Discipline: Biological Sciences
Room: Exhibit Hall A
Dijani Laplace - University of the Virgin Islands
Co-Author(s): Creightanya Brewley, University of the Virgin Islands, St. Thomas V.I; Deslyn Bartlett, University of the Virgin Islands, St. Thomas V.I
The Velvety Free-Tailed bat (Molossus molossus) is native to the United States Virgin Islands and provides an important role in its ecosystem. Yet, habitat-loss and climate change likely threaten their populations, while their elusiveness makes them difficult study targets for conservationists. Following the hurricanes that ravaged the island in 2017, the need to assess demographic data on these bats is greater than ever. Hence, we used data from a long-term monitoring project on St. Thomas to gain insight on population demographics. Our dataset contained bat morphometric data collected from multiple sites using mist net capture surveys conducted from 2008-2019. We compared mean bat captures per survey and mean Body Condition Index (BCI) across years using ANOVA and compared BCI for bats with or without ectoparasites using a chi- square test (X2). Two major sites on St. Thomas: Magens and Stumpy Bay, had their population sizes estimated using the Jolly-Seber Capture-Mark-Recapture method in RStudio. We then compared differences in demographics (X2¬¬¬), mean BCI (t-test), and estimated population size (t-test) between these two sites. To assess population characteristics, we tested three null hypotheses: 1) mean M. molossus captures per survey and mean Body Condition Index (BCI) of captures would not change across years, 2) here would be no significant difference in mean BCI of captures with and without ectoparasites, and 3) there would be no difference in age ratio, sex ratio, and estimated population size between the two study sites. We found no significant difference in mean M. molossus captures per survey at all survey sites from 2009-2019 (F(10,123)=1.41, p=0.184). Tukey HSD post hoc tests of mean BCI of captures across years following an ANOVA (F(10,545)=10.97, p< 0.0001) found significant difference between early years (2009-2011) relative to the latter years (2012-2019). Estimated population sizes between the two study sites were not significantly different from 2012-2016 (t=-1.49, df= 8, p=0.175). The Magens population had a higher proportion of females (X2= 5.53, df=1, p=0.0187) and juveniles (X2= 5.53, df=1, p=0.0187), and a lower mean BCI (X2= 5.53, df=1, p=0.0187) than did Stumpy Bay. The mean BCI of individuals with ectoparasites was significantly higher than those without (t-test, t=4.33, df= 344, p< 0.0001). M. molossus’ insectivorous diet may have attributed to their resiliency after their 2017 hurricanes, explaining the lack of change in their capture rates in this specific time frame. The demographic differences (age and gender ratios) observed between Magens Bay and Stumpy Bay may be due to localized habitat usage by sex, difference forest structure and roost sites. It is unclear why the BCI from 2009-2011 was higher than the remaining survey years (2012-19) collectively. Ectoparasites also did not appear to negatively affect bat BCI, suggesting that their overall health is unaffected by these parasites, possibly because they have coevolved. These results reveal important patterns in site occupancy by this species, which may provide direction for conservation management. These results indicate that longitudinal studies on population parameters are needed to determine species response to environmental change. References: Platenberg, R. J. and J. M. Valiulis (Eds). 2018. United States Virgin Islands Wildlife Action Plan, Vol. 2: Habitats and Species. Final report to the USVI Department of Planning and Natural Resources Division of Fish and Wildlife. University of the Virgin Islands and St. Croix Environmental Association, US Virgin Islands. VI Bat Team. 2019. Long-term bat monitoring on St. Thomas 2008-2019. Unpublished raw data. Funder Acknowledgement(s): We thank the ECS Honors Fund and the NSF HBCU-UP ACE grant award #1623126 for funding this research. Faculty Advisor/Mentor: Renata Platenberg, firstname.lastname@example.org
Funder Acknowledgement(s): We thank the ECS Honors Fund and the NSF HBCU-UP ACE grant award #1623126 for funding this research.We thank the ECS Honors Fund and the NSF HBCU-UP ACE grant award #1623126 for funding this research.
Faculty Advisor: Renata Platenberg, email@example.com
Role: I conducted research to find journal articles to help account for the population characteristics we found for the M. molosssus here on St. Thomas. Furthermore, I also used RStudio to conduct the population estimates for the two major sites of focus: Magens Bay and Stumpy Bay