Otters and Anglers Can Share the Stream! The Role of Social Science in Dissuading Negative Messaging About Reintroduced Predators

The reintroduction of mammalian predators often has been met with controversy among citizens near reintroduction sites primarily because of concern for predation of livestock, pets, and game species. The river otter (Lontra canadensis) is an example of a predator widely reintroduced in the United States that has in some cases been negatively depicted in the media because of its predatory habits (i.e., fish eating). The reintroduction of river otters in Missouri, Ohio, Kentucky, and Illinois was followed by negative media messages pertaining to otters preying on fish. In contrast, the reintroduction of river otters in Pennsylvania (PA) was accompanied by positive media portrayals and overwhelming public support. This opinion piece reviews factors that likely contributed to public acceptance of river otter reintroduction in PA, emphasizing the importance of applying social science theories and methodologies as a basis for determining and accurately depicting public attitudes toward the reintroduction of mammalian predators.     

Evaluation of injury severity and hematologic and plasma biochemistry values for recently captured North American river otters (Lontra canadensis).

As part of a reintroduction program, blood samples from free-ranging, recently captured Nearctic river otters (Lontra canadensis) in eastern New York state were collected and analyzed to determine baseline hematology and plasma biochemistry values for the source population, and to determine whether these values were significant predictors of trap-injury status. Based on physical exam, each otter was classified as uninjured, moderately injured, or severely injured. Clinical pathology parameters were compared across sex, age class, and injury classification. The increase in likelihood of a change in each parameter in injured versus uninjured otters was determined using logistic regression. Baseline hematology and plasma biochemistry values did not differ significantly from published values for captive otters in zoos or other reintroduction programs. Plasma aspartate aminotransferase levels increased as time from capture to venipuncture decreased. Some otters in this study showed clinical signs consistent with exertional myopathy, possibly altering our calculation of baseline values. Our results suggest that the hematology and plasma biochemistry values obtained in this recently captured population of otters are generally not good predictors of capture-related injury. This could be due to disease processes that are not readily visible upon physical examination or because changes in these values may be associated with factors independent of capture-related injury.     

Surgical technique for intra-abdominal radiotransmitter placement in North American river otters (Lontra canadensis).

Twenty-two free-ranging North American river otters (Lontra canadensis) from northern and eastern New York were captured and surgically implanted with radiotransmitters as part of a relocation project. The surgical technique involved an incision in the paralumbar fossa and transection through the abdominal musculature to introduce a radiotransmitter into the abdominal cavity. Two complications were encountered. Excessive hemorrhage occurred during one procedure. The otter was treated for blood loss with fluids, and it recovered uneventfully. Surgical incision infection occurred in a second animal. The otter was treated with metronidazole and enrofloxacin, and the wound was cleaned daily with chlorhexidine. The otter recovered uneventfully. Otters were released in western New York state. Postrelease monitoring via radiotelemetry revealed that the otters became established in their new ranges. The intra-abdominal implants did not affect their survival or reproductive potential.     

Serologic evaluation of vaccinated American river otters

The Oklahoma Department of Wildlife Conservation acquired 20 American river otters (Lutra canadensis) between 1984 and 1985 for reintroduction into Oklahoma waterways. In 1985, 10 otters were evaluated for serum antibody titers after vaccination with canine distemper virus, canine adenovirus type 2, canine parvovirus (CPV), feline panleukopenia virus (FPV), feline rhinotracheitis virus (FRV), and feline calicivirus. Prevaccination serum-virus neutralization (SVN) antibody to feline rhinotracheitis virus was found in 2 otters and to feline calicivirus in 1 otter. Using an indirect fluorescent antibody (IFA) assay, prevaccination antibody to CPV and FPV was found in 2 otters. A significant increase in SVN antibody titers was found after vaccination of otters with canine adenovirus type 2 (6 of 8 animals) and feline calicivirus (1 of 8 animals). One of 8 otters developed significant antibody titers to CPV and FPV, as measured by IFA assay. Otters did not develop SVN antibody titers to canine distemper virus after vaccination. Antigens of feline leukemia virus, using ELISA, or antibodies to feline infectious peritonitis, using IFA assay, were not found in the 20 otters.     

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.     

Clinical evaluation and prerelease management of American river otters in the second year of a reintroduction study

In the first year (1984) of a reintroduction study, 10 American river otters (Lutra canadensis) from Louisiana were transported to Oklahoma, held for 5 days for clinical evaluation, surgical implantation with intra-abdominal radiotelemetry devices, and then released in Oklahoma. Four of 10 otters released died within 32 days. Clinical evaluation indicated that respiratory tract disease, bacterial and parasitic infections, and inanition may have contributed to the death of these otters. In the second year (1985) of the study, an exotic feline diet was fed, and the holding period for 10 otters was increased to provide time for evaluation and treatment before surgery, postsurgical acclimation to Oklahoma, and reevaluation before release. Although the initial clinical findings on otters in the second year were similar to those found in the first year, otter body weights increased, and the prevalence and severity of clinical abnormalities decreased with treatment during the second-year holding period. Three of 10 second-year otters died during the holding period, and contributing causes of death were determined to be: trauma (hepatic hematoma), inanition, renal disease, pneumonia, salmonellosis (Salmonella anatum), and a retropharyngeal abscess (Klebsiella pneumoniae). Seven healthy otters were reintroduced into Oklahoma in 1985, and postrelease deaths were not experienced.     

Mortality associated with melarsomine dihydrochloride administration in two North American river otters (Lontra canadensis) and a red panda (Ailurus fulgens fulgens).

Two adult North American river otters (Lontra canadensis) and an adult red panda (Ailurus fulgens fulgens) at three separate institutions died within 22 hr after receiving single 2.5- to 2.7-mg/kg doses of melarsomine dihydrochloride administered in the epaxial musculature as a treatment for filarid nematodes. One otter had a suspected Dirofilaria immitis infection, the other had a confirmed D. lutrae infection, and the red panda had a confirmed Dirofilaria sp. infection, presumably with D. immitis. Postmortem examinations revealed similar gross lesions, although they were less severe in the red panda. The trachea and primary bronchi contained abundant foamy fluid, the lungs were mottled with areas of consolidation, and the pulmonary parenchyma exuded abundant fluid at the cut section. Histologic evaluation revealed acute pulmonary edema, which resulted in respiratory failure and death. There may have been direct pulmonary cellular toxicity of melarsomine dihydrochloride or a severe systemic anaphylactic reaction to antigens released after parasite death. An idiosyncratic drug reaction or a low therapeutic index of melarsomine probably caused the death of the three individuals. Melarsomine dihydrochloride use should be avoided in North American river otters and red pandas.     

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.     

Pulmonary silicosis in three North American river otters (Lutra canadensis).

Three adult female North American river otters (Lutra canadensis) demonstrated severe anesthetic complications shortly after being immobilized for dental procedures. Two of the animals died shortly after anesthesia, and the third otter died 2 mo after immobilization. All three animals were diagnosed with pulmonary silicosis on the basis of histopathology, polarized light microscopy, and mass spectrometry. One animal also had primary pulmonary bronchoalveolar carcinoma. Significant concurrent disease was not found in other organs. Analysis of the lung tissue by laser microbe mass spectrometry confirmed the presence of an aluminum silicate in the lung tissue associated with insulation material used in nest box construction.     

Measurement of serum immunoglobulin concentration in killer whales and sea otters by radial immunodiffusion

Killer whales and sea otters maintained in captivity are the subjects of routine health monitoring programs, and interest in immunologic studies in sea otters has been rising recently in response to potential impacts from infectious disease and environmental pollution on the threatened southern sea otter population. Development of species-specific reagents for immunologic studies in these two marine mammals is currently in its infancy. In this study, killer whale and sea otter immunoglobulin-specific polyclonal antibodies were generated, and used to develop tests for serum Ig concentration in the killer whale (Orcinus orca) and the southern (Enhydra lutris nereis) and northern sea otter (Enhydra lutris lutris). Killer whale serum IgG was purified using caprylic acid/ammonium sulfate precipitation. Sea otter plasma IgG was purified using protein-A-agarose. Polyclonal anti-Ig antisera were produced in rabbits, and specificity confirmed by immunoelectrophoresis. Radial immunodiffusion was used to measure Ig concentration in serum or plasma samples derived from 21 captive killer whales, 18 wild and 4 captive southern sea otters and 15 wild and 4 captive northern sea otters grouped by age. Mean killer whale serum Ig concentration (+/-95% confidence interval) ranged from 15.04 +/- 3.97 g/l for animals aged 0-5 years to 26.65 +/- 9.8 g/l for animals aged >10 years. Mean sea otter serum Ig concentration (+/-95% confidence interval) ranged from 28.39 +/- 11.00 g/l for southern sub-adults to 32.76 +/- 11.58 g/l for southern adults. No significant difference in serum Ig concentration was found between southern and northern sea otters. Serum Ig concentrations in two northern sea otter pups were low compared to those of adult sea otters. The two serum Ig quantitation assays produced were highly specific and reproducible and will be useful additions to the limited number of tests available for immune function in these marine mammal species.     

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.     

Reintroduction of the Eurasian otter (Lutra lutra) in northeastern Spain: trapping, handling, and medical management.

In 1993 a reintroduction project for the Eurasian otter (Lutra lutra) was initiated in northeastern Spain (Girona, Catalonia) to restore extirpated populations. Between 1996 and 2000, 43 otters were captured from southwestern and northern Spain and from Portugal with modified foot-hold traps and transported to Barcelona Zoo. Lesions produced by capture were classified into four categories of increasing severity. Thirty four (79%) animals had category I, three (7%) had category II, five (12%) had category III, and only one (2%) had category IV injuries. During captivity five (11%) animals died, including one from a precapture problem. Radiotransmitter devices were implanted i.p. into 36 otters to monitor postrelease movement and survival. At least three radio-implanted otters have bred successfully in Girona province, Catalonia, after release in that area.     

Surgical implantation of radiotelemetry devices in American river otters

The Oklahoma Department of Wildlife Conservation elected to investigate the feasibility of reintroducing American river otters (Lutra canadensis) into Oklahoma waterways. Intra-abdominal radiotelemetry devices were selected to monitor otter movements following release. For implantation of those devices, the anesthetic regimen included a mixture of ketamine HCl, xylazine, and acepromazine maleate given intramuscularly followed by delivery of isoflurane through precision vaporizers. A ventral midline approach and adherent surgical barrier drapes facilitated aseptic placement of the devices, with minimal tissue damage and loss of insulating pelage. Absorbable monofilament suture (polydioxanone) was used in a buried 3-layer closure of surgical incisions. The incisions healed rapidly and without complications.     

Heinz-body hemolytic anemia associated with ingestion of methylene blue in a river otter

Heinz-body hemolytic anemia and nephrosis associated with hemoglobinuria were diagnosed in a North American river otter. Fluids were administered, and the signs of renal failure improved immediately. Severe anemia developed, and the otter received a semisynthetic hemoglobin product to maintain the oxygen-carrying capacity of the blood until a blood transfusion could be given. Immediate clinical improvement was observed following hemoglobin administration, and adverse effects were not seen. Six days after admission, the otter began to produce its own RBC and recovered without complications. The Heinz-body anemia was determined to be caused by methylene blue that was in the water of minnows consumed by the otter the night before it became ill. Methylene blue is a common ingredient in products used to extend the life of bait fish. Bait fish kept in water treated with methylene blue should not be used as food for fish-eating animals.     

Glucosuria associated with renal calculi in Asian small-clawed otters

Urine from one female and 2 male Asian small-clawed otters (Aonyx cinerea) with bilateral renal calculi, one female with unilateral calculi, and one nonaffected male were evaluated for abnormal urinary crystalloid excretion. One otter with bilateral renal calculi had cystic calculi composed of calcium oxalate monohydrate and dihydrate. The 2 affected males were littermates, as were the 2 affected females, but the 2 litters were from different parents. At the time of the study, the otters did not have clinical signs of disease. Hematologic and serum biochemical, electrolyte, and enzyme values were normal. The urinary excretion of calcium, oxalate, uric acid, phosphate, citrate, and amino acids in otters with renal calculi was similar to that of the nonaffected otter. The 4 otters with renal calculi had glucosuria but the nonaffected otter did not have glucosuria. The glucosuria, in the absence of hyperglycemia, suggested a renal tubular transport defect for glucose. Other renal abnormalities were not found.     

Evaluation of cardiac lesions and risk factors associated with myocarditis and dilated cardiomyopathy in southern sea otters (Enhydra lutris nereis)

OBJECTIVE: To describe cardiac lesions and identify risk factors associated with myocarditis and dilated cardiomyopathy (DCM) in beach-cast southern sea otters. ANIMALS: Free-ranging southern sea otters. PROCEDURE: Sea otters were necropsied at the Marine Wildlife Veterinary Care and Research Center from 1998 through 2001. Microscopic and gross necropsy findings were used to classify sea otters as myocarditis or DCM case otters or control otters. Univariate, multivariate, and spatial analytical techniques were used to evaluate associations among myocarditis; DCM; common sea otter pathogens; and potential infectious, toxic, and nutritional causes. RESULTS: Clusters of sea otters with myocarditis and DCM were identified in the southern aspect of the sea otter range from May to November 2000. Risk factors for myocarditis included age, good body condition, and exposure to domoic acid and Sarcocystis neurona. Myocarditis associated with domoic acid occurred predominantly in the southern part of the range, whereas myocarditis associated with S. neurona occurred in the northern part of the range. Age and suspected previous exposure to domoic acid were identified as major risk factors for DCM. A sample of otters with DCM had significantly lower concentrations of myocardial L-carnitine than control and myocarditis case otters. CONCLUSIONS AND CLINICAL RELEVANCE: Cardiac disease is an important cause of death in southern sea otters. Domoic acid toxicosis and infection with S. neurona are likely to be 2 important causes of myocarditis in sea otters. Domoic acid-induced myocarditis appears to progress to DCM, and depletion of myocardial L-carnitine may play a key role in this pathogenesis.     

Technique of mandibular salivary gland biopsy in river otters (Lutra canadensis).

A Franklin-Silverman biopsy needle was used to obtain 2-5- x 1-2-mm mandibular salivary gland tissue samples percutaneously from nine North American river otters (Lutra canadensis). The samples were suitable for fluorescent antibody or polymerase chain reaction rabies testing. Ninety-two percent (11/12) of the biopsy procedures yielded histologically confirmed salivary gland tissue, and the remaining biopsy yielded adipose tissue. No complications were noted after 5-21 days.     

Enteric bacterial pathogen detection in southern sea otters (Enhydra lutris nereis) is associated with coastal urbanization and freshwater runoff

Although protected for nearly a century, California’s sea otters have been slow to recover, in part due to exposure to fecally-associated protozoal pathogens like Toxoplasma gondii and Sarcocystis neurona. However, potential impacts from exposure to fecal bacteria have not been systematically explored. Using selective media, we examined feces from live and dead sea otters from California for specific enteric bacterial pathogens (Campylobacter, Salmonella, Clostridium perfringens, C. difficile and Escherichia coli O157:H7), and pathogens endemic to the marine environment (Vibrio cholerae, V. parahaemolyticus and Plesiomonas shigelloides). We evaluated statistical associations between detection of these pathogens in otter feces and demographic or environmental risk factors for otter exposure, and found that dead otters were more likely to test positive for C. perfringens, Campylobacter and V. parahaemolyticus than were live otters. Otters from more urbanized coastlines and areas with high freshwater runoff (near outflows of rivers or streams) were more likely to test positive for one or more of these bacterial pathogens. Other risk factors for bacterial detection in otters included male gender and fecal samples collected during the rainy season when surface runoff is maximal. Similar risk factors were reported in prior studies of pathogen exposure for California otters and their invertebrate prey, suggesting that land-sea transfer and/or facilitation of pathogen survival in degraded coastal marine habitat may be impacting sea otter recovery. Because otters and humans share many of the same foods, our findings may also have implications for human health.     

Disseminated pheochromocytoma in a North American river otter (Lontra canadensis)

A 21-yr-old male North American river otter (Lontra canadensis) with a chronic history of degenerative osteoarthritis was evaluated for acute posterior paralysis. Because no definitive cause was identified and a poor prognosis was expected, the otter was euthanatized. A malignant neoplasm of adrenal gland origin with disseminated metastases to the central nervous system, lymph nodes, diaphragm, pancreas, spleen, and liver was diagnosed on postmortem examination. No clinical signs of disseminated neoplasia had been noted throughout the otter's history. The adrenal neoplasm was composed of nests of epithelial cells surrounded by a fine fibrovascular stroma. Neoplastic cells were immunohistochemically positive for chromogranin A, PGP9.5, metencephalin, and endorphin and negative for melan A and inhibin, confirming a diagnosis of a malignant pheochromocytoma. On the basis of the necropsy finding, metastasis of the pheochromocytoma might have contributed to the observed clinical signs.