Management program for the saltwater crocodile in the Northern Territory of Australia 2009-2013
Fukuda, Yusuke; Delaney, Robyn; Leach, Gregory J
Northern Territory. Department of Natural Resources, Environment, The Arts and Sport
E-Publications; E-Books; PublicationNT
The draft program is open for public comment to Friday 29 May 2009. Includes Summary document.
Date:2009-04; Made available via the Publications (Legal Deposit) Act 2004 (NT).
Crocodylus porosus -- Northern Territory; Crocodiles -- Conservation -- Northern Territory; Crocodiles -- Control -- Northern Territory; Crocodiles -- Government Policy -- Northern Territory
Northern Territory Government
60 pages : illustration, maps ; 30 cm.
Attribution International 4.0 (CC BY 4.0)
Northern Territory Government
Draft Management Program for the Saltwater Crocodile in the Northern Territory 40 efforts over the last 30 years, the details of which are contained in a variety of publications (e.g. Bayliss and Messel 1990; Burbridge 1987; Messel et al. 1981; Messel and Vorlicek 1985, 1986; Taplin 1987, 1990; Webb et al. 1984, 1987; Webb and Manolis 1989, 1993). Table 1: Summary of the biological characteristics of C. porosus (Source: Webb and Manolis 1993 and citations therein) Characteristic C. porosus Biology Size and age at sexual maturity (males) 3.3 m; 16 yrs Size and age at sexual maturity (females) 2.3 m; 12 yrs Normal maximum length (males) 4.6-5.2 m Normal maximum length (females) 3.1-3.4 m Maximum length (males) 6-7 m Maximum body weight 900-1500 kg Nesting Season; months Wet Season; Nov.-May. Duration of egg laying 28 weeks Mean clutch size; (range) 50.0 (2-78) Mean egg weight; (range) 113.0 g (65-147) Mean hatchling weight Egg incubation time (days) 69.4 g 75 (at 33oC)-106 (at 29oC) Nest defence Common Nesting ecology Saltwater Crocodiles breed during in the wet season between October and May. Females construct a mound of grasses and reeds that is typically located close to permanent water. Freshwater swamps near tidal rivers and saltmarsh habitats are the most frequently used nesting habitats (Webb et al. 1984; Webb & Manolis 1989). Mangrove swamps can also be used for nesting. The extent and timing of nesting is related to rainfall and water levels in the late dry season (Webb 1991). Years with high rainfall and cool conditions between August and November are associated with high nesting effort. Conversely, years with poor rainfall and hot conditions between August and November are associated with low nesting effort (Webb 1991). The typical clutch size of C. porosus is approximately 50 eggs. The size of the clutch is proportional to the size of the individual female. The clutch of first-time breeders is normally around 30 eggs. Large crocodiles also produce larger eggs than smaller crocodiles (Webb & Manolis 1989). Around 6.5% of the eggs laid are infertile (Webb & Manolis 1989). There is a high mortality of Crocodylus porosus eggs with flooding being the major cause of deaths as it may kill over 50% of the eggs laid each year (Webb & Manolis 1989). Survivorship and population dynamics There is a high mortality rate of crocodiles from egg to maturity. Webb and Manolis 1993 estimated rates of survival for several size classes of C. porosus in the wild: approximately 30% of eggs usually hatch; 12% of hatchlings survive to one year; 85% of one year old crocodiles survive to two years; 85% of two year olds survive to three years of age; 85% of three year olds survive to four years of age; 85% of four year olds survive to five years of age. It follows that about 6 crocodiles would survive to five years from 1000 eggs laid. The