navajo Reservoir from 2004 to 2007 although beaver sign was common.  In apparent response to Navajo Reservoir’s highly fluctuating water levels, gradually sloping or rocky banks, and lack of a well-defined riparian tree border; beavers modify cracks in rocks by piling sticks to create a makeshift den. Beavers are forced to be opportunistic in choice and modification of shelters and otters respond accordingly. In other parts of their range beaver, with their den and dam-building behavior, augment otter habitat (Polechla, 1987; Melquist et al., 2003). In the present case, beavers provided insulation and protection with their cut branches in the resting site/den that otters had used.

Different lines of evidence document that a persistent, widely distributed, and growing population of river otters exists in the San Juan drainages along the New Mexico/Colorado border. Observations from the present study and by other wildlife biologists, from the Bureau of Reclamation (personal communication, 5 May 2005), New Mexico Game and Fish (personal communication, 28-29 November 2007), and Colorado Division of Wildlife (CDOW) (Polechla 2002 from CDOW files), and fishermen (e.g., Dr. J. Daggett, personal communication, 2001 in Polechla et al., 2004) indicate there is a persistent, resident river otter population in the Los Pinos, Piedra, and San Juan Rivers (plus possibly adjacent rivers) of the New Mexico/Colorado border (Figure 3).

Our observations of different-age scats indicated multiple use of the same latrine site by one otter many times or more than one otter a few times. Regardless, these observations demonstrate persistence and site fidelity.
Visits to the area revealed seasonally abundant fish during spawning runs of carp and kokanee salmon (Oncorhynchus nerka) during spring, summer, and fall. Fishermen often clean the salmon they catch on rod and reel and discard the remains in the water. This common practice probably attracts otters.

Different and widely separated locations where otters have been documented in the bi-state area (Polechla, 2002a) indicate that otters are more widely distributed than previously known, and that the population is likely growing. A combination of DNA and scat samples of river otters from both sides of the New Mexico/Colorado state border (Polechla, 2002a; Polechla et al., 2004) and 2 museum specimens salvaged on the Colorado side of the drainage indicate a wide distribution in the San Juan, Los Pinos, and Piedra Rivers.

From 1973 to 1975, a combination of aquatic ecologists, a fisherman, and trappers made seven observations of river otters, their tracks, scats, and dens (Polechla 2002a from CDOW files), prior to translocating 16-24 otters (of different subspecies) from Wisconsin, Nova Scotia, and an unknown location during 1979-1983 (Polechla 2002a). These observations demonstrate that the native, southwestern river otter (L. c. sonora) (Van Zyll de Jong, 1972; Wilson and Reeder, 2005) were extant prior to translocation of other subspecies (e.g., L. c. pacifica and L. c. canadensis).

Observer fatigue may be a factor why otters have gone unreported for so long in New Mexico. For novice trackers, eager to find otter sign but not familiar with it, the likelihood of making a false positive (Type I error) is initially greater than a false negative (Type II error) (e.g., New Mexico Otter Working Group 2002). Accuracy changes with experience, however. For an experienced tracker familiar with otter sign, the likelihood of making a Type II error (error of omission) is greater than a Type I error. The error of omission is great on rugged, rocky terrain on the reservoir’s (e.g., Navajo) shore, because scrambling and climbing across large boulders along an ever-changing waterline (Polechla, 2002a) is physically and mentally exhausting for the researchers. And, because an animal as large as the rare and endangered grizzly bear (Ursus arctos horribilis) was collected as late as 1979 on the Continental Divide separating the Navajo River of the San Juan River drainage (on the west side) and the Conejos River of the Rio Grande drainage (on the east side) (Murray 1987) underscores that this bi-state area still has many wild, inaccessible reaches where humans can easily overlook the presence of a grizzly bear, much less the smaller otter.

Existing Management and Management Recommendations

Currently, the New Mexico Game and Fish Department (NMGFD) is conducting intensive beaver trapping, trapping 26 beavers in a 5.6-km stretch of the tail waters of Navajo dam (M. Wethington, pers. communication, 5 May 2005). This threatens the river otter population because trapping is being conducted with Conibear 330 traps, which are body-constricting traps, usually set under the water. This trap can kill non-target otters (Polechla 1987) within minutes. The NMGFD reported that some unidentified person(s) have already been suspected of killing otters in these tail waters (Anonymous, 2006). Beaver activities benefit other wetland wildlife populations (Melquist et al., 2003), most notably macro-invertebrates and trout (Huey and Wolfrum, 1956). In almost all cases, beaver presence should be encouraged. In areas where populations are high, several effective mitigation techniques can be used. In circumstances where beavers are cutting trees in high profile recreation areas, trees can be wrapped with wire mesh. Pond levelers can be installed where beaver dams flood roads. Where trapping beavers is necessary to reduce populations, we recommend, with appropriate permits, live-trapping (e.g., Hancock live traps) and relocating to other parts of the same drainage. Where beaver relocation areas are not available and body-gripping kill-type (e.g. Conibear 330) traps will be used, to reduce non-target otter catches, the trap should be modified (Figure 4).

Figure 4 . Modifications to a body-gripping Conibear 330 style trap to reduce chance of catching a river otter (Lontra canadensis) (From International Association of Fish and Wildlife Agencies 2005, http://www.in.gov/dnr/fishwild/publications/otter/raccoon.htm, and Utah Division of Wildlife Resources 2007-2008). (click for larger version)

Each trap comes from the factory with a single trigger in the middle of the trap with the trigger wires forming a “V” or “T” (Figure 4a, b). First, triggers can be modified by: 1) moving the entire mechanism to the side (Fig. 4c), 2) bending the trigger wires so that they are; a) both parallel and up (Fig. 4c), b) both at right angles (Fig. 4d), or c) one wire up and one at a right angle (Fig. 4e), 3) cutting both trigger wires to 10.2-12.7 cm in length (Fig. 4f), or 4) adding another trigger mechanism and positioning them one on each side (Fig. 4g) (International Association of Fish and Wildlife Agencies, 2005, http://www.in.gov/dnr/fishwild/publications/otter/raccoon.htm, Utah Division of Wildlife Resources 2007-2008).  Second, the trap tension can be adjusted by installing a new “special tensioning trigger” (http://www.in.gov/dnr/fishwild/publications/otter/raccoon.htm). These modifications are supposed to work, because on average beavers are larger and less agile than otters and when they attempt to pass through the open trap, they are more likely to bump the trigger and close the trap than an otter.

Finally, other tributaries rivers within the Colorado River of New Mexico, Colorado, and neighboring states need to be surveyed.

ACKNOWLEDGMENTS - We would like to thank the following individuals and institutions for making this study possible logistically and financially: Shannon Heady, Steve Mueller, and Erica Otero of the New Mexico State Parks, plus Pamela Bingham and Paul Lauderback of the Tulsa Zoo and International Union for the Conservation of Nature and Natural Resource’s Otter Specialist Group. On a previous study (Polechla, 2002a), the Colorado Division of Wildlife provided monetary and logistical support, plus the Southern Ute tribe also allowed access to their lands by granting permits. The first author’s parents, Paul J. Polechla Sr. and Virginia B. Polechla, instilled in first author a joy for nature. This publication is dedicated to the late Wilbur “Strait” Johnson who introduced the first author to the world of the otter and Dr. John A. Sealander who inspired the first author to excel scientifically. Wayne Melquist read the manuscript and provided constructive criticism. Thanks to everyone for their encouragement.

REFERENCES

Anonymous (2006). Feasibility study: potential for restoration of river otters in New Mexico. New Mexico Game and Fish Department, Santa Fe, NM. Unpublished Report. 59 pp.
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Résumé : Essor et Situation d’une Population Stable de Loutre de Riviere (Lontra canadensis) au Nouveau Mexique
Avant 2004, certains biologistes prétendaient que les loutres de rivière (Lontra canadensis) avaient disparu du Nouveau Mexique. En novembre 2004, la première preuve de présence physique de la loutre de rivière a été trouvée entre les canyons de Grassy et Albino dans le bras de Los Pinos de la retenue Navajo située dans le département de San Juan. Suite à l’observation de loutres de rivière, leur répartition, leur voie, leur abri ou catiche (située dans un escarpement rocheux et empruntée aux castors) dans le canyon de La Jara en été 2007, la connaissance de cette espèce au Nouveau Mexique s’est étendue à une deuxième région (Rio Arriba) et à un deuxième cours d’eau (San Juan) de l’Etat. Nous avons également remarqué la présence d’une population stable de loutre de rivière dans différentes localités en ce début du 21ième siècle. Suite à ces dernières observations antérieures à l’introduction d’autres sous espèces de loutres de rivière, nous nous sommes posé la question de savoir si ces observations récentes appartiennent à ces sous espèces exotiques introduites, à l’espèce indigène L.c. sonora ou à un hybride des 2. D’autres espèces commensales des milieux humides, animaux et plantes liés aux rochers ont été observés. Des recommandations en matière de gestion sont proposées afin de protéger cette population de loutre de toute capture accidentelle liée à l’élimination du castor.
Revenez au dessus

Resumen:Desarrollo y Situación de una Población Estable de Nutria de Río (Lontra canadensis) en Nuevo México
Antes del año 2004. algunos biólogos sostenían que la nutria de río (Lontra canadensis) estaba extirpada del estado de Nueva México, Estado Unidos. En noviembre del año 2004, la primera evidencia física en 50 años de la presencia de nutria de río en Nueva México fue encontrada entre los cañones Grassy y Albino en la rama Los Pinos de la reserve navaja en el condado San Juan. Con la observación de nutrias de río y sus excrementos, huellas, y madrigueras (en escarpados rocosos y usurpadas a castores) en el cañon La Jara durante el verano del año 2007, el rango conocido de esta especies en Nueva México se ha extendido a un segundo condado (Río Arriba) y un segundo río (San Juan). Además ofrecemos evidencias de la persistencia de una población de esta especie en multiples localidades y fechas del principio del siglo XXI. Con avistajes previos a la translocación de otra subespecies de nutria de río, nosotros questionamos si las recientes observaciones corresponden a la translocada exotica subespecie, a la subespecies nativa L. c. sonora , o a un híbrido entre las dos. Otros humedales, animals y plantas viviendo entre rocas son listados. Proveemos recomendaciones de manejo para proteger esta población del trampeo accidental durante la remoción de castores.
Vuelva a la tapa

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