60
Marine Mammal Physiology: Requisites for Ocean Living
that occur as the percentage of body fat changes with season (e.g., Adachi et al. 2014), pregnancy (e.g., Dunkin et al. 2010), lactation and fasting (e.g., Costa et al. 1986; Crocker et al.
1997), will alter the ability of marine mammals to take advantage of these energy-saving
behaviors.
3.2.5 The high cost of foraging activities
For active predators like most marine mammals, behaviors associated with foraging represent a major component of daily energy costs. In particular, high speed chases, prey
handling, and prey consumption can entail high stroke frequencies and a large investment
of energy when submerged (Williams et al. 2004; Aguilar de Soto et al. 2008; Maresh 2014).
To mitigate these costs, marine mammals often switch between several swimming modes
during a foraging dive. Typically, a dive may begin with a series of quick, high amplitude
swimming strokes, followed by long periods of gliding on descent. Many deep-diving
pinnipeds including Weddell seals (Williams et al. 2004) and elephant seals (Mirounga
angustirostris, Adachi et al. 2014), as well as diving cetaceans including bottlenose dolphins
and blue whales (Williams et al. 2000), beaked whales (Ziphius cavirostris and Mesoplodon
densirostris) (Tyack et al. 2006), sperm whales (Physeter macrocephalus) (Miller et al. 2004),
and pilot whales (Aguilar de Soto et al. 2008), save energy on the ascent by using burstand-glide unsteady swimming, and by limiting continuous stroking periods to the short
interval on the initial turn around at depth.
Such variability and use of unsteady swimming modes are typical of swimming vertebrates from sharks to pinnipeds and have been shown to provide an energetic advantage
over continuous locomotion (Williams et al. 2000; Gleiss et al. 2011). In addition to foraging
dives, both large-scale migrations of birds and mammals (Davis and Weihs 2007; Gleiss
et al. 2011; Bishop et al. 2015) and the intra-dive foraging periods of pinnipeds often incorporate a roller-coaster series of powered and non-powered phases that result in performance, behavioral, and energetic benefits depending on the context. For example, active
foraging by Weddell seals feeding in an aggregation of Antarctic silverfish (Pleuragramma
antarcticum) involves a series of roller-coaster dips and rises that are associated with a
low-frequency (7.2 ± 0.7 strokes min −1 ) stroking descents followed by moderate stroke frequency (28.5 ± 0.8 strokes min −1 ) ascents and fish encounters (Williams et al. 2015b). Only
rarely do the seals feed on descent. Average instantaneous energetic costs are dictated by
the stroking patterns and alternate between 17.2 ± 1.6 and 68.2 ± 2.0 J kg −1 min −1 on each
gliding dip and powered rise of the foraging period, respectively (Williams et al. 2015a).
One of the most energetically costly feeding behaviors is displayed by lunge- feeding
rorqual whales (balaenopterids such as blue and humpback whales) and has been
described as “the largest biomechanical event on Earth and one of the most extreme feeding methods among aquatic vertebrates” (Brodie 1993). Balaenids are bulk filter feeders
that capture prey by engulfing large volumes of water containing dense aggregations of
plankton or nekton (Goldbogen et al. 2011). This lunge feeding behavior requires acceleration to high speeds toward a prey patch, and inflation of the accordion-like buccal cavity to
an 80 o gape angle. During engulfment, the whale presents the equivalent of a massive, flat
plate to oncoming water flow. The animal must overcome exceptionally high drag forces
due to a reduction in body streamlining and engulfment drag that rapidly decelerates
the whale to a near halt (Chapter 1; Goldbogen et al. 2007). The exceptionally high level
of biomechanical work required to lunge feed underlies the relatively short maximum
dive durations observed for foraging balaenids (Goldbogen et al. 2012), which are often
shorter than predicted based on allometric calculations of aerobic dive limits (Chapter 2).
Marine Mammal Physiology: Requisites for Ocean Living
that occur as the percentage of body fat changes with season (e.g., Adachi et al. 2014), pregnancy (e.g., Dunkin et al. 2010), lactation and fasting (e.g., Costa et al. 1986; Crocker et al.
1997), will alter the ability of marine mammals to take advantage of these energy-saving
behaviors.
3.2.5 The high cost of foraging activities
For active predators like most marine mammals, behaviors associated with foraging represent a major component of daily energy costs. In particular, high speed chases, prey
handling, and prey consumption can entail high stroke frequencies and a large investment
of energy when submerged (Williams et al. 2004; Aguilar de Soto et al. 2008; Maresh 2014).
To mitigate these costs, marine mammals often switch between several swimming modes
during a foraging dive. Typically, a dive may begin with a series of quick, high amplitude
swimming strokes, followed by long periods of gliding on descent. Many deep-diving
pinnipeds including Weddell seals (Williams et al. 2004) and elephant seals (Mirounga
angustirostris, Adachi et al. 2014), as well as diving cetaceans including bottlenose dolphins
and blue whales (Williams et al. 2000), beaked whales (Ziphius cavirostris and Mesoplodon
densirostris) (Tyack et al. 2006), sperm whales (Physeter macrocephalus) (Miller et al. 2004),
and pilot whales (Aguilar de Soto et al. 2008), save energy on the ascent by using burstand-glide unsteady swimming, and by limiting continuous stroking periods to the short
interval on the initial turn around at depth.
Such variability and use of unsteady swimming modes are typical of swimming vertebrates from sharks to pinnipeds and have been shown to provide an energetic advantage
over continuous locomotion (Williams et al. 2000; Gleiss et al. 2011). In addition to foraging
dives, both large-scale migrations of birds and mammals (Davis and Weihs 2007; Gleiss
et al. 2011; Bishop et al. 2015) and the intra-dive foraging periods of pinnipeds often incorporate a roller-coaster series of powered and non-powered phases that result in performance, behavioral, and energetic benefits depending on the context. For example, active
foraging by Weddell seals feeding in an aggregation of Antarctic silverfish (Pleuragramma
antarcticum) involves a series of roller-coaster dips and rises that are associated with a
low-frequency (7.2 ± 0.7 strokes min −1 ) stroking descents followed by moderate stroke frequency (28.5 ± 0.8 strokes min −1 ) ascents and fish encounters (Williams et al. 2015b). Only
rarely do the seals feed on descent. Average instantaneous energetic costs are dictated by
the stroking patterns and alternate between 17.2 ± 1.6 and 68.2 ± 2.0 J kg −1 min −1 on each
gliding dip and powered rise of the foraging period, respectively (Williams et al. 2015a).
One of the most energetically costly feeding behaviors is displayed by lunge- feeding
rorqual whales (balaenopterids such as blue and humpback whales) and has been
described as “the largest biomechanical event on Earth and one of the most extreme feeding methods among aquatic vertebrates” (Brodie 1993). Balaenids are bulk filter feeders
that capture prey by engulfing large volumes of water containing dense aggregations of
plankton or nekton (Goldbogen et al. 2011). This lunge feeding behavior requires acceleration to high speeds toward a prey patch, and inflation of the accordion-like buccal cavity to
an 80 o gape angle. During engulfment, the whale presents the equivalent of a massive, flat
plate to oncoming water flow. The animal must overcome exceptionally high drag forces
due to a reduction in body streamlining and engulfment drag that rapidly decelerates
the whale to a near halt (Chapter 1; Goldbogen et al. 2007). The exceptionally high level
of biomechanical work required to lunge feed underlies the relatively short maximum
dive durations observed for foraging balaenids (Goldbogen et al. 2012), which are often
shorter than predicted based on allometric calculations of aerobic dive limits (Chapter 2).