Mesoplodon densirostris (de
English: Blainville's beaked whale
Spanish: Zifio de Blainville
French: Mésoplodon de Blainville
Mesoplodon densirostris © Wurtz-Artescienza (see links).
The main colour pattern of this species is rather inconspicuous,
dark above, light below. There is an eye patch which is also dark,
with females alone developing both white upper and lower jaws. The
lower jaw is highly arched in the same fashion?? as the Right Whales',
with a prominent tooth erupting at the peak of this arch in males,
making it very distinctive among mesoplodonts. The dark areas of
larger animals tend to have round or oval white scars and widely
separated, paired scratches, presumably in males. There often is
an orangish sheen (presumably due to diatoms) covering the head.
Maximum recorded length has been 4.7 m and body mass reaches up
to 1,000 kg (Jefferson et al. 2008; Wang et al. 2006). Females seem
to reach sexual maturity at about 9 years age (Pitman, 2009).
In tropical oceans, M. densirostris is one of the more widespread
and common beaked whales (Pitman, 2002). Blainville's beaked whale
ranges north to Nova Scotia, Wales, Portugal, the western Mediterranean,
Japan, Midway Islands, and central California; and south to Rio
Grande do Sul in Brazil, South Africa, Tasmania, and central Chile
(Rice, 1998). Baker and van Helden (1999) also indicate its presence
in New Zealand waters. McAlpine and Rae (1999) report on a stranding
in New Brunswick, Canada. Aguayo et al. (1998) report on sightings
between Valparaiso and Easter Island in the south-eastern Pacific
Distribution of Mesoplodon densirostris (Taylor
et al. 2008; © IUCN; enlarge
map). It is found in
all tropical and warm temperate oceans and is probably the most
widespread and perhaps
most abundant mesoplodont (Pitman, 2009).
3. Population size
M. densirostris appears to be widespread and fairly common
in tropical oceans, and Pitman (2009) suggests it may be one of
the most common of all the species of Mesoplodon. Estimates
of abundance are generally not available for most areas, but there
are estimated to be 2,138 in Hawaiian waters. In the northern Gulf
of Mexico, an estimated 106 mesoplodonts occur, and these are considered
to be either M. densirostris or M.
In the eastern Pacific the total abundance is estimated around 30,000
beaked whales in the genus Mesoplodon (Taylor et al. 2008
and references therein). Pitman and Lynn (2001) believe that the
majority of these are M.
peruvianus and M. densirostris.
4. Biology and Behaviour
Habitat: Macleod and Zuur (2005) investigated habitat utilization
in Blainville's beaked whale in the northern Bahamas associated
with seabed gradient. The whales preferred gradients from 68 to
296 m/km and depths from 136 to 1,319 m. The authors hypothesize
that the relationships between habitat utilization and these topographic
variables relates to interactions between a deepwater current and
the seabed topography on preferred prey. Locally, prey animals may
be concentrated in areas with a northeast aspect, intermediate gradients
and depths between 200 and 1,000 m where the Deep Western Boundary
Current is forced towards the surface by the local topography. These
are the areas where Blainville's beaked whales preferentially occurred.
According to Casinos and Filella (1995 and references therein) M.
densirostris seems to prefer water depths of 700- 1000m. Ritter
and Brederlau (1999) sighted M. densirostris off La Gomera,
Canary Islands over mean depths of 320 m, with mean distance from
shore of 4.4 km.
McSweeny et al. (2007) investigated site fidelity, patterns of association,
and movements of Blainville's beaked whales using a 21-yr photographic
data set from the west coast of Hawaii. Resightings of individuals
spanned 15 yr, suggesting long-term site fidelity to the area. Long-term
resightings were documented primarily from adult females. Among
adult females, although repeated associations occurred up to 9 yr
apart, individuals were seen separately in intervening years. Individuals
seen on multiple occasions were typically documented in multiple
months-seasons, suggesting they may use the study area throughout
the year. Such long-term site fidelity has implications both for
potential population structure and for susceptibility of beaked
whale populations to anthropogenic impacts.
Behaviour: Baird et al. (2008) investigated diel variation
in diving behaviour using time-depth recorders deployed on six Blainville's
beaked whales. Deep foraging dives (>800 m) occurred at similar
rates during the day and night. Series of progressively shallower
'bounce' dives were documented to follow deep, long dives made during
the day; at night whales spent more time in shallow (<100 m)
depths. Dives to mid-water depths (100-600 m) occurred significantly
more often during the day. This diel variation in behaviour suggests
that beaked whales may spend less time in surface waters during
the day to avoid near-surface, visually oriented predators such
as large sharks or killer whales (Orcinus
Tyack et al. (2006) used sound-and-orientation recording tags (DTAGs)
to show that M. densirostris hunt by echolocation in deep
water between 222 and 1885 m, attempting to capture about 30 prey/dive.
The food source is so deep that the average foraging dives were
deeper (835 m) and longer (47 min) than reported for any other air-breathing
species. A series of shallower dives, containing no indications
of foraging, followed most deep foraging dives. The average interval
between deep foraging dives was 92 min. This duration may be required
for beaked whales to recover from an oxygen debt accrued in the
deep foraging dives, which last about twice the estimated aerobic
These results confirm earlier findings by Baird et al. (2006) who
whales in Hawaiian waters using suction-cup-attached time-depth
recorders. Blainville's beaked whales were found over median depth
of 922 m and regularly dove for 48-68 min to depths greater than
800 m (maximum 1408 m).
Schooling: Group sizes are small and most groups had only
a single adult male present. Repeated associations between adult
females and adult males were documented for all resightings of adult
males over periods from 1 to 154 d. (McSweeny et al. 2007).
Most strandings involved single individuals, although groups between
3 and 7 animals were observed in tropical waters (Jefferson et al.
1993). Ritter and Brederlau (1999) estimated group size to range
from 2 to 9 individuals (mean 3.44). Adult males and calves were
both observed during many encounters.
Food: Single specimens of Blainville's beaked whale stranded
on the Canary Islands had eaten both fish and cephalopod prey. The
most numerous prey remains belonged to gadid fish. This is consistent
with the limited published data on diet in these species, with Mesoplodon
species having a relatively higher proportion of fish in the diet
specialises on cephalopods (Santos et al. 2007).
Direct catches: According to Houston (1990c), the species
is of no commercial interest. However, Dolar et al. (1994) investigated
directed fisheries for marine mammals in the Philippines, where
small cetaceans, including M. densirostris are taken around
Pamilacan Island by hand harpoons or togglehead harpoon shafts shot
from modified, rubber-powered spear guns. Around 800 cetaceans are
taken annually at seven sites, mostly during the inter-monsoon period
of February-May. The meat is consumed or sold in local markets and
some skulls are cleaned and sold as curios. Although the Department
of Agriculture issued Fisheries Administrative Order No. 185 on
16 December 1992: 'banning the taking or catching, selling, purchasing,
possessing, transporting and exporting of dolphins', the order did
not stop dolphin and whale hunting but seems to have decreased the
sale of dolphin meat openly in the market (Dolar et al. 1994).
Similarly, Baker et al. (2006) report the results of molecular monitoring
of 'whalemeat' markets in the Republic of (South) Korea based on
nine systematic surveys from February 2003 to February 2005. The
only legal source of these products was assumed to be incidental
fisheries mortalities ('bycatch') as reported by the government
to the IWC . Species identification of 357 products using mitochondrial
DNA control region or cytochrome b sequences and the web-based programme
"DNA-surveillance" also included Blainville's beaked whales.
Incidental catches: Jefferson et al. (1993) report that
some specimens have been taken in the North Pacific by Taiwanese
whalers, and accidentally by Japanese tuna fishermen in the Indian
ocean. Forney and Kobayashi (2007) report on by-catch of a Blainville
beaked whale in the Hawaii-based longline fishery .
Pollution: Concerns regarding the impact of man-made debris
in the marine environment are increasing. Pollution in the form
of plastic debris has been recognised as a major threat to marine
wildlife, in terms of ingestion and entanglement. In 1993, a 419cm
adult female Blainville's beaked whale stranded near Sao Jose do
Norte, southern Brazil had a bundle of plastic threads occupying
a large part of the main stomach chamber. Both stomach and intestines
were completely free of parasites as well as food remains and faeces,
indicating that the whale had not fed for some time. Mistaken ingestion
of debris due to its resemblance to preferred prey is usually not
thought to occur in odontocete cetaceans because of their echolocation
capabilities. The ingested plastic may have resulted in a false
sensation of satiation for the animal, which could have reduced
the whale's appetite and meal size. In turn, this would have compromised
the energy consumption and health of the animal and subsequently
(at least indirectly), led to the death of the whale (Secchi and
One individual stranded in the Mediterranean sea was investigated
with respect to chlorinated hydrocarbons. Levels found were lower
than in other cetacean species (Jefferson et al. 1993).
Naval exercises: At least one animal died in September 2002
during a naval exercise conducted around Gran Canaria, Spain (Vidal
Martin, pers. comm.). Another two specimens live stranded during
a naval exercise off The Bahamas in March 2000 (Waring et al. 2001).
High intensity Low Frequency Active Sonar (LFAS) was used by US
and NATO vessels in both these areas, respectively, which led to
a multi species mass stranding also including Ziphius
But Moretti et al. (2006) report that passive sonar detection of
beaked whales has become increasingly important as part of the Office
of Naval Research (ONR) Marine Mammal Monitoring on Navy Range (M3R)
program. There is hope that based on these real-time data, trained
observers can verify the species on site and in time to avoid further
Confirmed and inferred Range states (Taylor et al. 2008)
Angola; Australia; Bahamas; Belize; Brazil; Cameroon; Canada; Cape
Verde; Cayman Islands; Chile; China; Cocos Islands; Colombia; Comoros;
Costa Rica; Ecuador; Fiji; Guam; Guatemala; Guyana; Honduras; India;
Indonesia; Japan; Kenya; Kiribati; Madagascar; Malaysia; Marshall
Islands; Mauritania; Mauritius; Mayotte; Micronesia, Federated States
of; Morocco; Mozambique; Myanmar; Namibia; Nauru; New Caledonia;
New Zealand; Nicaragua; Nigeria; Northern Mariana Islands; Oman;
Pakistan; Palau; Panama; Papua New Guinea; Peru; Philippines; Portugal;
Réunion; Saint Helena; Sao Tomé and Principe; Seychelles;
Solomon Islands; Somalia; South Africa; Spain; Sri Lanka; Taiwan,
Province of China; Tanzania; Tokelau; Tonga; United Kingdom; United
States of America; Uruguay; Vanuatu; Venezuela; Viet Nam; Wallis
and Futuna; Western Sahara; Yemen.
For recommendations on South American stocks, please see Hucke-Gaete
(2000) in Appendix 1 and for south-east Asian stocks Perrin et al.
(1996) in Appendix 2.
IUCN status: "Data Deficient". The species is not listed
by CMS. Listed in Appendix II of CITES.
8. Sources and further information
Mesoplodon - Beaked whales: Introduction and Sources"
© Boris Culik (2010) Odontocetes.
The toothed whales: "Mesoplodon densirostris".
UNEP/CMS Secretariat, Bonn, Germany. http://www.cms.int/reports/small_cetaceans/index.htm
© Illustrations by Maurizio Würtz, Artescienza. ©
Maps by IUCN.