Mesoplodon mirus 

Scope: Europe
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Cetartiodactyla Ziphiidae

Scientific Name: Mesoplodon mirus True, 1913
Regional Assessments:
Common Name(s):
English True's Beaked Whale
French Mésoplodon De True, Mésoplodon De True
Spanish Ballena De Pico De True, Ballena De Pico De True, Zifio De True, Zifio De True

Assessment Information [top]

Red List Category & Criteria: Data Deficient (Regional assessment) ver 3.1
Year Published: 2007
Date Assessed: 2007-01-26
Needs updating
Assessor(s): Species account by IUCN SSC Cetacean Specialist Group; regional assessment by European Mammal Assessment team
Reviewer(s): Philip Hammond
The range of this species does not qualify as threatened under criterion B. It cannot be ruled out that the regional population of this species is small enough to warrant listing under criteria C-D. Population trend or abundance data for this species are unavailable. As with other beaked whales, threats that could cause widespread declines include high levels of anthropogenic sound, especially military sonar and seismic surveys, and bycatch.

The combination of possible declines driven by vulnerability to high-level anthropogenic sound sources and bycatch is believed sufficient that a 30% reduction over three generations could not be ruled out. Therefore, the species is currently considered to be Data Deficient.

Geographic Range [top]

Range Description:True's beaked whales appear to have a disjunct, antitropical distribution (Mead 1989, MacLeod et al. 2006). In the Northern Hemisphere, they are known only in the North Atlantic, from records in eastern North America (Nova Scotia to Florida), Bermuda, Europe to the Canary Islands, the Bay of Biscay, and the Azores. They also occur at least in the southern Indian Ocean, from South Africa, Madagascar, southern Australia and the Atlantic coast of Brazil (MacLeod et al. 2006). The species does not generally occur within 30° north or south of the equator, which may indicate that the northern and the southern subpopulations are isolated from one another. This is supported by morphological and coloration differences (Ross 1969, Ross 1984). This peculiar disparate distribution pattern suggests that there may actually be separate species or subspecies in the Northern and Southern Hemispheres; however, this is not confirmed.
Countries occurrence:
France; Ireland; Portugal; Spain (Canary Is.); United Kingdom
FAO Marine Fishing Areas:
Atlantic – western central; Atlantic – northeast; Atlantic – northwest; Atlantic – southeast; Indian Ocean – eastern
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Until recent years, True’s beaked whales had been only rarely identified at sea, and there are no estimates of abundance. The species is not rare, however, at least in the North Atlantic. Abundance of beaked whales is often underestimated using visual survey methods because they dive for long periods and are inconspicuous when they surface (Barlow 1999).
Current Population Trend:Unknown
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:Since True’s beaked whale has rarely been identified alive in the wild, and is not one of the most commonly-stranded species, there is little information available on its natural history (see Pitman 2002). Groups observed at sea have consisted of up to three individuals. They may show their beaks when surfacing. Known mainly from stranded specimens, M. mirus is probably a deep water pelagic species, like other ziphiids (Houston 1990).

Like other members of the genus, stranded animals have had squid (mostly Loligo spp.) in their stomachs. They may also take fish, at least occasionally. Stable isotope analysis has found that this species feeds at a similar trophic level to other Mesoplodon species with which it is sympatric, but at lower trophic level than Cuvier’s beaked whale and the northern bottlenose whales which suggests that it feeds on smaller prey than these latter species (MacLeod 2005).

Threats [top]

Major Threat(s): Almost no information is available on the threats and status of this species. It appears never to have been hunted. Mesoplodonts have been taken occasionally by whalers but are not presently the main targets of any hunt. Entanglement in fishing gear, especially gillnets in deep water (e.g. for billfish and tuna), is probably the most significant threat. Like other beaked whales, this species is likely to be sensitive to disturbance and mortality from loud anthropogenic sounds such as naval sonar exercises (Cox et al. 2006).

As a temperate water species, True's beaked whale may be vulnerable to the effects of climate change as ocean warming may result in a shift or contraction of the species range as it tracks the occurrence of its prefered water temperatures (Learmonth et al. 2006).

Finally, all beaked whales seem to be susceptible to the ingestion of plastic bags, which are of widespread occurrence at sea and have been linked to detrimental health effects in several cetacean species.

Conservation Actions [top]

Conservation Actions: No conservation measures for this species are known.

Citation: Species account by IUCN SSC Cetacean Specialist Group; regional assessment by European Mammal Assessment team. 2007. Mesoplodon mirus. The IUCN Red List of Threatened Species 2007: e.T13250A3430572. . Downloaded on 14 August 2018.
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