Fig 1.
Sampling sites within rivers Kakadu National Park, Northern Territory, Australia.
Crocodiles were sampled in three rivers and their respective floodplain areas (grey): Wildman, South and East Alligator Rivers.
Table 1.
Observations of feeding habits and stomach content of crocodiles in Kakadu National Park.
Fig 2.
Correlation between isotopic value of crocodile scute (δ13C and δ15N; ‰) and body size (mm).
Red circles are values from this study, blue circles are values from C. porosus in Cape York, Australia, from Hanson et al. 2015 [7]. Both datasets follow a linear trend of higher isotope values with increasing total body length (mm).
Table 2.
Mean ± se (min-max) of δ13C, δ15N and δ34S values of crocodiles and potential prey from Kakadu National Park, Australia.
Fig 3.
Isotopic composition (δ34S, δ13C and δ15N) of crocodiles (black diamonds) and potential prey.
Samples were obtained fromthe East Alligator River (A,C, E) and South Alligator River (B,D,F), terrestrial prey includes water buffalo (orange circle), pigs (red circle) and wallabies (yellow circle); riverine is represented by mullet (green circle); riverine-marine prey is represented by barramundi (purple circle) and marine prey is represented by giant sea catfish (blue circle). Crocodile data were corrected to the level of prey by subtracting 1.4 ‰ from δ13C values [7]. The effect on the crocodile value of different fractionation factors is shown as a box of possible values around the crocodile mean in panel B.
Fig 4.
3D plot of the isotopic composition (δ13C, δ15N and δ34S) of crocodiles (diamonds) and potential prey.
Samples are from the East and South Alligator Rivers; terrestrial prey includes water buffalo, pigs and wallabies; riverine prey is represented by mullet; riverine-marine prey is represented by barramundi and marine prey is represented by giant sea catfish.
Fig 5.
Proportion of contribution of prey to the nutrition ofestuarine crocodiles in Kakadu National Park.
Crocodiles were caught during the dry and wet season and isotope values were analysed with SIAR solo. Terrestrial prey includes water buffalo, pigs and wallabies; riverine prey is represented by mullet; riverine-marine prey is represented by barramundi and marine prey is represented by giant sea catfish. Box plots represent the 5, 25, 75 and 95% credibility intervals.
Fig 6.
Contribution of (A) terrestrial, (B) riverine, (C) riverine-marine and (D) marine prey to the diet of estuarine crocodiles. The contribution was assessed with SIAR solo using data from crocodiles ranging from 0.85 to 4.2 m long (TL).