Five species of amphibians and one species of reptile are confirmed to occur in the NWT. One additional species of amphibian is expected to be present.

Globally, amphibians and reptiles are experiencing precipitous declines due to a suite of all-too-familiar causes, including habitat loss and degradation, invasive species, and infectious diseases. Compounding these causes of declines are human behaviours such as persecution (especially snakes) and collection for the pet trade. Amphibians and reptiles are mostly found in the forested areas of the NWT, although, as with many northern species, much remains to be learned about their ecology. We have not observed any new species of amphibians and reptiles in the NWT since 2016 but new information about their biology continues to come to light, and in 2017, a multi-species amphibian management plan was implemented in the NWT.

In 2019, amphibian surveys in the Fort Liard area detected previously undocumented boreal toad (Anaxyrus boreas) breeding sites. The 2019 surveys also detected several breeding populations of wood frogs (Lithobates sylvaticus = Rana sylvatica). Interestingly, no boreal chorus frogs (Pseudacris maculata) of any life stage were detected during the surveys although the species is known to occur in the area. It is possible that the time of year and local weather conditions at the time of the surveys may have interfered with detecting the small, secretive species.

Boreal chorus frogs in the NWT are the focus of an ongoing collaborative project that will allow a more complete understanding of the ecology of the species at the northern edge of its expansive, poorly resolved range. The project involves information on population demographics, development rates, and breeding site characteristics, as well as information serendipitously collected by automated recording units that were deployed for unrelated projects across the NWT. Tissue samples collected from boreal chorus frogs in the Fort Smith area 2015 – 2017 have also been included in a phylogenetic study that is investigating the evolutionary relationships among populations across the species’ range.

Two amphibian pathogens linked with global amphibian declines have been detected in the NWT: the chytrid fungus Batrachochytrium dendrobatidis (Bd), and ranaviruses. Bd was first detected in multiple amphibian species in the Dehcho and South Slave in 2007 and 2009, respectively. Subsequent work in the South Slave 2015 – 2016 confirmed Bd is persistently present there, although at relatively low prevalences. Amphibian health surveys in the Sahtu 2007 – 2008 did not detect Bd but the region has not been surveyed for the pathogen since.

No amphibian die-offs attributable to Bd have been documented in the NWT, which is consistent with other findings of Bd in Canadian amphibian populations. Sublethal effects of Bd infections (i.e., fitness costs) have not been examined in northern amphibian populations although they are well documented in species in the southern USA and elsewhere.

Ranaviruses were first documented in wood frogs in the Dehcho and Sahtu in 2007, and the South Slave in 2009. Amphibian surveys in 2019 in the Fort Liard area encountered wood frog mortalities that were attributed to ranaviruses, indicating ranaviruses are also persistent in northern amphibian populations. Intensive field work 2015 – 2017 focussed on the ecology and evolution of amphibian ranaviruses in the Fort Smith area. That research detected at least two distinct strains of lethal ranaviruses circulating among wood frogs, boreal chorus frogs, and Canadian toads. There is also evidence that the particular composition of amphibian species present in an ecological community affects infection dynamics. Although it is unknown precisely how long ranaviruses have been circulating in northern amphibian populations, multiple lines of evidence suggest it has been less than 100 years.

One aspect of ranavirus ecology that remains relatively unexplored is the role of reptiles. Several ranavirus strains originally isolated from North American amphibians, including wood frogs, can cause lethal infections in multiple species of snakes and turtles.

As a first attempt at examining the role of reptiles in ranavirus ecology in boreal ecosystems, road-killed red-sided garter snakes that were encountered in the Fort Smith area 2015 – 2017 were tested for ranavirus infection. Although all snake carcasses tested negative, the small sample size and opportunistic nature of the sampling precluded drawing any broad conclusions about ranavirus disease in snakes in the NWT.

An additional infectious disease, snake fungal disease (caused by Ophidiomyces ophiodiicola), is of potential concern with respect to snakes in the NWT. The fungus is capable of causing debilitating and lethal infections in several North American snake species, including members of Thamnophis, and its range appears to be expanding. Wood frog tissue and wetland water samples were collected from several wetlands in the South Slave Region (Fort Smith and Fort Resolution areas) in 2012 and 2015 to test for metals including mercury and arsenic, and organic contaminants (polycyclic aromatic hydrocarbons and naphthenic acids). Water analyses were completed shortly after each year’s respective collection, but tissue analyses were not completed until early 2018 for various technical reasons. Statistical analyses and interpretation of these data are underway.

Information that may be helpful for amphibian monitoring initiatives includes that amphibians begin calling very soon after ice melts from pond edges in the spring and does not continue all spring/summer. Any methodology that relies on detecting breeding calls should begin no later than 15 May (earlier if possible) and should recognize that most individuals of all species will have stopped calling before 15 June.

Another important aspect of northern amphibian biology is that northern populations of amphibians tend to be more colourful and have more diverse patterns than conspecifics farther south and east in their respective ranges. Wood frogs have particularly diverse, spotted colour patterns in the north and may be misidentified as northern leopard frogs or toads so care must be taken with identification.

Comment is warranted about the growing use of eDNA to detect rare/hard-to-locate species as well as wildlife pathogens. Although this important methodology solves many logistical issues associated with field sampling, it is not a panacea, and its limitations must be recognized. For example, poorly timed and improperly handled samples, cross-contamination in the field, and rampant PCR inhibitors in natural wetland waters can completely negate the utility of test results. Biologists are encouraged to consult with experts well in advance of incorporating eDNA into any study and should also anticipate the ramifications of false positives and/or false negatives in their study.

Finally, it’s important to practice good field hygiene to prevent accidentally moving the propagules of invasive species and pathogens among locations – a person needn’t be studying them, or even aware of them, to do a very good job of accidentally spreading them across the landscape.

Anyone can help gather meaningful information about amphibians and reptiles in the NWT by learning how to identify species and by reporting their observations on user-friendly websites such as iNaturalist or to their nearest ECC office. Mass mortality events should be immediately reported to the nearest ECC office.