Nonnative invasive species are one of the top threats to global biodiversity. Due to Florida’s subtropical climate and peninsular geography, it hosts more nonnative species of reptiles and amphibians than native. One invader of immediate concern is the Nile monitor (Varanus niloticus), which is established in three distinct locations in Florida: Cape Coral, Lee County, the C-51 canal in West Palm Beach County, and Homestead Air Reserve Base and surrounding canals in southern Miami-Dade County, FL. Our objective was to describe the diet of Nile monitors to inform impact assessments and improve removal efforts. We examined gastro-intestinal tracts of 36 Nile monitors collected by shooting during 6 August 2012 to 19 January 2016 from the C-51 Canal. The ratio of males to females did not differ from 1:1, with 16 males, 19 females, and one undetermined hatchling. Size classes were categorized by total length; hatchling/YOY were 30≤ 50 cm, juvenile/sub-adult were >50 ≤ 90 cm, and adults were >90 cm. Of the males, there were 15 adults and 1 juvenile, and of the females, there were 16 adults and 3 juveniles.
Results/Conclusions
Thirty-one (86.1%) of the 36 V. niloticus examined contained prey items in their stomachs. Frequency of occurrence of main prey items was invertebrates (56%), reptiles (31%), eggs and egg masses (28%), amphibians (19%), bones (17%), fish (3%), and mammals (3%). Snails were the most common invertebrate followed by ants and beetles. Notable prey items include cane toads (Rhinella marina), glass lizards (Ophisaurus ventralis), iguanas (Iguana iguana), leopard frogs (Lithobates sphenocephalus), basilisks (Basiliscus vittatus), and reptile eggs and amphibian egg masses. The composition of prey items suggests that Nile monitors forage along the aquatic/terrestrial ecotone with impacts on reptiles, amphibians, and their eggs being of concern. We recommend trapping efforts focus on the upland edge of the ecotone, and evaluating use of prey items consumed locally for potential trapping bait.