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. (2014) Feeding across the food web: The interaction between diet, movement and body size in estuarine crocodiles (Crocodylus porosus). Austral Ecology, 40 3: 275-286. doi:10.1111/aec.12212


Author Hanson, Jeffrey O.
Salisbury, Steven W.
Campbell, Hamish A.
Dwyer, Ross G.
Jardine, Timothy D.
Franklin, Craig E.
Title Feeding across the food web: The interaction between diet, movement and body size in estuarine crocodiles (Crocodylus porosus)
Formatted title
Feeding across the food web: The interaction between diet, movement and body size in estuarine crocodiles (Crocodylus porosus)
Journal name Austral Ecology   Check publisher's open access policy
ISSN 1442-9993
1442-9985
Publication date 2014-12-08
Year available 2014
Sub-type Article (original research)
DOI 10.1111/aec.12212
Open Access Status
Volume 40
Issue 3
Start page 275
End page 286
Total pages 12
Place of publication Richmond, VIC, Australia
Publisher Blackwell Publishing
Collection year 2015
Formatted 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.
Keyword Acoustic telemetry
Apex predator
Discrimination factor
Home range
Stable isotope
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2015 Collection
School of Biological Sciences Publications
 
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