Despite their massive appearance, the largest whales (and also the largest predators) have shorter dive time compared to other smaller fishes. Our hypothesis is that ‘lunge-feeding’ (the whales’ feeding behavior), is energetically expensive resulting to inability to dive at lower depths and at longer time intervals. This study is aimed at determining how and why the largest whales exhibit shorter dives by examining how lunge-feeding affects their behavior and dive duration. Methods
In order to determine how and why the largest whales exhibit shorter dive times compared to other fishes, we have to study how its lunge-feeding behavior affects whales’ overall behavior and their dive time limit. In gathering data, we used remote sensing techniques. In this experiment, we used the TDR “time/depth recorders” technique since it is the most applicable method considering that the subjects were not in a controlled environment. The TDRs actually recorded the oxygen level of each tagged whale. After some time, the TDRs were collected and the results were analyzed through specialized software that translates the data from the TDRs.
Results showed that the whales move faster when at the ascent (or climbing) portion of the dive while it showed that whales move significantly slower during descent. Recovery time spent at the surface was also viewed as an important factor in determining the effect of lunge-feeding. Our tests showed that there is a correlation between the number of lunges and the time spent recovering at the surface. Finally, using optimality models, we were able to compare the results of the actual study to the predicted outcome.
The result was a common cost for lunge dives which indicated the high energy cost during lunge dives resulting to shorter dive duration. Results and Discussion Results of this experiment showed that there is a relationship between the number of lunges and the surface recovery intervals. The TDR analysis showed that whales move faster during ascent and move significantly slower when at descent. This indicated that lunge-feeding is energetically expensive. We were able to measure the high energy cost of lunge-feeding using the remote sensing technique.
Whales usually recover at the surface after each dive and the length of stay at the surface is relative to the number of lunges it makes during the dive. The more lunges the whales make during feeding, the more time it spent at the surface for recovery. The optimality models showed the relative differences between the lunging-costly model versus the no-cost model. In the lunging-costly model, observed forage depths, vertical speed, number of lunges, time spent recovering at the surface, are some of the variables that were examined to provide an outright solution. Conclusion
Based on the results of this experiment, it has been found out that lunge-feeding in large whales is an energetically expensive activity. Using the TDR technique to record the energy cost of lunge, we were able to deduce that the more lunges a whale makes, the more time it spends recovering at the surface, usually regaining oxygen levels. Therefore, the high energy requirements of lunge-feeding limit the dive time and depth of dive in large whales. Reference: Acevedo-Gutierrez, A. , Croll, D. A. , and Tershy, B. R. (2002). “High Feeding Costs Limit Dive Time in the Largest Whales”. The Journal of Experimental Biology, 205, 1747-1753.