Ecological and physiological determinants of dive duration in the freshwater crocodile

Campbell, H. A., Sullivan, S., Read, M.A., Gordos, M.A. and Franklin, C.E. (2010) Ecological and physiological determinants of dive duration in the freshwater crocodile. Functional Ecology, 24 1: 103-111. doi:10.1111/j.1365-2435.2009.01599.x


Author Campbell, H. A.
Sullivan, S.
Read, M.A.
Gordos, M.A.
Franklin, C.E.
Title Ecological and physiological determinants of dive duration in the freshwater crocodile
Journal name Functional Ecology   Check publisher's open access policy
ISSN 1365-2435
Publication date 2010-02
Year available 2009
Sub-type Article (original research)
DOI 10.1111/j.1365-2435.2009.01599.x
Volume 24
Issue 1
Start page 103
End page 111
Total pages 9
Editor Charles W Fox
Place of publication UK
Publisher Wiley-Blackwell Publishing
Collection year 2010
Language eng
Subject C1
970106 Expanding Knowledge in the Biological Sciences
0608 Zoology
Formatted abstract
1. Body mass is a key determinant of diving performance in endotherms. In air-breathing ectotherms however, this paradigm occurs with considerably less force. Here, through remote recordings of dive behaviour over a wide size range (5–42 kg body mass, n = 17) of freshwater crocodiles (Crocodylus johnstoni), we demonstrate why body mass is such a poor determinant of dive duration for ectothermic divers.

2. Crocodiles were released into the wild with a time-depth-recorder attached to their dorsal scutes, and a movement activated radio-tag attached to their tail. Over 15 days, 652·6 ± 58·4 (mean ± SE, n = 17) dives were recorded, with all individuals exhibiting two specific dive-types. These were, a resting-dive (62·7 ± 5·4% of total dive no.), where no activity occurred during the dive, and an active-dive (37·1 ± 6·3% of total no.) associated with swimming.

3. The durations of resting-dives (∼12 min) were similar for all crocodiles. Smaller crocodiles (6·3 ± 0·7 kg, mean ± SE, n = 9) exhibited a significant correlation between dive duration and post-dive surface-interval, whilst larger crocodiles (17·9 ± 3·75 kg, mean ± SE, n = 8) did not. This demonstrated that aerobic dive duration was mass-specific during resting-dives, but other mass specific factors, presumably ecological, determined dive duration.

4. The durations of active-dives were never >1 min, showed no relationship with body mass and no correlation with the post-dive-surface interval. In crocodiles, aerobic metabolic scope is independent of body mass but anaerobic capacity is mass dependent, suggesting that active-dive duration was determined by sustained activity and dives were terminated before anaerobic metabolism became significant.

5. All individuals showed similar diel phase shifts in dive duration, type and depth, illustrating the overwhelming influence of the external environment on dive behaviour. Dive durations which resulted in significant anaerobic debt occurred rarely, but were undertaken in response to a potential threat.

6. Body mass was a poor predictor of diving in C. johnstoni because the external environmental and ecological factors exerted a greater influence on dive duration than oxygen reserves.
Keyword crocodylus johnstoni
ectotherm
diving behaviour
aerobic dive limit
body size
Q-Index Code C1
Q-Index Status Confirmed Code

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2010 Higher Education Research Data Collection
School of Biological Sciences Publications
Ecology Centre Publications
 
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Citation counts: TR Web of Science Citation Count  Cited 18 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 16 times in Scopus Article | Citations
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Created: Tue, 24 Nov 2009, 15:50:10 EST by Gail Walter on behalf of School of Biological Sciences