Studying Beaked Whales entangled in Tuna nets in the northwest Indian Ocean.

Beaked Whales, Ziphiidae, spend the majority of their time in deep oceanic waters, spending most of their lives beyond the continental shelves, and little at the surface. This makes them one of the least well-understood groups of Cetaceans, or Mammals of any kind. Some species have few, if any, sitings ar sea, being known almost exclusively from bodies washed ashore in varying states of decomposition. Because of this, the taxonomy of Beaked Whales is less well-established than is the case for most Mammal groups, with new species and nomenclature revisions being published every few years. 

Studying Whales caught as bycatch offers a cost-effective way to study poorly understood Cetacean populations, providing insights into populations which can help shape conservation policies. Such data collection is often accomplished by training fishermen themselves as citizen scientists. Drift gillnets are widely used many parts of the world to target Tuna, but are also noted for the large amount of large-Vertebrate bycatch they produce. In the northwest Indian Ocean drift gillnets are widely used by the fishing fleets of Iran and Pakistan, presenting a threat to Whales in this area, but also presenting an opportunity for scientists to gather data on these Animals.

In a paper published in the journal Zoology in the Middle East on 13 February 2025, Muhammad Shoaib Kiani of the Institute of Marine Science at the University of Karachi, Mohsen Rezaie-Atagholipour of the Qeshm Environmental Conservation Institute, Rab Nawaz and Muhammad Moazzam of the World Wide Fund for Nature - Pakistan, Bushra Shafiq also of the  Institute of Marine Science at the University of Karachi, Haleh Ali Abed of the Midaf Nature Conservation Society, and Koen Van Waerebeek, also of the Qeshm Environmental Conservation Institute and of the Centro Peruano de Estudios Cetológicos, present the results of a long-term study of Beaked Whale entanglements in Tuna gillnets in Iranian and Pakistani waters.

A citizen science program was established in Pakistan in 2012, in which fishermen on pelagic gillnet Tuna vessels were trained to collect data on Cetacean bycatch. In Iran reviews of mass media at local and national levels, looking for Cetacean-related stories, have been carried out since 2018, and a series of interviews of fishermen was carried out in 2022.

Kiani et al. discovered eight incidents in which entangled Cetaceans could be identified as Beaked Whales in the waters of the Gulf of Oman and Arabian Sea, two in Iranian territory, five in Pakistani territory, and one in international waters.

The first recorded incident happened on 10 February 2015, when fishermen on board the Pakistani vessel Al-Azaan discovered a live Beaked Whale caught in a gillnet they had deployed 95 km to the west of the Swatch (the undersea canyon formed where the Indus River enters the ocean) and 177 km off the coast of Sindh, an area where the seafloor is about 1.5 km deep. 

Based upon video evidence, this Whale was estimated to be 5-6 m long, and slender with a slightly protrudent melon (mass of adipose tissue on the forehead), and a long snout without protruding teeth. This Animal lacked the scars associated with tooth-raking typically seen in male Beaked Whales, and is therefore assumed to have been a female.

The Whale had a brownish-grey dorsal surface, slightly paler on the head, and had a large, Dolphin-like fin about two thirds of the way along its body. This is, along with its location in the tropical Indian Ocean, is considered to be consistent with a Longman’s Beaked Whale, Indopacetus pacificus. This species was first described in 1928 from the skull of a Whale found in Queensland Australia in 1882, with a second skull being found on the shore of Somalia, East Africa, in 1955. For a long time, these two specimens were all that was known of this species, however, recent studies have established that Whales washed up on the shores of the Philippines, Maui (Hawaii), Taiwan, Myanmar, the Andaman Islands, South Africa, and Japan, previously identified as Southern Bottlenose Whales, Hyperoodon planifrons, were in fact Longman’s Beaked Whales, and based upon this data, 65 sightings of live Whales in the  Indian and Pacific oceans have been assigned to the species.

The Whale encountered by the Al-Azaan became entangled in a net as it was being retrieved, allowing the crew to release it without apparent harm by cutting away part of the net. This process took about 30 minutes, and while the Whale is thought to have been unharmed, one of the fishermen received minor injuries.

(a)-(h). Successive steps in gillnet disentanglement operation of a Longman’s Beaked Whale, Indopacetus pacificus, in Pakistani waters. Note the head with moderately bulbous melon (e), (h), long rostrum (f), (g), (h) tubular in dorsal view (h), limited linear scarring (e) and large falcate dorsal fin (f, g). Selected frames were taken from a video. Kiani et al. (2025).

The second recorded incident happened on 31 March 2017, when an un-named Pakistani vessel encountered a 4 m long Whale 383 km off the coast of Pakistan, again in the Swatch area, an area where the sea slightly more than 3 km deep. 

This Whale had a distinct, but non-bulbous melon, a long slender snout, and a low, sub-triangular dorsal fin. The skin of the Whale was a uniform grey, slightly darker towards the tail, and it had no visible scarring of any type. It was not possible to identify this Whale to species level, but it was probably a member of the genus Mesoplodon, possibly Deraniyagala’s Beaked Whale, Mesoplodon hotaula, or Ginkgo-toothed Beaked Whale, Mesoplodon ginkgodens, although this species has never been recorded in the Indian Ocean, or even Ramari’s Beaked Whale, Mesoplodon eueu, although this species tends  to lighten towards the tail, and is a cold-water species, never previously recorded in the western Indian Ocean north of Mozambique. 

The third incident was recorded in August 2017, when a fisherman from Bandar-e-Konarak on the coast of Sistan and Baluchestan Province, Iran, sent a video to the Iranian National News Agency, IRIB News, showing a Whale entangled in a gill net. This incident is thought to have happened in the waters of Iran’s Exclusive Economic Zone, and probably close to Bandar-e-Konarak. 

The Whale could be seen to blow, suggesting that it was alive and breathing. It appears to be a Beaked Whale with no visible teeth. The bulbosity of the melon cannot be determined from the video. The fluke (tail) of the Whale can be seen, and from comparison to the arm of a fisherman, is estimated to be between about 140 cm wide, which would equate to a Whale 4.7-4.9 m in length. The fluke also lacks a median notch, confirming that the Animal is a Ziphiid.

An unidentified middle-sized Beaked Whale, with a melon of unclear bulbosity, net-entangled within Iran’s Exclusive Economic Zone waters off Sistan and Baluchistan Province, northern Gulf of Oman, in August 2017. (a), (b) Flukes without central notch and tailstock; (c) the only registered blow and vague view of the head. Both Mesoplodon sp. and Indopacetus pacificus would be possible. Kiani et al. (2025).

The fourth incident occurred on 18 January 2018, when a small-to-medium sized Beaked Whale was recorded trapped in gillnet 474 km from the coast of Pakistan, an area where the sea is slightly under 3.2 km deep. This Whale was 3.5-4.5 m long, with a medium length snout and a non-bulbous melon and no central notch on its fluke; its colour and/or markings could not be determined due to poor light. This is consistent with it being a member of the genus Mesoplodon. The Pakistani fishermen who encountered this Whale were able to disentangle it from their nets, and report if swam away in good condition. 

The fifth incident occurred on 19 March 2019, when two Beaked Whales, interpreted as a mother and calf, became entangled in the same gillnet off Churna Island, 96 km from the coast of the Pakistani Mainland. The waters here are shallow, at 295 m.

The calf was described as the size of an adult Common Bottlenose Dolphin, making it 3.0-3.5 m in length, while it was not possible to estimate the size of the larger Whale. The smaller Whale had a dark grey upper surface,  and a whitish underside. It had a short snout, and no sign of a bulbous melon, its dorsal fin hooked, no notch could be seen in the tail. These Whale are also interpreted as belonging to the genus Mesoplodon. The fishermen reported successfully disentangling both Whales.

The sixth recorded incident happened in February 2022, when Iranian fishermen reported encountering a Whale caught in a drift gillnet 1300 km off the coast of Bandar-e-Beris in eastern Sistan and Baluchestan Province. Video footage of the incident shows a medium-sized Beaked Whale with a medium-length Dolphin-like beak, and a non-steeply sloping melon, consistent with a member of the genus Mesoplodon. The video also shows that the Whale has two apical or slightly sub-apical mandibular teeth, indicating that it was male, as well as a dark eye-patch, an almost straight mouth, and a small, slightly hooked tail. The length of the Whale is uncertain, but it appears to be about 4.5-5.5 m.

An unidentified Mesoplodon sp. bycaught in far offshore waters of the northern Arabian Sea, 1300 km from Bandar-e-Beris at the eastern side of Iran’s Sistan and Baluchestan Province, in February 2022. (a), (c) Two erupted (sub)apical mandibular teeth indicate an adult male. (b) Dolphin-like, medium-length rostrum, gently sloping melon and smallish dorsal fin. Kiani et al. (2025).

The final incident happened in early June 2023, when a large Beaked Whale became entangled in a drift gillnet in the coastal Iranian Gulf of Oman, about 37 km from the port of Chabahar in eastern Sistan and Baluchestan Province. This Animal was clearly an adult male, with numerous took-rake scars and erupted apical teeth. It was estimated to have been 5.8-6.0 m in length, with an erect, Dolphin-like dorsal fin, and way brownish grey in colour with a lighter head. This is interpreted as being consistent with either a Longman’s Beaked Whale, Indopacetus pacificus, or a Cuvier’s Beaked Whale, Ziphius cavirostris. 

An adult male Beaked Whale being liberated after accidental entanglement in Tuna gillnet in coastal waters of the Gulf of Oman, some 37 km from Chabahar, Iran, in early June  2023. (a) Large body size with two erupted teeth at the apex of the mandibula; (b) a tall, erect, falcate, Dolphin-like dorsal fin, a moderately long and well-defined rostrum; (c) with numerous tooth rakes on anterior body; and (d) some degree of bulbosity in the melon. The morphology of the Beaked Whale is congruent with Indopacetus pacificus, but Ziphius cavirostris cannot be excluded. Kiani et al. (2025).

The first of these incidents is regarded as the first record of Longman’s Beaked Whale, Indopacetus pacificus, in Pakistani waters, with incidents five and seven representing potential additional sightings. A beached individual assigned to the species was recorded in Gujarat State, India, in 2014, making the Pakistan entanglement the second record of the species in the northwest Indian Ocean. Previously a skull has been recorded from the coast of Somalia in 1955, a member of the species was sighted from Socotra Island, Yemen in 1971, and another in the waters of the southern Bay of Bengal in 2009. Five Longman’s Beaked Whales have been recorded as bycatch from Sri Lanka, although these have been disputed, and fourteen sightings and a stranding recorded from the Maldives. 

Incidents two, four, six, and possibly five represent the first records of Mesoplodon sp. in Iranian and Pakistani waters, although none of these specimens could be confidently identified to species level. 

Drift gillnets are considered to be one of the most significant anthropogenic threats to Whales, although evidence to support this is absent in many areas. Kiani et al.'s study shows entanglement is a clear threat to Beaked Whales in the northwestern Indian Ocean, as while all of the reported Whales were freed, it is likely that a greater number of Whales were not released safely, and therefore not reported.

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Fucaia humilis: A Mysticete Whale from the Latest Eocene of Washington State.

Modern Mysticete Whales are noteworthy for the presence of a keratinous baleen, which they use as a filter feeding device, having lost all conventional dentition. The earliest members of the group, which retained teeth, first appeared in the Late Eocene, with the group undergoing a significant diversification event in the Oligocene. To date, only two species of Mysticete Whales are known from the Eocene, both from the Southern Hemisphere (one from Peru and one from Antarctica). This has led to the hypothesis that the Mysticetes are of Southern Hemisphere origin, and that the Oligocene radiation within the group is likely to have been driven by the End Eocene opening of a seaway between Antarctica and South America, and the subsequent formation of the Antarctic Circumpolar Current, which in turn led to a Southern Ocean with superabundant and highly-concentrated nutrients, an environment which could have favoured the evolution of the baleen filter-feeding system. 

In a paper published in the journal Current Biology on 28 March 2024, Cheng-Hsiu Tsai of the Department of Life Science and Institute of Ecology and Evolutionary Biology at the National Taiwan University, and the Department of Geology at the Japanese National Museum of Nature and Science, James Goedert of the Burke Museum of Natural History and Culture at the University of Washington, and  Robert Boessenecker, formerly of the Charleston Center for Paleontology*, describe a third species of Eocene Mysticete Whale, from the Lincoln Creek Formation of Washington State, the first known Mysticete Whale from the Eocene of the Northern Hemisphere.

The new species is placed in the genus Fucaia, which contains two previously described species from the Oligocene of the northwest coast of North America, and given the specific name humilis, meaning 'humble', in reference to the apparent minor role of Mysticete Whales in Eocene ecosystems. The new species is described from a single specimen (UWBM  109363), comprising posterior portion of a skull with right periotic and bulla attached, partial mandible, and the hyoid apparatus.

Geological column and species of Fucaia.  (A) Geological occurrences of Fucaia spp. in Washington State, USA. (B) Dorsal view of Fucaia goedertorum (NTUM-VP 240224, cast of the holotype); (C) dorsal view of Fucaia humilis (UWBM 109363); (D) ventral view of Fucaia goedertorum (NTUM-VP 240224, cast of the holotype); (E) and ventral view of Fucaia humilis (UWBM 109363). Tsai et al. (2024).

The precise location that the specimen was collected from is not given, but is described as being a site on the Middle Fork of the Satsop River, Mason County, dated to 34.5 million years before the present, which is 600 000 years before the Eocene/Oligocene boundary.

(A) The stratigraphic and geological interpretations of the Fucaia humilis discovery site, and (B) field photo, August 2023. Tsai et al. (2024).

Based upon the size of the specimen, the living Whale is estimated to have been between 286 and 206 cm in length, which is fairly typical for small Aetiocetid Whales (the group of toothed Mysticete Whales to which the genus Fucaia belongs).

The discovery of Fucaia humilis in deposits dated to the Latest Eocene of North America has serious implications for our understanding of the evolution of Mysticete Whales. Both previously described Eocene Mysticete Whales came from the Southern Hemisphere, which led palaeontologists to the conclusion that the group came from that part of the world, and that the subsequent Oligocene radiation of Mysticete Whales was driven by events there, notably the formation of the Antarctic Circumpolar Current.

Phylogenetic relationships of Fucaia humilis. Tsai et al. (2024).

The presence of a member of the genus Fucaia, which has been found nowhere else, on the Pacific Northwest of North America in the Latest Eocene suggests a presence of Aetiocetid Whales in this region for around 10 million years, whereas the occurrence of toothed Mysticete Whales in other parts of the world appears to have been somewhat sporadic, with Whales only present some of the time, gaps in the record, and a high turnover of genera, implying unstable environments intermittently colonised by Whales. Notably, the appearance of Fucaia humilis appears to coincide with the development of a Kelp forest ecosystem in this area, something which persists to this day. Kelp forests provide a stable, nutrient rich environment, which was apparently favourable to small Aetiocetid Whales. 

*Robert Boessenecker was arrested on 14 March 2024 along with his wife, the former museum collection manager at the Mace Brown Natural History Museum, accused of stealing fossils with a value of US$8634 from the collection of the Mace Brown Museum when both were employed there.

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Pebanista yacuruna: A new species of South Asian River Dolphin from the Miocene of Peru.

Toothed Whales, Odontocetes, are known to have colonised freshwater systems multiple times during the Neogene, resulting in four distinct lineages of 'River Dolphins' in different geographical areas, the Iniidae, Lipotidae, Platanistidae, and Pontoporiidae. The Lipotidae had a single species which persisted into modern times, Yangtze River Dolphin, Lipotes vexillifer, but which is thought to have become extinct in the late twentieth century due to Human activities. The Platanistidae comprises two species of completely freshwater-dwelling Dolphins from South Asia, Platanista minor from the Indus River system, and Platanista gangetica from the Ganges River and associated waterways. The Iniidae comprises a single genus of River Dolphins from South America, Inia, as well as a number of fossil species in four extinct genera. The single known species of Pontoporiidae, the La Plata River Dolphin, Pontoporia blainvillei, is also found in South America, but is not an obligate freshwater dweller, also venturing into coastal waters.

The two species of Platanista are among the most highly specialised Cetaceans, with large enlarged, thin and pneumatic supraorbital crests enclosing their melons (fatty organs used in echolocation), and eyes reduced to the point where they are almost blind; an evolutionary adaptation to living in sediment laden waters. A number of fossil Dolphins have been assigned to the Platanistidae, but all are from marine sediments, leaving no clear indicator as to when the group moved into freshwater systems. The South American Iniidae present a similar situation, with most known fossil species coming from marine deposits, although one freshwater species, Ischyrorhynchus vanbenedeni, has been described from the Late Miocene of Argentina.

In a paper published in the journal Science Advances on 20 March 2024, Aldo Benites-Palomino of the Department of Paleontology at the University of Zurich, and the Departamento de Paleontología de Vertebrados at the Museo de Historia Natural of the Universidad nacional Mayor de San Marcos, Gabriel Aguirre-Fernández, also of the Department of Paleontology at the University of Zurich, Patrice Baby of Geosciences-Environnements Toulouse at the Université de Toulouse, Diana Ochoa of the Centro de Investigación para el Desarrollo integral y Sostenible at the Universidad Peruana Cayetano Heredia, and the Departmento de Geología at the Universidad de Salamanca, Ali Altamirano, also of the Departamento de Paleontología de Vertebrados at the Museo de historia natural of the Universidad nacional Mayor de San Marcos, John Flynn of the Division of Paleontology at the American Museum of Natural History, the Department of Earth & Environmental Sciences at Columbia University, and the Graduate Programs in Biology and Earth and Environmental Sciences at the City University of New York, Marcelo Sánchez-Villagra, again of the Department of Paleontology at the University of Zurich, Julia Tejada, again of the Departamento de Paleontología de Vertebrados at the Museo de Historia Natural of the Universidad nacional Mayor de San Marcos, the Division of Paleontology at the American Museum of Natural History, and of the Division of Geological and Planetary Sciences at the California Institute of Technology, Christian de Muizon of the Departement Origines et Evolution at the Muséum Nation-al d’Histoire Naturelle, and Rodolfo Salas-Gismondi, once again of the Departamento de Paleontología de Vertebrados at the Museo de Historia Natural of the Universidad nacional Mayor de San Marcos, the Centro de Investigación para el Desarrollo integral y Sostenible at the Universidad Peruana Cayetano Heredia, and the Division of Paleontology at the American Museum of Natural History, describe a new species of  Platanistid Dolphin from the Early to Middle Miocene Pebas Formation of Peruvian Amazonia.

The new species is named Pebanista yacuruna, where 'Pebanista' is a combination of Pebas, after the formation from which the fossil came, and Platanista, the only living genus of Platanistid Dolphin, and 'yacuruna' is a mythical water creature from the folklore of the Kichua peoples of the Peruvian Amazon. The new species is described from a single partial skull, comprising the posterior part of the rostrum, the facial region including part of the right supraorbital crest, the temporal and occipital regions.

Pebanista yacuruna, MUSM 4017. holotype skull in dorsal (A) and (B), ventral (C) and (D), left lateral (E) and (F), and anterodorsal views (F) and (G). Benites-Palomino et al. (2024).

The skull has a preserved length of 698 mm and an estimated width of 281 mm. The sutures of the skull are well fused, indicating that it was an adult at the time of death. The vertex of the skull is deviated leftwards, the premaxillae in the rostrum and facial areas is asymmetric, the braincase is anteroposteriorly shorter than wide; and the palatines lack contact and project dorsolaterally, all of which are diagnostic of the Platanistidae. Based upon the width of the skull, the living Dolphin is estimated to have been between 281 cm and 247 cm in length. Although Pebanista yacuruna undoubtedly occupied an inland, freshwater environment, it is similar in size to marine members of the group, considerably larger than living Platanista spp., and recent River Dolphins in general.

Size comparison between 'River Dolphins' and marine Platanistoids and River Dolphins. White silhouettes indicate the minimum body length calculated or recorded; gray body outlines indicate the largest size recorded or estimated in: (A) Macrosqualodephis ukupachai, (B) Zarhachis flagellator, (C) Pontoporia blainvillei, (D) Pebanista yacuruna, (E) Inia geoffrensis, (F) Platanista gangetica, and (G) Lipotex vexillifer. (H) Artistic reconstruction of Pebanista yacuruna. Jaime Bran in Benites-Palomino et al. (2024).

All known living members of the Platanistidae are restricted to the river systems of South Asia. Fossil Platanistid Dolphins are fairly common in the Oligocene and Miocene, when they appear to have had a global distribution and to have occupied a range of ecological niches, but all previously described fossils of the group are considered to have been marine. The group reached peak diversity in the Early Miocene, declining in numbers and diversity after this time, following the emergence of f other toothed Cetacean groups such as Delphinoids, Beaked Whales, and Physeteroids around the time of the Middle Miocene Climatic Optimum. 

The Early Miocene was a time of global cooling, as well as increased subsidence in the Andean-Amazonian foreland basin system, with most of the modern west Amazon rainforest area in Colombia, Peru, and Brazil covered by a continental-scale fresh water to brackish water foreland system (the Pebas System) parallel to the Andes. During the Early Miocene there were at least two large scale marine influxes from the Caribbean Sea into this basin. This wetland ecosystem reached its maximum extent during the Middle Miocene Climatic Optimum, as a complex arrangement of terrestrial and aquatic environments rich in nutrients and prey types, inhabited by a wide range of Fish, Turtles, Crocodylians (Caimans and Gharials), and mammals (Marsupials, Sloths, Rodents, Primates, and Ungulates), among others. This resource rich ecosystem appears to have favoured large sizes in predators such as Pebanista yacuruna and Gharials, a group of Crocodilians which also have marine ancestry, but which today are restricted to South Asia.

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Balaenoptera physalus: Fin Whale found dead on Cornish beach.

A sixteen metre long Fin Whale, Balaenoptera physalus, has been found dead on a beach in Cornwall, southwest England. The female subadult Whale was found on Fistral Beach at Newquay, on the north coast of the peninsula on the morning of Wednesday 15 November 2023. It had previously been sighted in an apparent state of distress of Towan Head the previous day. The cause of death has not yet been determined, but the Whale is reported to have been emaciated and heavily infected with parasites, suggesting it had been in poor health for some time. 

A Fin Whale, Balaenoptera physalus, found dead on Fistral Beach, Cornwall, UK, on Wednesday 15 November 2023. Ashley Abbot/BBC.

Fin Whales are the second largest Whale species, reaching about 27 m in length with an estimated maximum mass of about 114 tonnes. Fin Whales were hunted heavily until 1989, when it was given full protection by the International Whaling Commission. Since the introduction of the moratorium on Whaling the species has recovered well and is now only considered to be Vulnerable under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species (one step short of 'Least Concern').  The reporting of greater numbers of dead Whales on our shores is often distressing, and can appear to be sign of more Whales dying in inshore waters, but in fact this greater number of dead Whales reflects a larger population of living Whales being present offshore, and is a symptom of recovering populations.

This is the second Fin Whale to have been found on a Cornish Beach this year, with another Animal found on Perranuthnoe Beach, Marazion, in January. Other Fin Whales were found on a beach in Bridlington, Yorkshire in May, and Baile Uí Chuill Strand, in County Kerry, Ireland in July. In November 2021 a Fin Whale was found on a beach near Calais in France, and in February 2020 a Fin Whale was found dead on the Lizard Peninsula, Cornwall. The growing number of Fin Whale strandings in the UK and neighbouring countries, while individually tragic, suggests a growing population of these Animals in the area.

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Monitoring Cetaceans in the Azores.

Gathering data on the numbers and movements of far-ranging ocean Animals such as Cetaceans is notoriously difficult, which is unfortunate, as such Animals are considered to be key indicators of the condition of marine ecosystems, with current concerns about the long-term health of the marine environment making such data particularly crucial. The Marine StrategyFramework Directive requires European Union member states with coasts to monitor the biodiversity of their territorial waters in order to maintain the marine environment. However, this does not include dedicated Cetacean surveys, due to the complexity and expense of maintaining such programs. This leaves Cetacean surveys largely in the hands of citizen scientists and commercial organizations.

The highly charismatic nature of Whales and Dolphins makes them ideal for citizen science projects, with the public often keen to take a role in their conservation. Whale watching tours have become popular tourist activities in many parts of the world in recent decades, providing both a tool for educating the public about marine ecology and an excellent opportunity for scientific programs studying Whales to piggyback onto the commercial activity. Such programs have proven particularly good for gathering long-term data on Whales within areas where tours are carried out. Whale-watching tours are therefore a cost-effective tool for monitoring Whale populations, particularly in areas where funding is limited or unavailable. Successful examples include the ORCA Survey Network operating in UK waters, the Fixed Line Transect Mediterranean monitoring Network, which works from European Atlantic and Mediterranean ferries, the CETUS project, which operates from cargo boats out of Macaronesia (the Azores, Madeira, the Canaries, and the Cape Verde islands) and mainland Portugal, and the Kakila database, which gathers data from Whale watching tours in the Caribbean. Data gathered from such sources has led to numerous publications on the distribution, movements, and habitat preferences of Cetaceans.

The Azores Islands are located in the North Atlantic Ocean at 36-41° North and 24-32° West. The archipelago is composed of nine volcanic islands organised into three groups separated by deep waters (i.e. deeper than 2000 m): the Western (Flores and Corvo), Central (Faial, Pico, Graciosa and Terceira) and Eastern groups (São Miguel and Santa Maria). The archipelago presents a well-defined oceanographic seasonality: March is usually the coldest month (average sea surface temperature 15°C), while the highest temperatures are generally reached in September (average sea surface temperature 25°C). The spring bloom is noticeable each year by the increase in chlorophyll concentrations, which drastically drop to oligotrophic conditions during summer. 

The people of the Azores have been linked to Cetaceans since the islands were first colonised in the fifteenth century, when early settlers are known to have harvested Whales stranded on beaches or found dead at sea. In the mid eighteenth century, whalers from North America began to visit the islands in pursuit of Sperm Whales, Physeter macrocephalus, often recruiting local people as crew for their vessels. The Azoreans learned the techniques used by the Americans, and adapted them to their own needs, replacing spotters mounted high upon ships with spotters at high points on land, and using these to guide small boats towards sited Whales in the same way. 

Over time the oil for which Sperm Whales was hunted was replaced by oil from other sources, making Whaling less profitable, and the practice began to die out in the 1960s. In 1982, Portugal ratified the Moratorium of theInternational Whaling Commission, and in 1986 Whaling was officially banned in all Portuguese territories, including the Azores, where the last two Sperm Wales were killed in 1987. 

The whaling industry provided the first accurate data on Whales collected in the Azores, with whalers collecting data on changes in the distribution of Whales over time, the first accurate descriptions of the Animals, and even the first records of their eating giant Cephalopods. In 1987 the government of the Azores, with support from the European Union, invited the International Fund for Animal Welfare to carry out a feasibility study on the potential for developing a Whale-watching industry in the Islands. The first tours were carried out from Pico Island in 1989, and rapidly became popular with tourists. Some the earliest recruits to the new business were former lookouts from the Whaling industry, and they were soon followed by former whalers, who worked as skippers on the new boats, brining with them their expertise in the ecology and behaviour of the Whales. In 1993 Whale-watching tours also began from São Miguel Island, with tours later starting from Faial and Terciera islands.

To date, 28 species of Whales and Dolphins have been observed around the Azores, making the islands one of the most popular Whale-watching destinations in the world. From the outset, the Whale-watching industry in the Azores was built on an ecotourism model, with regulations developed through collaboration between the tour operators, the scientific community, and the government of the Azores. The first Bienal das Baleias conference was held in Lajes do Pico in October 1998, with the various groups involved seeking to come to a consensus on further developing an ecologically friendly industry. As a consequence of this, legislation was introduced in 1999, which required the mandatory collecting of data on Whales by the tour boats, although this proved to be highly impractical, and was quickly dropped, although all parties involved agreed that a system of gathering this data was needed, both to develop the Whale-watching industry and to further the study and conservation of the Whales. 

The MONICET project grew out of a discussion at the 2006 Bienal das Baleias conference, with a scientific consortium working with three Whale-watching companies to develop a methodology for collecting data in a scientifically usable manner, and a remit to develop a database to store this data, all funded by a grant from the Azores government. 

In a paper published in the Biodiversity Data Journal on 8 August 2023, Laura González García of the  Institute of Marine Sciences at the University of the Azores, Marc Fernández of the Marine and Environmental Sciences Centre of the Agência Regional para o Desenvolvimento da Investigação Tecnologia e Inovação, and José Azevedo, also of the Institute of Marine Sciences at the University of the Azores, describe the methodology used by the MONICET project, the data gathered by that project so far, and ways in which this data might be used by researchers outside the Azores. 

González García et al. describe eleven years of MONICET data, collected between 2009 and 2020, and provided by 11 of the 23 Whale watching companies active in the Azore, operating out of four of the nine volcanic islands which make up the Azores (Azores Experiences and Peter Whale Watch from Faial Island; Aqua  Açores and Espaço Talassa from Pico Island; Futurismo Azores Adventures, Picos de Aventura, Terra Azul, Terra do Pico and Sea Colors from São Miguel Island and Atlantiangra, Ocean Emotion and Picos de Aventura from Terceira Island). Not every company reported data every year; participitation in the project is voluntary, and data will always be accepted from any company wishing to participate. In the first year of the project only three companies reported data, while the greatest number was reached in 2019, when nine companies reported.

The Azores Archipelago, with the locations (white dots) of all the sightings recorded between 2009 and 2020 in the MONICET database. Base ports of contributing companies are indicated by black triangles. González García et al. (2023).

MONICET uses a collaborative platform to collect and disseminate data on Cetacean sightings and movements, as well as photo images used for Whale identification. The data is collected on a voluntary basis, and is available to all interested persons, including the general public. 

Whale-watching tours in the Azores typically last 2.5-3 hours, with most companies operating two tours per day, although some run three per day in the peak of the tourist season. Tours operate from São Miguel Island year-round, but from the other islands is more seasonal, typically running from May to September. In all cases, Whales are first spotted from land, with experienced spotters guiding boats to the Cetaceans. This typically results in at least one Whale encounter per trip, with boats moving to the Whales then slowing down for periods of observation. 

The data used by MONICET is typically gathered by trained guides on board the boats (often trained biologists), who record the times at which the boats leave and return to their home ports, the location of the boats throughout their voyage (recorded with a GPS system), and the time, location, and species of any Whales encountered, as well as the number of Whales, their approximate age (adults, juveniles or calves), and behaviour, as well as other data about weather, sea conditions etc. Guides are provided with annual training on data collection by MONICET.

Tourists encountering a group of Cetaceans on a Whale-watching tour in the Azores. Futurismo Azores Adventures.

During the period recorded in González García et al.'s data, 37 000 sightings were recorded of 22 Cetacean and three Turtle species, including Minke Whale, Balaenoptera acutorostrata, Sei Whale, Balaenoptera borealis, Bryde's Whale, Balaenoptera edeni, Blue Whale, Balaenoptera musculus, Fin Whale, Balaenoptera physalus, Humpback Whale, Megaptera novaeangliae, Common Dolphin, Delphinus delphis, Short-finned Pilot Whale, Globicephala macrorhynchus, Long-finned Pilot Whale, Globicephala melas, Risso's Dolphin, Grampus griseus, Killer Whale, Orcinus orca, False Killer Whale, Pseudorca crassidens, Striped Dolphin, Stenella coeruleoalba, Atlantic Spotted Dolphin, Stenella frontalis, Bottlenose Dolphin, Tursiops truncatus, Pygmy Sperm Whale, Kogia breviceps, Sperm Whale, Physeter macrocephalus, North Atlantic Bottlenose Whale, Hyperoodon ampullatus, Sowerby's Beaked Whale, Mesoplodon bidens, Blainville's Beaked Whale, Mesoplodon densirostris, True's Beaked Whale, Mesoplodon mirus, and Cuvier's Beaked Whale, Ziphius cavirostris, as well as Loggerhead Turtle, Caretta caretta, Green Turtle, Chelonia mydas, and Leatherback Turtle, Dermochelys coriacea.

One problem noted by González García et al. is that the MONICET data tends to reflect the commercial preferences of the tourist industry. Thus spotters will guide boats towards more appealing Cetaceans, such as families of Sperm Whales or active pods of Dolphins, over Beaked or diving Whales which spend little time at the surface. The data set is presumed to be good, given the training and experience of the guides, but some caution needs to be applied to sightings of more elusive Whales, as these are less often seen, and spend less time at the surface where they can be identified. 

Some types of Whale will alter their behaviour in response to the presence of boats; this is particularly true of Dolphins, which tend to break off other activities in order to investigate Human visitors. For this reason, the activity of Whales is recorded when the boats first arrive, although there is a danger that the Whales may already have been affected by the presence of earlier boats.

Whales active at the surface are more attractive to tour boats than deep diving Whales. Azores Experiences.

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Perucetus colossus: A Basilosauridae Whale from the Eocene of Peru, which may have had a mass exceding that of the modern Blue Whale.

The fossil record of the Cetacea gives us one of the most remarkable examples of an evolutionary transition in a group of organisms, from small, Mouse Deer-like, and entirely terrestrial, Artiodactyls to the largest Animals ever to have lived in out oceans. The early marine Whales developed specialisms for life in the water during one of the Earth's most extreme greenhouse phases, quickly growing in body size, and by the end of the Eocene becoming extremely elongate as well. However, the extreme gigantism seen in modern Whales is a apparently a relatively recent development which appeared in Baleen Whales in the cooling oceans of the Late Cainozoic. One of these, the extant Blue Whale, Balaenoptera musculus, is currently considered to be the heaviest Animal ever to have lived on Earth. This trend in developing large body-size as a development to active pelagic swimming is not unique in Cetaceans, among Tetrapods it can be observed in several clades of Mesozoic Marine Reptiles, such as the Ichthyosaurs.

As Animals make the transition from living in a terrestrial one to living in a marine one, buoyancy control becomes a key aspect of their biology. In Vertebrates, bone is the densest tissue, and large amounts of this tissue are present in the bodies of most Vertebrates. This has resulted in a variety of specialist bone-adaptations appearing in Tetrapods that have returned to an aquatic lifestyle. In Animals with a slow-moving, shallow-diving lifestyle, such as Sirenians, this typically manifests as an increase in bone mass. This increase has been observed in the earliest Whales, and is seen in many Basilosaurids (an extinct Cetacean family which was the most numerous and widespread Whale group in the Eocene). The reverse situation is seen in more active, pelagic swimming marine Tetrapods, including all modern Whales, with bone mass becoming severely reduced, and other tissues taking on a greater role in providing structural support to the body. The Basilosaurids were a unique group, growing to lengths of up to 20 m and having a much higher relative bone mass than modern Whales, although, this has not until now been shown to be close to that of the extant Sirenians.

In a paper published in the journal Nature on 2 August 2023, Giovanni Bianucci of the Dipartimento di Scienze della Terra at the Università di Pisa, Olivier Lambert of the Direction Opérationnelle Terre et Histoire de la Vie at the Institut Royal des Sciences Naturelles de Belgique, Mario Urbina of the Departamento de Paleontología de Vertebrados at the Museo de Historia Natural of the Universidad Nacional Mayor de San Marcos, Marco Merella and Alberto Collareta, also of the Dipartimento di Scienze della Terra at the Università di Pisa, Rebecca Bennion, also of the Direction Opérationnelle Terre et Histoire de la Vie at the Institut Royal des Sciences Naturelles de Belgique, and of the Evolution & Diversity Dynamics Lab at the Universite de Liege, Rodolfo Salas-Gismondi, also of the Departamento de Paleontología de Vertebrados at the Museo de Historia Natural of the Universidad Nacional Mayor de San Marcos and of the Facultad de Ciencias y Filosofía and Centro de Investigación para el Desarrollo Integral y Sostenible at the Universitad Peruana Cayetano Heredia Lima, Aldo Benites-Palomino, again of the Departamento de Paleontología de Vertebrados at the Museo de Historia Natural-Universidad Nacional Mayor de San Marcos, and of the Department of Paleontology at the University of Zurich, Klaas Post of the Natuurhistorisch Museum Rotterdam, Christian de Muizon of the Département Origines et Évolution at the Muséum National d’Histoire Naturelle, Giulia Bosio of the Dipartimento di Scienze dell’Ambiente e della Terra at the Università degli Studi diMilano-Bicocca, Claudio Di Celma of the School of Science and Technology at the University of Camerino, Elisa Malinverno, also of the Dipartimento di Scienze dell’Ambiente e della Terra at the Università degli Studi di Milano-Bicocca, Pietro Paolo Pierantoni, also of the School of Science and Technology at the University of Camerino, Igor Maria Villa of the Institut für Geologie at the Universität Bern, and  Eli Amson of the Staatliches Museum für Naturkunde Stuttgart, describe a new species of Basilosaurid Whale from the Late Eocene Paracas Formation of Peru, which combines a gigantic size with the highest degree of bone mass increase ever seen in a Whale, which was potentially heavier than the living Blue Whale.

The new species is described from a single specimen, MUSM 3248, which was recovered from the upper part of the Yumaque Member of the Paracas Formation exposed in the Ica valley a few kilometres south of the Zamaca locality, and is now housed in the collection of the Museo de Historia Natural of the Universidad Nacional Mayor de San Marcos. This was five metres below a tephra layer radioisotope dated to 36.8 million years ago. Based upon this, and biostratigraphic data from the silts of the Yumaque Member, the specimen is estimated to be between 39.8 and 37.84 million years old, making it Bartonian, or Middle Eocene in age. The species is named Perucetus colossus, where 'Perucetus' means 'Peru Whale' and 'colossus' means gigantic.

Location and stratigraphic position of Perucetus colossus MUSM 3248. (a) Map showing the position of the Coastal Batholith and major trench-parallel structural highs along the coast of Peru. (b) Stratigraphic column of the Cainozoic succession exposed in the East Pisco Basin. (c) Measured stratigraphic section of the type locality of Perucetus colossus, indicating the stratigraphic height of the holotype MUSM 3248, the dated tephra layer, and the identified bioevents. Bianucci et al. (2023).

The specimen comprises a partial skeleton including 13 vertebrae (two tentatively referred to the last thoracics and the others to the anterior lumbars), four ribs and right innominate lacking the distal portion of the ilium. It is believed to have been nearing skeletal maturity when it died. 

Perucetus colossus differs from all other known Cetaceans in the extremely pachyosteosclerotic (thick and dense) nature of the bones of its post-cranial skeleton. Pachyosteosclerosis has been reported in Cetaceans before, and is a defining feature of the Basilosaurid Subfamily Pachycetinae, but never to the extent seen in Perucetus colossus. 

Partial skeleton of the Perucetus colossus MUSM 3248 holotype. (a) Schematic body and skeletal reconstruction reporting the preserved bones (red). (b), (c) Right rib in anterior (b) and lateral (c) views. (d)–(f) Right innominate in medial (d), dorsal (e) and lateral (f) views. (g)–(i) Last preserved lumbar vertebra in anterior (g), left lateral (h) and dorsal (i) views. (j)–(l) Articulated sequence of the 13 collected vertebrae in dorsal (j), ventral (k) and right lateral (l) views. Scale bars, 50 cm (b), (c) and (g)–(l) and 10 cm (d)–(f). All of the images were generated from 3D surface models. Bianucci et al. (2023).

Although heavily modified by the presence of additional dense bone material, the transverse processes of the vertebrae are sufficiently similar to those of other Basinosaurids for Biannucci et al. to be confident about their placement as the two thoracic and the first eleven lumbar vertebrae. About half the vertebrae are missing their centrum epiphyses, a sign that these bones were not fused at the time of death. In a terrestrial Mammal, this would be taken as a sign of immaturity, but in Whales this condition frequently persists into adult life, and is therefore considered to be of no significance for determining the age of the specimen. 

One of the vertebrae of Perucetus colossus being moved during the recovery of the specimen. Universitad Peruana Cayetano Heredia Lima.

The best preserved rib displays a simple proximal end without distinct tuberculum and capitulum and a weak overall curvature in anterior or posterior view, which is consistent with a placement in the posterior region of the rib cage. Since pachyosteosclerosis of the ribs tends to develop in the foremost ribs first, this is consistent with the entire rib cage being pachyosteosclerotic.

Specimen MUSM 3248, shows no signs of having been pathological in any way (pathological pachyosteosclerosis tends to produce highly variable bone density distribution), but rather appears to have been a healthy specimen of a species with a highly pachyosteosclerotic skeleton. The apophyses of the vertebrae are distinctive in having a 'bloated' appearance, unlike that of any other Mammal, whereas in all other Cetaceans, including the largest Balaenopterids and Balaenids, the vertebral apophyses tend to be relatively thin.

Pachyostosis in the Perucetus colossus MUSM 3248 holotype. (a)–(c) Skeleton (a) preserved bones in dark grey, life reconstruction (b), and 3D models of a rib (c) and lumbar vertebra (d) of Perucetus colossus. (e)–(j) Skeletons (e), (h), posterior rib (f), (i) and last lumbar vertebra (g), (j) of the Wexford Blue Whale, Balaenoptera musculus; (e)–(g) and another Basilosaurid, Cynthiacetus peruvianus (h)–(j). Scale bars, 50 cm for isolated bones in (c), (d), (f), (g), (i) and (j) and 2 m for the skeletons and reconstruction in (a), (b), (e) and (h). The dagger symbols (†) indicate extinct species. Bianucci et al. (2023).

The ribs which were found were also highly pachyosteosclerotic, leading Bianucci et al. to conclude that this state would have applied to the whole skeleton. If this was the case, then the volume of the entire skeleton would have been 2.9-4.1 m², and would have weighed 5.3 to 7.6 tonnes, which is 2.0–2.9 times as much as that of a 25 m long Blue Whale.

The total range of skeletal masses found in Tetrapods varys between about 26 mg in the Dwarf Chameleon Brookesia nana, and an estimated 9.9 tonnes in the giant Titanosaur, Argentinosaurus huinculensis. Modern Cetaceans have relatively light skeletons, compared to the rest of their tissues, perhaps making up 2.2-5.1% of their entire body mass, while that of terrestrial Mammals varies between 4 and 10%. The skeletons of Sirenians, aquatic Mammals with a lifestyle similar to that presumed for pachyosteosclerotic Basilosaurs such as Perucetus colossus. tend to have skeleton-mass-to-body-mass ratios similar to that of terrestrial Mammals. 

Estimating the body mass of extinct Animals such as Basilosaurs is complicated, and in the case of Perucetus colossus is made more challenging by the extreme skeletal morphology. It is likely that the heavy skeleton would have been counterbalanced by a large volume of buoyant blubber, which would have had a strong impact on the overall density and mass of the soft tissue of the living Whale. If it is assumed that Perucetus colossus has a skeleton-mass-to-body-mass ratio similar to that of modern Sirenians, then the living Animal would have had a total mass of about 85 tonnes, but if the ratio was comparable to that of living Whales, then it would have been between about 180 and 340 tonnes. Adult Blue Whales typically have a total body mass of about 130-150 tonnes, so it is possible that Perucetus colossus was more massive than a Blue Whale.

Scaling of the skeletal mass across Amniotes’ body mass range. Regressions based on extant terrestrial Mammals (grey line) and extant Cetaceans (blue line). The estimated values for extreme terrestrial Amniotes, Sirenians (either measured or estimated) as well as the results of the estimations for Perucetus colossus are also shown. Each data point corresponds to a distinct species (specific mean for the largest extant cetaceans, Balaenoptera musculus and Physeter macrocephalus), except for extant sirenians (represented by two species). The horizontal and vertical bars indicate the maximum and minimum estimates (some are too small to be visible). Scales are logarithmic. Human height, 1.8 m (scale for larger silhouettes); penny diameter, 2 cm. Bianucci et al. (2023).

Among Tetrapods, high levels of pachyosteosclerosis are only known in fully aquatic species capable of bearing young in the water. The morphology of Perucetus colossus makes it highly unlikely that it was ever able to pull itself onto land for any reason, and therefore it is presumed to have given birth at sea. Its presumed morphology and high level of pachyosteosclerosis make it likely that it lived in shallow waters, such as those inhabited by living Manatees, although the large mass of the Animal may have made it more resilient to wave actions, something which has also been proposed for the more recently extinct t Steller’s Sea Cow, Hydrodamalis gigas. Coastal habitats have previously been proposed for Basilosaurids, based upon their skeletal anatomies and stable isotope data.

 

Reconstruction of Perucetus colossus in its coastal habitat. Because portions of the skeleton are unknown, several aspects of the reconstruction are tentative: the overall proportions of the axial postcranium are based on a close relative Cynthiacetus peruvianus, which was scaled-up and dilated according to the elements recovered for Perucetus colossus; the skull and limbs were only scaled-up; the tail fluke and forelimb use (bottom-walking) are based on the Manatee, Trichechus, sp, the extant Marine Mammal with the closest degree of pachyosteosclerosis in the postcranial skeleton; the hind limb of Perucetus colossus was not recovered, but the anatomy of its innominate indicates the presence of a reduced, articulated leg. The associated Sawfish, Pristis sp., was recovered from the same unit in the East Pisco Basin, the Yumaque Member of the Paracas Formation. Alberto Gennari in Bianucci et al. (2023).

Although Perucetus colossus is known only from a single fragmentary skeleton, lacking a head or any teeth (which would be needed to make any assumption about its diet or feeding habits), some conclusions can be made about the way in which it lived. The vertebrae of Perucetus colossus have elongated centra, something also found in other Basilosaurids, as well as in living Manatees, Trichechus spp., where it is associated with swimming by means of axial undulation. Interestingly, another living Sirenian, the Dugong, Dugong dugon, which lives in more open waters and swims in a similar way to living Whales, by oscillation of a lunate tail, lacks such elongate centra. 

A previous study examined motion in another Basilosaurid, Cynthiacetus peruvianus, providing a methodology to analyse the movement of Perucetus colossus. Doing this showed that dorsal and lateral flexation was extremely limited in Perucetus colossus, but that its capacity for ventral flexation was actually higher than in Cynthiacetus peruvianus, suggesting that swimming was driven entirely by downward strokes of the posterior part of the body. Such a form of motion has also been proposed for early Whales Antaecetus and Pachycetus, and would have been particularly useful for pushing the Animal away from the seafloor suddenly; in the smaller Whales it has been suggested that this might have indicated they were Ambush predators, but this seems unlikely for an Animal as large as Perucetus colossus; instead a strong upward swimming capacity might have been needed to help it breath. 

Estimates of the osteological range of motion. Extension and flexion of the preserved portion of vertebral column of Perucetus colossus holotype (MUSM 3248) is compared with an equivalent vertebral column portion of Cynthiacetus peruvianus holotype (MNHN.F.PRU10) using the respective 3D models. Intervertebral spaces were reconstructed based on the Common Dolphin, Delphinus delphis. Scale bar is 50 cm. Bianucci et al. (2023).

The large size and undulatory motion of early Whales such as Perucetus colossus and Basilosaurus spp., is similar to that seen in the large Ichthyosaurs of the Early Triassic. In these Marine Reptiles it has been suggested that their large size might have helped to compensate for the high energetic cost of undulatory locomotion. It has also been observed that the earliest members of several Mesozoic Marine Reptile groups shared a small size (less than 1 m), pachyosteosclerotic skeleton, and serpentiform body adapted for undulatory motion, suggesting that all these Animals were the subjects of similar selective pressures, associated with shallow diving in a coastal environment. Having adopted such a lifestyle, all would then have been under further selective pressure to grow in size, allowing longer and deeper dives.

While the absence of a skull makes it impossible to accurately reconstruct the feeding habits of Perucetus colossus, its large size and a body apparently adapted to slow swimming and diving in near-shore environments, do make some speculation possible. Such a large Animal must have required very large quantities of food, and therefore that food must have been fairly abundant. Perucetus colossus has been observed to share a number of features with extant Sirenians, a group which feeds almost exclusively on Seagrass and Macroalgae, but no other Cetacean has ever been recorded to follow a herbivorous lifestyle, so this seems a little unlikely. An alternative might be sessile or sedentary benthic Animals such as Crustaceans, demersal Fish, and Molluscs. Such organisms could be harvested with a sucking and/or filter feeding technique, similar to that used by the living Grey Whale, Eschrichtius robustus, or possibly to have fed on sunken carrion, in a way similar to many large, bottom-dwelling Sharks.

The discovery of Perucetus colossus extends the range of known skeletal phenotypes for Vertebrates, and our understanding of the maximum achievable body mass for a healthy Animal. It further shows that masses close to or exceeding 100 tonnes are not a recent phenomenon in Cetaceans, as has previously been assumed, but had also been achieved by the second half of the Eocene; a time during which the maximum size was also achieved by several other Mammal groups. While the remains of the only known specimen of Perucetus colossus are fragmentary, preventing a full reconstruction of the living Animal and its lifestyle, it appears to have been adapted for a slow-swimming, most likely coastal, benthic habit, showing that a fully pelagic lifestyle is not necesarily a prerequisite for achieving large size in Cetaceans. It further expands the known ecological niche of the Basilosaurids, but supports the hypothesis that this group was essentially restricted to coastal environments, which are known to have been highly productive during the Eocene.

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