Diving and foraging behavior of toothed whales:
Do toothed whales compete for prey in the deep sea?
Yasuhiko Naito1 & Yoko Mitani2

1National Institute of Polar Research

Bio-logging Institute2-31-10, Rex Yushima 301, Yushima Bunkyo, Tokyo 113-0034

Yasuhiko Naito

2Tokyo Institute of Technology, School of Bioscience4259 Nagatsuta-cho, Midori-ku, Yokohama-shi, Kanagawa Pref. 226-8501,
JAPAN
Contact e-mail: bls@saturn.dti.ne.jp

Abstract
Recent studies on diving and foraging behavior of three species of toothed whales: the sperm whale,
Cuvier's beaked whale and Blainville's beaked whale, are introduced. Their characteristic diving behaviors
are summarized, compared and discussed. Despite a smaller physiological capacity of diving, Cuvier's
beaked whales and Blainville's beaked whales forage smaller prey items at higher frequencies (28.9/diveand 27.8/dive) in deeper waters, whereas sperm whales forage larger prey, mostly squids, at lower
frequency in shallower waters than the two beaked whales. The two species of beaked whales regularly
exceeded their calculated ADL in their deep foraging dives, but sperm whales dived within their calculated
ADL. The obvious differences in foraging depth and prey size of these three species indicate possible
changes in mesopelagic prey fauna with depth.

Introduction
It is widely confirmed that many marine endotherms dive deep and long (Table 1). Since some birds
can dive surprisingly deep and long despite a small body mass, the remarkable diving capacities of theseanimals raised two major questions about, (1) how they can dive so deep for so long and (2), how bodymass affects diving capacity.
Regarding question (1), physiological studies have already provided answers. The diving animals
generally extend their dives by increasing their capacity to store oxygen and by decreasing metabolic rateduring dives (Butler, 2001). In other words, capacity to store oxygen and level of metabolic rate determine

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Table 1. Known maximum dive depth and maximum dive duration recorded by animal-borne instruments andacoustic tools. These extraordinary ability raised questions: how are they able to tolerate to anoxia andhow do they take preys?
Species

Maximum depth (Reference)
Maximum duration (Reference)

King penguin

343m (Putz & Cherel 2005)
9.2min (Charrassin et al. 1998)

Emperor penguin

564m (Kirkwood & Robertson 1997)
27.6mim, (Sato K. unpublished data)

Weddell seal

741m (Testa 1994)
67.0min, (Plotz et al. 2001)
1525m (Delong and Stewart 1991)
77min (Delong and Stewart 1991)

Southern elephant seal

1926m (Australian Antarctic Magazine 3, 2002)
120.0min, (Slip et al. 1994)

Sperm whale

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Northern elephant sea

2085m (Watkins et al. 1993)
112.0min (Clark 1976)

Northern bottlenose whale

1453m (Hooker & Baird 1999)
70.5 (Hooker & Baird 1999)

Cuvier's beaked whale

1888m (Barlow et al. 1997)
88.0min (Tyack et al. 2006)

Brainville beaked whale

1408m (Barid 2006)
57.4min (Tyack et al. 2006)

Beruga647m (Ridgway et al. 1984)
22.9min (Martin & Smith 1992)

Narwhal

2370m (Laidre et al. 2003)
26.2min, (Laidre et al. 2003)

diving ability unless animals rely on anaerobic metabolism, which is less efficient and produces lactic acidthat needs further oxygen for it to proceed. To express the diving abilities of animals, Kooyman (1980)
proposed the Aerobic Dive Limit (ADL), which indicates duration of aerobic metabolism and start ofanaerobic metabolism (accumulation of lactic acid). Showing the calculated ADL in a formula:
ADL=Stored O2 /Metabolic rate, Kooyman et al. (1981) first measured ADL for adult Weddell seals(Leptonychotes weddellii) to be 21 minutes and suggested that 90% of their dives did not exceed ADL andseals extended surface time after ADL dives to release accumulated lactic acid.
Regarding question (2), allometric studies on air-breathing diving animals provided the answer.
Comparing the diving performance of many endotherms, Schreer and Kovacs (1997) found strong
allometric relationship for maximum dive duration and depth in relation to body mass among air-breathing
diving animals. However, they noted mysticete whales and flying diving birds, which do not show
significant relationships between diving capacity and body mass, as exceptions to this relationship. On theother hand, penguins, odontocete whales and phocid seals showed higher relationship than did othergroups.

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It might be simply inferred from the above answers that larger toothed whales can dive deeper andlonger than the smaller toothed whales within ADL dives, and that sperm whales would be the deepest andthe longest divers since they have largest body mass among Odontocetes (known maximum: 24 metric tons
for 11m female and 57 metric tons for 18m male, Rice, 1989). However, as seen in table 2, Cuvier's beaked
whales and Blainville's beaked whales dive deeper depths and longer durations to sperm whales despite
small body sizes (known maximum either body mass or body length: 2950kg for Cuvier's beaked whaleand 4.3m for Blainville's beaked whale, Mead, 1989). This reversed diving capacity has already beenstudied and discussed from the point of view of physiological adaptation to extreme diving (Tyack et al.,2006). To understand the diving behavior of beaked whales we also need to study various aspects,

Yasuhiko Naito

One dive cycle
Dive time

Surface time

Regular clicks
BuzzesDive depth
Foraging phase

BottomDescent phase

Search phase(Revised from Watwood et al. 2006)
Ascent phaseFig. 1. Schematic dive profile of toothed whales and general dive parameters. The toothed whales start toproduce regular clicks from a certain depth and cease them when they start to ascend (search phase).
They also produce number of buzzes near bottom time (from first ascent to last descent) during theirdives (foraging phase).

particularly foraging behavior, which may be affected by factors such as prey type and prey distribution.
Beaked whales, just the opposite of sperm whales, are still mysterious species. However, recently Tyack etal. (2006), using advanced techniques, revealed the unique diving behavior of two beaked whales, Cuvier's
beaked whale (Ziphius cavirostris) and Blainville's beaked whale (Mesoplodon densirostris), which
provided us an opportunity to consider their foraging behavior also. Here we discuss the diving behavior

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and foraging behavior of these two species of beaked whales, comparing them with sperm whales, thebest-known species among the odontocete whales.

Diving physiology of sperm whales and beaked whales
Among the odontocete whales, sperm whales are the best-known species in terms of foraging
ecology and behavior (Clark, 1976; Clark, 1980; Kawakami, 1980; Watkins, et al., 1993; Amano andYoshioka, 2003) and beaked whales are the opposite. Recently, Watwood et al. (2006) studied diving
behavior of sperm whales in Atlantic Ocean, the Gulf of Mexico and the Ligurian Sea, where sperm whales

Table2. Diving behavior data of sperm whale, cuvier’s beaked whale and Blainville beaked whale. (Numbers in parenthesis:mean)
Max. depth

Dive duration

Descent rate Pitch

Ascent rate Pitch

Surface

Sperm whale

643.6~985.2 44.2~45.7

1.1~1.3 51.7~57.9

1.3~1.5 52.8~64.0

8.1~9.9

Cuvier’s beaked whale

737~1322

50.8~84.5

1.3~1.7 60~83

0.3~1.1 13~58

10~142(1070)(58.0)

(1.5)

(0.7)

(63)

640~125134.3~57.4

1.3~1.9 62~82

0.4~0.9 11~49

25~181(835)(46.5)

(1.6)

(0.7)

(92)

Blainville’s beaked whale

(72)
(74)

(35)
(28)

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are abundant, and we summarized the data they obtained using acoustic recording tags (Dtag) (Table 2).

( From Watwood et al. 2006 & Tyack P. et al. 2006)

With regard to beaked-whale diving behavior, however, almost nothing is known. They are supposed toinhabit deep waters (Mead, 1989; Heyning, 1989) and thus be deep divers. There were no reports on theirdiving behavior except for one observation of a dive of 30 minutes duration for a Cuvier's beaked whale(Heyning, 1989) and one dive of 1453m depth and 80 minutes duration for a northern bottle-nosed whale,
Hyperodon ampullatus recorded by a time-depth recorder (Hooker and Baird, 1999). Using Dtags, Tyack etal. (2006) studied two species of beaked whales from the Ligurian Sea and the Canary Islands. They alsopresented dive depth and duration data together with unique dive profiles. Dive data of sperm whales andbeaked whales are summarized in Table 2, and dive profiles of three species of toothed whales are modified
and shown in figures 1-3. It is very clear that both species of beaked whale dived deeper and longer thansperm whales (Table 2). Both species of beaked whale dived with higher slightly descent rates and steeper
dive angles than did sperm whales, but they ascended slowly at lower angles than sperm whales, and they
had longer surface times than sperm whales. These data suggest that generally the beaked whales dive todeep waters at high speeds and surface slowly and rest longer at the surface than sperm whales. Distinct
differences between sperm whales and the beaked whales were found again in their dive profiles. Spermwhales dived a regular pattern without extending their surface time, but the beaked whales made several
sequential shallow dives following deep dives (deep foraging dive (DFD) by Tyack et al., 2006). Hooker
and Baird (1999) also presented a dive profile for the northern bottlenose-whale similar to the dives of theCuvier's beaked whale and the Blainville's beaked whale in this study. Although it was the first report of46

DepthTime

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Sperm whale,
Physeter macrocephalus
Fig. 2. Typical dive profiles of sperm whale (revised from Amano and Yoshioka 2003and Watwood et al 2006).

Depth

Time

Cuvier’s beakedwhale,
Ziphius cavirostris

Blainville’s beaked whale,
Mesoplodon densirostrisFig. 3. Typical dive profiles of Cuvier’s beaked whale and Blainville’s beaked whale.

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beaked whales, shallow dives were not noted. Tyack et al. (2006) explained the dive patterns of the beaked
whales as a physiological adaptation to the extremely deep and long dives. Assuming the super-saturation
condition of PN2 that causes decompression sickness, they hypothesized that the subsequent shallow divesfollowing deep dives serve for recompression, much like the process adopted to prevent decompression
sickness by human divers, and also serve to extend the time needed to metabolize lactic acid accumulated
by ADL-exceeding dives. Indeed, Watwood et al. (2006) and Tyack et al. (2006) estimated ADL for sperm
whales and beaked whales using scaling by a power of -0.25 and the measured ADL of Weddell seals.
Those were 43~54 minutes, 25 minutes and 33 minutes for lean mass 8000~20000 kg of sperm whales, andlean mass 2000 kg of Cuvier's beaked whale and lean mass 630 kg of Blainville's beaked whale

Table 3. Depth and duration of seach phase and foraging phase and number of buzzes during foraging phase.
Foraging phase

Search phase
Sperm whale

start~end

duration% of divestart~end

duration% of dive96.7~611.5

36.0~37.4

80.7~81.4

514.7~679.8

28.2~28.7

61.3~63.5

457~856

32.8

56.6

863 (Buzz depth: m)

426~738

26.4

56.8

724( Buzz depth: m)

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respectively (Table 3). These data suggest that sperm whales stay within their ADL but that beaked whales(No. busses:18)
Cuvier’s beaked whale(No. buzzes: 29.8)
Blainville’s beaked whale(N0. Buzzes: 28.6)( From Watwood et al.2006 & Tyack P. et al. 2006)

Prey size estimated from buzz accountRegular clicks

Sperm whale (Body mass: 8000~20000kg, Feeding rate: 3% of BM)
Buzzes25.2 DFD/day→453.6buzzes/day→529.1g~1322.8g/buzz(320~360buzz/day, 800g~2300g/buzz for Mediterranean and Gulf of Mexico-Miller P.(2004))

Cuvier’s beaked whale (Body mass: 2500kg, Feeding rate: 3% of BM)
11.2DFD/day→333.8buzzes/day→224.7g/buzz
Brainville beaked whale (Body mass: 800kg. Feeding rate:3% BM )10.46DFD/day→299.2buzzes/day→80.2g/buzz

Foraging phase

Bottom(Revised from Watwood et al. 2006)

Search phase
Descent phase
Ascent phase
Fig.4. prey size was estimated using average buzz numbers of three species of the toothed whales and feeding
rate of body mass (BM) per day. Sperm whale feed large prey by low emission rate of buzzes comparedwith the beaked whales.

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far exceed their $'/Foraging behavior
Watwood et DO  and T\DFN et DO  studied foraging EHKDYLRU of VSHUP whales andCuvier's EeaNed whales and %ODLnville's EeaNed whales using Dtags which can record two t\Ses of
echo-location acoustic sounds SURGXFHG E\ the toothed whales during dives: regular FOLFNV and EX]]HV (alsocalled FUHDNV  According to WKHP regular FOLFNV were made most of time during descent and ERWWRP SKDVHV
of their dives and rarely during DVFHQW whereas EX]]HV were emitted mostly during ERWWRP SKDVHV )LJ 
They imSlicated clicNs as Eeing long-range echolocation for meVRSelagic SUey and EX]]Hs as Eeing
SUH\ORFDWLQJ and SUH\FDSWXUH HFKRORFDWLRQ Assuming that EX]]HV are equivalent to SUH\ FDSWXUH and
Yasuhiko Naito

success in FDSWXULQJ SUH\ located E\ EX]]HV it can EH VXSSRVHG that the QXPEHU of EX]]HV UHSUHVHQWV theQXPEHU of SUH\ successfully FDSWXUHG E\ the whales during GLYHV &OLFN and EX]] data E\ Watwood et DO and T\DFN et DO  are VXPPDUL]HG in Fig  suggesting that Cuvier's EHDNHG whales and%ODLQYLOOH V EHDNHG whales FDSWXUH SUH\ in GHHSHU waters than VSHUP ZKDOHV From SURSRVHG EX]] data anddiving data and DSSO\LQJ  of ERG\ mass as feeding UDWH we can estimate SUH\ VL]H for the three VSHFLHV
of toothed ZKDOHV 6SHUP whales forage SUH\ VL]HG EHWZHHQ J and  J whereas Cuvier's EHDNHG
whales and %ODLQYLOOH V EHDNHG whales forage SUH\ averaging  g s and  g UHVSHFWLYHOy Miller et DO UHSRUWHG the SUH\ VL]H of VSHUP whales varied EHWZHHQ  g in the Gulf of Mexico and  g in
the Mediterranean 6HD These data shows that there is some variation according to UHJLRQ 'HVSLWH theYDULDWLRQ the distinct difference in SUH\ VL]H of the toothed whales may indicate three SRVVLEOH scenarios:(1) VSHUP whales SUHIHU large SUH\ and select large SUH\ exclusively  EHDNHG whales cannot forage large
SUH\ that can flee TXLFNO\ and are REOLJHG to GHSHQG on small SUH\ that are SUHGRPLQDQW in GHHSHU waters
than the shallow GHSWKV where VSHUP whales IRUDJH and/or  severe FRPSHWLWLRQ EHWZHHQ VSHUP whales
and the EHDNHG whales has led small EHDNHG whales to forage in GHHSHU waters where there is less SUHy andwhere there is no choice of SUH\ VL]H EHFDXVH the small EHDNHG whales have less diving FDSDFLW\ at suchGHSWKV We also FRPSDUHG feeding efficiency as shown in TDEOH  Feeding efficiency was shown E\ ratio of
DFD time to dive F\FOH When we include sequential shallow dives following DFD into surface WLPH
efficiencies of ERWK EHDNHG whales were very low Indeed it is REYLRXV that the EHDNHG whales do not forage
Case (1): shallow dives were not included into surface time
6SHUPZKDOH IURPWDEOH WDWZRRG
&XYLHr’VEHDNHGZKDOH IURPYRFDOGXUDWLRQLQWDEOH T\DFN
%UDLQYLOOHEHDNHGZKDOH IURPYRFDOGXUDWLRQLQWDEOH T\DFN
&DVH  VKDOORZGLYHVZHUHLQFOXGHGLQWRVXUIDFHWLPH
6SHUPZKDOH IURPWDEOH WDWZRRG
&XYLHr’VEHDNHGZKDOH IURPYRFDOGXUDWLRQLQWDEOH T\DFN
%UDLQYLOOHEHDNHGZKDOH IURPYRFDOGXUDWLRQLQWDEOH T\DFN
Table 4. Dive Efficiency (dive time/ dive cycle) of three toothed ZKDOHV Efficiency of Cuvier’s EHDNHG whale
DQG%ODLQYLOOH’VEHDNHGZKDOHGLfIHUVUHPDUNDEO\E\LQFOXVLRQRIVKDOORZGLYHVLQWRVXUIDFHWLPH

49

in their shallow dives. Low efficiency may also suggest that the beaked whales have no choice of prey size
and were obliged to forage on any size prey found during chance encounters. There have been no studies to
explain the differences in foraging behavior between them. However, using swim-speed/depth-data loggers,
Amano and Yoshioka (2003) found burst swimming in sperm whales, which occurred several times per
dive during bottom phases. They suggested that sperm whales might be chasing squid, their preferred prey.
Burst-swimming during deep dives increases metabolic rate exponentially resulting in a reduction of dive

Yasuhiko Naito

time or exceeding ADL. However sperm whales kept regular interval dives and no extended surface time

Unpublished data from K. Aoki
Fig. 5. Amano and Yoshioka (2003) found burst swimming of during bottom phase of dive and suggested ad
prey chasing behavior (Figure prepared by K. Aoki).

for recovery from anaerobic dive was found. This suggests that sperm whales can make burst swims within
ADL. Given that burst swimming is prey capturing behavior, this also suggests that prey obtained by burst
swimming might be qualitatively or quantitatively beneficial, because cost of burst swims needs to becompensated by prey income. Thus only sperm whales can afford to forage large size prey selectively andthe beaked whales do not. However we cannot explain the reason why the beaked whales forage in such
depths and why sperm whales do not and We hypothesize that competition for squids between toothed
whals and vertical prey distribution patterns affect the diving and foraging pattern of the toothed whale
species. Although we are not sure about the differences between burst-swimming cost and additional diving
cost for sperm whales and the foraging depths of beaked whales, sperm whales will not be rewarded if only
small prey is distributed in deep water, since judging from the number of buzzes by the beaked whales
feeding rate does not increase exponentially with depth. This suggests that burst swimming is much more
beneficial than deep diving for sperm whales.

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To ensure understanding of deep foraging behavior of the toothed whales, prey information isessential. Although toothed whales prefer to forage for squid, unfortunately our information on squids isstill very poor. We need to study both toothed whale and squid behaviors simultaneously.

Acknowledgements
The authors extend sincere thanks to Dr. Senzo Uchida, Director General of Okinawa Churaumi
Aquarium for the invitation to this Deep Sea symposium. We also thank Dr. Keiichi Sato and Mr. Masanoru
Nonaka for kindly making arrangements for our attendance and thank many staff of the Aquarium for theirlogistic support and assistance during the Symposium.

Yasuhiko Naito

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