The Shrinking World of Bandicoots

A bandicoot is a very disagreeable animal to clean, therefore it should be done as soon after killing as possible, and then the flesh can be left in strong vinegar and water for a few hours before dressing. Sweet potatoes and onion make a good stuffing for bandicoot, which is good either boiled or baked.--Mrs Lance Rawson, Australian Enquiry Book of Household and General Information.

Golden bandicoots Isoodon auratus barrowensis, copyright Kathie Atkinson.

Back when I used to work on Barrow Island in the north-west of Australia, one of the more noticeable animals to be seen around the place was the golden bandicoot Isoodon auratus. In the evenings, the place seemed to absolutely swarm with them. About the size of a guinea pig, with no tails to speak of (bandicoots are actually born with fairly long tails but tend to lose them in the course of their quite vicious fights with one another; few if any individuals reach maturity with their tails intact), there was no question about their qualifications when it came to cuteness.

Bandicoots are a group of twenty-odd species of marsupial found in Australia and New Guinea (one species, the Seram bandicoot Rhynchomeles prattorum, was described from montane forest on the Indonesian island of Seram to the west of New Guinea). Most are primarily insectivorous, but they also eat varying amounts of small vertebrates and plant matter such as bulbs and fruit. The largest bandicoot, the giant bandicoot Peroryctes broadbenti, has been recorded to reach close to five kilograms in weight. The smallest, the Papuan bandicoot Microperoryctes papuensis, weighs less than 200 grams. I suspect many people in Australia assume that the name 'bandicoot' comes from one of the the Aboriginal languages, but it is in fact Indian (specifically Telugu) in origin. The original bandicoot Bandicota indica is a large rat that is widespread in southern Asia and Australian bandicoots were named for their resemblance to this species. Personally, I have maintained in the past that Australian bandicoots look more like rats than rats do: with their relatively long snouts, bandicoots bear a distinct resemblance to the sort of cartoon figure that comes to most people's minds when they hear the word 'rat'.

New Guinea spiny bandicoot Echymipera kalubu, copyright Michael Pennay.

Bandicoots are highly distinctive from all other marsupials in appearance. Their hind legs are noticeably longer than their forelegs and more or less specialised for cursorial locomotion (especially so in one example that I'll get to shortly). The fourth and fifth toes of the hind foot are much larger than the other three; the first toe in particular is reduced to a non-functional stub. The second and third toes of the hind foot, as in diprotodontian marsupials such as kangaroos and possums, are externally joined together with the two claws at the end forming a comb that is used in grooming more than in locomotion. The fore feet, in contrast, are mostly functionally three-fingered (with the first and fifth fingers reduced) and adapted for digging with the claws large and flat.

Many bandicoots are rapid reproducers with their gestation periods among the shortest of any mammal, less than two weeks between fertilisation and birth. Bandicoots also have the most developed placentas of any marsupial group (yes, most marsupials do have a placenta, albeit a much simpler one than found in placental mammals); it is presumably because of this that, despite their short gestation, bandicoot young are born at a more advanced stage of development than those of some other marsupials. When the young are born, they initially remain attached to their mother via the umbilical cord; this latter does not become detached and the placenta ejected until after the joey is firmly attached to a teat in the rearward-opening pouch. The young remain in the pouch for about two months and grow rapidly; they may reach full sexual maturity at the age of only three months. As a result, bandicoot populations may increase rapidly if conditions permit.

Greater bilby Macrotis lagotis, copyright Bernard Dupont.

In terms of classification, there is a general consensus that Recent bandicoots can be divided between four groups though there has been some disagreement about exactly these groups are interrelated (and hence exactly how they should be ranked). The most diverse, but probably also the least studied, group of modern bandicoots are the rainforest bandicoots of the Peroryctidae or Peroryctinae. These are about a dozen species found mostly in New Guinea with the aforementioned Rhynchomeles prattorum on Seram and the the long-nosed spiny bandicoot Echymipera rufescens extending its range to the northern tip of Queensland. Most of continental Australia is home to the dry-country bandicoots of the Peramelidae sensu stricto or Peramelinae, of which there are six Recent species (one of these, the northern brown bandicoot Isoodon macrourus, is also found in southern New Guinea). Peramelids tend to have shorter snouts and flatter skulls than peroryctids. The other two groups are both very small and also native to arid regions of Australia. Two Recent species are known of the genus Macrotis, the bilbies, though one of these is extinct and the other is endangered. Bilbies are larger than most other bandicoots, with long ears (hence their alternative vernacular name of 'rabbit-bandicoots') and a long, silky-haired tail.

Gerard Krefft's 1857 illustration of the pig-footed bandicoot Chaeropus ecaudatus, from here.

The final representative of the Recent bandicoots is unquestionably the weirdest of them all. Unfortunately, it is also now extinct, last recorded some time about the middle of the 20th Century, a fact that cannot be called anything less than a fucking tragedy. The pig-footed bandicoot Chaeropus ecaudatus was the most cursorial of all bandicoots. Its forelegs, rather than being adapted for digging as in other bandicoots, had only two functional toes on which the claws were modified into hooves. The hind legs went a step further and had only a single functional toe (raising the question of how this animal groomed itself without the aforementioned claw-comb of other bandicoots Edit: That was a bit of a blonde moment; a second look at the Krefft illustration above shows that the comb is definitely there). The most extensive observations of its habits seem to have been made by Gerard Krefft (1866) who kept a pair alive for about six weeks in 1857 on a trip to the Murray-Darling region before killing them to provide specimens because, you know, 19th-Century naturalist. Krefft recorded that his bandicoots subsisted primarily on plant foods such as lettuce, grass and roots, refusing all meat offered to them (Krefft also refers to providing grasshoppers for them but his account is unclear about whether they were ever eaten). A herbivorous diet was also indicated by the animals' droppings, which where dry and similar to a sheep's. The bandicoots constructed a covered nest from grass and leaves in the tin enclosure in which Krefft kept them in which they sheltered during the day, only becoming active after nightfall. Krefft notes that he acquired "about eight" specimens of pig-footed bandicoot during his six-month camp, admitting that some met a stickier end than others: "They are very good eating, and I am sorry to confess that my appetite more than once over-ruled my love for science; but 24 hours upon "pig-face" (mesembryanthemum) will dampen the ardour of any naturalist". Krefft also noted that several of the specimens found were female, and that despite being provided with eight teats the females never carried more than two joeys. A particularly interesting detail was that the fourth toe of the joeys' fore foot, rather than being reduced as in the adults, remained large so that the feet resembled those of other bandicoots. Presumably this was so that the fore-claws could still be used to allow the newborn joeys to climb from the birth canal to the pouch.

Krefft also noted that the pig-footed bandicoot was already declining in abundance, blaming its increased rarity on competition with introduced grazing livestock. Sadly, changing habitats and introduced predators have caused other bandicoot species to also become endangered since Krefft's time. Please, don't let them go the way of the pig-footed bandicoot.

REFERENCES

Gordon, G., & a. J. Hulbert. 1989. Peramelidae. In: Fauna of Australia vol. 1B. Mammalia. Australian Biological Resources Study: Canberra.

Krefft, G. 1866. On the vertebrated animals of the lower Murray and Darling, their habits, economy, and geographical distribution. Transactions of the Philosophical Society of New South Wales 1862–1865: 1–33.

The Diprotodontids: Marsupials Go Large

Reconstruction of Diprotodon optatum by Anne Musser, from Long et al. (2002). Offhand, running a search for Diprotodon through Google Image brings up some true horrors of digital imagery.

Prior to the arrival of humans, the Australian fauna included many strange, and often dramatic, animals that are sadly no longer with us. Enormous python-like snakes, monitors that would have made a Komodo dragon look underwhelming, drop bears, and of course the notorious demon duck of doom. But among the most iconic of Australia's extinct fauna were the Diprotodontidae, heavyset herbivores that included the largest of all marsupials. Diprotodontids are sometimes referred to in the popular press as giant wombats, but this is a bit misleading: though more closely related to wombats than any other living marsupials, they were a quite distinct group of animals (besides, they shared their world with actual giant wombats that reached the size of a cow). A potentially more appropriate descriptor that has been suggested is 'marsupial rhinos', though at least some diprotodontids were decidedly not like rhinos either.

Skull of Zygomaturus trilobus in Museum Victoria, photographed by Nigel Waring.

The most famous of the diprotodontids was also the first to be described, and indeed the first fossil mammal of any kind described from Australia. Diprotodon optatum, named by Richard Owen in 1838, was the largest of the diprotodontids, sometimes standing more than six feet tall at the shoulder, and reaching estimated weights of around two and a half tonnes. At the time of human arrival, Diprotodon would have been one of the dominant herbivores in the arid central region of Australia. A number of species of Diprotodon have been named over the years, but a review of the genus by Price (2008) recognised only a single species, with the two different size classes present probably representing the different sexes. In the less arid coastal regions, Diprotodon was replaced by various species of the slightly smaller (but still formidably sized) genus Zygomaturus (Long et al. 2002). The best known species in this genus, Z. trilobus, bore a distinctive large bony boss on the snout, giving its skull a profile reminiscent of a cartoon bear. Two other diprotodontid species that would have come into contact with humans are known from the Pleistocene of montane New Guinea, Hulitherium tomasettii and Maokopia ronaldi. Both these species were smaller than the mainland Australians, being about the 100 kg mark. Maokopia has been interpreted as a grazer, while Hulitherium has been seen as a browser, and suggested as a direct analogue of the Asian giant panda (Long et al. 2002).

Reconstruction of Hulitherium tomassettii as a panda analogue, by Peter Schouten.

The broader record of diprotodontids goes back to the Oligocene, with two main lineages being recognised, the Diprotodontinae and Zygomaturinae. Of the species referred to above, all but Diprotodon optatum are zygomaturines. The two groups are primarily distinguished by their dentition, with the premolars being generally more complex in zygomaturines than diprotodontines. In both lineages, the earlier members were smaller: Long et al. (2002) describe a number of genera as 'sheep-sized'. The smallest known diprotodontid, the late Oligocene Raemeotherium yatkolai, they describe as 'lamb-sized'. Black et al. (2012) estimated the weight of the middle Miocene Nimbadon lavarackorum as abut 70 kg. They also suggested that it was an adept climber, in a similar manner to the modern koala, making it the largest known arboreal mammal from Australia. It might seem odd to picture an animal of this size up in a tree, even allowing for the higher density of the canopy in Australia's Miocene rainforests. However, there are larger arboreal mammals alive even today: male orangutans, for instance, may weigh over 100 kg.

Reconstruction of a climbing pair of Nimbadon lavarackorum (adult and juvenile) by Peter Schouten, from Black et al. (2012).

Interestingly, Nimbadon is not placed as a particular basal diprotodontid in the phylogeny of zygomaturines presented by Mackness (2010). As other related marsupial families, such as koalas or thylacoleonids (marsupial lions), also include climbers, it would not be unreasonable to consider such habits plesiomorphic for diprotodontids as a whole. The 'rhino-like' appearance of the later giants would then be something of a novelty, an adaptation to the drier conditions and more open woodlands that arose at the end of the Miocene. If we are to regard the diprotodontids as marsupial rhinos, then we must consider the possibility of rhinos in trees.

REFERENCES

Black, K. H., A. B. Camens, M. Archer & S. J. Hand. 2012. Herds overhead: Nimbadon lavarackorum (Diprotodontidae), heavyweight marsupial herbivores in the Miocene forests of Australia. PLoS ONE 7 (11): e48213. doi:10.1371/journal.pone.0048213.

Long, J., M. Archer, T. Flannery & S. Hand. 2002. Prehistoric Mammals of Australia and New Guinea: One hundred million years of evolution. University of New South Wales Press: Sydney.

Mackness, B. S. 2010. On the identity of Euowenia robusta De Vis, 1891 with a description of a new zygomaturine genus. Alcheringa 34 (4): 455–469.

Price, G. J. 2008. Taxonomy and palaeobiology of the largest-ever marsupial, Diprotodon Owen, 1838 (Diprotodontidae, Marsupialia). Zoological Journal of the Linnean Society 153: 389–417.

Barrallier's Monkey

"Gogy told me that they had brought portions of a monkey (in the native language "colo"), but they had cut it in pieces, and the head, which I should have liked to secure, had disappeared. I could only get two feet through an exchange which Gogy made for two spears and one tomahawk. I sent these two feet to the Governor in a bottle of spirits."

In November 1802, Governor Philip King sent an exploratory expedition west of Sydney under the command of Ensign Francis Barrallier, a French ex-pat who had taken service with the British after fleeing France with his parents following the French revolution. As well as finding a passage across the mountains that barred Sydney from the interior, Barrallier was trying to find the seat of a figure that Governor King later referred to in letters as the 'King of the Mountains'. Who exactly this King of the Mountains was supposed to be is unclear. Many have thought he was supposed to be some sort of overlord of the local Aboriginals. David Levell, in his 2008 book Tour to Hell, argues the King of the Mountains to have been the head of a secret inland settlement that many of the convicts imprisoned in Sydney believed would offer sanctuary to any who escaped there. Barrallier returned to Sydney in late December, having failed to locate either passage or king (the one would be discovered later, the other would prove to be mythical under any interpretation). Barralier's journal of his expedition languished in relative obscurity until an English translation was published in 1897.

The main interest for later readers of Barrallier's account has been in his dealings with the indigenous people he encountered and worked with. Barrallier had an interest in developing a rapport with the local people he met that was not shared by most of his British associates and his notes, sparse as they may be, provide one of the few direct records available of pre-colonial life in the Sydney region. I've brought Barrallier into this post, however, because of an incident he describes briefly in his journal where the game procured by some of Barrallier's aboriginal associates included an animal that Barrallier refers to as a 'monkey'. Barrallier did not see the animal's remains before it had already been butchered, but he is still the first European known to have acquired a specimen of one of Australia's most iconic animals: the koala.

Koalas Phascolarctos cinereus, photographed by Dinkum.

Koalas are widespread in the east of Australia, though loss of habitat has rendered their distribution localised in some areas. To most people outside Australia, the koala seems like a plush toy come to life, the essence of cuteness manifest in a single animal. The Australians themselves often have a more ambivalent attitude: while the koala is certainly a high-ranking member of the pantheon of the Australian fauna, together with such luminaries as the kangaroo, the platypus, the kookaburra and the gumnut baby, Australians also tend to look upon it as indolent, bad-tempered, and steeped in the kind of aroma that only an exclusive diet of eucalyptus leaves can give an animal (many Australians look more affectionately on the koala's closest living cousin, the wombat). To zoologists, Phascolarctos cinereus is the only surviving species of a lineage that goes back at least to the late Oligocene. Three subspecies of koala have been recognised, but these probably represent clinal variations rather than geographically discrete units (Houlden et al. 1999).

At just what point koalas became eucalyptus specialists is something we don't know for sure. The late Oligocene Perikoala palankarinnica possesses an ankylosed lower jaw (i.e. one that has the two sides fused together at the front) that may indicate a diet of tough leaves (Long et al 2002). Eucalyptus would be at least one candidate for such a diet. However, Perikoala's rough contemporary, Madakoala, lacked such a fused jaw and may have taken softer browse. Nor is a fused lower jaw present in the Miocene genera Litokoala or Nimiokoala (Louys et al. 2009). It seems likely that specialisation on Euclayptus may only have developed with the modern genus Phascolarctos, corresponding with the rise of eucalypt dominance in the Australian flora in the late Miocene. As well as being potentially less specialised, the fossil genera of koalas were also distinctly smaller than the living species. Koala evolution reached an apogee of sorts in the Pliocene and Pleistocene with the fossil species Phascolarctos yorkensis, which tipped the scales at nearly twice the size of P. cinereus (Long et al. 2002) (somewhat disappointingly, no-one seems to seen fit to present a fossil koala with the name of Katastaxarctos).


Koalas can be very vocal animals, using bellows and grunts as their main method of communicating. This video of a vocalising bull comes from here.

The specialisation of the modern koala is truly a remarkable thing. True exclusivity of diet seems to be a rarity among large terrestrial vertebrates (and as it can reach sizes of 20 kg, there is no denying that the koala is a large vertebrate). Many have their preferred delicacies but remain far from averse to the occasional variation (something that I really wish the ABC had been more aware of with that lorikeet article). Thus we have cattle gnawing on bones, cats eating grass, or deer killing and eating birds. Even the giant panda, perhaps the other specialist mammal most familiar to the general public, has been known to supplement its bamboo diet with roots and small animals. But the koala turns up its nose at almost anything other than Eucalyptus leaves—and usually only a small number of Eucalyptus species at that. The toughness of Eucalyptus leaves mean they require a great deal of digestive processing, and the small nutritive return is responsible for the extended periods of inactivity that koalas are known for. Early British naturalists often compared the koala to the South American sloth, which functions under similar constraints. The low nutrition of their diet is also reflected in the notoriously small brains of koalas, which have one of the smallest brains relative to body size of any mammal. So noxious is the eucalypt diet that koala joeys have to be weaned onto it through stages. When a joey is about six months old, its mother starts producing a faecal pap of half-digested leaves that the joey eats direct from her cloaca before moving to a more direct leaf diet about a month later.

Nevertheless, by specialising on Eucalyptus leaves, koalas have access to an abundant food source that few other mammals can handle. Even after the arrival of Europeans, koalas have handled the incursion of foreign predators better than many other Australian natives. The main threat to their continued existence is clearing of the forests on which they depend for food. The koala deserves its position as an icon, and an icon is worthy of respect.

Video of a koala joey feeding on pap, from Arkive.

REFERENCES

Houlden, B. A., B. H. Costello, D. Sharkey, E. V. Fowler, A. Melzer, W. Ellis, F. Carrick, P. R. Baverstock & M. S. Elphinstone. 1999. Phylogeographic differentiation in the mitochondrial control region in the koala, Phascolarctos cinereus (Goldfuss 1817). Molecular Ecology 8 (6): 999–1011.

Long, J., M. Archer, T. Flannery & S. Hand. 2002. Prehistoric Mammals of Australia and New Guinea: One Hundred Million Years of Evolution. University of New South Wales Press: Sydney.

Louys, J., K. Aplin, R. M. D. Beck & M. Archer. 2009. Cranial anatomy of Oligo-Miocene koalas (Diprotodontia: Phascolarctidae): stages in the evolution of an extreme leaf-eating specialization. Journal of Vertebrate Paleontology 29 (4): 981–992.

The Mysterious Name of Queen Lestoros

The shrew-opossum Caenolestes fuliginosus. Photo from here.

Those of you who are familiar with the more encyclopaedically-arranged natural history books will almost certainly have encountered the phenomenon of the Mysterious Name. In the introductory section of the book, where the scope of the text is indicated, there'll be some sort of taxonomic listing - the phyla of animals, for instance, or the families of birds - with each of the taxa listing being described in a subsequent part of the book. But often, if you're the sort that will pore over such a listing closely enough, you'll notice that the listing includes at least one name, one taxon (often more) on which the remainder of the book is silent. It's there in the beginning, it has its place firmly indicated in the hierarchy - and then silence.

One taxon that throughout my youth remained to me a mysterious name was the Caenolestidae. Caenolestids are small South American marsupials, commonly known as shrew-opossums*. In most lists of marsupial families, they'll be near the beginning, after the true opossums of the Didelphidae. But all the books I read as a child would skip straight from Didelphidae to Dasyuridae, with nary a hint of anything in between.

*Another sign of their obscurity in the public eye - that they are only given the names of other animals, rather than being thought deserving of a name of their own.

Admittedly, the caenolestids are not a large family. Gardner (2005) lists just six species in three genera, Caenolestes, Lestoros and Rhyncholestes. Four of those species are in Caenolestes, the other two genera are regarded by Gardner as monotypic (though one effect of their understudied status is that no two authors will entirely agree on the caenolestid species list, and some authors may recognise two species in either or both of the smaller genera, while others will recognise only a single genus with as few as three species). Of course, that's still more species than other mammal families such as Rhinocerotidae or Hominidae that have no trouble claiming page space for themselves, and while caenolestids may be few in number now, they were more abundant in the past. Caenolestids were the most abundant small marsupials in South America during the early Miocene (Marshall, 1980).


Lestoros inca. Photo by Phil Myers.

Living caenolestids are widespread, and probably not particularly uncommon, but specimens are few and far between. This has mainly been blamed on their unobliging choice of habitat - they prefer very dense, humid forest, though they may be concentrated close to open meadows (Nowak, 1999). They are shrew-like in appearance (hence the common name), and females lack a pouch (presumably the young just hang directly onto the teats, but females with emerged young seem to have not yet been observed). The front of the lower jaw contains an elongate, procumbent pair of incisors, on which more in a moment.

The most detailed account of their behaviour comes from Kirsch & Waller (1979), who trapped and observed specimens of four caenolestid species. Though stomach contents indicate that the caenolestid diet is mostly invertebrates (Nowak, 1999), Kirsch and Waller found that specimens were most attracted to traps baited with meat, and when offered a choice between insects and meat, they would more readily take the latter. A male caenolestid offered newborn rats proved an efficient predator:

The animal would move toward a rat, sniffing vigorously, seize and lift the rat with its forepaws or pin it to the substrate, and bite it several times quickly with its incisors. The caenolestid would then commence eating the rat by biting off a section of the head with its cheek teeth and take successive bites posteriorly.

In fact, the large incisors were used rarely by caenolestids in feeding - almost all biting and chewing was done with the cheek teeth, and the incisors are primarily for dispatching prey. Caenolestids have a distinct flap on either side of the upper lip, and this probably protects the face and whiskers from getting clogged up with blood and dirt while the animal is busy stuffing prey towards the back of its mouth. When offered larger food items such as earthworms, the caenolestids would sit upright on their tails and use their front paws to manipulate their food, similar to the way a mouse does.


Skull of Caenolestes condorensis, so you can get a better look at those lower incisors which a such bad news if you're a baby mouse. Image from here.

Fossil caenolestids (or near-caenolestids, depending on your preferred classification) were ecologically more diverse than modern species, and a number appear to have been herbivorous. One such genus, the Miocene Abderites, had a large sharp and multi-grooved first molar like the teeth of the multituberculates. Marshall (1980), in the last major review of the fossil caenolestids, suggested that the arrival of the caviomorph rodents in South America was what triggered the demise of the caenolestid herbivores, while the more generalised insectivores/carnivores were able to keep sailing on.

Phylogenetically, caenolestids have been difficult. Perhaps the most honest representation of our current state of knowledge of marsupial phylogeny would be a trichotomy between the caenolestids, didelphids and australidelphians (Australian marsupials), with all possible relationships between these three having been suggested in the past. Some earlier authors suggested a relationship between caenolestids and the Australian diprotodont marsupials on the basis of the procumbent incisors, but this hypothesis was pretty firmly flattened when it was established that a different pair of incisors was involved in each of the two groups. Perhaps the most popular option at present is that caenolestids are the sister to australidelphians, to the exclusion of didelphids, as supported by some molecular data (Springer et al., 1998). However, a relationship between didelphids and caenolestids remains a distinct possibility due to the occurence in both of sperm pairing. After leaving the testes, sperm of members of these two families connect up to each other, forming a single moving pair (perhaps enabling them to swim faster through the uterus). However, the homology of this character is debatable, as the sperm connect in a different place in the different families.

REFERENCES

Gardner, A. L. 2005. Order Paucituberculata. In D. E. Wilson & D. M. Reeder (eds.) Mammal Species of the World: A taxonomic and geographic reference pp. 19-20. JHU Press.

Kirsch, J. A. W., & P. F. Waller. 1979. Notes on the trapping and behavior of the Caenolestidae (Marsupialia). Journal of Mammalogy 60 (2): 390-395.

Marshall, L. G. 1980. Systematics of the South American marsupial family Caenolestidae. Fieldiana: Geology, new series 5: 1-145.

Nowak, R. M. 1999. Walker's Mammals of the World, 6th ed. JHU Press.

Springer, M. S., M. Westerman, J. R. Kavanagh, A. Burk, M. O. Woodburne, D. J. Kao & C. Krajewski. 1998. The origin of the Australasian marsupial fauna and the phylogenetic affinities of the enigmatic monito del monte and marsupial mole. Proceedings of the Royal Society of London Series B - Biological Sciences 265 (1413): 2381-2386.