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Feeding across the food web: The interaction between diet, movement and body size in estuarine crocodiles (Crocodylus porosus)

Hanson, Jeffrey O., Salisbury, Steven W., Campbell, Hamish A., Dwyer, Ross G., Jardine, Timothy D. and Franklin, Craig E. (2015). Feeding across the food web: The interaction between diet, movement and body size in estuarine crocodiles (Crocodylus porosus). Austral Ecology,40(3):275-286.

Document type: Journal Article
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IRMA ID 81144320xPUB220
Title Feeding across the food web: The interaction between diet, movement and body size in estuarine crocodiles (Crocodylus porosus)
Author Hanson, Jeffrey O.
Salisbury, Steven W.
Campbell, Hamish A.
Dwyer, Ross G.
Jardine, Timothy D.
Franklin, Craig E.
Journal Name Austral Ecology
Publication Date 2015
Volume Number 40
Issue Number 3
ISSN 1442-9985   (check CDU catalogue  open catalogue search in new window)
Scopus ID 2-s2.0-84927909969
Start Page 275
End Page 286
Total Pages 12
Place of Publication Australia
Publisher Wiley-Blackwell Publishing Asia
HERDC Category C1 - Journal Article (DIISR)
Abstract The estuarine crocodile (Crocodylus porosus) is an apex predator across freshwater, estuarine and coastal environments. The impact of a changing C. porosus population upon the ecosystem is unknown, but due to large ontogenetic changes in body mass (>1000-fold) their impact may be wide reaching and substantial. Here we investigated the relationship between diet, movement and body size in a population of C. porosus inhabiting a tidal river in northern Australia. Subcutaneous acoustic transmitters and fixed underwater receivers were used to determine the activity space and movement patterns of 42 individuals (202–451 cm in total length). There was no size-related spatial partitioning among different sized crocodiles. Large individuals (snout–vent length (SVL): 160 cm < SVL < 188.5 cm) did, however, exhibit a much larger activity space than other size classes. Diet and individual specialization was assessed using the composition of stable carbon (δ13C) and nitrogen (δ15N) isotopes in tissues with different turnover rates. There was a quadratic relationship between body size and δ15N, suggesting that medium-sized individuals (110 cm < SVL < 160 cm) incorporated a greater proportion of high trophic prey into their diets than small (SVL < 110 cm) or large individuals (SVL > 160 cm). Tissue δ13C composition on the other hand was positively correlated with body size, indicating that different size classes were trophically linked to primary producers in different habitats. Individual-level analyses showed that small crocodiles were generalist feeders while medium and large size classes specialized on particular prey items within the food webs they fed. The findings further our understanding of ontogenetic variation in C. porosus diet, and suggest that change in C. porosus population size or demographics may be influential at various levels across the local food web.
DOI http://dx.doi.org/10.1111/aec.12212   (check subscription with CDU E-Gateway service for CDU Staff and Students  check subscription with CDU E-Gateway in new window)
 
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