Lontra Canadensis Research Articles

Gastric dilatation‐volvulus in two North American river otters (Lontra canadensis)

AbstractTwo adult, zoo‐housed, North American river otters (Lontra canadensis), a male and a female, presented emergently for profound lethargy. The second case had abdominal distension with tympany, tachypnoea, tachycardia and poor pulse quality noted. A single radiograph from that case showed dilated bowel loops and a caudodorsally‐deviated gastric axis but lacked the characteristic compartmentalized gas appearance common in canine gastric dilatation‐volvulus (GDV). Unfortunately, both animals died within approximately an hour, before other treatments or surgery could be performed. Necropsy in both cases revealed a 180‐degree volvulus of the stomach, resulting in infarcts to the gastric wall. In this first report of GDV in otters, both cases were from the same institution, 10 years apart, which suggests GDV may not be an uncommon presentation in otters. Consequential diagnostic and treatment delays may occur if veterinarians are not aware of the not‐so‐remote possibility of GDV occurring in otters.

An Evaluation of Body‐grip Trap Trigger Configurations for Reducing River Otter Take Incidental to Beaver Trapping

ABSTRACTRiver otter (Lontra canadensis) populations in North America have been the focus of significant restoration efforts. Wildlife management agencies, concerned about the unintentional take of river otters incidental to beaver (Castor canadensis) trapping, may recommend techniques to avoid capturing river otters. River otter avoidance techniques that are ineffective or diminish trap performance for beavers are undesirable. We conducted a field evaluation in 2015 and 2016 in Wisconsin to assess how two trigger configurations (offset and center) on body‐grip traps would affect the incidental capture rate of river otters during beaver trapping. We also evaluated effects of each configuration on beaver capture rates, body lengths, and anatomical locations of trap‐jaw strikes. We used size 330 body‐grip traps equipped with identical triggers and alternated between trigger configurations during beaver damage management activities. We captured 8 river otters with each trap trigger configuration. Trap‐jaw strikes on beavers differed between trigger configurations, with offset triggers resulting in more abdomen strikes and center triggers causing more cervical vertebrae strikes. We found that an offset trigger configuration did not reduce incidental take of otters and was less effective for trapping beavers. © 2021 The Wildlife Society. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

A Longitudinal Study of Parenting Conditions on Two Adult, North American River Otters’ (Lontra Canadensis) Repetitive Behavior

ABSTRACT Captive animal welfare research focuses on husbandry, enrichment, enclosure space, visitor effects, and opportunities for species-typical behavior (e.g., foraging, territoriality, and social interaction). And yet, one of the most biologically relevant opportunities for species-typical behavior, parenting, has received little attention. The goal of this longitudinal investigation was to explore the differential variability of repetitive behavior across three parenting conditions (i.e., No parenting, parenting, and foster parenting) among captive, wild-rescued, North American river otters. This study represents anatural ABAC design, the conditions reflect differential parenting phases: No parenting (A), Parenting biological pups (B), and Alloparenting nonbiological pups (C). The behavior of two adult North American river otters at the Oregon Zoo were observed from April2016 through March2020 during the different parenting contexts. The frequency of repetitive behaviors was lowest during parenting and highest during the non-parenting conditions. Although data for season, weather, and visitor variables were also collected throughout this study; parenting condition was the only consistent moderator of abnormal repetitive behavior observed.

Variation in diet and activity of river otters (Lontra canadensis) by season and aquatic community

Abstract Keystone predators can impact many prey species, including those that are endangered. A requisite to assess the impact predators have on different prey populations is to identify the species being consumed in different types of communities, while accounting for possible seasonal variation in consumption. Here we used analysis of North American river otter (Lontra canadensis) scat to assess the impact river otters have on their prey populations, particularly endangered salmonids and migrating birds. We analyzed the prey composition of 1,411 river otter scats collected from 10 sites in Humboldt County, California, between 2011 and 2012. Analysis of prey items in scat placed study sites into four distinct clusters based on diet. Fish, mostly from the families Gasterosteidae, Cottidae, and Pholidae, formed the primary prey component, and crustaceans, birds, amphibians, and insects, also were important components of river otter diet. Salmonids constituted < 5% of overall diet, but river otters consumed the largest percentage of salmon during salmon spawning season at the inland cluster where salmonids spawn. Scat marking intensity varied between clusters and seasons, with the most scats collected in the autumn and the fewest in the winter/spring, except at the inland cluster where the pattern of marking activity was reversed. River otters may be responding to seasonal migrations of endangered and threatened salmonids. Diet surveys of this type are useful for monitoring resource use by top predators in aquatic ecosystems.

BEHAVIOR OF NORTHERN RIVER OTTERS IN RELATION TO SOCIAL GROUP SIZE AND PUP PRESENCE: RESULTS FROM 15 YEARS OF CITIZEN SCIENCE

We describe activity patterns of North American River Otters (Lontra canadensis) in relation to social group size and the presence of young. Over the course of 15 y, we collected observations of 8 River Otter behaviors from a network of citizen scientists in northern California, retaining 1692 records following a rigorous data-cleaning process. Observers were asked to indicate 1 or more of the following 8 behaviors: “diving”, “swimming”, “walking”, “running”, “digging”, “turning rocks”, “pursued birds”, and “retreating from observer.” We treated “digging”, “turning rocks”, and “pursued birds” as alternative foraging strategies in some comparisons. Assessment of these reports showed that families were seen diving, running, and retreating from the observers more frequently than adult groups. Likewise, adult social groups behaved differently than solitary adult otters. Propensity to retreat from humans increased with increasing group size in social otters, whereas diving behavior also increased with group size. Solitary adults employed alternative foraging strategies more than adults in social groups. Citizen observers also reported that diving and styles of foraging behavior varied among months for adult otters. Taken together, these results provide evidence that citizen-science questionnaires can be used to provide insight into the natural behaviors of species that are difficult to observe.

Effect of Stream Permanence on Predation Risk of Lotic Crayfish by Riparian Predators

Given the importance of crayfish in stream ecosystems, gaining insight into the role of stream permanence in maintaining predator–prey interactions is critical. Our objectives were to determine the influence of stream permanence and season on crayfish predation and assess the role of stream permanence and crayfish density on the presence of predators, while accounting for imperfect detection. We conducted surveys of crayfish density, mammalian scat, and environmental variables within 10 intermittent and 10 permanent streams in the Ozark Highlands. We used occupancy modeling to assess the relationship between predator presence, crayfish density, and environmental variables. Stream permanence did not play a role in determining relative frequency of occurrence or percent volume of crayfish prey in mammalian diets. However, percent volume and relative frequency of crayfish prey found in scats differed by season, with both highest in spring and summer. The relative frequency and percent volume of fish prey showed a significant interaction of season by stream permanence, which may be the first instance of this observation. Procyon lotor (Raccoon) had the highest detection probability (p = 0.39), whereas Neovison vison (American Mink; p = 0.15) and Lontra canadensis (River Otter; p = 0.03) had low detection probabilities. Further study into predator–prey interactions in the context of hydrology, particularly when related to imperiled groups like freshwater crayfishes, is needed since climate change is expected to alter hydrologic patterns.

Co-exposures to trace elements and polycyclic aromatic compounds (PACs) impacts North American river otter (Lontra canadensis) baculum

Environmental loadings of polycyclic aromatic compounds (PACs) and trace elements are increasing in areas with marked oil and gas extraction, such as in the Athabasca oil sands region, Alberta, Canada. Some of these chemicals are recognized as potent endocrine disrupting compounds (EDCs). The impacts of co-exposure to PACs and metals on free-ranging wildlife is of considerable concern. River otters (Lontra canadensis) are sentinel species of aquatic ecosystem health. The baculum (penile bone) is an important part of the reproductive system in otters that ensures successful copulation. Although baculum health is critical to male reproductive success and is sensitive to exposure to EDCs, there is no information available regarding the impact of PAC and metal exposures on measures of baculum health. River otter baculum and livers were dissected from carcasses obtained from the fur trade. Trace element and PAC analyses were carried out in liver with matching baculums subjected to dimensional analysis, bone mineral density (BMD) and mechanical loading testing. Trace elements and select PACs exhibited both protective and deleterious effects on baculum bone health metrics. Alkylated four ring PACs were negatively associated with baculum bone material properties (ex: C4-Chrysene and C4-pyrene). The same compounds have been shown to exhibit strong anti-androgenic activities. Few comparable studies exist related to contamination and adverse effects of PACs in wild terrestrial mammals. Baculum health metrics may be an important tool to include in biomonitoring studies as to date, there are limited means to assess male reproductive performance in wildlife biomonitoring programs.

Sociality and signaling activity modulate information flow in river otter communication networks

Abstract Animal communication networks are built from interactions between senders and receivers of signals. The drivers of signaling decisions, which are the building blocks of such networks, are not well understood. Theory predicts that conditions which ensure information spread to the largest possible number of receivers should be favored. Several carnivores use latrine sites for visual, olfactory, and auditory signaling. We tested the hypotheses that signaling behavior at latrine sites is influenced by social structure and locally acquired information on the presence of conspecifics, using coastal river otters (Lontra canadensis), in Alaska. River otters exhibit a flexible social system of mostly males that communicate through scent marking at latrines. During scent marking, river otters also perform feet stomping, which may add a visual component to their signal. Using trail camera footage, we found that solitary otters were more likely to perform both sniffing and scent marking compared with otters in groups. Feet stomping was more intense for solitary otters but less pronounced during overmarking. Signalers demonstrated a greater tendency to scent mark when in smaller groups at highly active latrines, whereas feet stomping was more intense in recently visited sites. When in groups, scent-marking frequency increased when other individuals were signaling, suggesting a positive feedback, possibly driven by feet stomping. In concert, our results suggest that in river otters, scent-marking decisions minimize signal dilution by being performed in small groups and maximize the receivers through preferential signaling at latrines with higher, more recent activity. Because signaling decisions in social animals are linked to key life-history events such as mating and group membership shifts, understanding their individual and population-level drivers can be crucial.

The Gut Microbial Community Structure of the North American River Otter (Lontra canadensis) in the Alberta Oil Sands Region in Canada: Relationship with Local Environmental Variables and Metal Body Burden

The Alberta Oil Sands Region in Canada is home to one of the largest oil bitumen deposits in the world. The North American river otter (Lontra canadensis) is a top predator with a small home range and is sensitive to disturbances; it has been designated as a sentinel species for the potential impacts of the natural resource exploitation on freshwater ecosystems in the Alberta Oil Sands Region. With an increasing interest in noninvasive biomarkers, recent studies suggest that gut microbiota can be used as a potential biomarker of early biological effects on aquatic wildlife. The goal of the present study was to determine the river otter gut microbial structure related to environmental variables characterizing mining activities and metal body burden. We obtained 18 trapped animals from and surrounding the surface mineable area of the Alberta Oil Sands Region. The gut microbial community structure was characterized using high-throughput sequencing of 16S rRNA gene amplicon analyses. Trace metal concentrations in the liver were measured by inductively coupled plasma-mass spectrometry. Our study revealed that the gut bacteria of river otters in the Alberta Oil Sands Region clustered in 4 groups dominated by Peptostreptococcaceae, Carnobacteriaceae, Enterobacteriaceae, Clostridiaceae, and Nostocaceae. We show that arsenic, barium, rubidium, liver-body weight ratio, and δ15 N were associated with each cluster. When comparing affected versus less affected sites, we show that river otter gut bacterial community and structure are significantly related to trophic level of the river otter but not to Alberta Oil Sands Region mining activities. Our study reveals that the gut bacterial dynamics can provide insights into the diet and habitat use of river otters but that more work is needed to use it as a pollution biomarker. Environ Toxicol Chem 2020;39:2516-2526. © 2020 SETAC.

Causes of Mortality in a Population of Marine-Foraging River Otters (Lontra canadensis).

Retrospective analysis of diagnostic findings from 30 marine-foraging river otter (Lontra canadensis) carcasses opportunistically acquired between 2003 and 2013 revealed trauma as the most common cause of mortality (47%). Within this focal population, causes of trauma included vehicular, gunshot, and one case of suspect intraspecific aggression. Other causes of death included idiopathic (20%), infectious (13%), metabolic (10%), nutritional (7%), and neoplasia (3%). One case of neoplasia, a pancreatic islet cell adenoma, was identified in a 12-yr-old female. In six animals, diffuse renal interstitial fibrosis and multifocal glomerulosclerosis of unknown clinical significance were noted.

Spatial patterns of the exposure-response relationship between mercury and cortisol in the fur of river otter (Lontra canadensis)

Fur has been validated as a useful biomarker medium for chemical exposures and biological responses in wildlife. Mercury (Hg) is known to act as an endocrine disruptor by altering brain neurochemistry. In this study, we investigated the spatial patterns of relationships between total Hg (THg) and cortisol in the fur of river otter (Lontra canadensis). Geotagged fur samples were obtained from a wildlife biomonitoring program (n = 72) and the North American Fur Auction (n = 37) between 2014 and 2017. Fur THg was measured using direct thermal decomposition and fur cortisol was measured using an enzyme-linked immunosorbent assay (ELISA). The average fur THg concentration was 11.50 ± 12.40 μg/g fur weight (f.w.), and the fur cortisol concentration was 5.71 ± 8.24 pg/mg. Results from the global ordinary least squares regression show no relationship between THg and fur cortisol concentrations. However, both Hg and cortisol were heterogeneously distributed across the landscape. When a localized geographically weighted regression (GWR) was used, a geographically distinct bi-phasic relationship was observed. We suggest this bi-phasic relationship is associated with a threshold THg concentration, beyond which, there was a negative association with measured fur cortisol. Results of a break-point analysis, with one break, indicate that the threshold is 16 ± 1.27 μg/g f. w of THg in fur. This research highlights the need to use appropriate spatial methods when assessing exposure-response relationships in wildlife across large geographical areas. The identified threshold can be used for regulatory purposes.

AN APPROACH FOR LONG-TERM MONITORING OF RECOVERING POPULATIONS OF NEARCTIC RIVER OTTERS (LONTRA CANADENSIS) IN THE SAN FRANCISCO BAY AREA, CALIFORNIA

We present results from the first 5 y of a long-term monitoring study of recovering populations of the North American River Otter, Lontra canadensis, in Marin County, California. Historically present, but extirpated due to trapping and habitat loss, this apex aquatic predator is recolonizing coastal, lentic, and riverine habitat areas around San Francisco Bay. Using camera traps and a community science effort, we estimated an annual minimum population size at each of 14 focal study sites (FSS). Based on those estimates over 5 y, we developed a new Bayesian-statistics model to estimate population parameters for each FSS, including initial population abundance, annual rate of change in abundance, and probability that abundance is in decline. Our results show significantly different changes in abundance among the various FSS, with annual rates ranging from a high of 0.86 to a low of –0.44. Using a Random Forest framework, we then investigated the relative value of select spatial, environmental, and anthropogenic variables as predictors for each FSS population parameter. In our analysis spatial factors, and specifically latitude, were the best predictor of differences in FSS population parameters. Higher latitudes correlated with higher initial population abundance, greater annual increase in abundance, and lower probability that abundance is in decline. Our results provide new information about the rate and pattern of natural River Otter recolonization of areas from which they have been absent for decades. The results also serve as a demonstration of an approach to long-term monitoring, with the goal of increased understanding of the ecological function of River Otters in the San Francisco Bay Area.

A noninvasive environmental monitoring tool for brominated flame-retardants (BFRs) assisted by conservation detection dogs

Fecal matter is a useful noninvasive/nondestructive media for evaluating contaminants in wildlife, as residues therein have been observed to correlate with body burdens. Conservation detection dog-handler teams can be used to optimize the acquisition of fecal samples. To build on previous work, sentinel-species’ (i.e. mink (Mustela vison) and otter (Lontra canadensis)) fecal matter was opportunistically located by a detection dog team along the tri-river system of Missoula, Montana, USA. Sediments were also collected. Samples were used to develop an analytical method from fecal matter to determine habitat exposure to the brominated flame-retardants (BFRs): polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD), 2-ethylhexyl 2, 3, 4, 5-tetrabromobenzoate (EH-TBB), di (2-ethylhexyl)-2, 3, 4, 5-tetrabromophthalate (BEH-TEBP) and decabromodiphenyl ethane (DBDPE). Sediments contained PBDEs (BDE-99 and BDE-209) and EH-TBB at detection rates of 67%, 33% and 67%, respectively. BDE-99, -209 and EH-TBB were also detected in mink and otter feces, at rates of 81%, 25% and 81%, respectively; plus BEH-TEBP at 13%. BFR levels correlated positively with human population density except along the lower Bitterroot River, where BDE-209 sediment and feces levels exceeded other sites by several orders of magnitude. Fecal matter body burden estimates indicated marginal PBDE exposure. However, exposure to their replacements, EH-TBB and BEH-TEBP, were at levels that may adversely affect healthy Mustelidae populations. Proof-of-concept was achieved; validation results were within established standards for the development of analytical methods. The established application of conservation dog-handler teams to facilitate the collection of fecal matter for BFR analysis represents a valuable, but currently underutilized environmental monitoring tool.

Space Use and Enrichment in a North American River Otter (Lontra canadensis) Exhibit

Exhibit design and environmental enrichment can influence the space use of captive animals. On May 2, 2014, the Tennessee Aquarium opened a new, expanded North American river otter (Lontra canadensis) exhibit, “River Otter Falls.” The exhibit housed 6 otters (5 male and 1 female). A group of three otters was rotated in the exhibit every 2-2 ½ hours. Using a scan sampling procedure with 30 second intervals, the location and number of the otters was marked in one 9 areas of the exhibit. The number of otters not visible was also counted. The study lasted for 4 months, with 43 sessions each lasting ~45 min. The results showed that the otters tended to use all areas of the exhibit rather than confining themselves to one or a few areas. (total SPI = 0.35) and were visible 98% of the time. G-tests showed that the otters were using the areas significantly different from chance with variations in how they are using each individual area of the exhibit. Comparisons of the visibility and location after enrichment showed that the otters tended to use the exhibit less uniformly during enrichment, but increased time spent in areas of the exhibit with greater visibility and proximity to guests. During enrichment sessions, otters were more visible in the areas of the tank that visitors may see most easily, empathizing the role that enrichment can have on space use of an enclosure and visibility of animals in captivity.

LEPTOSPIRA, PARVOVIRUS, AND TOXOPLASMA IN THE NORTH AMERICAN RIVER OTTER (LONTRA CANADENSIS) IN NORTH CAROLINA, USA.

The North American river otter (Lontra canadensis) is the largest mustelid in North Carolina, US, and was once extirpated from the central and western portions of the state. Over time and after a successful reintroduction project, otters are now abundant and occur throughout North Carolina. However, there is a concern that diseases may have an impact on the otter population, as well as on other aquatic mammals, either through exposure to emerging diseases, contact with domestic animals such as domestic cats (Felis catus), or less robust condition of individuals through declines in water quality. We tested brain and kidney tissue from harvested otters for the pathogens that cause leptospirosis, parvovirus, and toxoplasmosis. Leptospirosis and toxoplasmosis are priority zoonoses and are maintained by domestic and wild mammals. Although parvovirus is not zoonotic, it does affect pets, causing mild to fatal symptoms. Across the 2014-15 and 2015-16 trapping seasons, we tested 220 otters (76 females, 144 males) using real-time PCR for Leptospira interrogans, parvovirus, and Toxoplasma gondii. Of the otters tested, 1% (3/220) were positive for L. interrogans, 19% (41/220) were positive for parvovirus, and 24% (53/220) were positive for T. gondii. Although the pathogens for parvovirus and toxoplasmosis are relatively common in North Carolina otters, the otter harvest has remained steady and the population appears to be abundant and self-sustaining. Therefore, parvovirus and toxoplasmosis do not currently appear to be negatively impacting the population. However, subsequent research should examine transmission parameters between domestic and wild species and the sublethal effects of infection.

North American River Otters Followed by Piscivorous Birds, and a River Otter Parental Distraction Display

We observed 2 Lontra canadensis (North American River Otter), likely an adult female and her nearly-grown pup, on a fall 2018 afternoon at a remote lake in Piscataquis County, ME. We witnessed 2 notable animal behaviors, a possible bird-otter foraging association and a River Otter parental display, serendipitously while canoeing. An Ardea herodias (Great Blue Heron) and a Megaceryle alcyon (Belted Kingfisher) watched and followed the River Otters as they fished along the shore of a small cove of the lake. Although neither bird was seen to strike directly at or eat a fish during this episode, the behavior of the piscivorous birds was suggestive of a foraging association with the River Otters, a novel observation in North America. After fishing, the River Otters began traveling along the lake shore and noticed the canoeing human observers. Upon becoming aware of the canoe, the pup apparently hid as the adult female swam toward the canoe while noisily blowing. She then dove and resurfaced farther away from her pup's last-seen position. This routine was repeated several times until the observers paddled away from the female. Despite the large behavioral repertoire known for otters generally, this parental distraction display has not been previously reported.

Metal contamination of river otters in North Carolina.

Aquatic apex predators are vulnerable to environmental contaminants due to biomagnification. North American river otter (Lontra canadensis) populations should be closely monitored across their range due to point and nonpoint pollution sources. Nonetheless, no information exists on environmental contaminants in the North Carolina otter population. Metals and metalloids occur naturally across the landscape, are essential for cellular function, and become toxic when concentrated unnaturally. We conducted our study across the three Furbearer Management Units (FMU) and 14 river basins of North Carolina. We determined the concentrations of arsenic, cadmium, calcium, cobalt, copper, iron, lead, magnesium, manganese, mercury, molybdenum, selenium, thallium, and zinc in liver and kidney samples from 317 otters harvested from 2009 to 2016. Arsenic, lead, and thallium samples were tested at levels below the limit of detection. With the exception of cadmium, we detected all other elements at higher levels in the liver compared with the kidney. Specifically, cadmium, cobalt, copper, iron, magnesium, manganese, mercury, molybdenum, and zinc levels differed by tissue type analyzed. Most element concentrations remained stable or increased with otter age. We detected higher levels of mercury and selenium in the Lower Pee Dee and Cape Fear river basins. River basins within the Mountain FMU were higher in cadmium, copper, iron, lead, and zinc, whereas the Coastal Plain FMU was lower in cobalt and manganese. None of the elements occurred at toxic levels. Our research establishes baseline concentration levels for North Carolina, which will benefit future monitoring efforts and provide insight into future changes in the otter population.

Digestible Energy Intake and Digestive Efficiency of Human-Managed North American River Otters (Lontra canadensis).

Diets currently provided to captive North American river otters (Lontra canadensis) are highly variable with different institutions providing various whole foods, commercial complete prepared diets, or combinations of both. This study investigated the digestible energy intake, gastrointestinal transit time, and digestive efficiency of three different diets being fed at three North Carolina institutions. Otters housed at Institution A (n = 3) were fed strictly fish. Otters housed at Institutions B (n = 3) and C (n = 2) were fed a majority fish based diet (58.5 and 74.1%, respectively), supplemented with fruits, vegetables, and supplemental protein sources as enrichment. There was an apparent trend between increased percentage of fish in the diet and faster transit time and higher digestive efficiency. As less fish was included in the diets, the GI transit time was longer (Institution A, 106 minutes; Institution B, 145 minutes; Institution C, 208 minutes). Median digestive efficiency was high for all three groups (A, 91.4%; B, 87.8%; C, 89.8%) but was higher for the institutions feeding fish. Additionally, the overall median gross energy intake for the eight animals in this study was 163.1 kcal/kgBM0.75/day (range: 92.2 to 260.7 kcal/kgBM0.75/day). While all three institutions had healthy otter populations, it appears that a higher fish diet should be further studied as the model North American river otter diet.

River Otter Status, Management, and Distribution in the United States: Evidence of Large-Scale Population Increase and Range Expansion

Abstract River otter Lontra canadensis populations in the United States have expanded during the past 50 y as a result of improvements in habitat quality and effective management programs implemented by state and federal agencies and native tribes. Periodic assessments of river otter status, population trends, and geographic distribution are needed to detect changes in populations, assess management approaches, and to identify and prioritize conservation efforts. We surveyed state wildlife agency experts to assess the current population and regulatory status of river otters in their jurisdictions. River otters were legally harvested in 40 states as of 2016. Twenty-two states reported increasing populations while 25 reported stable populations. Most states used multiple methods to monitor river otter populations including harvest-based surveys, presence–absence surveys, and empirically derived population model predictions; harvest-based surveys were the most commonly used monitoring approach. As populations have expanded, river otter reintroduction efforts have become less frequent; two additional states had conducted reintroductions since 1998 and only one state had conducted a reintroduction since 2010. We estimated that river otter distribution increased by 10.2% in the continental United States and by 13.7% in the contiguous United States during an 18-y period. Although populations may continue to increase numerically, river otters may be approaching their potential maximum geographic distribution in the United States.

Characteristics of a River Otter (Lontra canadensis) Maternal Den in the Central Platte River Valley, NE

Characteristics of a River Otter (Lontra canadensis) Maternal Den in the Central Platte River Valley, NE