A specialist surrounded by suburbia: the ecology of a newly described Four-toed Salamander population in New Brunswick

Background Urbanisation can negatively impact biodiversity, often resulting in smaller and more isolated populations—which can be particularly detrimental for habitat specialists. Yet, under the right ecological conditions, urbanised greenspaces can also act as refugia for remnant populations to persist. The Four-toed Salamander ( Hemidactylium scutatum ) is an example of a macrohabitat specialist; it is an amphibian which relies specifically on habitat with bogs/fens and adjacent upland forests. In New Brunswick, Canada, this salamander is presumed to be critically imperilled as it had previously only been observed in a single location, a protected national park. A second population, however, was recently discovered within an urbanised greenspace in Riverview, New Brunswick. Notably, this area is enveloped by anthropogenic landscape features ( e.g. , roads, parking lots, housing, businesses), which demonstrates how this species can also occur in more urbanised areas. Our study aims to understand the population ecology of Four-toed Salamanders at this newly described site and investigate how its habitat use allows it to persist in an area with strong anthropogenic disturbance. Methods We estimated the current relative abundance and density, and quantified the demographics, of Four-toed Salamanders at the Riverview site, while also testing to see if these salamanders favoured specific microhabitats within both fen and upland forest habitats. We contrasted a wide range of suitable environmental variables ( e.g. , substrate temperature, acidity, canopy cover, humidity, and plant percent coverage) between locations containing a salamander to nearby, unoccupied locations. Results We found a total of 67 salamanders across all surveys, which translates to a conservative relative population density estimate of 2.12 individuals/ha. We observed few differences in microhabitats between where salamanders were seen and random locations, which suggests that suitable microhabitats were not limited for these amphibians at this site. These differences were that salamanders preferred higher slopes within moss hummocks in fens, cooler substrates in the forest, and the presence of woody debris in the forest. Discussion & Conclusion Our study provides key insights into the habitat characteristics of Four-toed Salamanders at the northern extent of their range, a species with a cryptic lifestyle that is widely considered to be a macrohabitat specialist. By quantifying the ecological features of an urban habitat being used by Four-toed Salamanders in New Brunswick, we expand the types of ecosystems conservation biologists and wildlife managers should consider viable when conducting additional surveys and assessments for this species. This study increases our knowledge about the niche of an amphibian whose conservation and protection in New Brunswick, and more broadly in Canada, is hindered by a lack of foundational natural history data.