Evaluating invasive reptile control efforts: nocturnal bulk removal of green iguanas (Iguana iguana Linnaeus, 1758) in Florida, USA

The green iguana ( Iguana iguana Linnaeus, 1758) ranges from Mexico to Brazil and portions of the Lesser Antilles. In Florida, iguanas are an invasive species responsible for numerous adverse impacts, prompting a demand for removal. Removal efforts have been inconsistent throughout Florida and the effects of removal on population size have not been evaluated. We conducted diurnal count surveys between 2018 and 2019 to estimate iguana abundance across two populations, treatment and control, along the C-11 Canal in Broward County, FL. We applied a nocturnal removal method for iguanas in the treatment population between the first and second period to assess its effect on the overall population. We removed 808 iguanas from the treatment population. We observed decreasing iguana captures with continued removal efforts, which was corroborated with an impact on daytime abundance estimates from count surveys. However, a seasonal reduction of iguana abundance was observed in the control population, with the number of iguanas observed in the control population not significantly different than the treatment population by the last period. While reductions of iguanas in the control population were not as extreme as those observed for the treatment population, this indicates that the biology of invasive iguanas likely plays a role in seasonal variation in abundance and stresses the need to fill knowledge gaps concerning the ecology of iguanas in Florida. Our results demonstrate why one-time removal efforts, or repeated efforts conducted over a short duration, are insufficient to control population growth, highlighting the need for continuous and persistent efforts.