The Mauritius scops owl (Otus sauzieri), also known as the Mauritius owl or Mauritius lizard owl, is an extinct species of scops owl that lived on the Mascarene island of Mauritius. Contemporary accounts of owls include mentions in 17th-century reports from Mauritius, a drawing made around 1770, and a detailed description of a killed specimen from 1837. After the owls had disappeared, subfossils were found in the Mare aux Songes swamp. These remains became the basis of the new species Strix sauzieri in 1893 and two other species were later named: Scops commersoni based on the drawing and description in 1896, and Strix newtoni based on a smaller fossil in 1907.
Later writers doubted whether three distinct owl species had lived on Mauritius, and concluded in 1994 that the known evidence represented a single species. It was placed in the new genus Mascarenotus along with the extinct owls of the two other Mascarene Islands, the Rodrigues scops owl and the Réunion scops owl. A 2018 ancient DNA study found the Mascarene owls to be derived from different lineages within the scops owl genus Otus that originated in Southeast Asia, therefore not constituting their own genus, leaving the Mauritian species as O. sauzieri.
Based on the contemporary accounts and subfossils, the Mauritius scops owl was a large owl with an average body length of , larger than extant scops owls, and a wingspan of . The wings were proportionally short and the legs were long. It had prominent brown ear-tufts and featherless . The upper parts of its plumage were brown and the rest was wholly or partially white. Its white eyebrows (or supercilia) and bristles were unique among the owl species in the Indian Ocean region. Its skull and eye sockets were small for its size.
Little is known about the behaviour of the Mauritius scops owl. Based on its long legs, it probably hunted lizards and small birds, like some other island owls. Its long legs and featherless tarsi indicate they were probably more terrestrial than other owls, and their proportionally small heads and eye sockets could indicate they were less nocturnal. The last two accounts based on observations state it had become scarce after formerly being plentiful, due to deforestation and poaching; it was gone by 1859. Researchers point to other extinction causes, including the effects of introduced animals, and the increased terrestriality of these owls could also have made them more vulnerable.
Taxonomy
Early reports mentioned owls on the Mascarene island of Mauritius, the first being those of the Dutch sailors Willem van Westzanen in 1602 and Cornelis Matelief de Jonge in 1606, and of the British traveller Sir Thomas Herbert in 1627. No more owls were recorded until the French officer Paul de Jossigny illustrated several Mauritian specimens obtained by the French botanist Philibert Commerson around 1770, including the only known illustration a Mauritian owl. The French zoologist Julien Desjardins described a killed specimen in detail in 1837; his report and Jossigny's drawing were made widely known in 1896, after the owls had disappeared. The British ornithologist and Colonial Secretary for Mauritius Edward Newton mentioned in his diary that an owl skin was present at the Mauritius Institute until it was lost during a cyclone in 1870. It is uncertain whether this was the correct year or if a storm was the cause at all, and no skins of this species exist today.
In 1889, the Mauritian government requested exploration of the Mare aux Songes swamp for "historical souvenirs", where vast amounts of dodo remains had been found. The new excavations, under the direction of the French naturalist , were successful; apart from dodo bones, subfossil remains of other extinct animals, including both previously known and new species, were found. These bones were sent to the Cambridge University Museum of Zoology, where they were examined and described by Newton and the German ornithologist Hans Gadow in 1893. Based on two humeri (upper arm bones), three tibiae (shinbones), and four tarsometatarsi (lower leg bones that fuse the ankle bones with the metatarsi of the feet), they determined the existence of an owl.
Newton and Gadow stated that owls are generally classified according to features of the skull, sternum, or external characters, none of which were available for this owl. They noted that the length of the tibia relative to that of the metatarsus is characteristic of various families and genera and indicated that the owl from Mauritius belonged to what they termed "long-footed owls"; typical members of this group are the short-eared owl (Strix flammea) and its relatives. The Mauritius owl differed from those owls in some proportions, so Newton and Gadow named it the new species Strix sauzieri. Although the largest metatarsi were long, a pair were shorter and slenderer than the others at , yet also fully ossified (turned into hard bone). These writers did not feel the differences were due to age or sexual dimorphism. Unless the island possessed two Strix species, the smaller bones would have been from a small individual of the same species, although they found it unlikely that a species confined to a small island would range as much in size as the short-eared owl of Britain.
Naming of additional Mauritian owl species In 1896, the French zoologist Émile Oustalet reported the discovery of a drawing by Jossigny in the Commerson collection in Paris depicting an owl from Mauritius. It appeared life-sized, roughly the same size as the marsh owl (Asio capensis) of Madagascar, but with different plumage. Oustalet did not think the drawing depicted the owls of earlier reports and fossils from Mauritius, which supposedly represented a barn owl without ear-tufts. Instead he considered it similar to a scops owl but much larger, and identical to the owl described in detail by Desjardins in a by-then-little-known 1837 report; the drawing matched the description and was the same size as that given. Desjardins had considered it a scops owl new to science, and stated it was killed in October 1836 in Anse des Bambous, Grand Port District, and sent to him barely gutted. He foresaw that the species would soon be extinct, which Oustalet confirmed, and expressed hope that bones or even a stuffed specimen would be discovered. Oustalet named the owl Scops commersoni as a tribute to Commerson, who had long remained unrecognised. He also found the Rodrigues owl (then Athene murivora), described from subfossils and descriptions from the Mascarene Island of Rodrigues in 1873, to be unrelated.
In 1907, the British zoologist Walter Rothschild stated that he did not believe Oustalet's Scops commersoni truly belonged to the genus Scops, being too large, but that it had to be left there due to the lack of physical specimens. Rothschild also considered the smaller owl mentioned by Newton and Gadow a new species, Strix newtoni, named after the by-then-late Newton. He noted that although those writers had not considered the smaller owl distinct, the short-eared owl co-occurs throughout much of its range with either the eastern grass owl (then Strix candida) or the African grass owl (then S. capensis). These species are popularly termed grass owls, which have longer legs than the true barn owls, to which the short-eared owl and its relatives belong. Rothschild suggested that two species of Strix owls co-occurred on Mauritius, S. sauzieri being the local representative of the grass owls and the smaller S. newtoni belonging to the barn owl.
The Japanese ornithologist Masauji Hachisuka recognised the three proposed Mauritius owl species in 1953, considering Rothschild's view justified by the fact that Mauritius had two species of flightless rails, two pigeons, and three parrots. He concluded that the features of Strix sauzieri were more consistent with the genus Tyto and assigned it and Strix newtoni there, and added there was no way to determine whether Scops commersoni did belong in Scops or in Tyto. He also listed common names for the species; Sauzier's grass owl for Tyto sauzieri, Newton's barn owl for Tyto newtoni, and Commerson's scops owl for Scops commersoni.
Synonymisation of species and naming of new genus The American ornithologist James Greenway stated in 1967 that if enough bones were available, it would be apparent that the difference of 6 mm between Tyto sauzieri and Strix newtoni was due to individual variation rather than specific differences; he found it questionable there would have been two species of owls on Mauritius. He concurred with Rothschild that the size given for Scops commersoni was too large for a scops owl, and considered it more consistent with the genus Asio, perhaps being related to the Madagascar owl (Asio madagascariensis), but conceded that the unfeathered legs were more in line with scops owls.
In 1987, the British ornithologist Anthony S. Cheke considered the owl described in the contemporary accounts to refer to Scops commersoni, which could possibly be a member of the genus Otus (by then the senior synonym of Scops), but found the T. sauzieri subfossils (including those of T. newtoni) to belong to a different genus. In the same book, the British ornithologist Graham S. Cowles stated that owl bones found on the Mascarene island of Réunion in 1974 showed that owls once inhabited all three Mascarene Islands. The bones from Réunion were so similar to those from Mauritius that he was unable to find osteological features that distinguished the two. He noted that the genus Strix now applied to the wood owls while Tyto were the barn owls, but that reexamination showed that sauzieri did not belong to that genus, and that the Mascarene owls were in need of their own, new genus, perhaps related to the genus Ninox. Cowles found that the pelves of the Mauritius owl and the Rodrigues owl (by then Tyto murivora) shared distinct features, suggesting a close relation between the two, but kept them as separate species since the former had longer and slimmer legs. In 1994, Cowles formally assigned the material from Réunion, consisting of limb bones, to S. sauzieri, expanding the range of the species.
In 1994, the French palaeontologist Cécile Mourer-Chauviré and colleagues coined the new genus Mascarenotus to contain the Mascarene owls, which they thought were probably derived from Otus scops owls. The generic name combines the name of the Mascarene Islands with that of the genus Otus, and S. sauzieri was designated the type species. They characterised the genus by its large size and elongated legs. These writers also considered Scops commersoni to represent the same species as M. sauzieri, as their size and features were consistent, concluding there was only one species of owl on Mauritius. They named the Réunion owl M. grucheti as its limb bones were very similar to those of the Mauritius owl but differed in some details. They found the Mascarene owls to have similar limb shape and dimensions to the extinct Grallistrix owls of Hawaii, probable adaptations to the same environmental conditions. Cheke and the British palaeontologist Julian P. Hume accepted the genus Mascarenotus for the Mascarene owls in 2008, calling them "lizard-owls". They noted that although their closest relatives among the scops owls were yet to be identified, they were so distinct among the group that they may have started diverging on older islands of a hot spot island chain, reaching Mauritius and Rodrigues from St. Brandon.