20
Marine Mammal Physiology: Requisites for Ocean Living
Groups of whales and dolphins swim in side-by-side and echelon formations to draft
(Weihs 2004; Fish et al. 2013). Small dolphins often position themselves beside and slightly
behind the maximum diameter of a larger animal (Tavolga and Essapian 1957; Norris and
Prescott 1961; Reid et al. 1995; Marino and Stowe 1997; Noren 2008). While the larger dolphin will experience increased drag, the smaller gains an energetic benefit (Weihs 2004;
Noren 2008; Noren et al. 2008). This effect is beneficial particularly for young whales in
order to maintain speed with their mothers. A neonatal dolphin could use this mechanism
to gain up to 90% of the thrust needed to move alongside its mother.
Dolphins are able to reduce energy costs by riding the bow waves generated by large
whales and boats (Fish and Hui 1991; Williams et al. 1992b). Williams et al. (1992b) found
that wave-riding dolphins could swim at a higher speed while reducing or maintaining
metabolic rate, heart rate, lactate production, and respiratory rate. Dolphins can either ride
bow waves like a surfer (Caldwell and Fields 1959), or they make use of the pressure front
created by the boat (Scholander 1959; Fejer and Backus 1960). This behavior is complex
with any energy savings to the dolphin related to bow design, swimming depth, body
orientation, and distance from the ship (Fish and Hui 1991).
Wind-wave riding and surf-wave riding can use gravity to reduce the energy cost of
swimming (Caldwell and Fields 1959). These wave riding behaviors differ from bow-wave
riding because they use the interaction of the dolphin’s weight and slope of the wave front
to produce movement analogous to human surfers (Hayes 1953; Fejer and Backus 1960;
Perry et al. 1961). Dolphins and sea lions have been observed to surf on inshore waves
(Norris and Prescott 1961; Riedman 1990). Dolphins ride waves with a forward slope of
10°–18° at velocities of 5–6 m/s (Hertel 1969). In the open sea, the flukes of large whales can
absorb energy from ocean waves (Bose and Lien 1990). Whales absorb 25% of their propulsive power from head seas and 33% from following seas, by synchronizing the motion of
the wave with the motion of the flukes. This energetic advantage is not generally available
to dolphins, due to the difference in length between the animal and the wavelength of
oceanic waves (Curren 1992).
1.4 Tools and methods for hydrodynamics research
There are a variety of tools and methodologies available to researchers to study marine
mammal hydrodynamics that include both theoretical and empirical approaches. As we
have shown, body shape and mechanical design are critically important aspects that influence hydrodynamic performance. Traditional techniques for quantifying morphology
include direct measurement and photogrammetry (Bose et al. 1990; Fish and Battle 1995;
Ginter et al. 2012). Surface and internal morphology can be quantified using advanced
bioimaging techniques such as computed tomography (CT) (Fish et al. 2006, 2007; Weber
et al. 2009a,b, 2014).
How bodies and appendages move relative to flow, both actively and passively, is also
a fundamental aspect of hydrodynamic research (Fish and Lauder 2006). The kinematics
of bodies and appendages can be quantified using high-speed video cameras (Feldkamp
1987a; Fish 1993). Multiple cameras at orthogonal axes can provide movement data in three
dimensions (Friedman and Leftwich 2014), although the size and large-scale trajectories
of most marine mammal movements may often preclude this approach. However, the
recent advent of animal-borne tags equipped with movement sensors can provide some
information on the kinematics of swimming and maneuvering in free-ranging animals
(Goldbogen et al. 2006). Common sensors within contemporary tags include tri-axial accelerometers, magnetometers, and more recently, gyroscopes. Data from these tags can be
Marine Mammal Physiology: Requisites for Ocean Living
Groups of whales and dolphins swim in side-by-side and echelon formations to draft
(Weihs 2004; Fish et al. 2013). Small dolphins often position themselves beside and slightly
behind the maximum diameter of a larger animal (Tavolga and Essapian 1957; Norris and
Prescott 1961; Reid et al. 1995; Marino and Stowe 1997; Noren 2008). While the larger dolphin will experience increased drag, the smaller gains an energetic benefit (Weihs 2004;
Noren 2008; Noren et al. 2008). This effect is beneficial particularly for young whales in
order to maintain speed with their mothers. A neonatal dolphin could use this mechanism
to gain up to 90% of the thrust needed to move alongside its mother.
Dolphins are able to reduce energy costs by riding the bow waves generated by large
whales and boats (Fish and Hui 1991; Williams et al. 1992b). Williams et al. (1992b) found
that wave-riding dolphins could swim at a higher speed while reducing or maintaining
metabolic rate, heart rate, lactate production, and respiratory rate. Dolphins can either ride
bow waves like a surfer (Caldwell and Fields 1959), or they make use of the pressure front
created by the boat (Scholander 1959; Fejer and Backus 1960). This behavior is complex
with any energy savings to the dolphin related to bow design, swimming depth, body
orientation, and distance from the ship (Fish and Hui 1991).
Wind-wave riding and surf-wave riding can use gravity to reduce the energy cost of
swimming (Caldwell and Fields 1959). These wave riding behaviors differ from bow-wave
riding because they use the interaction of the dolphin’s weight and slope of the wave front
to produce movement analogous to human surfers (Hayes 1953; Fejer and Backus 1960;
Perry et al. 1961). Dolphins and sea lions have been observed to surf on inshore waves
(Norris and Prescott 1961; Riedman 1990). Dolphins ride waves with a forward slope of
10°–18° at velocities of 5–6 m/s (Hertel 1969). In the open sea, the flukes of large whales can
absorb energy from ocean waves (Bose and Lien 1990). Whales absorb 25% of their propulsive power from head seas and 33% from following seas, by synchronizing the motion of
the wave with the motion of the flukes. This energetic advantage is not generally available
to dolphins, due to the difference in length between the animal and the wavelength of
oceanic waves (Curren 1992).
1.4 Tools and methods for hydrodynamics research
There are a variety of tools and methodologies available to researchers to study marine
mammal hydrodynamics that include both theoretical and empirical approaches. As we
have shown, body shape and mechanical design are critically important aspects that influence hydrodynamic performance. Traditional techniques for quantifying morphology
include direct measurement and photogrammetry (Bose et al. 1990; Fish and Battle 1995;
Ginter et al. 2012). Surface and internal morphology can be quantified using advanced
bioimaging techniques such as computed tomography (CT) (Fish et al. 2006, 2007; Weber
et al. 2009a,b, 2014).
How bodies and appendages move relative to flow, both actively and passively, is also
a fundamental aspect of hydrodynamic research (Fish and Lauder 2006). The kinematics
of bodies and appendages can be quantified using high-speed video cameras (Feldkamp
1987a; Fish 1993). Multiple cameras at orthogonal axes can provide movement data in three
dimensions (Friedman and Leftwich 2014), although the size and large-scale trajectories
of most marine mammal movements may often preclude this approach. However, the
recent advent of animal-borne tags equipped with movement sensors can provide some
information on the kinematics of swimming and maneuvering in free-ranging animals
(Goldbogen et al. 2006). Common sensors within contemporary tags include tri-axial accelerometers, magnetometers, and more recently, gyroscopes. Data from these tags can be