Islands - New Caledonia

New Caledonia was the ‘lost world’ of the Holocene (11,650-Present). The final bastion of ancient groups of birds and reptiles. Where horned turtles lumbered about the rocky shorelines, land-living crocodiles prowled the jungles in search of ground pigeons, and giant fowl traversed vast metallic scrublands. About 3,000 years ago the primeval land was discovered by man and the giants of New Caledonia vanished. Can this extinction be placed squarely at the feet of the first human settlers?

New Caledonia is an archipelago located in Melanesia. Despite being closer geographically to Vanuatu and Fiji, New Caledonia is part of the mostly submerged continent plate of Zealandia (15), itself a part of Gondwana (the southern supercontinent) until the Late Cretaceous (145-66mya) (15). The fauna and flora of the archipelago are usually of Gondwanan origin, despite the islands being fully submerged from the End Cretaceous until sometime before the Early Oligocene (34–28mya), with most of the Holocene taxa likely descended from the other nearby Gondwanan landmasses (24) . The region can broadly be broken into four biomes (11): tropical rainforest, sclerophyllous (hard-leaved) forest, savannah, and the maquis, which is a metal-rich scrubland. These habitats contain an astounding 3,000 different plant species, some 80% of which are endemic. This vast array of diversity is likely due to large varieties in conditions within each habitat, creating microhabitats. (14)

Figure 1. Position of New Caledonia within Australasia

In this diverse backdrop, an incredible array of vertebrate fauna has evolved and thrived until the late Holocene. Surprisingly, the fauna lacked any terrestrial mammals or amphibians prior to human arrival (1), the exact reason for this is unclear but mirrors a similar situation in New Zealand. Much like other archipelagos, New Caledonia had its cast of large flightless birds including landfowl, rails, and the endemic kagu. The archipelago was also home to a few large reptiles including the terrestrial crocodile Mekosuchus inexpectatus, the glyptodont-like turtle Meiolania mackayi, and a large species of goanna (1). The remaining diversity of land reptiles are made up of skinks and geckos, with 51 and 33 known species respectively (10).

Figure 2. The New Caledonian Maquis during the Holocene, prior to human arrival. The animals shown in art-piece are the Glyptodon-like Meiolania mackayi, the giant galliform Sylviornis neocaledoniae, the large endemic hawk Accipiter efficax, and the yellow-bellied robin (Cryptomicroeca flaviventris)

Terms of use: Art commissioned by The Extinctions from Hodari Nundu.

These species may only constitiute part of the Holocene assemblage as the fossil record is poor, restricted largely to three sites on the archipelago: Kanumera, Pindai caves and Gilles cave (4). Kanumera dates to 3450 ya and contains no trace of human habitation. Gilles cave show human habitation but hasn’t been properly dated. The majority of finds and studies have been conducted at Pindai caves as it has the most complete record on the island with remains dating to both prior to and after human habitation (1). All three locations represent lowland habitats, thus any inferences about the fossil fauna may not be applicable to highland habitats, and the quantity of extinct taxa may be heavily undersampled.

The extent of the extinction may further be underestimated as only non-passerine birds have been adequately sampled and studied (1,4). A large abundance of reptile fossils has been collected under expeditions but remain uncategorised, however large declines in their abundance have been noted (1) and it would seem unlikely that extinctions within this taxonomic group did not occur.  Likewise, with passerines.

Figure 3. The main islands of New Caledonia with the position of the three main fossil sites indicated in red.

Despite these severe limitations, the available literature reveals much about the extinction timeline, at least at Pindai. Human arrival occurs locally around 2600-2800 ya, based on the presence of pottery shards. Almost concurrent with this is the extinction of various common terrestrial bird species including species of snipe (Coenocorypha neocaledonica), kagu (Rhinochetos orarius), swamphen (Porphyrio kukwiedei), and probably landfowl (Sylviornis newcaledoniae) between 2500-2800 ya (1). Though the mechanism isn’t evident in the fossil record a human cause seems hard to dispute given the incredibly close timeline. Hunting would seem a likely explanation as there is a bias towards largely terrestrial birds, which would have constituted a much more accessible food source. It is possible that these species may even have been docile towards man, as is common of island ecosystems lacking terrestrial predators, though the presence of Mekosuchus makes this uncertain. A lack of evidence for hunting of extinct species may not be surprising either, the temporal overlap is at most a few hundred years so a fairly small proportion of fossils should be from this period.  On top of this, evidence of consumption of any kind is limited to a single specimen of goliath imperial pigeon (Ducula goliath) (4), which could mean the excavated parts of Pindai weren’t permanently settled or that cooking and butchering was conducted elsewhere.

At around 2200 ya we see the introduction of the Polynesian rat (Rattus exulans), probably as stowaways on the ships of early migrants.  Though the extinction of the terrestrial taxa could be caused by the arrival of rats, the timeline doesn’t line up, there is a noticable gap of at least 300 years. R. exulans is notably an herbivore (17) and probably wasn’t a large consumer of nests, so it is also a poor explanation for the extinction of terrestrial birds. Instead, what we see is a drastic decline in the abundance of lizard fossils (1). This could indicate that the Polynesian rat outcompeted herbivorous lizards for local plant resources, or perhaps even caused habitat loss from overconsumption of plant matter, as has been suspected in Hawaii (2). New Caledonia unfortunately lacks studies on the change in vegetation types. Unsurprisingly this reptile decline has been reflected in the predator composition, which is best recorded in the owl species at Pindai. The site is colonized by barn owls (Tyto alba) concurrently with the polynesian rat. The barn owl feeds primarily on small mammals (16, 18), and would presumably have thrived on the abundant rodents. At almost the same time Tyto letocarti , an endemic species thought to have preyed on reptiles, goes extinct (1).

The loss of native species has also lead to several apparent invasions, including that of the rails Gallirallus philippensis (4) and Porphyrio porphyrio (4), which probably colonised to replace the niche of the extinct Porphyrio kukwiedei. Though displacement is also possible if large habitat changes did indeed take place.

Figure 4. Fossil replica of Meiolania platyceps, a close relative of Meiolania mackayi. This species inhabited Lord Howe Island rather than New Caledonia

Terms of use: This image is licensed under a creative commons attribution-ShareAlike 2.0 Generic. It is attributed to Steven & Courtney Johnson & Howitz. The image is unedited and the original can be found here

Reptillian megafauna has a much scarcer fossil record. The youngest Meiolania mackayi specimen has been dated to around 1750 ya based on charcoal from the same site (6), but due to lack of a transparent methodology this dating may inaccurate (1), no other published specimen has been dated. Though a direct connection can’t be drawn between the demise of M. mackayi and human arrival, the record of the extinction of Meiolania damelipi from Fiji and Vanuatu is much clearer. Archaeological digs here from 2700-3100 ya shows M. damelipi bones with signs of butchery, charring and cutting at sites of human settlement (8) and cemetaries (21), indicating a strong hunting pressure. Likely a similar fate befell the Meiolania of New Caledonia. The picture is murkier for Mekosuchus inexpectatus. The evidence of exploitation is limited to a single specimen of another species of Mekosuchus found at a human settlement in vanuatu (13). Fossil evidence from Pindai caves does indicate that the crocodile survived initial human settlement (1), but it’s unclear for how long. It’s possible that it was hunted to extinction much like Meiolania, its small size and terrestrial nature makes it a realistic prey item. Trophic cascades seem less likely as Mekosuchus is thought a generalist (3, 9) but it can’t be discounted.

Additional research in New Caledonia is sorely needed, with only a single site thoroughly dated and studied, there are heavy biases at play, Gilles cave would make for a useful corroboration on the extinction timeline. As for other taxonomic groups, an abundance of Holocene lizard and passerine remains have been collected at Pindai (1) hopefully these will be analysed in the future and expand our understanding of the extinction extent. Even so, based on the available evidence the timeline suggests two waves of avian extinctions, one coinciding with human arrival and a second with the arrival of the polynesian rat, the mechanism behind these extinctions remain unstudied but hunting and trophic cascades appear most reasonable. Evidence from neighbouring Vanuatu and Fiji demonstrate a probable mechanism of the extinction of reptile megafauna though an accompanying timeline is missing. Thus it seems very reasonable to suggest human agency in the Holocene extinction of New Caledonia, even with the limited data available.

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Table 1. Species of Reptillian megafauna known from the Holocene of New Caledonia. Extinct species denoted with ‘ †’ and species mentioned in the text are written in bold.

Reptilian Megafauna
Meiolania mackayi † (12,19,20,21)	A turtle possessing horns at the back of its skull and a bony spiked tail. It belongs to a clade of Gondwanan stem-turtles called the Meiolaniformes, with Meiolania constituting the last surviving genus. The ecology of M. mackayi is disputed. The resemblance to terrestrial turtles indicates a terrestrial herbivorous lifestyle and this diet has been corroborated using carbon-13 concentrations in bones of the related Meiolania damelipi, however a quantitive analysis of Meiolania platycepsusing limb length and carapace dimensions suggests an aquatic lifestyle, perhaps analogous to the marine iguanas of galapagos.
Mekosuchus inexpectatus† (3, 9)	A small species of terrestrial crocodile about a metre in length. Crushing teeth at the back of its jaws are speculated to be an adaptation to feed on snails and moluscs with the species being a generalist comparable to the Dwarf Crocodile.
Varanus sp.† (1)	A large goanna, known from a few fossils, its affinity to other taxa is unknown, but it likely constitutes a unique species.

Table 2. All known species of non-passerine birds found in the New Caledonian Holocene fossil record. Extinct species denoted with ‘ †’ and species mentioned in the text are written in bold.

Accipitriformes (Hawks, Eagles, Vultures & Kites)
Accipiter efficax? † (1,4)	An extinct species of large goshawk endemic to New Caledonia. It is Plentiful in the fossil records at Pindai caves. Though it may be synonymous with Accipiter fasciatus.
Accipiter fasciatus (1)	Brown goshawk, medium sized and extant in Caledonia and Australia.
Accipiter haplochrous (1)	White-bellied goshawk. An extant and endemic species of goshawk to New Caledonia
Accipiter quartus ? † (1,4)	An extinct species of small goshawk endemic to New Caledonia. Less plentiful than, yet co-existing with Accipiter efficax. Probably not unlike the Northern goshawk and European sparrowhawk. Though it may be synonymous with Accipiter haplochrous.
Haliastur sphenurus (1)	Whistling kite. An extant species of kite.
Pandion haliaetus (1)	Osprey. Extant global species of Osprey.
Aegotheliformes (Owlet-Nightjars)
Aegotheles savesi †? (4)	The New Caledonian Owlet-Nightjar, endemic and possibly extinct. It is known only from fossils and a single specimen from 1880.
Anseriformes (Waterfowl)
Anas gracilis (4)	Grey teal. Extant species quite common in New Caledonia, though fossil remains are smaller and may not have close affinity to current populations.
Apodiformes (Swifts & Hummingbirds)
Collocalia spodiopygia (1,4)	White-rumped swiftlet. An extant widespread species of swiftlet.
Collocalia esculenta (1,4)	Glossy swiftlet. An extant widespread species of swiftlet.
Caprimulgiformes
Eurostopodus exul †? (1)	New Caledonian nightjar. A nightjar endemic to the islands and possibly extinct.
Charadriiformes (Shorebirds)
Charadrius bicinctus (1)	Double banded plover. A plover species found primarily in New Zealand.
Charadrius mongolus (4)	Lesser sand plover. Extant and probably a rare visitor to New Caledonia, known only from a single fossil.
Coenocorypha neocaledonica † (1,4,22)	This extinct species of austral snipe is endemic to New Caledonia and the second largest species in its genus. It has unusually good adaptations for flying within its genus.
Pluvialis dominica (4)	American golden plover. Extant and has been reported as a rare visitor to New Caledonia.
Columbiformes (Doves and Pigeons)
Caloenas canacorum † (1,4)	An endemic extinct species of pigeon. Thought most closely related to the nicobar pigeon, which is a primarily terrestrial pigeon. C. canacorum is estimated at about 38cm in length.
Chalcophaps indica (1,4)	Common emerald dove. Extant and widespread species.
Columba vitiensis (1,4)	Metallic Pigeon. Extant bird found throughout the region, local subspecies found in New Caledonia.
Drepanoptila holosericea (1,4)	Cloven-feathered dove, an extant species native to New Caledonia.
Ducula goliath (1,4)	The goliath imperial pigeon, an extant endemic species of pigeon. Known to be hunted by locals and a single example at Pindai shows this in the fossil record.
Ducula pacifica (1)	Pacific Imperial Pigeon. A extant species of pigeon found through much of melanesia and polynesia.
Gallicolumba longitarsus † (1,4)	An endemic and extinct species of ground pigeon. Largest known species of the Gallicolumba genus, which is found through much of the region.
Gallicolumba stairi (1)	Tongan ground dove, locally extinct species of ground pigeon.
Ptilinopus greyi ( 1)	Red-bellied fruit dove. An extant species of pigeon found in New Caledonia and Vanuatu.
Coracifomes
Halcyon sancta (4)	Sacred Kingfisher. Extant regional species with a local subspecies.
Cucliformes (Cuckoos)
Cacomantis flabelliformes (1)	Fan-tailed cuckoo. An extant species of cuckoo found in much of Australiasia.
Chrysococcyx lucidis layardi (1)	Shining Bronze-cuckoo. An extant species of cuckoo found in much of Australiasia.
Urodynamis taitensis (1,4)	Pacific long tailed cuckoo. An extant migratory cuckoo to New Caledonia.
Eurypygiformes (Kagus & Sunbitterns)
Rhinochetos orarius? † (1,4,5)	The lowland kagu. It is one of only two species of Kagu, both endemic to New Caledonia. Rhinochetos jubatus the sister taxa is extant but not known from fossil remains, though the two taxa could be synonymous. R. orarious is somewhat larger than its living relative, it is thought to have inhabited lowlands, with the R. jubatus occupying highlands. Kagus are unique group most closely related to the sunbitterns of South America and belong to ancient gondwanan clade
Falconiformes (Falcons & Caracaras)
Falco peregrinus (4)	Peregrine falcon, global extant species though rare in New Caledonia.
Gruiformes (Rails and Cranes)
Gallinula tenebrosa? (4)	Dusky moorhen or close relative. Though currently uncommon in New Caledonia the species is observed in the fossil record, it is unclear if the extant population is synonymous with the fossil remains.
Gallirallus philippensis (1,4)	Buff-banded rail. A common species of rail found both in New Caledonia and regionally. Only appears in upper layers of Gilles cave and may be a recent arrival.
Lewina pectoralis (1)	Lewin’s rail. Locally extinct species of rail found in Australia and Wallacea.
Porphyrio kukwiedei † (1,4)	New calledonian gallinule. An extinct and endemic species of rail. It is about 25% larger than the related Porphyrio porphyrio and has reduced wings and other flight adaptations, indicating it may have been flightless.
Porphyrio (porphyrio) melanotus (1,4)	Purple swamphen. A widespread common swamphen, however it is only found in upper deposits concurrent with man.
Porzana tabuensis (1,4)	Spotless crake. An extant widespread species of rail, though locally restricted in its range
Tricholimnas lafresnayanus †? (1,4)	New Caledonian Wood Rail. Potentially extinct, with few reports in the 20th century and endemic to New Caledonia. The species has a very reduced keel, indicating it may have been flightless.
Pan-Galliformes (Landfowl)
Megapodius molistructor † (1,4)	An extinct endemic species of megapode (mound building birds). It was the largest known species of its genus, which is found throughout much of the region.
Sylviornis neocaledoniae † (1,4,23)	The largest known flightless bird of New Caledonia, both extinct and endemic to the archipelago. It was one of the most common species, with over 5000 known fossils. It stood at around 80cm with a weight of around 30kg and comprises an extinct sister clade to the galliformes.
Psittaciformes (Parrots)
Charmosyna diadema †? (1)	New Caledonian Lorikeet. An endemic and potentially extinct species of lorikeet.
Cyanorhamphus saisetti (1)	New Caledonian Parakeet. An extant species of parakeet endemic to New Caledonia.
Eunymphiscus cornutus (1)	Horned parakeet. An endemic species of parakeet.
Procellariiformes
Fragetta grallaria ( 1)	White-bellied storm petrel. Extant.
Pseudobulweria rostrata (1,4)	Tahiti petrel. Extant and breeding in New Caledonia.
Pterodroma brevipes (1)	Collared Petrel. Extant.
Strigiformes (Owls)
Ninox novaseelandiae? †? (1,4)	A species of Ninox either synonymous with Ninox novaseelandiae (Morepork) or a very similar endemic species. The species or subspecies is extinct in New Caledonia.
Tyto? Letocarti † (1,4)	An extinct endemic owl species possibly closely related to Tyto alba. The fossils of T. letocarti are found in proximity to large amounts of lizard fossils it appears to be adapted to feed primarily on these, though bones of endemic birds have also been found in association.
Tyto alba (1,4)	Extant, global species. Found in the upper layer of both Gilles cave and Pindai caves but absent in lower layers.
Unclear affinity
Turnix (varia) novacaledoniae †? (4)	Either a subspecies of the painted buttonquail of Australia or a distinct closely related species. Likely extinct, not observed in over a century. Species is smaller at least prior to human arrival than the painted buttonquail.
Corturnix pectoralis (1)	Stubble quail. Locally extinct but still found in Australia.

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Works cited

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10) IUCN 2020. The IUCN Red List of Threatened Species. Version 2020-2. https://www.iucnredlist.org.

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18) Smal, C. M. (1987). The diet of the Barn Owl Tyto alba in southern Ireland, with reference to a recently introduced prey species— the Bank Vole Clethrionomys glareolus, Bird Study, 34(2). 113-125, DOI: 10.1080/00063658709476946

19) Sterli, J. (2015). A Review of the Fossil Record of Gondwanan Turtles of the Clade Meiolaniformes. Bullettin of the Peabody Museum of Natural History. 56(1). 21-45.

20) Sterli, J. & de la Fuente, M.. (2012). New evidence from the Paleocene of Patagonia (Argentina) on the evolution and palaeobiogeography of Meiolaniformes (Testudinata, new taxon name). Journal of Systematic Palaeontology, 11(7), 835-852, DOI: 10.1080/14772019.2012.708674

21) White, A. W., Worthy, T. H., Hawkins, S., Bedford, S., & Spriggs, M. (2010). Megafaunal meiolaniid horned turtles survived until early human settlement in Vanuatu, Southwest Pacific. Proceedings of the National Academy of Sciences of the United States of America, 107(35), 15512–15516.

22) Worthy, T. H., Anderson, A., Sand, C.. (2013) An extinct Austral snipe (Aves: Coenocorypha) from New Caledonia. Emu, 113, 383-393.

23) Worthy, T. H., Mitri, M., Handley, W. D., Lee, M. S. Y., Anderson, A., Sand, C.. (2016) Osteology Supports a Stem-Galliform Affinity for the Giant Extinct Flightless Bird Sylviornis neocaledoniae (Sylviornithidae, Galloanseres). PLoS ONE 11(3): e0150871. doi:10.1371/journal.pone.0150871

 24) Garrouste, R., Munzinger, J., Leslie, A., Fisher, J., Folcher, N., Locatelli, E., Foy, W., Chailon, T., Cantrill, D., Maurizot, P., Cluzel, D., Lowry II, P., Crane, P., Bahain, J-J., Voinchet, P., Jourdan, H., Grandcolas, P., Nel, A. (2021) New fossil discoveries illustrate the diversity of past terrestrial ecosystems in New Caledonia. Scientific Reports 11, 18388.