49
Chapter three: Exercise energetics
evaluating these costs, as it provides an index of the instantaneous and long-term energy
requirements, fuel utilization, and heat production of an animal. For marine mammals,
the rate of metabolism also serves as an important indicator of the consumption rate of
oxygen stores within the lungs, blood, and muscle that represent a major determinant of
breath-hold duration (Chapter 2). Thus, the metabolic rates from rest to high activity, and
the associated energetic costs ultimately dictate the diving capacity and survival of individual marine mammal species.
50
40
30
20
10
0
0
50
100
150
200
250
Maximum dive depth (m)
(5)
(4) (7)
(2)
(24)
(8)
(24)
(a)
Minimum heart rate (bpm)
16
14
12
10
8
6 0
50
100
150
200
250
300
350
Maximum dive depth (m)
(5)
(10)
(4)
(5)
(5)
(1)
(7)
(6)
(7)
(7)
(6)
(5)
(3)
(7)
(b)
Minimum heart rate (bpm)
Figure 3.1 Cardiac responses during diving and exercise in marine mammals. The minimum heart
rate (level of bradycardia achieved) is plotted in relation to the maximum dive depth for bottlenose
dolphins (a) and Weddell seals (b).
(Continued )