Invasive Predator Control at a Selected Hawksbill Nesting Beach: Bath Pilot Project – Final Monitoring Report

Bath Beach, St John, Barbados is an important nesting site for hawksbill sea turtles
(Eretmochelys imbricata), with sixty-three (63) and seventy-two (72) confirmed nests
during the 2021 and 2022 nesting seasons, respectively. The site provides habitat for
various Invasive Alien Species (IAS) including mongooses (Urva auropunctata) and
rodents (Rattus norvegicus and Mus musculus). This project aimed to assess the impact
of IAS on hawksbills and endemic green anoles (Anolis extremus) over an 18 month
period from June 2021 – August 2022. Monitoring indicated that mongooses were
more widespread across the site while rodents were more localised. Mongooses were
frequently observed in densely vegetated areas near concentrated hawksbill sea turtle
nesting sites. Mongooses predated hawksbill nests on detection; nests in vegetation
showed predation rates of 63.16% in 2021 & 33.33% in 2022, experiencing greater
predation than those in open beach areas (29.55% in 2021 & 5% in 2021). In
comparison to previous research, the nest predation rate of 39.7% (n = 25) in 2021
marginally surpassed annual predation rates reported by Leighton et al. (2010), which
ranged from 17.9 to 38.9%. Nest predation decreased significantly by 75.6% in 2022 to
9.7%; possibly due to trapping which removed 57 mongooses from the population in 2022.

The Tomahawk 205 Collapsible Live Trap and DOC 250 Kill Trap had the greatest
capture success rates and the DOC 250 proved to be the most efficient method for
euthanization. The reduced predation rate following trapping demonstrates the
positive impact that invasive species control measures can have on the incubation
success of turtle nests. Monitoring research indicated that mongooses appeared to be
the only nest predator of hawksbill sea turtles throughout the 2021 and 2022 nesting
seasons at Bath Beach. The project did not identify any impact of mongooses on green
anoles at Bath Beach. To ensure project sustainability eighteen (18) staff members of
5 various government agencies and three (3) members of the Welch Bathland community
group were trained in mongoose trapping methods.