Genetic evidence for invasive rat‐caused vegetation damage has implications for endemic Caribbean mammal management

Abstract Invasive murid rodents have disrupted native biodiversity, including vegetation composition and structure, across island systems such as the Caribbean ecoregion. However, translocations of the Bahamian hutia ( Geocapromys ingrahami ), a threatened Caribbean rodent, have also prompted concerns about vegetation damage, raising complex challenges for management of this species. Extensive vegetation damage reported on John Higgs Cay (Turks and Caicos Islands), along with the presence of abundant large faecal pellets and local traditions of large‐bodied rodents called ‘hootees’, was suggestive of possible survival of a remnant hutia population. Fieldwork was conducted to document vegetation damage and collect faecal samples for genetic analysis, which was carried out using ancient DNA protocols for degraded specimens. Extensive areas of damaged shrubs exhibiting stripped vegetation and gnawed branches were present on John Higgs Cay, with damage to 15 species including the highly toxic Metopium toxiferum . Although observed vegetation damage differed somewhat from a Bahamian cay exhibiting damage reportedly made by hutias, differences in local ecology and plant diversity between islands could influence rodent food selection and plant survival. An ancient DNA approach designed to remove PCR inhibitors provided robust identification of faecal pellets as being from black rats ( Rattus rattus ) based upon mitochondrial and nuclear genomic data, indicating that vegetation damage on John Higgs Cay was caused by this invasive species rather than by hutias. Local respondent descriptions of ‘hootees’ were found to refer to invasive brown rats ( Rattus norvegicus ) that nested in mangroves. Practical implication . Our findings highlight the potential for species misidentification when using indirect signs to survey small mammals in ecologically novel landscapes, providing an important note of caution when assessing unverified reports of species survival. Our study also demonstrates that invasive rodents can cause extensive disruption to native vegetation on tropical islands, highlighting the possibility that damage previously blamed upon hutias may instead be made by rats. Invasive rodents have been present in Caribbean ecosystems for centuries, and the vegetation damage they cause may now be overlooked and perceived as ‘natural’, raising important questions about interpreting native biodiversity states and defining management targets.