Modeling the effects of invasive species on crocodilian populations

Karin Ebey

Vol. 2 Issue 1. p. 18- 24 (2020)

https://doi.org/10.36838/v2i1.4

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ABSTRACT: Invasive species are a growing threat to biodiversity. Crocodilians have been impacted by many invasive species; their effects are not well understood. A model was created using Python code to explore the effects of invasive species on crocodilians, including a crocodilian and seven prey species. A novel adaptation of the Lotka-Volterra equations was developed to model the complex predator-prey interactions, accounting for many species, species that act as both predator and prey, and a timescale of months with reproduction once a year. Invasive species effects on individual species, pairs of species, and combinations of multiple species were modeled and found to cause one of two ecosystem responses: 1) the crocodilian population increases and the populations of other species in the ecosystem decline; 2) the reptile population increases and the populations of other species in the ecosystem decline. When invasive species effects were stopped midway through the simulation, to represent invasive species eradication, the same responses were observed at a slightly later timescale, indicating that eradication is not sufficient to restore the ecosystem. The model was validated by comparisons with data of responses to invasive species observed in the wild. Following an invasive species establishment, the best first step is to determine which species are impacted as this indicates which ecosystem response will occur and informs management strategies to protect the ecosystem.

KEYWORDS: Ecology; Invasive Species; Simulation; Crocodilians