PS 39-14 - Detecting the potentially invasive Capybara (Hydrochoerus hydrochaeris) in Trinidad via non-invasive methods

Background/Question/Methods

Capybaras are a recent addition to lowland and wetland areas in Trinidad; however, their means of introduction remains contentious. Since capybaras are semi-aquatic, their foraging habits can alter vegetation structure and nutrient inputs, and they can act as important connectors across ecotones, having major implications for the ecosystems they inhabit. The central plains of Trinidad contain limited lowland areas which contrast with that of their native range on the mainland of South America. The distribution and patterns of habitat use for capybaras are particularly important given their non-native status in an island system, with finite space. Establishing abundance estimates are increasingly useful as a baseline to guide management decision-making. Traditional mark and recapture methods can be invasive, costly, impractical, and impose limits to collecting data on large mammals such as capybaras. Therefore, the data collected for this preliminary study used a combination of field surveys and camera traps. The motion-triggered cameras were set up randomly between April to August (2021) at 5 locations within the Caroni Watershed in areas of claimed sightings. The collected imagery was used to estimate activity, occupancy, and population demographics. Images were processed using machine learning technology via Camelot Project software, PRESENCE, and the r-package CamtrapR.

Results/Conclusions

Image collection effort was carried out for 165 camera trap days and showed that capybaras were most frequently active between 0500-0600hrs in the morning period and at 1800-1900hrs in the evening. The presence of capybaras was confirmed from field-site surveys within the Caroni Watershed through scat identification, footprints, trails, wallowing pits, access points into the river and body-shaped tunnels through the vegetation. Using the non-independent image captures, the proportion of capybaras positively identified consisted of different sexes (41.29% female and 58.71% male) and age classes (81.9% adult and 18.2% juveniles), found along the main rivers and tributaries, with a naïve occupancy estimate of 0.833. They occupied a range of habitat types including riverine, mangrove swamps and agricultural lands. Data collected from this study can inform future long-term monitoring strategies, as it is a crucial conservation objective to accurately account for any wildlife population, before determining a management strategy.