Florida Key Deer Abundance and Recovery Following New World Screwworm Infestation

Authors: Israel D. Parker, Roel R. Lopez, Nova J. Silvy, Brian L. Pierce, Kate G. Watts, Erin P. Myers, Samantha E.J. Gibbs, Donald S. Davis, Jared T. Beaver, and Alison A. Lund

An infestation of Cochliomyia hominivorax (New World Screwworm, hereafter Screwworm) was detected in the endangered Odocoileus virginianus clavium (Florida Key Deer) population in July 2016. We assessed the impact of this infestation on Florida Key Deer population abundance and recovery potential. We synthesized historical mortality and population data with new analyses including monitoring of Florida Key Deer mortalities and estimation of abundance on Big Pine Key and No Name Key (islands that support 75% of the Florida Key Deer population). We documented 135 Screwworm-related Florida Key Deer mortalities (~9–20% of the total population) during the Screwworm outbreak (July 2016–January 2017). Most mortalities occurred in the adult male population, as Screwworm flies laid eggs on open wounds sustained from sparring during mating season. The Screwworm incident was contained prior to the 2017 fawning season, which prevented substantial negative impacts on females or fawns. Historical growth rates at similar population levels and sex ratios indicated that, absent other external variables (e.g., Hurricane Irma in September 2017), the population was likely to recover.

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