14
Marine Mammal Physiology: Requisites for Ocean Living
of limbs for stabilization, maneuvering, tactile reception, or food capture and processing
(Dagg and Windsor 1972; Fish 2001). With the development of pectoral or pelvic paddling,
specialization of the limbs to increase thrust and improve stability would be selected for
as a greater commitment to life in water. These specializations include (1) the development of a short, robust humerus and femur, (2) the elongation of digits, (3) an increase in
the propulsive surface by the addition of interdigital webbing or fringe hairs, and (4) an
increase in the bone density for buoyancy control (Fish 1996).
Paddling modes work well for surface swimming, where the orientation of the limbs
helps to maintain stability (Fish and Stein 1991) and their propulsive forces are applied
under the body and away from the water’s surface. Buoyancy provided by lungs and a
non-wettable fur keeps the body in trim and at the surface. However, swimming at the
surface is energetically demanding. Wave drag (see Section 1.2.2 and Figure 1.2) occurs
when an animal swims at or near the surface (Hertel 1966). Kinetic energy from the animal’s motion is transformed into potential energy in the upward displacement of water,
forming surface waves, and also lost due to friction and pressure drag. This energy loss can
be substantial, up to a maximum of five times the frictional drag (Hertel 1966). The cost of
transport in surface paddling is 69% greater than that associated with submerged swimming (Williams 1989). Furthermore, the wave patterns produced at the bow and stern of the
Fossil
whales
Modern mammals
Pelvic
oscillation
Lateral pelvic
undulation
Lateral caudal
undulation
Pectoral
oscillation
Alternating pectoral
paddling
Alternating pectoral
rowing
Alternating pelvic
rowing
Dorsoventral
caudal
undulation
Giant
freshwater
otter
Caudal
oscillation
All modern
cetaceans
Dorudon
Basilosaurus
Dorsoventral
pelvic
undulation
Muskrat
O tter shrew
Sea
lion
Platypus
Polar bear
Seal
Mink
Hippo
Pakicetids
Ambulocetus
River otter
Sea otter
Remingtonocetids ?
Quadrupedal
walking/wading
Quadrupedal
paddling
Pelvic
paddling
Figure 1.5 The evolution of swimming modes in mammals with examples of extant and extinct
aquatic taxa. The transition is shown from quadrupedal walking, through drag-based paddling
modes to highly derived lift-based oscillatory swimming. Arrows show how swimming modes are
related. The boxes contain fossil and modern species that swim similarly. The bars are indicative
that some of the species employ more than one swimming mode. (Reprinted from Thewissen, J.G.M.,
The Walking Whales, University of California Press, Berkeley, CA, 2014, Figure 20. With permission.)
Marine Mammal Physiology: Requisites for Ocean Living
of limbs for stabilization, maneuvering, tactile reception, or food capture and processing
(Dagg and Windsor 1972; Fish 2001). With the development of pectoral or pelvic paddling,
specialization of the limbs to increase thrust and improve stability would be selected for
as a greater commitment to life in water. These specializations include (1) the development of a short, robust humerus and femur, (2) the elongation of digits, (3) an increase in
the propulsive surface by the addition of interdigital webbing or fringe hairs, and (4) an
increase in the bone density for buoyancy control (Fish 1996).
Paddling modes work well for surface swimming, where the orientation of the limbs
helps to maintain stability (Fish and Stein 1991) and their propulsive forces are applied
under the body and away from the water’s surface. Buoyancy provided by lungs and a
non-wettable fur keeps the body in trim and at the surface. However, swimming at the
surface is energetically demanding. Wave drag (see Section 1.2.2 and Figure 1.2) occurs
when an animal swims at or near the surface (Hertel 1966). Kinetic energy from the animal’s motion is transformed into potential energy in the upward displacement of water,
forming surface waves, and also lost due to friction and pressure drag. This energy loss can
be substantial, up to a maximum of five times the frictional drag (Hertel 1966). The cost of
transport in surface paddling is 69% greater than that associated with submerged swimming (Williams 1989). Furthermore, the wave patterns produced at the bow and stern of the
Fossil
whales
Modern mammals
Pelvic
oscillation
Lateral pelvic
undulation
Lateral caudal
undulation
Pectoral
oscillation
Alternating pectoral
paddling
Alternating pectoral
rowing
Alternating pelvic
rowing
Dorsoventral
caudal
undulation
Giant
freshwater
otter
Caudal
oscillation
All modern
cetaceans
Dorudon
Basilosaurus
Dorsoventral
pelvic
undulation
Muskrat
O tter shrew
Sea
lion
Platypus
Polar bear
Seal
Mink
Hippo
Pakicetids
Ambulocetus
River otter
Sea otter
Remingtonocetids ?
Quadrupedal
walking/wading
Quadrupedal
paddling
Pelvic
paddling
Figure 1.5 The evolution of swimming modes in mammals with examples of extant and extinct
aquatic taxa. The transition is shown from quadrupedal walking, through drag-based paddling
modes to highly derived lift-based oscillatory swimming. Arrows show how swimming modes are
related. The boxes contain fossil and modern species that swim similarly. The bars are indicative
that some of the species employ more than one swimming mode. (Reprinted from Thewissen, J.G.M.,
The Walking Whales, University of California Press, Berkeley, CA, 2014, Figure 20. With permission.)