Feeding across the food web

The interaction between diet, movement and body size in estuarine crocodiles (Crocodylus porosus)

JEFFREY O. HANSON, STEVEN W SALISBURY, Hamish Campbell, R Dwyer, Tim Jardine, Craig Franklin

Research output: Contribution to journalArticleResearchpeer-review

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.
Original languageEnglish
Pages (from-to)275-286
Number of pages12
JournalAustral Ecology
Volume40
Issue number3
DOIs
Publication statusPublished - May 2015
Externally publishedYes

Fingerprint

Crocodylus porosus
food webs
food web
body size
diet
crocodiles
freshwater environment
estuarine environment
generalist
body mass
coastal zone
population size
acoustics
partitioning
predator
fold
ecosystem
habitat
crocodile
demographic statistics

Cite this

HANSON, JEFFREY O. ; SALISBURY, STEVEN W ; Campbell, Hamish ; Dwyer, R ; Jardine, Tim ; Franklin, Craig. / Feeding across the food web : The interaction between diet, movement and body size in estuarine crocodiles (Crocodylus porosus). In: Austral Ecology. 2015 ; Vol. 40, No. 3. pp. 275-286.
@article{6811c77efbb347d9bc735ee87a3bc7ed,
title = "Feeding across the food web: The interaction between diet, movement and body size in estuarine crocodiles (Crocodylus porosus)",
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.",
author = "HANSON, {JEFFREY O.} and SALISBURY, {STEVEN W} and Hamish Campbell and R Dwyer and Tim Jardine and Craig Franklin",
year = "2015",
month = "5",
doi = "10.1111/aec.12212",
language = "English",
volume = "40",
pages = "275--286",
journal = "Australian Journal of Ecology",
issn = "1442-9985",
publisher = "Blackwell Publishing",
number = "3",

}

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; Dwyer, R; Jardine, Tim; Franklin, Craig.

In: Austral Ecology, Vol. 40, No. 3, 05.2015, p. 275-286.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Feeding across the food web

T2 - The interaction between diet, movement and body size in estuarine crocodiles (Crocodylus porosus)

AU - HANSON, JEFFREY O.

AU - SALISBURY, STEVEN W

AU - Campbell, Hamish

AU - Dwyer, R

AU - Jardine, Tim

AU - Franklin, Craig

PY - 2015/5

Y1 - 2015/5

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=84927909969&partnerID=8YFLogxK

U2 - 10.1111/aec.12212

DO - 10.1111/aec.12212

M3 - Article

VL - 40

SP - 275

EP - 286

JO - Australian Journal of Ecology

JF - Australian Journal of Ecology

SN - 1442-9985

IS - 3

ER -