Islands of otters and strange foxes

Some people who come to Tet Zoo seem to absolutely despise all those annoying teasers, preemptives and references to things that are yet to come. Others regard these as one of Tet Zoo's key points of awesomeness. Whatever, I am pleased to say that I congratulate you all on your patience and tolerance, for there are some subjects that I advertise and am then unable to publish for weeks, or months, or months and months and months. Yes, unable... I don't delay things on purpose. Obscure island-dwelling, recently extinct animals are a case in point: there's this map from October, and there are all those mentions of monster pigeons and titan-hawks and so on. In the first of several articles, my aim here is to talk about 'recently extinct island-endemic animals that you hardly ever hear anything about'.

A lot of these animals are of that most frustrating type: the ones you see mentioned - just mentioned - time and time and time again, yet no matter how hard you try you never find any information of substance (well, unless you're a specialist and have gone to the trouble of getting hold of the primary literature). Giant iguanas and dodo-mimics from the south-west Pacific, titan-hawks and strange insectivores from the Caribbean, giant island otters, and the controversial island foxes. We begin with the otters and foxes, and will get to the others later...

Island otters

I'm not sure whether it's surprising or not, but otters have been particularly good at colonizing islands, and between the Miocene and the present the Mediterranean was home to more than ten island-endemic otters, six of which probably owe their extinction to human persecution (Alcover & McMinn 1994). Among the Pleistocene taxa, Crete was home to Lutrogale cretensis, Sardinia was inhabited by both Sardolutra ichnusae and the huge Megalenhydris barbaricina, Corsica had Cyrnolutra castiglionis, both Corsica and Sardinia were also inhabited by Algarolutra majori, Sicily had Lutra trinacriae and Malta L. euxena. Some of these otters - like the Cretan otter Lutrogale cretensis [shown in the image immediately below] - were well adapted for terrestrial life and might have preyed on birds and mammals as much as fish and other aquatic prey (Willemsen 1992).

Sardolutra ichnusae, originally described in 1977 but not given its own genus until 1992, was a broad-muzzled, short-necked, long-tailed otter with proportionally large feet. The morphology of its baculum - the bone that many mammals have within the penis - is remarkable and unique, with a large blade-like process that supports two smaller processes. Quite what this otter (the males at least) did with this remarkable penis bone remains unknown so far as I know, but because the living sea otter Enhydra lutris has the biggest baculum of any modern otter it has been speculated that Sardolutra was also marine, and did its mating at sea.

Perhaps the most interesting island otter was Megalenhydris barbaricina from Sardinia: described and named in 1987, its geological age is unknown but Willemsen & Malatesta (1987) thought it most likely that the only known specimen is from the Late Pleistocene or even the Holocene. Its jaw, teeth and limb bones are all quite massive and robust and, uniquely, its proximal caudal vertebrae are dorsoventrally flattened, indicating that its tail was flattened. This suggests that the species was strongly adapted for swimming. While we don't know enough to come up with an accurate length estimate, Megalenhydris was huge - bigger than Pteronura, the Brazilian giant otter. This species reaches 1.6 m and old reports indicate that it previously reached 2.4 m (Carter & Rosas 1997). Characters of its teeth led Willemsen (1992) to tentatively conclude that Megalenhydris is part of Aonyxini, the otter group that includes the clawless otters of Africa and Asia. It would actually be somewhat ironic if the biggest otter of all time was part of this group, given that the living species are small compared to the members of the other otter clades (the river otters and sea otters) [I don't have any images of Megalenhydris; the image below is one of Neil's photos of an Asian short clawed otter Amblonyx cinereus].

During the Pleistocene, Sardinia had yet another endemic mustelid: Enhydrictis galictoides. Regarded by some workers as a member of the same mustelid group as the grisons (all of which are American: a grison is shown at the very bottom of the composite image at the top of the article), it has also been argued to be an otter, and authors have disagreed as to whether it was terrestrial or semi-aquatic (Masseti 1995). Enhydrictis also occurred on Corsica during the Pleistocene (Ferrandini et al. 1995): between the Miocene and the Late Pleistocene, Sardinia and Corsica were connected, so they share the same prehistoric fauna. A dwarf megacerine deer, Megaloceros cazioti, also lived here in the Pleistocene, as did the Mediterranean pika Prolagus sardus, the extinct vole Tyrrhenicola henseli and field mouse Rhagamys orthodon and an endemic canid, and more on that last species in a minute.

Island foxes

Also relatively little known is that canids have successfully colonized islands and evolved into endemic forms on several occasions. One island-endemic small canid, the Californian Channel Island fox Urocyon littoralis is still with us, and is closely related to the Grey fox U. cinereoargenteus of the American mainland. Because it is known that Channel Island foxes were kept as pets by Native American people, it's likely that some of the Channel Island fox populations were transported and introduced by people, but an original colonisation at the northern end of the island group probably occurred naturally (George & Wayne 1991). There are in fact six subspecies, most of which are critically endangered and one of which (U. l. clementae) has been significantly reduced in numbers by - get this - a euthanasia programme instigated to protect another island endemic, the extremely rare San Clemente loggerhead shrike Lanius ludovicianus mearnsi (Roemer & Wayne 2003). Incidentally, Urocyon isn't really a fox in the strict sense as recent phylogenetic work indicates that it's the most basal crown-group canid, and hence not at all close to true foxes (Bardeleben et al. 2005, Lindblad-Toh et al. 2005. Make sure you check to see how many authors were involved in the latter study).

As you'll know well if you're familiar with books on recently extinct animals, the Falkland Islands were home to an endemic canid: the Falkland Islands wolf (or fox) Dusicyon australis, also known sometimes as the Malvinas fox, Antarctic wolf or Warrah. First reported during the late 1600s, the Warrah was described by various mariners and explorers over the years, some of whom thought of it as scary, wolf-like, and dangerous to people, and others who correctly described it as fairly small, naïve and tame (Day 1989). During the 1830s its fur could be seen for sale in New York and in 1868 one specimen was displayed at London Zoo. Belief that the Warrah was a menace to sheep led to its massive persecution, and by 1876 it was extinct. Charles Darwin famously encountered it: I wrote about this briefly here on ver 1 [adjacent image is John Keulemans' painting of a live warrah].

The affinities and origin of the Warrah have been the subject of much discussion. Its tameness, its presence on the Falkland Islands (a place devoid of other terrestrial mammals), and several of its morphological features (white tail-tip, enlarged frontal sinuses and wide muzzle) have led some workers to argue that it was a domesticated form brought over to the islands by the Yahgan people (Clutton-Brock 1977). However, its unusual morphological features are more likely the result of its isolation on the Falklands, and its dispersal to the Falklands is just as well explained by lowered sea levels in the Pleistocene (Berta 1987). Indeed, what appears to be its closest relative, D. avus, is from the late Pleistocene of Argentina and Chile (various other South American canids have been included in Dusicyon, but I here follow Berta (1987) in restricting the generic name to D. australis and D. avus). The two share short, high-crowned premolars and relatively small second molars, and appear to have been most closely related to the South American wolf-like Pleistocene taxa Theriodictis and Protocyon (Berta 1987). These canids were all specialised hypercarnivorous forms with a particularly well-developed shearing dentition. Strongly developed mastoid processes at the back of the skull indicate that the Warrah had a high degree of head and neck manoeuvrability compared to other canids, and this might be something to do with the fact that it was reportedly a specialist bird-hunter: it preyed on geese and penguins, though also killed young sea lions. Unfortunately we know very little about its behaviour and biology [adjacent image shows one of the taxiderm mounts: only 11 are in existence].

Perhaps the most mysterious of all island canids is the Sardinian fox Cynotherium sardous, a species first named (from bones) in 1857 and apparently hunted to extinction some time around 8000 years ago. Despite the common name (which to be honest is not that widely used), it's again misleading to regard this animal as a fox as the most recent work indicates that it is part of Canini, the clade that includes domestic dogs and wolves, and is in fact most closely related to Lycaon, the African hunting dog* (Lyras et al. 2006). Having said that, over the years Cynotherium has been considered allied with raccoon-like dogs, with wolves and jackals, with dholes, and with the jackal-sized fossil canid Eucyon.

* Close relatives of Lycaon, usually placed in the genus Xenocyon but argued by some workers to be congeneric with Lycaon (Martínez-Navarro & Rook 2003), were important in the Pliocene and Pleistocene of Eurasia.

The small size of Cynotherium (it's estimated to have weighed about 10 kg: in the adjacent image it's shown to scale with its wolf-sized Xenocyon-type ancestor) suggests that it hunted small prey such as the endemic rodents and lagomorphs, and this is further supported by its dentition and skeletal anatomy. A low neck carriage, increased mobility of the head and neck, and relatively short limb bones with muscle attachments suggesting more powerful extension and retraction of the forelimbs than that normal for canids indicate that Cynotherium was a stalking predator, able to flatten its body low to the ground prior to a final high-speed rush where rapid head movements were needed to grab prey (Lyras & van der Geer 2006). Similar stalking behaviour among canids is practised by the Ethiopian wolf Canis simensis, a highland predator of burrowing rodents, but this species is less well adapted for this lifestyle than was Cynotherium.

More soon! I also have to do more froggy stuff before Christmas, plus finally a long-awaited publication is out, which means go go go on azhdarchoid pterosaurs, Cretaceous pleurodires and basal birds. While running from the pub to the bus-stop the other day my left ankle gave way with a sickening crunch. Just in time for Christmas, I am semi-crippled.

Refs - -

Alcover, J. A. & McMinn, M. 1994. Predators of vertebrates on islands. BioScience 44, 12-18.

Bardeleben, C., Moore, R. L., & Wayne, R. K. 2005. A molecular phylogeny of the Canidae based on six nuclear loci. Molecular Phylogenetics and Evolution 37, 815-831.

Berta, A. 1987. Origin, diversification, and zoogeography of the South American Canidae. Fieldiana: Zoology 39, 455-471.

Carter, S. K. & Rosas, F. C. W. 1997. Biology and conservation of Giant Otter (Pteronura brasiliensis). Mammal Review 27, 1-26.

Clutton-Brock, J. 1977. Man-made dogs. Science 197, 1340-1342.

Day, D. 1989. The Encyclopedia of Vanished Species. Universal Books, London.

Ferrandini, J., Salotti, M., de Salvador Bailon, Bonifay, M. F., Mourer-Chauviré, C. & Real-Testud, A. M. 1995. Découverte d'importants remplissages fossilifères d'âge pléistocène supérieur et holocène dans le karst de la région d'oletta (Haute corse). Geobios 28, 117-124.

George, S. B. & Wayne, R. K. 1991. Island foxes - a model for conservation genetics. Terra 30 (1), 18-23.

Lindblad-Toh, K., Wade, C. M., Mikkelsen, T. S., Karlsson, E. K., Jaffe, D. B., Kamal, M, Clamp, M., Chang, J. L., Kulbokas, E. J., Zody, M. C., Mauceli, E., Xie, X., Breen, M., Wayne, R. K., Ostrander, E. A., Ponting, C. P., Galibert, F., Smith, D. R., deJong, P. J., Kirkness, E., Alvarez, P., Biagi, T., Brockman, W., Butler, J., Chin, J.-W., Cook, A., Cuff, J., Daly, M. J., Decaprio, D., Gnerre, S., Grabherr, M., Kellis, M., Kleber, M., Bardeleben, C., Goodstadt, L., Heger, A., Hitte, C., Kim, L., Koepfli, K.-P., Parker, H. G., Pollinger, J. P., Searle, S. M. J., Sutter, N. B., Thomas, R., Webber, C., Broad Institute Genome Sequencing Platform (Baldwin, J., Abebe, A., Abouelleil, A., Aftuck, L., Ait-Zahra, M., Aldredge, T., Allen, N., An, P., Anderson, S., Antoine, C., Arachchi, H., Aslam, A., Ayotte, L., Bachantsang, P., Barry, A., Bayul, T., Benamara, M., Berlin, A., Bessette, D., Blitshteyn, B., Bloom, T., Blye, J., Boguslavskiy, L., Bonnet, C., Boukhgalter, B., Brown, A., Cahill, P., Calixte, N., Camarata, J., Cheshatsang, Y., Chu, J., Citroen, M., Collymore, A., Cooke, P., Dawoe, T., Daza, R., Decktor, K., Degray, S., Dhargay, N., Dooley, K., Dooley, K., Dorje, P., Dorjee, K., Dorris, L., Duffey, N., Dupes, A., Egbiremolen, O., Elong, R., Falk, J., Farina, A., Faro, S., Ferguson, D., Ferreira, P., Fisher, S., Fitzgerald, M., Foley, K., Foley, C., Franke, A., Friedrich, D., Gage, D., Garber, M., Gearin, G., Giannoukos, G., Goode, T., Goyette, A., Graham, J., Grandbois, E., Gyaltsen, K., Hafez, N., Hagopian, D., Hagos, B., Hall, J., Healy, C., Hegarty, R., Honan, T., Horn, A., Houde, N., Hughes. L., Hunnicutt, L., Husby. M., Jester, B., Jones, C., Kamat, A., Kanga, B., Kells, C., Khazanovich, D., Kieu, A. C., Kisner, P., Kumar, M., Lance, K., Landers, T., Lara, M., Lee, W., Leger, J.-P., Lennon, N., Leuper, L., Levine, S., Liu, J., Liu, X., Lokyitsang, Y., Lokyitsang, T., Lui, A., Macdonald, J., Major, J., Marabella, R., Maru, K., Matthews, C., McDonough, S., Mehta, T., Meldrim, J., Melnikov, A., Meneus, L., Mihalev, A., Mihova, T., Miller, K., Mittelman, R., Mlenga, V., Mulrain, L., Munson, G., Navidi, A., Naylor, J., Nguyen, T., Nguyen, N., Nguyen, C., Nguyen, T., Nicol, R., Norbu, N., Norbu, C., Novod, N., Nyima, T., Olandt, P., O'neill, B., O'neill, K., Osman, S., Oyono, L., Patti, C., Perrin, C., Phunkhang, P., Pierre, F., Priest, M., Rachupka, A., Raghuraman, S., Rameau. R., Ray, V., Raymond, C., Rege, F., Rise, C., Rogers, J., Rogov, P., Sahalie, J., Settipalli, S., Sharpe, T., Shea, T., Sheehan, M., Sherpa, N., Shi, J., Shih, D., Sloan, J., Smith, C., Sparrow, T., Stalker, J., Stange-Thomann, N., Stavropoulos, S., Stone, C., Stone, S., Sykes, S., Tchuinga, P., Tenzing, P., Tesfaye, S., Thoulutsang, D., Thoulutsang, Y., Topham, K., Topping, I., Tsamla, T., Vassiliev, H., Venkataraman, V., Vo, A., Wangchuk, T., Wangdi, T., Weiand, M., Wilkinson, J., Wilson, A., Yadav, S., Yang, S., Yang, X., Young, G., Yu, Q., Zainoun, J., Zembek. L., Zimmer, A.) & Lander, E. S. 2005. Genome sequence, comparative analysis and haplotype structure of the domestic dog. Nature 438, 803-819

Lyras, G. & van der Geer, A. 2006. Adaptations of the Pleistocene island canid Cynotherium sardous (Sardinia, Italy) for hunting small prey. Cranium 23, 51-60.

- ., van der Geer, A. A. E., Dermitzakis, M. D. & De Vos, J. 2006. Cynotherium sardous, an insular canid (Mammalia: Carnivora) from the Pleistocene of Sardinia (Italy), and its origin. Journal of Vertebrate Paleontology 26, 735-745.

Martínez-Navarro, B. & Rook, L. 2003. Gradual evolution in the African hunting dog lineage. Systematic implications. C. R. Palevol 2, 695-702.

Masseti, M. 1995. Quaternary biogeography of the Mustelidae family on the Mediterranean islands. Hystrix 7, 17-34.

Roemer, G. W. & Wayne, R. K. 2003. Conservation in conflict: the tale of two endangered species. Conservation Biology 17, 1251-1260.

Willemsen, G. F. 1992. A revision of the Pliocene and Quaternary Lutrinae from Europe. Scripta Geologica 101, 1-115.

- . & Malatesta, A. 1987. Megalenhydris burbaricina sp. nov., a new otter from Sardinia. Proceedings Koninklijke Nederlandse Akademie van Wetenschappen B, 90, 83-92.