Lontra Canadensis Research Articles

Summer Habitat Preferences and Activity Patterns of River Otters In Grand Teton National Park

I studied the natural history of river otters. (Lontra canadensis) during the summers of 1982-1986 and 1995-1997 in Grand Teton National Park, Wyoming. Habitat preferences were analyzed by tallying sightings on 5 types of habitat along 16 km of the Snake River. Otters were seen on all 5 habitat types and exhibited a strong preference for the logjam/beaver lodge category. Beavers and otters sometimes occupied a lodge simultaneously. I recorded daytime activity directly in 1982 and noted a large peak in mid-morning and a small one in late afternoon. To obtain information indirectly on round-the-clock activity I employed 6 modified camera monitors activated by treadle-switches at frequently used sites. Pooled records for 3 summers showed almost two and a half times higher activity by day than by night, a finding opposite of what was expected. The hypothesis I suggest is that diurnal activity exceeds nocturnal activity because of the habituation of otters to humans over a half century's tradition of frequent exposure and non-harassment in the national park. In the summers of 1982-1986 and 1995-1997 I made a study of the natural history of river otters (Lontra canadensis), in Grand Teton National Park under auspices of the University of Wyoming - National Park Service Research Center. Occasional observations were made along the Snake River from Flagg Ranch near the north boundary of the park to the north end of Jackson Lake and from Pacific Creek to Deadman's Bar. However, the 3 km stretch of river from just below Jackson Lake Dam to the Oxbow was the site of most intensive study. (See Fig. 1)

NATURAL EXPOSURE OF COASTAL RIVER OTTERS TO MERCURY: RELATION TO AGE, DIET, AND SURVIVAL

We evaluated effects of location (i.e., Jackpot Bay, a naturally contaminated site, and Herring Bay, reference site), diet as determined by stable isotopes, and age on mercury concentrations in individual river otters (Lontra canadensis) from Prince William Sound, Alaska, USA. We also investigated the effects of mercury accumulation on survival of river otters from these two locations. Our results indicated that mercury concentrations in fishes from Jackpot Bay were significantly higher than those in fishes from Herring Bay and those in pelagic fishes. In addition, a predominant intertidal fish diet in both areas influenced the accumulation of mercury concentrations in otters. Concentrations of mercury in fur of river otters from Jackpot Bay were significantly higher than those of animals from Herring Bay. Nonetheless, we did not detect significant differences in survival between otters inhabiting the two areas, suggesting that this natural contamination was not high enough to impair survival. Our ability to investigate the effects of various factors such as location, diet composition, and age on mercury accumulation and subsequent survival of individuals offers an example for a link between individual-based captive studies and population-level field investigations.

Spatial Variation in Mercury Concentrations in Wild Mink and River Otter Carcasses from the James Bay Territory, Québec, Canada

Mercury concentrations were analyzed in different organs/tissues of wild minks (Mustela vison) and river otters (Lutra canadensis) trapped during two seasons in the James Bay territory (49 degrees N to 55 degrees N, Québec, Canada). In 1993-94, mean total Hg concentration (microg/g, wet weight) in 39 wild mink and 12 river otter carcasses was greatest in fur/hair samples (30.1 and 20.7 microg/g, respectively) and least in brain samples (0.96 and 0.8 microg/g, respectively) with liver, kidney, and muscle samples showing intermediate values. Pooling data from the 1993-94 and 1994-95 trapping seasons revealed mean (SD) liver total Hg concentrations of 3.71 microg/g (3.91) in 316 wild mink carcasses and 4.05 microg/g (3.41) in 153 river otter carcasses. Log liver total Hg concentration increased with age in wild mink but not in river otter. Log liver total Hg concentration in each species was greatest in areas with moraine deposits and least in areas with rich clay deposits, but the effect of soil deposits could be confounded by uneven deposition of anthropogenic Hg. Controlling for type of soil deposits, log liver total Hg concentration decreased with increasing distance from local industrial centers in each species but varied little with changes in distance from hydroelectric reservoirs. In a subsample of carcasses from the moraine sector, log liver total Hg concentration was higher in wild mink than in river otter. Spatial variation in log liver total Hg concentration in relation to soil deposit type and proximity to industrial centers suggests that the two wild furbearer species could be useful indicators of environmental contamination.

Hematological and biochemical reference intervals for wild caught Eurasian otter from Spain.

Hematologic and serum chemistry reference intervals were determined from 33 wild caught Eurasian otters (Lutra lutra lutra) between November 1995 and May 1998 during a reintroduction project. Blood was obtained by jugular venipuncture after administration of ketamine and medetomidine. The mean, standard deviation, and range for 19 hematology parameters and 28 serum chemistry values are presented. There were no significant differences between sexes in most analytes. The results are in agreement with those reported previously for Eurasian otters with the exception of higher leukocyte and neutrophil counts, lower eosinophil and lymphocyte counts and higher activities for aspartate aminotransferase and creatine kinase. The Eurasian otters have lower erythrocyte counts but higher mean corpuscular volume and mean corpuscular hemoglobin values than the river otter (Lutra canadensis) in North America.

CLINICAL ANATOMY OF THE NORTH AMERICAN RIVER OTTER (LONTRA CANADENSIS)

Published anatomic studies of North American river otters (Lontra canadensis) include only comparative reviews of single anatomic systems, but this paper includes multiple clinically relevant anatomic features. Both captive and free-ranging North American river otters were studied by gross dissection of nine specimens, radiography of 18 live otters, and physical examination of 170 otters. Body fat in North American river otters is stored primarily subcutaneously at the base of the tail and in the axillae, so lack of visceral detail on abdominal radiographs is due to a lack of coelomic fat. The heart and great vessels are oriented as in the dog. The cardiac radiographic silhouette measures three intercostal spaces laterally between the fourth and sixth ribs and 4-4.5 intercostal spaces between the seventh through 11th ribs on the ventrodorsal projection. Subjective estimation of age by evaluation of tooth wear is confirmed by histologic examination of cementum annuli. Structures of the feet were imaged by high-resolution mammographic technique. The adult thymus was prominent, but the gland was small in the one juvenile animal studied. The spleen was unexpectedly large but consistent with findings in European otters (Lutra lutra). As in other otters and mammals, kidneys are reniculated.

Infectious and parasitic diseases and contaminant-related problems of North American river otters (Lontra canadensis): a review.

The aquatic North American river otter (Lontra canadensis), a charismatic nonendangered mustelid, presently occupies a greatly reduced range. The species is common in zoos and has economic value as a furbearer. At least 17 states and one Canadian province have undertaken recent reintroduction programs. Nevertheless, little has been published on nonparasitic diseases of river otters, and little is known of the clinical significance of most of their parasitic infections. Records of environmental contaminant-related diseases and traumatic injuries in free-ranging North American river otters are also rare. This paper reviews present knowledge of North American river otter diseases, especially those with the greatest potential for impacting reintroduction programs.

Hematology and serum biochemistry parameters of North American river otters (Lontra canadensis).

Blood samples were obtained from 155 North American river otters (Lontra canadensis; 94 adult males, 38 adult females, 10 juvenile males, and 13 juvenile females) to establish baseline hematology and from 50 adult river otters (40 males and 10 females) for baseline serum biochemistry parameters for the species. The otters were livetrapped from eastern North Carolina (USA) during a 4-yr period. Data for 14 routine hematologic parameters and 22 serum chemistry assays showed significant differences in total leukocyte count and absolute neutrophil and monocyte numbers for adults versus juveniles, red blood cell counts and hemoglobin between adult and juvenile males, and calcium and alkaline phosphatase values for adult males between years of the study and an increase in leukocyte counts and absolute neutrophils with increased degree of trap injury sustained.

Profiles of Fecal Porphyrins in River Otters Following the Exxon Valdez Oil Spill

Median levels of Coproporphyrin III (Copro III) in fecal samples of river otters ( Lontra canadensis) collected from an oiled area in Prince William Sound, Alaska, USA, during 1990 were significantly higher than in samples collected from the same oiled area during 1996 ( p=0.011, one way analysis of variance), a nonoiled reference area in Prince William Sound during 1996 ( p=0.002) and a reference area in southeast Alaska during 1998 ( p=0.004). An overall test of significance that combined probabilities from the statistical analysis of this porphyrin study with those from other biomarker studies revealed a significant difference in physiological response of river otters between oiled and nonoiled areas of the Sound for 1990 ( p < 0.01). We demonstrated that changes in levels of fecal porphyrins may serve as a biomarker that may contribute to a health assessment of wild river otters.

Mercury levels in tissues of otters from Ontario, Canada: Variation with age, sex, and location

AbstractConcentrations of mercury in hair, brain, and liver tissues of river otter (Lutra canadensis) from several townships in Ontario, Canada, were determined. Levels of Hg in these tissues were highly intercorrelated but differed from tissue to tissue. The highest concentration was in hair, followed by liver and brain. The high correlation between Hg in hair and brain, as well as the ease and precision of Hg determinations on hair, demonstrate that Hg in hair holds considerable promise for monitoring the Hg in otters. Within the sampled otters, Hg varied with respect to age. The Hg concentrations increased over the first two to three years of age, remained stable over the next two to three years of age, and then declined in the remaining age‐groups. Mean age of otters in townships with high‐Hg concentrations was about half the mean age of otters in low‐Hg townships. In areas where mercury levels are high, otters may have reduced survivorship because of Hg‐induced stress on their health.

Distribution of Inorganic and Methylmercury among Tissues in Mink (Mustela vison) and Otter (Lutra canadensis)

Total mercury and methylmercury concentrations were measured in brain, kidney, liver, and fur from several mink and otter collected in south-central Ontario. There was a large range in concentrations of both total and methylmercury. The percentage of the total mercury present as methylmercury varied among the various tissues; however, the percentage mercury found as the methyl form was relatively constant within a given tissue for all tissues in mink but highly variable in otter. For both species the highest percentage of methylmercury was found in the brain, whereas the lowest percentage was found in the kidneys for the otter and in the fur for the mink. Comparison of mercury concentrations in otter reveals that animals with higher body fat have higher mercury concentrations. Measurements of mercury in fur can be used as a general indicator of internal tissue concentrations.

Ingestion of crude oil: effects on digesta retention times and nutrient uptake in captive river otters.

Studies following the Exxon Valdez oil spill in Prince William Sound, Alaska indicated that river otters (Lontra canadensis) from oiled regions displayed symptoms of degraded health, including reduced body weight. We examined the fate of ingested oil in the digestive tract and its effects on gut function in captive river otters. Fifteen wild-caught males were assigned to three groups, two of which were given weathered crude oil in food (i.e., control, 5 ppm day(-1), and 50 ppm day(-1)) under controlled conditions at the Alaska Sealife Center. Using glass beads as non-specific digesta markers and stable isotope analysis, we determined the effects of ingested oil on retention time and nutrient uptake. Our data indicated that oil ingestion reduced marker retention time when we controlled for activity and meal size. Fecal isotope ratios suggested that absorption of lipids in the oiled otters might have been affected by reduced retention time of food. In addition, a dilution model indicated that as much as 80% of ingested oil was not absorbed in high-dose animals. Thus, while the ingestion of large quantities of weathered crude oil appears to reduce absorption of oil hydrocarbons and may alleviate systemic effects, it may concurrently affect body condition by impacting digestive function.

Comparison of Spectrofluorometric and HPLC Methods for the Characterization of Fecal Porphyrins in River Otters

A spectrofluorometric method (B. Grandchamp et al., 1980, Biochem. Biophys. Acta 629, 577–586) developed for the determination of amounts of uroporphyrin I (Uro I), coproporphyrin III (Copro III), and protoporphyrin IX (Proto IX) in skin fibroblasts was compared with a high-performance liquid chromatography (HPLC) method for the analysis of porphyrins in fecal samples of river otters (Lutra canadensis). Heptacarboxylate porphyrin I and coproporphyrin I, two porphyrins determined to be critical in defining the porphyrin profile in fecal samples of river otters with the HPLC method, contributed substantially to the calculation of the concentrations of Uro I and Copro III, respectively, in standard solutions of porphyrins with the spectrofluorometric method. Fluorescent components of the fecal matrix complicated the determination of the concentrations of Uro I, Copro III, and Proto IX with the spectrofluorometric method and resulted in erroneous values for the concentrations of these porphyrins compared with values determined with the HPLC method. These results indicate that the complexity of the sample, particularly with regard to the potential presence of interfering fluorescent compounds, as well as porphyrins additional to Uro I, Copro III, and Proto IX, should be considered prior to the application of the spectrofluorometric method. An alternative HPLC method developed for the rapid characterization of porphyrin profiles in fecal samples of river otters is described.

Effects of oiling on exercise physiology and diving behavior of river otters: a captive study

Following the Exxon Valdez oil spill (EVOS), river otters (Lontra canadensis) on oiled shores had lower body mass, selected different habitat characters, and had larger home ranges and less diverse diets than did otters living in non-oiled areas. We explored the possibility that these changes were due to the effect of crude oil contamination on physiological and behavioral processes in otters. Fifteen otters were exposed to two levels of oil contamination under captive controlled conditions at the Alaska Sealife Center in Seward, Alaska, U.S.A. We collected blood samples for hematological examinations and measured oxygen consumption in otters exercising on a motorized treadmill. We also observed diving and foraging behavior of otters offered live fish. Otters exposed to oil became anemic relative to controls. While oxygen consumption of resting river otters was not related to changes in hemoglobin concentration, exercising river otters with decreased hemoglobin levels displayed significantly increased oxygen consumption (P = 0.042). Oiled otters also performed fewer dives when chasing fish (P = 0.04), representing a potential decrease of 64% in the capture rate of prey. Our data strongly support the hypothesis that changes in prey types and home-range utilization by oiled river otters following EVOS were influenced by hematological changes, associated increases in energetic costs, and reduced diving ability.

Serologic survey of selected viral agents in recently captured wild North American river otters (Lontra canadensis).

Blood samples were collected from 64 wild North American river otters (Lontra [Lutra] canadensis) from northern and eastern New York State and analyzed for serologic evidence of exposure to selected viral agents during a 1995 1996 translocation program. No clinical signs of disease nor lesions suggestive of prior viral exposure were seen. Titers were detected for antibodies against canine distemper virus, canine herpesvirus-1, and canine parvovirus-2 but not for antibodies against canine adenovirus-1, canine coronavirus, canine parainfluenza virus, rabies virus, feline herpesvirus-1, feline calicivirus, or feline coronavirus. This is the first report of titers for antibodies against canine herpesvirus-1 in North American river otters, and it suggests a low prevalence of antibody titers against most canine viruses in otter populations in northern and eastern New York. Confounding variables in this study could include exposure to domestic dogs associated with the project, prolonged time spent in captivity, and concurrent bacterial or parasitic infection. Stress-associated humoral immune suppression could have altered serologic profiles, especially in otters exposed to dogs after trapping but before venipuncture.

Exertional myopathy in translocated river otters from New York.

Lesions consistent with exertional myopathy (EM) were documented postmortem in four North American river otters (Lutra canadensis) during translocation for a population restoration project. Clinical signs in these otters included depression, anorexia and shock. Gross lesions in one otter included locally extensive linear, pale areas within the subscapularis, rectus abdominis, quadriceps, and dorsal laryngeal muscles. Microscopic lesions were characterized by acute to subacute myofiber necrosis of varying severity, and occurred in a variety of skeletal muscles as well as cardiac muscle in one otter. Based on these observations, we conducted a retrospective review of records of otters which experienced similar capture, transfer, and holding protocols between 1995 and 1997, but with a successful outcome (n = 69). Significant elevations in serum aspartate aminotransferase (AST) and creatine kinase (CK) were observed in 19 (28%) of the otters, but may have been higher due to delayed sample collection from some otters. However, none of the otters with elevated enzymes exhibited clinical signs suggestive of EM. These findings indicate that river otters may develop EM when translocated, but many cases may be mild or clinically inapparent.

Ecological risk assessment in a large river-reservoir: 4. Piscivorous wildlife

Over 50 years of operations of facilities on the Oak Ridge Reservation (ORR), Tennessee, has resulted in the release of contaminants into the water, sediment, and biota of the Clinch River and Poplar Creek, downstream of the ORR. An iterative, weight-of-evidence approach was employed to assess risks these contaminants present to four piscivorous wildlife species (osprey [Pandion haliaetus], great blue heron [Ardea herodias], mink [Mustela vison], and river otter [Lutra canadensis]) in the Clinch River/Poplar Creek (CR/PC) watershed. Available data consisted of literature-derived NOAELs and LOAELs, field surveys, and toxicity tests. Contaminants of potential ecological concern (COPECs) were identified by comparing point estimates of exposure to NOAELs and included mercury and PCBs. Exposure to COPECs was reestimated using Monte Carlo methods, first at individual locations, then over ecologically relevant spatial scales. These exposure distributions were compared to LOAELs. Estimated exposure for mink was not sufficient to present a risk from any COPEC. Mercury and PCBs presented a significant risk to river otter at one location each. Exposure of osprey and great blue herons to mercury represented a significant risk at one and two locations, respectively. Field surveys of heron rookeries and osprey nests indicated no adverse effects on reproduction. Mink fed fish from the Clinch River displayed reduced reproduction only in the most contaminated of five toxicity test diets; this reduction was not statistically significant, however. The maximum mercury and PCB exposures estimated for mink along the Clinch River were significantly lower than the toxicity test exposures associated with adverse effects The weight of evidence indicates that contaminants from the ORR do not present a risk to mink, great blue heron, or osprey along the Clinch River; river otter, however, may be at risk from mercury and PCBs.

Reproductive and morphological condition of wild mink (Mustela vison) and river otters (Lutra canadensis) in relation to chlorinated hydrocarbon contamination.

We assessed chlorinated hydrocarbon contamination of mink and river otters on the Columbia and Fraser River systems of northwestern North America, in relation to morphological measures of condition. We obtained carcasses of mink and river otters from commercial trappers during the winters 1994-1995 and 1995-1996. Necropsies included evaluation of the following biological parameters: sex, body mass and length, age, thymus, heart, liver, lung, spleen, pancreas, kidney, gonad, omentum, adrenal gland and baculum masses, baculum length, and stomach contents. Livers were analyzed, individually or in pools, for residues of organochlorine (OC) pesticides, polychlorinated biphenyls (PCBs), dibenzo-p-dioxins, and dibenzofurans. Contaminant levels were relatively low compared to those documented in other North American populations, although they ranged higher than those detected during an earlier survey (1990-1992) of these regional populations. Body condition varied slightly among collection regions, but showed no relationship with contaminant burden. Mink from the upper Fraser River had less fat stores and also had some of the lowest OC contamination levels observed. Similarly, a few individuals with enlarged livers and kidneys had low contaminant levels. Although a few individual animals with gross abnormalities of reproductive systems did not show high levels of contamination, there was a significant negative correlation between total PCB concentrations (as Aroclor 1260) and baculum length in juvenile mink (r = 0.707; p = 0.033; n = 8). The association of juvenile baculum length with eventual reproductive success is unknown, but further characterization of reproductive organ morphology and relationship to contaminants should be undertaken in a larger subset of these populations.

Reproductive and Morphological Condition of Wild Mink (Mustela vison) and River Otters (Lutra canadensis) in Relation to Chlorinated Hydrocarbon Contamination

We assessed chlorinated hydrocarbon contamination of mink and river otters on the Columbia and Fraser River systems of northwestern North America, in relation to morphological measures of condition. We obtained carcasses of mink and river otters from commercial trappers during the winters 1994-1995 and 1995-1996. Necropsies included evaluation of the following biological parameters: sex, body mass and length, age, thymus, heart, liver, lung, spleen, pancreas, kidney, gonad, omentum, adrenal gland and baculum masses, baculum length, and stomach contents. Livers were analyzed, individually or in pools, for residues of organochlorine (OC) pesticides, polychlorinated biphenyls (PCBs), dibenzo-p-dioxins, and dibenzofurans. Contaminant levels were relatively low compared to those documented in other North American populations, although they ranged higher than those detected during an earlier survey (1990-1992) of these regional populations. Body condition varied slightly among collection regions, but showed no relationship with contaminant burden. Mink from the upper Fraser River had less fat stores and also had some of the lowest OC contamination levels observed. Similarly, a few individuals with enlarged livers and kidneys had low contaminant levels. Although a few individual animals with gross abnormalities of reproductive systems did not show high levels of contamination, there was a significant negative correlation between total PCB concentrations (as Aroclor 1260) and baculum length in juvenile mink (r = 0.707; p = 0.033; n = 8). The association of juvenile baculum length with eventual reproductive success is unknown, but further characterization of reproductive organ morphology and relationship to contaminants should be undertaken in a larger subset of these populations.

Butyltin compounds in river otters (Lutra canadensis) from the northwestern United States.

Butyltin compounds, including mono-, di-, and tributyltin (MBT, DBT, and TBT) were measured in livers of 40 adult river otters (Lutra canadensis) collected from rivers and coastal bays in Washington and Oregon, USA. Butyltins were found in all the river otters, at a concentration range of 8.5-2,610 ng/g, WW. The greatest concentration of total butyltins of 2,610 ng/g, WW, was found in a river otter collected in Puget Sound from Fort Ward, Washington. River otters collected near areas with major shipping activities, such as the Puget Sound, contained significantly greater concentrations (geometric mean: 367 ng/g, WW) of butyltins than those from rivers. Among butyltin compounds, MBT and DBT predominated in livers. The concentrations of butyltins in river otters ranged from comparable (Puget Sound) to less (rivers) than what was found in coastal cetaceans.

Chlorinated hydrocarbons in livers of American mink (Mustela vison) and river otter (Lutra canadensis) from the Columbia and Fraser River Basins, 1990-1992

We investigated chlorinated hydrocarbon contaminants in aquatic mustelid species on the Fraser and Columbia Rivers of northwestern North America. Carcasses of river otter (Lutra canadensis) (N=24) and mink (Mustela vison) (N=34) were obtained from commercial trappers during the winters of 1990–91 and 1991–92. Pooled liver samples were analyzed for organochlorine pesticides, polychlorinated biphenyls (PCBs), including non-ortho congeners, polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). Most samples contained detectable concentrations of DDE, PCBs, although there was substantial variability in patterns and trends among neighboring samples. Concentrations of DDE were in some mink and several otter samples from the lower Columbia River elevated (to 4700 μg/kg wet weight); excluding one mink sample from the Wenatchee area, mean DDE levels generally decreased between 1978–79 and 1990–92. PCBs were present in all samples. PCB concentrations in otter livers collected from the lower Columbia were ten-fold lower than measured a decade previously; nevertheless, a sample taken near Portland had a mean concentration of 1500 μg/kg, within a range of concentrations associated with reproductive effects in captive mink. Concentrations of 2,3,7,8-TCDD and TCDF were generally below detection limits, except for one otter collected near a pulp mill at Castlegar, on the upper Columbia, with 11 ng TCDD/kg in liver. Elevated concentrations of higher chlorinated PCDD/Fs, probably resulting from use of chlorophenolic wood preservatives, were found in both species; one otter sample from the lower Columbia had 2200 ng OCDD/kg. International TCDD toxic equivalent levels in mink (31 ng/kg) and otter (93 ng/kg) from the lower Columbia River approached toxicity thresholds for effects on reproduction in ranch mink.