Ontogenetic changes of swimming kinematics in a semi-aquatic reptile (Crocodylus porosus)

Seebacher, Frank, Elsworth, Peter G. and Franklin, Craig E. (2003) Ontogenetic changes of swimming kinematics in a semi-aquatic reptile (Crocodylus porosus). Australian Journal of Zoology, 51 1: 15-24. doi:10.1071/ZO02036


Author Seebacher, Frank
Elsworth, Peter G.
Franklin, Craig E.
Title Ontogenetic changes of swimming kinematics in a semi-aquatic reptile (Crocodylus porosus)
Journal name Australian Journal of Zoology   Check publisher's open access policy
ISSN 0004-959X
Publication date 2003-01-01
Sub-type Article (original research)
DOI 10.1071/ZO02036
Volume 51
Issue 1
Start page 15
End page 24
Total pages 10
Place of publication Collingwood
Publisher CSIRO Publishing
Collection year 2003
Language eng
Subject 270604 Comparative Physiology
779903 Living resources (flora and fauna)
Abstract Semi-aquatic animals represent a transitional locomotor condition characterised by the possession of morphological features that allow locomotion both in water and on land. Most ecologically important behaviours of crocodilians occur in the water, raising the question of whether their 'terrestrial construction' constrains aquatic locomotion. Moreover, the demands for aquatic locomotion change with life-history stage. It was the aim of this research to determine the kinematic characteristics and efficiency of aquatic locomotion in different-sized crocodiles (Crocodylus porosus). Aquatic propulsion was achieved primarily by tail undulations, and the use of limbs during swimming was observed only in very small animals or at low swimming velocities in larger animals. Over the range of swimming speeds we examined, tail beat amplitude did not change with increasing velocity, but amplitude increased significantly with body length. However, amplitude expressed relative to body length decreased with increasing body length. Tail beat frequency increased with swimming velocity but there were no differences in frequency between different-sized animals. Mechanical power generated during swimming and thrust increased non-linearly with swimming velocity, but disproportionally so that kinematic efficiency decreased with increasing swimming velocity. The importance of unsteady forces, expressed as the reduced frequency, increased with increasing swimming velocity. Amplitude is the main determinant of body-size-related increases in swimming velocity but, compared with aquatic mammals and fish, crocodiles are slow swimmers probably because of constraints imposed by muscle performance and unsteady forces opposing forward movement. Nonetheless, the kinematic efficiency of aquatic locomotion in crocodiles is comparable to that of fully aquatic mammals, and it is considerably greater than that of semi-aquatic mammals.
Keyword Zoology
Fresh-water Crocodiles
Body-temperature
Locomotion
Johnstoni
River
Thermoregulation
Performance
Energetics
Movements
Force
Q-Index Code C1

 
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Created: Wed, 15 Aug 2007, 05:07:28 EST