Loutre de Cánada

Threats to otter populations in North America vary among regions and are influenced by type, distribution, and density of aquatic habitats and characteristics of human activities. Prior to settlement of North America by Europeans, otters were widespread among aquatic habitats throughout most of the continent (Hall 1981, Melquist et al. 2003). The synergy of unregulated trapping and loss or degradation of aquatic habitats through filling of wetlands and development of coal, oil, gas, tanning, timber, and other industries resulted in extirpations or declines in otter populations in many areas (Toweill and Tabor 1982, Melquist and Dronkert 1987). River otter declines were particularly severe in the USA, where, by 1980, populations were considered completely extirpated from 11 states and had experienced severe declines in nine other states (Nilsson (1980). The most severe population declines occurred in interior regions where fewer aquatic habitats supported smaller otter populations. Over the last 40 years reintroduction projects and factors that control trapping intensity have facilitated the recovery of extirpated river otter populations in many areas of North America (Raesly 2001, Bricker et al. 2016). Improvements in the conservation status of river otter populations in North America, particularly the USA, constitutes a substantial conservation success story, but efforts are still needed to guard against complacency in conserving the species and in addressing ongoing and potential threats that may be overlooked by failing to understand ecological aspects of the species throughout its range.

Fur trapping - The River otter has transitioned from a species of conservation concern in many areas of North America to one that is now widely legally trapped for fur, including states where the species was reintroduced (Bricker et al. 2016). This trapping of river otters is generally considered by management authorities in the USA and Canada to be sustainable. However, increases in river otter harvest have furthered the need for implementing reliable approaches for monitoring the long-term status of populations, which is currently lacking throughout most of North America, especially where river otters are trapped for fur. Bricker et al. (2016) showed that relatively few USA states or Canadian provinces and territories that harvest river otters have formal monitoring protocols for assessing either the density or the distribution of populations, except for recording annual trapper-kill levels and sometimes deriving demographic data from those killed otters.

An important issue that has not been meaningful, relates to levels of trapping that may enable perpetuation of local populations at levels below biological carrying capacity, but inhibits natural expansion. Interestingly, reintroduced river otter populations appear to have expanded rapidly with protection from legal trapping (Becker et al. in press). Such outcomes necessitate an introspective review of why legally trapped, native populations seemingly did not expand at rates comparable to reintroduced populations. This outcome suggests that trapping native populations of river otters, even if sustainable at local levels may, have diminished natural expansion by some of these populations. A better understanding of the dynamics of sustainable trapping in relation to natural expansion of river otter populations is in need of additional research attention. Expansion of river otter populations is undoubtedly associated with the combination of better trapping regulations, downward trends in the number of trappers, and periods of lower fur prices, which further diminishes levels of trapping intensity. Understanding the interaction between trapping and expansion of populations will be particularly important in areas where there is relatively high levels of river otter trapping (and the trapping of species that often result in the unintended capture of river otter, e.g., American beavers) or if there is a general increase in number of trappers and intensity of trapping pressure. However, particularly lacking is an integrated approach that can be applied overtime and conservation jurisdictions to meaningful assess population trends.

Monitoring - Trapping river otters for fur is regulated, but population-level effects need better monitoring. The influence of water quality and riparian disturbance need better evaluation based on categories of pollutants and disturbances. Formalized monitoring is important for examining expansions and contractions of river otter populations in relation to various management schemes (e.g., reintroductions and trapping) or environmental conditions (e.g., presumed habitat quality). Science-based trapping management is based on the premise that wildlife populations can be harvested sustainably. To ensure that this criterion is met, some level of monitoring to understand changes in the size, age and gender structure, as well as the distribution of trapped populations is necessary. The Appendix II listing of the river otter by CITES mandates the tagging of all river otter pelts intended for export outside of the U.S. and Canada (USFWS 2014). Records kept as part of the pelt tagging process ensure that wildlife agencies in jurisdictions where river otter are legally trapped will document the number of individuals harvested annually. Most conservation jurisdictions do not have population estimates for river otter populations. Instead, trapping data where river otters are legally trapped or accidental captures of otters (where otters are protected, but caught in traps intended for legally trapped species) is often used to assess population trends (e.g., Chilelli et al. 1996). Unfortunately, in contrast to the grid-based monitoring protocol followed for the Eurasian otter (Lutra lutra) in portions of Europe, no standardized landscape-level approaches are in place to serve as a basis for meaningful landscape-level assessments to levels of population declines or recoveries of the North American river otter – past of present. Erb et al. (2018) provided rationale to justify adequacy of current techniques used to monitor river otter populations in North America, and presented a map depicting the extensive, range-wide recovery of river otters. However, this depiction does not portray the overall paucity of uniform and consistently applied approaches for monitoring river otter populations at various scales and among conservation jurisdictions. The map presented by Erb et al. (2018) highly overestimates the actual occurrence of river otter in the landscape by not portraying the species in relation to the availability and abundance of suitable aquatic habitats, and serves to demonstrate the inadequacy of current approaches to monitor river otter populations (see Hubbard and Serfass (2005) for an example of limitations in depicting the distribution of river otters at various landscape scales, and as an example of the standardized, large-scale, and integrative approach used to monitor population Eurasian otters). Development of formal monitoring techniques, standardized (and thus comparable) across conservation jurisdictions and regimes (e.g., trapped versus non-trapped populations), should be regarded as a priority for assessing and mitigating long-term threats to river otter populations.

Limited research on native populations - Understandably, a large portion of research with river otters over the last 40 years has focused on evaluating aspects of reintroduced populations. However, comparable focus on native populations has lagged, with the notable exception of basic information derived largely from examination of carcasses obtained in areas where river otters are trapped, including carcass tagging associated with CITES requirements associated with the river otter’s Appendix II listing. Basic natural history information is lacking for river otters inhabiting coastal environments, particularly along the Atlantic coast of North America, and northern portions of Canada.

Sub-optimal habitat use and oil spills - Water pollution and other degradation of aquatic and riparian habitats may limit distribution of otters and pose long-term threats if enforcement of water quality standards is not maintained and enforced. Acid drainage from coal mines is a persistent source of water pollution in some areas that eliminates prey base for otters and thereby inhibits recolonization or expansion of otter populations. Expansion of reintroduced and, in some cases, native river otter populations has resulted in the species now sometimes inhabiting areas formerly considered sub-optional habitats (i.e., areas with degraded water quality and riparian conditions). Consequently, there is potential for the paradigm to develop that river otters are tolerant of perturbations to aquatic environments, in lieu of long-term supporting evidence. Current optimism about river otters being able to tolerate a wider range of aquatic habitat disturbances may be misleading and unfounded in that such disturbed areas could represent sink habitats, where populations are sustained by dispersing individuals and not through adequate levels of reproduction and survival by individuals occupying the area. Assessments of source-sink dynamics is needed for river otter populations inhabiting aquatic system with various types and levels of pollutants, and riparian perturbations. The threat of oil spills to river otters has been well studied and documented in Alaska Oil spills (e.g., Bower et al. 2003). Additional research is needed to clearly delineate the impact of possible threats to populations that various forms of water pollution, agricultural and other development along riparian habitats, industrial and housing development in coastal areas, cumulative impacts related to loss or alterations of wetlands, large flood control structures, and interactions that these and other factors have on otter populations.

River otter-human conflicts - The reintroduction of river otters in many states has in some cases been negatively depicted in the media because of the species’ predatory (i.e., fish eating) habits. The successful reintroduction of river otters in the states of Missouri, Ohio, Kentucky, and Illinois was followed by strikingly similar patterns of negative media messages suggesting that river otter predation was having widespread negative impacts on commercially-reared fish and game fish important to anglers (Serfass et al. 2014). Management actions, including opening trapping seasons, subsequently were implemented in these states purportedly to alleviate the public concern and animosity portrayed in the media about river otters. Wildlife agencies responsible for managing trapping of river otters in some cases appear to have been complicit in fostering negative portrayals about river otter predation to gain public support for trapping seasons. Such negative portrayals have the potential to contribute long-term deleterious consequences regarding public attitudes towards river otters, thereby liming the value of this species in serving as a flagship to promote conservation of aquatic ecosystem (Stevens et al. 2011). In contrast, the Eurasian otter has been used extensively and successfully as a flagship to promote clean-water initiatives in Europe.

River otter genetics - River otters from Louisiana have most commonly been used as a source for reintroduction projects in the US—about 64% of river otters reintroduced in the US were obtained from this state. Serfass et al. (1998) and Brandt et al. (2014) discussed genetic implications for river otter reintroductions in North America. Ultimately, how genetic introgression associated with expansion of reintroduced populations will influence the genetic structure and subspecies delineations of river otter populations in North America is unknown and should be the focus of future investigations as a basis for developing strategies to that best ensure maintenance of the species’ historic levels of genetic variability.

Disease - Diseases in wild otter populations is poorly understood and has received relatively little study (Serfass et al. 1995). Lontra canadensis may be affected by canine distemper (Harris 1968, Park 1971), rabies (Serfass et al. 1995), respiratory tract disease, and urinary infection (Hoover et al. 1984, Route and Peterson 1991). In addition, North American Otters can contract jaundice, hepatitis, feline panleucopenia, and pneumonia (Harris 1968). North American Otters host numerous endoparasites such as nematodes (Hoberg et al. 1997), cestodes (Greer 1955), trematodes (Hoover et al. 1984), the sporozoan Isopora (Hoover et al. 1984), and acanthocephalans (Hoberg et al. 1997, Hoover et al. 1984). Ectoparasites include ticks (Eley 1977, Serfass et al. 1992), sucking lice Latagophthirus rauschi (Kim and Emerson 1974), and the flea Oropsylla arctomys (Serfass et al. 1992).

The North American river otter is included in CITES Appendix II. This listing is in place to assure that the ongoing legal trade does not contribute to illegal trade of similar species of otters with a higher level of conservation concern (i.e., what is referred to as “look-alike” species, which could be illegally integrated with the legal trade of species with a similar appearance. See USFWS, 2014). Although trapped for fur, the overall trade in the fur of North American river otter generally should be regarded as sustainable. Considering that the river otters had experienced substantial declines caused by unregulated fur harvest in the 1800s and degradation of aquatic habitats through the mid-1900s, the current status of the species should be regarded as a substantial conservation success story. These declines were particularly severe in the USA, where, by 1980, populations were considered completely extirpated from 11 states and endangered in 9 others (Bricker et al. 2016). However, populations have since expanded to occupy at least portions of the river otter’s historic range in all USA states and Canadian Provinces, except Prince Edwards Island (where there is recent evidence that some individuals may be pioneering the Province). The overall increase in the distribution and abundance of river otters was facilitated by a combination of reintroduction projects implemented in 22 states, improvements in aquatic habitat quality, and the natural expansion of native populations range (Bricker et al. 2016). The conservation status of river otter populations in North America has improved considerably through progressive conservation efforts, including implementation of clean water regulations (e.g., the federal Clean Water Act, EPA undated).

Camp (2017) provides a comprehensive literature review for the North American river otter, which will be extremely useful in developing conservation planning and developing conservatin0related research projects.