Find me if you can: Pre- and Post-hurricane Densities of the Red-bellied Racer (Alsophis rufiventris) on St. Eustatius, and a review of the genus in the Caribbean

Abstract

We estimated population densities of the red-bellied racer (Alsophis rufiventris) on the Caribbean island of St. Eustatius in 2011, 2018 and 2019 to determine the likely influence of hurricanes Irma and Maria (September 2017), in addition to evaluating abiotic parameters which may be correlated with its presence. Surveys were conducted at seven sites in 2011 prior to the hurricanes, and at 81 and 108 sites in 2018 and 2019 respectively posterior to the hurricanes. A total of 8.2 ha was surveyed in 2011, and 11.42 ha in 2018/2019. The pre-hurricane (2011) racer density estimate was 9.2/ha (min 7.3 - max 11.6); post-hurricane estimates were 4.6/ha (min 3.4 - max 6.0) in 2018 and 5.0/ha (min 3.8 - max 6.5) in 2019. The pre-hurricane encounter rate of individual racers was 16.0 snakes/hour compared to 0.34 snakes/hour in 2018 and 0.41 snakes/hour in 2019 (post-hurricane). The decrease in encounter rates between 2011 and 2019 implies a negative impact of the hurricanes on racer abundance. Based on calculations of detection probability (0.02 in 2018 and 0.03 in 2019), post-hurricane lambda estimates were 1.82 (95% CI 0.66 - 5.01) in 2018 and 1.60 (95% CI 0.39 - 6.65) snakes/ha in 2019. Given the current small size of the remaining population and the presence of invasive species across the snake's range, this species could be at risk of local extirpation. We suggest conservation actions such as invasive species management and habitat restoration to enable further recovery.

Hurricane‐associated population decrease in a critically endangered long‐lived reptile

“…Effect assessments of the 2017 Atlantic hurricane season demonstrate its broad impact on ecosystems and their trophic levels; for example, beach, mangrove, and forest ecosystems (Barreto‐Orta et al, 2019; Hall et al, 2020; Liu et al, 2018; Walcker et al, 2019), salt and freshwater fish communities (Meléndez‐Vazquez et al, 2019; Neal et al, 2020), insect species and communities (Cabrera‐Asencio & Meléndez‐Ackerman, 2021), birds (Lloyd et al, 2019; Palmer et al, 2018), and sea slugs (Middlebrooks et al, 2020). For St. Eustatius specifically, our data add to the understanding of an ecosystem‐wide hurricane impact during 2017 which, besides iguanas, affected forests (Eppinga & Pucko, 2018), as well as populations of Bridled Quail‐dove (River‐Milan et al, 2021) and Red‐bellied racer (Madden et al, 2021). Importantly, these insights and novel risk assessments demonstrate the high extinction risk that endemic, island species will face under projected climate change (Manes et al, 2021).…”

“…For St. Eustatius specifically, our data add to the understanding of an ecosystem-wide hurricane impact during 2017 which, besides iguanas, affected forests (Eppinga & Pucko, 2018), as well as populations of Bridled Quail-dove (River-Milan et al, 2021) and Red-bellied racer (Madden et al, 2021). Importantly, these insights and novel risk assessments demonstrate the high extinction risk that endemic, island species will face under projected climate change (Manes et al, 2021).…”

“…Models were based on four assumptions: (i) The iguana population in each site was closed to colonization and extinction during the sampling period; (ii) iguanas were either detected or not detected during surveys; (iii) iguanas were not falsely detected during surveys; and (iv) iguana detections at each site were independent (Murray & Sandercock, 2020). We followed the methods described by Madden et al (2021). Briefly, we used likelihood‐based single‐season occupancy models (MacKenzie et al, 2017), using the R packages “wiqid” and “unmarked” (Fiske & Chandler, 2011; MacKenzie et al, 2002; Meredith, 2020), to estimate site occupancy ( ψ ) in relation to habitat and elevation, while accounting for detectability ( p ).…”