Movements and home ranges of radio-tracked Crocodylus porosus in the Cambridge Gulf region of Western Australia

Abstract

VHF radio-tags were attached to 16 estuarine crocodiles that were tracked between October 2001 and May 2003. Male (n = 12) and female (n = 4) crocodiles exhibited distinctly different patterns of movement. Females occupied a small core linear range (1.3 ± 0.9 km) on the main river channel during the dry season and moved up to 62 km to nesting habitat during the wet season, returning to the same core area the following dry season. They occasionally made excursions away from their core areas during the dry season. Males moved considerable distances along the Ord River throughout the year. The largest range recorded was 87 km for a 2.5-m juvenile male. However, ranges of males did not appear to be related to body size, with the largest two ranges being recorded for the smallest (2.5 m) and largest (4.3 m) males tagged. Rates of movement of males did not differ significantly between three size classes of males but there were significant seasonal differences, with the highest mean rates of movement occurring during the summer wet season (4.0 ± 5.4 km day–1). However, males were quite mobile during the dry season and the highest rate of movement detected was 23.3 km day–1 for a 4.3-m male at the end of July. The highest rate of sustained movement was 9.8 km day–1 for a translocated 2.6-m juvenile male, which travelled 118 km in 12 days to return to the area of its capture. Neither males nor females showed exclusive habitat preferences for any of four broad riverine habitats identified on the Ord River. However, the three largest males had activity centres that they returned to frequently despite numerous excursions throughout the year, both up- and downriver. Males had substantial range overlaps with no obvious spatial partitioning, suggesting that territoriality is not an important behavioural characteristic of free-ranging male crocodiles along the Ord River.

Testing reintroduction as a conservation strategy for the critically endangered Chinese alligator: Movements and home range of released captive individuals

“…Many studies have identified temperature as one of the main factors influencing crocodilians' ranging behavior, and the warmer season usually resulted in stronger movement and a larger home range [27][28][29][30][31]33]. Although temperature significantly influenced the movement of the two alligators, its influence on home-range variations of the two alligators in the three seasons was not significant (Table 5).…”

Conservation genetics of American crocodile, Crocodylus acutus, populations in Pacific Costa Rica

“…This could explain why moderate differentiation was observed between most population pairs. However, the highly mobile nature of crocodiles (Kay 2004;Campos et al 2006;Read et al 2007;Campbell et al 2013) could be facilitating gene flow between populations along the Pacific coast. A recent study on the spatial ecology of C. acutus in Panama, suggests that males have a larger home ranges, but females have larger average movement distances (Balaguera-Reina et al 2016).…”

“…A series of estuaries provide pockets of suitable crocodile habitat along the Pacific coast which made it an optimal area for studying gene flow between potential metapopulations. Crocodiles are known to migrate long distances (Kay 2004;Campos et al 2006;Read et al 2007;Campbell et al 2013). There have been accounts of C. acutus migrating over 35 km for nesting (Cherkiss et al 2006) and movements over 388 km (Cherkiss et al 2014) in southern Florida.…”

Nile crocodile Crocodylus niloticus telemetry: observations on transmitter attachment and longevity

“…However, the types of data thus generated remain insufficient for most crocodilians other than the American alligator Alligator mississippiensis (Kay 2004a). Various radio transmitter attachment configurations have been used on crocodilians outside of Africa, including ingestion (Grigg et al 1998), tethering (Munoz & Thorbjarnarson 2000), implantation (Magnusson & Lima) and attachment of transmitters to the nuchal scales using bone pins and/or glue (Kay 2004b;Read et al 2007).…”