The habitats and ecology of True’s Beaked Whales in the European assessment region are poorly known, due to the low number of confirmed records.

Like other Mesoplodon species, it appears to inhabit deep waters along, or seaward of, the continental slope. In many European areas such oceanic habitats occur far from shore (e.g., west of Ireland: Rogan et al. 2018). However, around the volcanic offshore islands of the Azores and the Canary Islands, suitable deep-water habitat can occur within kilometres of the shoreline. Five confirmed sightings in the Azores and Canary Islands occurred at water depths varying from 600 to 1,600 m (Aguilar de Soto et al. 2017), while all sightings in the Bay of Biscay have been in water >2,000 m deep, with a mean of 3,159 m (Robbins et al. 2019). Aguilar de Soto et al. (2017) considered that the species might occur further offshore in deeper waters than some other sympatric mesoplodonts. Along the Atlantic seaboard of Ireland, Mesoplodon species (including possible True’s Beaked Whales) occurred almost exclusively off the edge of the continental shelf, and predicted abundance remained high all the way to the western limit of the survey area located 550 km offshore and in waters over 4,000 m deep (Rogan et al. 2018).

Its North Atlantic range is mostly limited to warm temperate to subtropical areas, and it is not known to regularly occur in the colder waters north of the United Kingdom, or in tropical waters. Considering its apparent preferences for warm oceanic habitats, it might be inferred that a large swathe of potentially suitable, and largely unsurveyed habitat exists in the warm offshore waters located between the Atlantic coasts of Spain and Portugal, and the westward limits of the European assessment region to the west of the Canary Islands and the Azores.

Group sizes observed in European waters include single animals and small groups of 2 to 4 animals (Weir et al. 2004, Aguilar de Soto et al. 2017, Robbins et al. 2019). The only records of mother-calf pairs in European waters, appears to be a stranding in Ireland in May 2013 (Hernandez-Milian et al. 2017) and a sighting off São Miguel in the Azores in May 2015 (Aguilar de Soto et al. 2017).

Estimated dive depths calculated from the echolocation clicks of Gervais’/True’s Beaked Whales indicated a weighted average of 870 m average depth and 1,480 m maximum depth (DeAngelis et al. 2017). Dive data from Blainville’s Beaked Whale (M. densirostris) indicate that True’s Beaked Whale may be able to remain submerged for almost an hour (Tyack et al. 2006). Little is known about its diet, but the stomach contents of two adults stranded in Ireland contained the remains of bathypelagic and mesopelagic fish from at least 13 families, indicating that the animals had been feeding in the deep scattering layer (Hernandez-Milian et al. 2017). Eye lenses belonging to unidentified squid were also found (Lusher et al. 2015).

Global
Until recently it was considered that True’s Beaked Whale had a disjunct, antitropical, distribution, inhabiting temperate waters in the North Atlantic and Southern Hemisphere. However, recent genetic and morphometric work has confirmed that the Southern Hemisphere animals documented in South Africa, Mozambique, southern Australia, New Zealand, Brazil and Tristan da Cunha (Aguilar de Soto et al. 2017), are actually a separate species, the newly-described Ramari’s Beaked Whale (Mesoplodon eueu: Carroll et al. 2021). Consequently, the True’s Beaked Whale is now considered to be endemic to the North Atlantic, where it inhabits warm temperate waters from the east coast of North America (Bahamas to Nova Scotia) across to Europe (Canary Islands to the UK and Ireland). Similar to most Mesoplodon species, the distribution of True’s Beaked Whale has primarily been documented from strandings. Sightings of the species at sea are scarce, both due to the cryptic behaviour typical of beaked whale species, and the difficulties with distinguishing it from similar mesoplodonts, especially Gervais’ Beaked Whale (M. europaeus).

European
Within the Pan-European region, the majority of True’s Beaked Whale records are from warmer waters in southernmost Europe. In the Canary Islands, strandings include an adult male at Lanzarote in 1984, an immature female at Fuerteventura in 2004, and an immature male at El Hierro in 2012 (Martín et al. 2011, Aguilar de Soto et al. 2017). Additionally, there was a confirmed sighting off Lanzarote in 2009 (Aguilar de Soto et al. 2017). In the Azores, a deceased male was recorded in 2004 (Silva et al. 2014), and there have been four confirmed sightings of the species since 2010 (Aguilar de Soto et al. 2017).

Rare strandings have been reported in the Algarve area of mainland Portugal (Ferreira et al. 2016), Galicia in north-west Spain (Covelo et al. 2016), and on the Biscay coast of France (Barriety 1962), and sightings have been recorded in the Bay of Biscay (Weir et al. 2004, Robbins et al. 2019). The highest number of True’s Beaked Whale records in Europe is along the Atlantic seaboard of Ireland, where 14 strandings have been documented since the late 1800s (Berrow et al. 2010, Rogan and Hernandez-Milian 2011, McGovern et al. 2018). The modelled predicted distribution of Mesoplodon species (including possible True’s Beaked Whales) highlighted the shelf edge west of Ireland, the Rockall Trough, and the Porcupine Seabight, as important areas (Rogan et al. 2018). In 2020, a female True’s Beaked Whale stranded on the north coast of Scotland at 58.6ºN (Kitchener et al. 2020), which is the northernmost record to date in Europe.

There are no confirmed records from the Mediterranean Sea (ACCOBAMS 2021), despite the presence of suitable deep-water habitat. Strandings reported from the Mediterranean coast of Turkey (Öztürk et al. 2016), were in fact misidentified Cuvier’s beaked whales (Ziphius cavirostris: Pitman and Brownell Jr. 2020).

It is listed on Appendix II (strictly protected species) of the Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention). It is included with all cetaceans on Annex IV Council Directive 92/43/EEC on the Conservation of Natural Habitats and of Wild Fauna and Flora (the Habitats Directive) as a species requiring strict protection across its entire natural range within the EU. All Mesoplodon species are included in Appendix II (species that are not necessarily threatened with extinction but may become so unless trade is closely controlled) of the Convention on International Trade in Endangered Species (CITES), which requires an export permit or re-export certificate for international trade.

It is included in two regional management agreements in Europe, comprising the Agreement on the Conservation of Cetaceans of the Black Sea, Mediterranean Sea and contiguous Atlantic area (ACCOBAMS), and the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS). These agreements aim to maintain favourable conservation status of cetacean species within their defined areas, managing threats and working towards the long-term sustainability of populations.