The origin of the enigmatic Falkland Islands ‘wolf’ (FIW) — first observed by European explorers in the late 17th century — may have been determined at last by geneticists working from a fragment of a skull bone preserved by none other than Charles Darwin.
The animal is actually a genus of canid called Dusicyon (Dusicyon australis). Previous analyses of museum specimens concluded that Dusicyon split from its nearest relative — the South American maned wolf (Chrysocyon brachyurus) — around 7 million years ago (Ma). It was formerly held that the FIW colonized the islands “by unknown means” approximately 330,000 years ago (ka).
Misnamed as a “wolf’, the canid was actually more closely related to foxes (genus: Vulpes) than wolves (genus: Canis). In fact, Darwin refers to the creature as a “wolf-like fox” in his journal. Unlike its ancient wolf cousins, however, the canid — commonly called a warrah — was known to be easily tamed and unusually friendly towards humans. It is this trait that most likely led to its extinction (i.e., its friendliness made it easier for explorers to kill it) over a hundred and twenty years ago.
But there are actually two mysteries here: the warrah’s evolutionary (phylogenetic) origin, and, its geographic origin on the islands
Dusicyon was the only terrestrial mammal known to have inhabited the islands. Owing to the Falkland Islands’ (also known as the Malvinas Islands) considerable distance (450 km, or about 300 miles) from the mainland of what is now Argentina, how the canid came to be on the island in the first place has been a question that puzzled even Darwin when he visited the islands in 1834.
But thanks to some mutually supportive genetic and geologic sleuthing, these questions may have been answered.
Researchers (Cooper et al) from the University of Adelaide conducted a genetic comparison between the island specimen (that Darwin bone fragment) and subfossil specimens from several of its mainland relatives (Dusicyon avus). This comparison allowed researchers to determine the approximate date of newer segments of (mitochondrial) DNA found in the FIW specimen.
This dating in turn provided the main clue as to when the warrah became isolated from its mainland cousins. Dating analysis found that the warrah became isolated only 16 ka (averaged from a date range of 8 – 31 ka) — nowhere close to the previously presumed time frame of 330 ka. This time frame matches up very nicely with the last glacial phase (which ended around 11 to 12 ka)
This dating also matched up with a fairly recent geological discovery; during this same period, a series of four submarine terraces had formed on the Argentine coastal shelf by low sea-stands. This suggests that Dusicyon’s earliest ancestors came to the islands via a narrow, shallow marine strait — most likely while it was frozen over.
“The Eureka moment was finding evidence of submarine terraces off the coast of Argentina,” said Cooper in a press statement, which he says would have formed around the time of the last glacial maxima (between 25,000 and 18,000 years ago). “At that time, there was a shallow and narrow (around 20km) strait between the islands and the mainland, allowing the Falkland Islands wolf to cross when the sea was frozen over, probably while pursuing marine prey like seals or penguins.”
As to why it was the only mammal ever found on the islands…The scientists believe that the journey across the strait was too treacherous for smaller mammals. However, this is not certain. Smaller mammals may have made it also, but it may have been that the warrah over-hunted all of the smaller mammals that had co-colonized the islands during the last glacial period. The canid may have consequently turned scavenger and/or found other food sources, such as seals, penguins, other nesting birds, reptiles and/or fish.
Over the three centuries since its first encounter with people, various waves of explorers had noted its docile, unusually friendly demeanor. The name Dusicyon, in Latin means “foolish dog”.
Results of the research were published on 5 March 2013 in the journal Nature Communications, under the title: ‘The origins of the enigmatic Falkland Islands wolf’; authors: Jeremy J. Austin,Julien Soubrier,Francisco J. Prevosti,Luciano Prates,Valentina Trejo,Francisco Mena & Alan Cooper,
Some source material for this post came from the io9.com article ‘Geneticists may have just solved a 320-year-old evolutionary mystery’ by Robert T. Gonzalez
Darwin’s Description of the Falkland Islands Wolf
Darwin writing about his 1834 visit to the Falklands in his Journal and Remarks (The Voyage of the Beagle) has the following to say of Canis antarcticus:
The only quadruped native to the island, is a large wolf-like fox, which is common to both East and West Falkland. Have no doubt it is a peculiar species, and confined to this archipelago; because many sealers, Gauchos, and Indians, who have visited these islands, all maintain that no such animal is found in any part of South America. Molina, from a similarity in habits, thought this was the same with his “culpeu“; but I have seen both, and they are quite distinct. These wolves are well known, from Byron’s account of their tameness and curiosity; which the sailors, who ran into the water to avoid them, mistook for fierceness. To this day their manners remain the same. They have been observed to enter a tent, and actually pull some meat from beneath the head of a sleeping seaman. The Gauchos, also, have frequently killed them in the evening, by holding out a piece of meat in one hand, and in the other a knife ready to stick them. As far as I am aware, there is no other instance in any part of the world, of so small a mass of broken land, distant from a continent, possessing so large a quadruped peculiar to itself. Their numbers have rapidly decreased; they are already banished from that half of the island which lies to the eastward of the neck of land between St. Salvador Bay and Berkeley Sound. Within a very few years after these islands shall have become regularly settled, in all probability this fox will be classed with the dodo, as an animal which has perished from the face of the earth. Mr. Lowe, an intelligent person who has long been acquainted with these islands, assured me, that all the foxes from the western island were smaller and of a redder colour than those from the eastern. In the four specimens which were brought to England in the Beagle there was some variation, but the difference with respect to the islands could not be perceived. At the same time the fact is far from improbable.
Top Image: (FIW Illustration) John Gerrard Keulemans (1842–1912)
Bottom Image (submarine topological map) the authors (Cooper et al) via Nature Communications