Ibiza Rail
Encyclopedia
The Ibiza Rail is a new species of rail, described from a late Pleistocene
to Holocene
cave deposit at Es Pouàs, on the island of Ibiza
. Ibiza is in the Pityuses group of the Spanish
Balearic Islands
in the Mediterranean Sea
. The Ibiza Rail was a relative of the extant Water Rail
(Rallus aquaticus) and may actually be derived from this species, but was a bit smaller and stouter, had shorter and more robust hind limbs and shorter wings, with probably reduced its flight capability. Consequently, it might have also occurred on neighbouring Formentera
, where no possible locations have been surveyed.
The extinction
of this species was more recent than 16,700 years BC
, probably roughly between 5,300 and 4,350 years BC. The latter dates broadly overlap a period of the possible arrival of humans at Ibiza, suggesting a relationship between the two events. The Ibiza Rail is somewhat unusual insofar as that most extinct insular rails were completely flightless, whereas the present species could still fly if it had to. However, it agrees in this respect with many species of rail still found on other continental islands worldwide, whereas most other forms were from oceanic islands.
Nonetheless, as there were no terrestrial predators on Ibiza before the arrival of humans, it is quite certain that this species would ultimately have evolved to complete flightlessness and probably rather small size, which is a trend that seems to hold true for all species of rail which evolved on small islands lacking terrestrial predators. The paleoecology
of the Pityuses group is peculiar because there were almost no mammal
s present and thus the trophic web in prehistoric times was more similar to the Hawaii
an island of Moloka‘i than to Mallorca
in the Baleares (Seguí & Alcover, 1999).
While it may be possible that the islands provided a higher amount of freshwater habitat due to better tree cover in the past, the Ibiza Rail's habitat was probably brackish swamps in the coastal lowland. Extinction was most probably due to overhunting by the expanding human population; as opposed to most other extinct island rails which were simply unable to escape hunters due to flightlessness, this species is more likely to have fallen victim to its small population size: Ibiza itself is not large, and available habitat was densely populated by various species of birds, which would leave little resources for a large population of any particular species. Thus, the Ibiza Rail was likely to succumb to an amount of hunting which could have been tolerated by a larger population of island rails, flightless or not.
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
to Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
cave deposit at Es Pouàs, on the island of Ibiza
Ibiza
Ibiza or Eivissa is a Spanish island in the Mediterranean Sea 79 km off the coast of the city of Valencia in Spain. It is the third largest of the Balearic Islands, an autonomous community of Spain. With Formentera, it is one of the two Pine Islands or Pityuses. Its largest cities are Ibiza...
. Ibiza is in the Pityuses group of the Spanish
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
Balearic Islands
Balearic Islands
The Balearic Islands are an archipelago of Spain in the western Mediterranean Sea, near the eastern coast of the Iberian Peninsula.The four largest islands are: Majorca, Minorca, Ibiza and Formentera. The archipelago forms an autonomous community and a province of Spain with Palma as the capital...
in the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
. The Ibiza Rail was a relative of the extant Water Rail
Water Rail
The Water Rail is a bird of the rail family which breeds in well-vegetated wetlands across Europe, Asia and North Africa. Northern and eastern populations are migratory, but this species is a permanent resident in the warmer parts of its breeding range...
(Rallus aquaticus) and may actually be derived from this species, but was a bit smaller and stouter, had shorter and more robust hind limbs and shorter wings, with probably reduced its flight capability. Consequently, it might have also occurred on neighbouring Formentera
Formentera
Formentera is the smaller and more southerly island of the Pine Islands group , which belongs to the Balearic Islands autonomous community .-Geography:...
, where no possible locations have been surveyed.
The extinction
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
of this species was more recent than 16,700 years BC
Anno Domini
and Before Christ are designations used to label or number years used with the Julian and Gregorian calendars....
, probably roughly between 5,300 and 4,350 years BC. The latter dates broadly overlap a period of the possible arrival of humans at Ibiza, suggesting a relationship between the two events. The Ibiza Rail is somewhat unusual insofar as that most extinct insular rails were completely flightless, whereas the present species could still fly if it had to. However, it agrees in this respect with many species of rail still found on other continental islands worldwide, whereas most other forms were from oceanic islands.
Nonetheless, as there were no terrestrial predators on Ibiza before the arrival of humans, it is quite certain that this species would ultimately have evolved to complete flightlessness and probably rather small size, which is a trend that seems to hold true for all species of rail which evolved on small islands lacking terrestrial predators. The paleoecology
Paleoecology
Paleoecology uses data from fossils and subfossils to reconstruct the ecosystems of the past. It involves the study of fossil organisms and their associated remains, including their life cycle, living interactions, natural environment, and manner of death and burial to reconstruct the...
of the Pityuses group is peculiar because there were almost no mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s present and thus the trophic web in prehistoric times was more similar to the Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
an island of Moloka‘i than to Mallorca
Mallorca
Majorca or Mallorca is an island located in the Mediterranean Sea, one of the Balearic Islands.The capital of the island, Palma, is also the capital of the autonomous community of the Balearic Islands. The Cabrera Archipelago is administratively grouped with Majorca...
in the Baleares (Seguí & Alcover, 1999).
While it may be possible that the islands provided a higher amount of freshwater habitat due to better tree cover in the past, the Ibiza Rail's habitat was probably brackish swamps in the coastal lowland. Extinction was most probably due to overhunting by the expanding human population; as opposed to most other extinct island rails which were simply unable to escape hunters due to flightlessness, this species is more likely to have fallen victim to its small population size: Ibiza itself is not large, and available habitat was densely populated by various species of birds, which would leave little resources for a large population of any particular species. Thus, the Ibiza Rail was likely to succumb to an amount of hunting which could have been tolerated by a larger population of island rails, flightless or not.