18
Marine Mammal Physiology: Requisites for Ocean Living
flexion of the peduncle in concert with twisting at the base of the flukes (Fish 2002). Such
unpowered turns for cetaceans have smaller minimum radii than turns in which the animal is actively swimming (Fish 2002). The increased flexibility of the body during unpowered turns in conjunction with mobility of the flippers and twisting of the flukes permits
small turn radii. Minimum radii for unpowered turns by cetaceans were reported to range
from 0.10 to 0.15 body lengths (Fish 2002). When scaled to the body length, cetaceans generally demonstrate unpowered turning radii of <50% of the body length with minimum
radii ranging from 11% to 17% of body length. The extremely flexible body and mobile flippers of the river dolphin I. geoffrensis enables some of the smallest radius turns (Fish 2002).
Both Delphinapterus and Inia inhabit structurally complex habitats (i.e., pack ice, flooded
forest), where increased flexibility for enhanced maneuverability is necessary.
Differences in turning performance between species are associated with swimming
speed, size, and habitat (Fish 2002). Inia and Delphinapterus produce low-speed, small
radius turns. Faster speed but larger radius turns are performed by pelagic delphinids.
Most turning maneuvers by cetaceans are performed at <200°/s and <1.5 g, although
turns of 453.3°/s and 3.6 g have been measured in fast-swimming Lagenorhynchus obliquidens (Fish 2002). Humpback whales, Megaptera novaeangliae, use long, mobile flippers to
effect highly aquabatic maneuvers (Edel and Winn 1978; Fish and Battle 1995; Fish et al.
2011). These flippers have an aspect ratio of 6.1 with a streamlined cross-sectional profile
similar to engineered foil sections (Fish and Battle 1995). The flippers generate lift that
produces a centripetal force for banked turns (Howland 1974; Weihs 1981; Fish and Battle
1995). Therefore, more lift is required to produce a tighter turn. Enhanced lift production
is achieved by increasing the angle of attack of the winglike flippers. However, at too high
an angle of attack, the flipper could stall and lose lift by instead generating too much drag.
The rounded tubercles along the leading edge of humpback whale flippers delay stall
to higher angles of attack by modifying the flow over the flippers surface. As the water flow
impacts the leading edge in the troughs between two adjacent tubercles, it was deflected
into the center of the trough producing a pair of vortices with opposite spins. Each vortex
that is immediately flanking the flow over the tubercle has a spin, which is in the same
direction as the flow. Sandwiched between two vortices, the flow over the tubercle is energized and accelerated to avoid separation from the wing surface and prevent stall (Fish
et al. 2011). Humpback whales use this advanced hydrodynamic feature of their flippers
during bubble-net feeding maneuvers, which consist of underwater exhalations from the
blowhole produce bubble clouds or columns, which completely encircle and concentrate
the prey in a spiral (Hain et al. 1982; Wiley et al. 2011).
1.3.8 Maneuverability in pinnipeds
The placement of the flippers of sea lions (Zalophus californicus) is dynamically unstable.
The roots of the large pectoral flippers are located near the center of gravity. The flippers
provide little rotational dampening about the yaw and pitch axes, although they could
retard rotational and translational motion in regard to roll and heave, respectively. The
smaller pelvic flippers are in the preferred location to develop sufficient torque to act like
an airplane stabilizer or ship rudder and resist rotational instabilities.
The attitude of the Zalophus flippers are highly variable, because of the high mobility
of the pectoral and pelvic flippers (English 1976; Godfrey 1985). The ability of the sea lion
to adduct the pectoral flippers against the body and also adduct the pelvic flippers can
effectively produce a condition where the animal is devoid of control surfaces and potentially susceptible to all instabilities. The mobility of the pectoral and pelvic flippers also
Marine Mammal Physiology: Requisites for Ocean Living
flexion of the peduncle in concert with twisting at the base of the flukes (Fish 2002). Such
unpowered turns for cetaceans have smaller minimum radii than turns in which the animal is actively swimming (Fish 2002). The increased flexibility of the body during unpowered turns in conjunction with mobility of the flippers and twisting of the flukes permits
small turn radii. Minimum radii for unpowered turns by cetaceans were reported to range
from 0.10 to 0.15 body lengths (Fish 2002). When scaled to the body length, cetaceans generally demonstrate unpowered turning radii of <50% of the body length with minimum
radii ranging from 11% to 17% of body length. The extremely flexible body and mobile flippers of the river dolphin I. geoffrensis enables some of the smallest radius turns (Fish 2002).
Both Delphinapterus and Inia inhabit structurally complex habitats (i.e., pack ice, flooded
forest), where increased flexibility for enhanced maneuverability is necessary.
Differences in turning performance between species are associated with swimming
speed, size, and habitat (Fish 2002). Inia and Delphinapterus produce low-speed, small
radius turns. Faster speed but larger radius turns are performed by pelagic delphinids.
Most turning maneuvers by cetaceans are performed at <200°/s and <1.5 g, although
turns of 453.3°/s and 3.6 g have been measured in fast-swimming Lagenorhynchus obliquidens (Fish 2002). Humpback whales, Megaptera novaeangliae, use long, mobile flippers to
effect highly aquabatic maneuvers (Edel and Winn 1978; Fish and Battle 1995; Fish et al.
2011). These flippers have an aspect ratio of 6.1 with a streamlined cross-sectional profile
similar to engineered foil sections (Fish and Battle 1995). The flippers generate lift that
produces a centripetal force for banked turns (Howland 1974; Weihs 1981; Fish and Battle
1995). Therefore, more lift is required to produce a tighter turn. Enhanced lift production
is achieved by increasing the angle of attack of the winglike flippers. However, at too high
an angle of attack, the flipper could stall and lose lift by instead generating too much drag.
The rounded tubercles along the leading edge of humpback whale flippers delay stall
to higher angles of attack by modifying the flow over the flippers surface. As the water flow
impacts the leading edge in the troughs between two adjacent tubercles, it was deflected
into the center of the trough producing a pair of vortices with opposite spins. Each vortex
that is immediately flanking the flow over the tubercle has a spin, which is in the same
direction as the flow. Sandwiched between two vortices, the flow over the tubercle is energized and accelerated to avoid separation from the wing surface and prevent stall (Fish
et al. 2011). Humpback whales use this advanced hydrodynamic feature of their flippers
during bubble-net feeding maneuvers, which consist of underwater exhalations from the
blowhole produce bubble clouds or columns, which completely encircle and concentrate
the prey in a spiral (Hain et al. 1982; Wiley et al. 2011).
1.3.8 Maneuverability in pinnipeds
The placement of the flippers of sea lions (Zalophus californicus) is dynamically unstable.
The roots of the large pectoral flippers are located near the center of gravity. The flippers
provide little rotational dampening about the yaw and pitch axes, although they could
retard rotational and translational motion in regard to roll and heave, respectively. The
smaller pelvic flippers are in the preferred location to develop sufficient torque to act like
an airplane stabilizer or ship rudder and resist rotational instabilities.
The attitude of the Zalophus flippers are highly variable, because of the high mobility
of the pectoral and pelvic flippers (English 1976; Godfrey 1985). The ability of the sea lion
to adduct the pectoral flippers against the body and also adduct the pelvic flippers can
effectively produce a condition where the animal is devoid of control surfaces and potentially susceptible to all instabilities. The mobility of the pectoral and pelvic flippers also