Variation in home range size and patterns in adult female American crocodiles Crocodylus acutus

Abstract

The American crocodile Crocodylus acutus is a threatened species that uses relatively deep, open-water habitats with low salinity. Adult female American crocodiles nest on sandy coastal beaches, islands or human-made berms, assist in the hatching process, and can travel long distances to nesting habitat. We satellite-tracked 15 adult female American crocodiles in 2 hydrologically distinct areas in Everglades National Park, Florida, USA, to quantify the home range sizes, test for intraspecific differences in home range and core area size and structure, and identify important crocodile high-use areas. Overall home ranges (95% kernel density estimate; KDE) for adult female crocodiles in South Florida ranged from 30.0 to 141.9 km 2 (mean ± SD, 84.4 ± 32.3 km 2 ), and core areas (50% KDE) ranged from 4.7 to 27.4 km 2 (17.8 ± 7.3 km 2 ). We identified patterns in home range and core area overlap, seasonally shifting patterns in core area use, and the Fox Lake complex as an important crocodile high-use area. As the population of American crocodiles continues to grow and expand into new areas, it is important for conservation managers to understand individual crocodile habitat-use patterns and spatial resource requirements.

American crocodiles (Crocodylus acutus) as restoration bioindicators in the Florida Everglades

“…This supports the hypothesis that freshwater diversion and the associated deterioration of habitat conditions in NEFB, an area that has historically supported high crocodile numbers, has negatively impacted the health and abundance of crocodiles there [22,28,30]. Crocodile numbers have increased in FLAM and CAPE areas [22,79], which is likely due to the cumulative effects of ongoing restoration efforts near these areas (Table 1). The plug at Buttonwood Canal may have reduced saltwater intrusion northward and improved nursery habitat in this area (Table 1).…”

“…By age six, subadult crocodiles have a 90% survival rate that continues into adulthood. The first few years of a crocodile's life are critical and are directly related to experiences during the first six months of life [26] and may be an indicator of environmental conditions [79]. Survival rates were highest in CRL (69%) and FLAM (53%) and much lower in NEFB (34%) and MADB (31%) areas.…”

“…Crocodiles in CAPE and FLAM areas maintained the highest body condition and fastest growth rates, while survival rates were also much higher in FLAM and CRL areas. These results are likely because of the plugging of canals at Cape Sable to reduce saltwater intrusion and of the ability for crocodiles to travel up into protected estuarine habitat in the nearby Fox Lakes for foraging [79]. Low crocodile hatchling survival has been correlated with greater travel distances to freshwater sources, low prey availability, and fewer refuge habitats [22,28,29].…”

Home range and habitat use of two sympatric crocodylians (Melanosuchus niger and Caiman yacare) under changing habitat conditions

“…In the last months of study, our data show that M. niger and C. yacare have the lowest average HR recorded, as compared to other studies. When reviewing the published HR data for crocodylians, it becomes clear that there is a large difference between the sizes of the HR reported, with the lowest average for Tomistoma schlegelii with 0.8 ha (Bonke et al, 2014) and the largest for Crocodylus acutus with 8436 ha (Beauchamp et al, 2018). Despite this large range in HR of crocodylians, we were surprised that MR's reported during the last month of our study were smaller than those reported for all other crocodylian species.…”

Space use and social interactions of Central African slender‐snouted crocodiles Mecistops leptorhynchus (Bennett, 1835) in Loango National Park, Gabon

“…Comprehensive studies of spatial ecology have been undertaken on many crocodylian species using a variety of methods. These studies have improved our knowledge on movement patterns and home range of Alligator mississippiensis (Rodda, 1984; Rootes & Chabreck, 1993; Rosenblatt et al, 2013), Alligator sinensis (Ding et al, 2004), Caiman yacare (Campos et al, 2006), Crocodylus acutus (Balaguera‐Reina et al, 2016; Beauchamp et al, 2018), Crocodylus intermedius (Munoz & Thorbjarnarson, 2000), Crocodylus johnstoni (Tucker et al, 1997), Crocodylus niloticus (Calverley & Downs, 2015; Combrink et al, 2017; Hutton, 1989), Crocodylus porosus (Brien et al, 2008; Campbell et al, 2013; Kay, 2004; Read et al, 2007), Gavialis gangeticus (Lang & Whitaker, 2010), Melanosuchus niger (Martin & da Silva, 1998), Paleosuchus trigonatus (Magnusson & Lima, 1991) and Tomistoma schlegelii (Bonke et al, 2014). Habitat use, homing abilities, dispersal and social interactions have also been described for some species (Balaguera‐Reina et al, 2016; Goodwin & Marion, 1979; Hutton, 1989; Read et al, 2007; Rodda, 1984; Rosenblatt et al, 2013; Tucker et al, 1997).…”