Conservation of rare and cryptic species: Challenges of uncertainty and opportunities for progress

Abstract

Effective conservation of at‐risk species presents a conundrum, often requiring rapid status assessments and timely actions regardless of the adequacy of best available information. Here, we present a case study on Humboldt martens (Martes caurina humboldtensis), a rare and cryptic carnivore listed as threatened in 2020 under the United States Endangered Species Act. Given their rarity, many aspects of Humboldt marten population ecology remain understudied. To help inform marten conservation, we conducted exploratory analyses to estimate population growth by incorporating empirically derived data into two demographic modeling approaches. Population growth rates from each approach exhibited substantial variability and were uninformative to evaluating population status. Our results highlight the inherent difficulties of studying cryptic animals and exemplify the issues of using sparse or uncertain data in potentially consequential circumstances. Considering the shortcomings of our findings, we provide a framework of reliable actions to improve future conservation outcomes for poorly‐understood species.

Structural complexity characterizes fine‐scale forest conditions used by Pacific martens

“…Our research indicates that fine-scale forest conditions of marten denning and resting locations were largely similar across study sites that were not entirely analogous, as martens consistently used large diameter woody structures (e.g., live trees, snags) that were surrounded by specific forest attributes (e.g., greater numbers of larger diameter replication in accumulating evidence and strengthening inference (Johnson 2002). This approach is particularly important for relatively rare species such as martens that may have large knowledge gaps and require substantial effort to study (Martin et al 2022b).…”

“…Compatible data collection methodologies allowed us to leverage research from both study sites by incorporating data into a single model framework, illustrating the value of replication in accumulating evidence and strengthening inference (Johnson 2002). This approach is particularly important for relatively rare species such as martens that may have large knowledge gaps and require substantial effort to study (Martin et al 2022 b ).…”

Uncertainty propagation in matrix population models: Gaps, importance and guidelines

“…Often, estimates for particular demographic rates are obtained from the literature or are based on expert opinion due to a lack of data from which to estimate them statistically. This data deficiency is particularly common for species with cryptic life‐cycle stages and for rare species (Beissinger, 2014; Fitzgerald et al., 2021; Martin et al., 2022). Yet, the use of the literature or expert estimates does not preclude the inclusion of uncertainty entirely.…”

High occupancy of European leaf-toed geckoEuleptes europaeain two island stands ofEucalyptus sp.: tree selection, co-occurrence and habitat effect

“…Yet sometimes, part of the ecology of a species can go unnoticed or be obscured by lack of knowledge or by 'expert' judgement that overlooks uncertainty (Burgman 2005). This is especially true for cryptic species, which are difficult to detect and have a restricted range, so are the least well studied and the least known (de Lima et al 2011;Martin et al 2022). This is the case for the European leaf-toed gecko (Euleptes europaea), a tiny cryptic gecko endemic to the western Mediterranean with a mainly insular distribution (Delaugerre 2004).…”

“…Yet sometimes, part of the ecology of a species can go unnoticed or be obscured by lack of knowledge or by ‘expert’ judgement that overlooks uncertainty (Burgman 2005). This is especially true for cryptic species, which are difficult to detect and have a restricted range, so are the least well studied and the least known (de Lima et al 2011; Martin et al 2022).…”