American crocodile nesting in sediment-nourished habitats on Crocodile Lake National Wildlife Refuge, Florida, USA

Abstract

The American crocodile (Crocodylus acutus) is the most widely distributed New World crocodile. However, the species has experienced severe declines due to overexploitation. In South Florida, loss of nesting habitat, with coastal degradation from sea level rise and urban development has prompted American crocodiles to nest in novel habitats. Crocodile Lake National Wildlife Refuge (CLNWR) serves as an important nesting site for the South Florida population of American crocodiles and more recently nesting habitat has been supplemented to manage coastal erosion. The goal of this study was to investigate the internal nest biology of American crocodile nests laid in sediment nourished sand mounds on CLNWR. We monitored internal nest temperature and volumetric water content of five live and two control sand nests in 2021 (N = 73 eggs) and 2022 (N = 84 eggs). The metabolic heat generated by incubating eggs in internal nest temperatures ranged from 0.8°C to 2.0°C warmer and more stable than ambient temperatures and reflecting a seasonal pattern. Average clutch size was 31.4 ± 7.09 eggs and incubation period ranged from 78 to 114 days until hatching. These data provide the first insight into thermal regimes of nests laid in novel/supplemented nesting habitat as is the case for a significant proportion of nests in the South Florida population of American crocodiles. Here we provide an opportunity to evaluate the importance of creating artificial nesting habitat for American crocodiles where habitat degradation from climate change threatens species survival.