Moved by that sinking feeling: variable diving geometry underlies movement strategies in whale sharks
Article first published online: 24 NOV 2010
© 2010 The Authors. Functional Ecology © 2010 British Ecological Society
Volume 25, Issue 3, pages 595–607, June 2011
How to Cite
Gleiss, A. C., Norman, B. and Wilson, R. P. (2011), Moved by that sinking feeling: variable diving geometry underlies movement strategies in whale sharks. Functional Ecology, 25: 595–607. doi: 10.1111/j.1365-2435.2010.01801.x
- Issue published online: 3 MAY 2011
- Article first published online: 24 NOV 2010
- Received 23 April 2010; accepted 23 September 2010 Handling Editor: Daniel Costa
- cost of transport;
- dynamic body acceleration;
1. A primary determinant of movement strategies is travel speed, which modulates both power consumption and distance travelled and thus varies according to ecological circumstance. Many dense animals moving in 3D media face costs according to their movement trajectory and it should therefore equally be optimized according to circumstance.
2. We investigated the power requirements (using dynamic body acceleration as proxy for power) in relation to movement geometry of nine whale sharks (Rhincodon typus) and discovered that movement geometry significantly affects power requirements in a manner similar to travel speed.
3. Whale sharks dive repeatedly and use their negative buoyancy to glide during descents, while ascents were characterized by strong locomotory activity. Power requirements of ascents increased with the square of degrees pitch and were significantly greater than both level and descent swimming.
4. The differences in geometry of five dive types are explored using four empirical optimality models based on minimum power based on our measurements. These models suggest that some dive types minimize the horizontal cost of transport, whereas others minimize the cost of vertical transport. Whale sharks are presumed to shift diving geometry with changing currencies and ecological context. The adaptive significance of appropriate diving geometry and associated power requirements is discussed with regard to current hypotheses for diving in gill-breathers: search, orientation and travel.
5. Movement geometry significantly affects the cost of locomotion and is probably modulated by animals according to ecological circumstance. The in situ measurement of animal trajectory and locomotory activity via accelerometers now permits testing context-dependent movement geometry in free-ranging animals.