The most common usage of purposeful taxon substitution in non-hypothetical situations thus far has been for the purpose of conserving island ecosystems. These are cases where the anthropogenic nature of local extinctions is not debatable, and the need to restore lost niches in order to conserve remaining biodiversity is obvious. Some of the most successful translocation projects that have been performed have been between islands with similar evolutionary histories, especially regarding keystone species like giant tortoises. In my search for ideal candidate islands on which to perform a large-scale rewilding operation, one of the islands, Reunion, struck me as particularly interesting. Of the three Mascarene islands, the others being Mauritius and Rodrigues, Reunion is the largest and has by far the most space devoted to nature conservation. Reunion has also lost numerous species many of which, unique for island ecosystems, either still exist or have close relatives elsewhere. In fact almost all of the twenty-three native avian taxa that have disappeared from the island could be in some way returned, and there exists the potential to more than double the bird diversity on the island though reintroductions alone. The introduction of bats, tortoises, and large skinks is also very feasible. None of the native Reunion species or potential substitutes are dangerous to humans, and all have the potential to seriously improve the environmental health and tourism potential of the island. The biggest challenge would be to eradicate the island’s invasive mammals which include rats, cats, dogs, and a few others. However this should be feasible, given that the total area of the island is only twenty-five-hundred square kilometres, and larger islands have successfully eradicated invasive mammals before. A smattering of introduced small birds and reptiles might be eliminated as well but these are perhaps less dangerous and should be evaluated to determine potential harm before embarking on expensive eradication procedures. I have outlined all of the native and introduced non-marine tetrapods of Reunion here as well as some potential ecological substitutes which might be imported from Madagascar, Africa, or other islands within the Indian Ocean. Some are more solid proxies than others, but it should be clear that what we are aiming to create is not exactly the ecosystem Reunion originally had, but one that is functionally and aesthetically similar.
Extant Native Avian Taxa – 2
Gallinula chloropus
- Common Moorhen
- Least Concern
Spatula querquedula
- Common Garganey
- Least Concern
Extant Endemic/Near-Endemic Avian Taxa – 10
Aerodramus franciscus
- Mascarene swiftlet
- Near-Threatened
Circus maillardi
- Reunion harrier
- Endangered
Coracina newtoni
- Reunion cuckooshrike
- Critically Endangered
Glareola ocularis
- Malagasy pratincole
- Vulnerable
Hypsipetes borbonicus
- Reunion bulbul
- Near-Threatened
Phedina borbonica
- Mascarene martin
- Least Concern
Saxicola tectes
- Reunion stonechat
- Least Concern
Tersiphone bourbonnensis
- Mascarene flycatcher
- Least Concern
Zosterops borbonicus
- Reunion grey white-eye
- Least Concern
Zosterops olivaceus
- Reunion olive white-eye
- Least Concern
Extant Introduced Avian Taxa – 9
Acridotheres tristis
- Commmon myna
- Can be an aggressive invader
- Should be more common in urban areas
- Not tolerant of closed woodland
- Least Concern
Estrilda astriid
- Common waxbill
- Least Concern
Geopelia striata
- Zebra Dove
- Least Concern
Leiothrix lutea
- Red-billed leiothrix
- Least Concern
Ploceus cucullatus
- Village weaver
- Least Concern
Pycnonotus jocosus
- Crested bulbul
- Least Concern
Quelea quelea
- Red-billed quelea
- Least Concern
Serinus canicollis
- Cape canary
- Least concern
Turnix nigricollis
- Madagasy buttonquail
- Least Concern
Extant Returnable Avian Taxa – 5
Butoroides striata
- Striated heron
- Formerly present
- Import from Mauritius, Least Concern
Egretta dimorpha
- Reef egret
- Reunion subspecies extinct
- Import from Madagascar, Least Concern
Phalacrocorax africanus, Least Concern
- Reed cormorant
- Reunion subspecies extinct
- Import from Madagascar
Phoenicopterus roseus
- Greater flamingo
- Formerly present
- Import from Madagascar, Least Concern
Psittacula eques
- Echo parakeet
- Reunion subspecies extinct
- Import from Mauritius, Endangered
Replaceable Avian Taxa Reunion – 18
Alectroenas pulcherrimus àAlectroenas sp
- Seychelles blue pigeon for the extinct Reunion blue pigeon
- Import from the Seychelles, Least Concern
Alopochen aegyptiaca àAlopochen kervazoi
- Egyptian goose for the extinct Reunion goose
- Import from mainland Africa, Least Concern
Anas bernieri àAnas theodori
- Malagasy teal for the extinct Mascarene teal
- Import from Madagascar, Endangered
Aythya innotata àAythya sp
- Malagasy pochard for the extinct Reunion pochard
- Import from Madagascar, Critically Endangered
Dryolimnas aldabrensis àDryolimnas augusti
- Aldabran flightless rail for the extinct Reunion flightless rail
- Import from Aldabra, Least Concern?
Falco punctatus àFalco duboisi
- Mauritian kestrel for the extinct Reunion kestrel
- Import from Mauritius, Endangered
Foudia madagascariensis àFoudia delloni
- Malagasy fody for the Reunion fody
- The Mauritian fody might be closer but the Malagasy species is already present
- Already introduced, Least Concern
Fulica cristata àFulica newtonii
- Red-knobbed coot for the extinct Mascarene coot
- Import from mainland Africa, Least Concern
Nesoenas picturatus àNesoenas sp
- Malagasy turtle-dove for Reunion turtle-dove
- Already introduced, Least Concern
Nesoenas mayeri àNesoenas duboisi
- Mauritian pink pigeon for the extinct Reunion pink pigeon
- Import from Mauritius, Vulnerable
Nycticorax nycticorax àNycticorax duboisi
- Black-crowned night-heron for the extinct Reunion night heron
- Import from Madagascar, Least Concern
Otus insularisàOtus grucheti
- Seychelles owl for the extinct Reunion owl
- Import from the Seychelles, Endangered
Porphyrio madagascariensis àPorphyrio caerulescens
- African swamphen for the extinct Reunion swamphen
- Import from Madagascar, Least Concern
Psittacula caniceps àPsittacula mascarin
- Nicobar parakeet for the extinct Mascarene parakeet
- Import from the Nicobar islands, Near-Threatened
Psittacula krameri àPsittacula bensoni
- Rose-ringed parakeet for the extinct grey parakeet
- Already present, Least Concern
Sturnia eryhtopygia àFregilupus varius
- White-headed starling for the extinct Reunion starling
- Ecological similarity unclear but habitat preference close
- Extinct species derived from ancestors very closely related to the Sturnia genus
- Import from Andaman/Nicobar islands, Least Concern
Tanygnathus megalorhynchosàNecropsittacus borbonicus
- Great-billed parrot for the extinct Reunion parrot
- Import from Indonesia, Least Concern
Threskiornis bernieri àThreskiornis solitarius
- Malagasy ibis for the extinct Reunion ibis
- Import from Madagascar, Endangered
Extant Endemic/Near-Endemic Reptilian Taxa – 2
Phelsuma borbonica
- Reunion day gecko
- Conservation status unknown
Phelsuma inexpecta
- Ornate day gecko
- Critically endangered
Extant Introduced Reptilian Taxa – 10
Astrochelys radiata
- Radiated tortoise
- Present in great number on the island
- Much smaller than extinct native tortoises
- Probably still useful ecologically
- Rodrigues had a tortoise of similar size in addition to larger tortoises
- Similar dynamic could be established on Reunion
- Critically endangered
Calotes versicolor
- Oriental garden lizard
- Present but largely confined to urban areas
- Conservation status unknown, but common
Furcifer pardalis
- Panther chameleon
- Possibly dispersed to Reunion naturally, unclear
- Least Concern
Gehyra mutilate
- Four-clawed gecko
- Present but largely confined to urban areas
- Conservation status unknown, but common
Hemiphyllodactylus typus
- Indo-Pacific tree gecko
- Present but largely confined to urban areas
- Conservation status unknown, but common
Indothyphlops braminus
- Island blind snake
- Parthenogenic, likely impractical/unnecessary to remove
- Native and conservation status unclear, but common
Lycodon capucinus
- Indian wolf snake
- Quite invasive, should be actively eradicated
- Least Concern
Phelsuma laticauda
- Gold dust day gecko
- Unclear if actively competing with native congenerics
- Present in areas where native species are not
- Least Concern
Phelsuma lineata
- Lined day gecko
- Unclear if actively competing with native congenerics
- Present in areas where native species are not
- Least Concern
Phelsuma madagascariensis
- Giant day gecko
- Probably not actively competing with native congenerics
- Present in areas where native species are not
- Least Concern
Extant Returnable Reptilian Taxa – 1
Gongylomorphus bojerii
- Bojer’s skink
- Reunion subspecies extinct
- Import from Mauritius, Critically Endangered but bred in captivity
Replaceable Reptilian Taxa Reunion – 2
Aldabrachelys giganteus àCylindraspis indica
- Aldabran/Seychelles giant tortoise for the extinct Reunion giant tortoise
- Along with radiated tortoises, will be an incredibly important grazer and seed disperser
- Import from Aldabra, the Seychelles, or existing Mascarene populations, Vulnerable
Leiopisma telfairii àLeiopisma sp
- Round island skink for the extinct Reunion skink
- Import from Mauritius, Vulnerable
Extant Endemic/Near-Endemic Mammalian Taxa – 3
Mormopterus acetabulosus
- Natal free-tailed bat
- Endangered
Scotophilus borbonicus
- Lesser yellow bat
- Critically Endangered, possibly extinct
- If extinct, investigate replacements, example Scotophilus robustus
Taphozous mauritianus
- Mauritian tomb bat
- Least Concern
Extant Returnable Mammalian Taxa Reunion – 1
Pteropus niger
- Greater Mascarene flying fox
- Reunion subspecies extinct
- Import from Mauritius, Endangered
Replaceable Mammalian Taxa Reunion – 1
Pteropus rodricensis àPteropus subniger
- Rodrigues flying fox for the extinct Lesser Mascarene flying fox
- Import from Rodrigues, Endangered
Of course some serious research would need to be performed to determine which species should be introduced first, with the emphasis best put on species which will work to rebuild forests through seed dispersal, such as tortoises, fruit bats, and parrots, thus setting the stage for the later introduction of species that might not be considered keystones. Some species are more resistant to the presence of mammals than others and might be introduced pre-emptively while eradication of rats and cats is ongoing. The early introduction of predatory birds, such as owls and kestrels, might assist in reducing rat and tenrec numbers, thus making eradication slightly easier. Extensive study will also be necessary to determine if some of the proxies I’ve proposed are ideal, or if there are better options, although in most cases potential substitutes are limited. Overall the potential for vertebrate diversity recovery is higher than any other island I investigated, though I will be discussing some others. I’m in the middle of writing an article on the potential for rewilding in New Zealand, and I also hope to write articles on the Hawaiian and South Pacific islands. I haven’t abandoned my other series, but I’ll be switching between them as my focus and interest periodically shifts from one topic to another.
