Top Dogs

Many thousands of years before the second invasion of man, Australia's first introduced species made landfall somewhere on the Papuan coastline. Traded with the local people by Indonesian seafarers, a primitive Malaysian dog was the first carnivoran to ever set foot on the continent. The indigenous peoples of Australia had never had a domestic companion before, but it would not be long before the canines would return to their wild roots and once again become subject to the laws of natural selection. The last of the Holocene's glacial cycles exposing land between New Guinea and the mainland allowed the dogs to spread south on two separate occasions, developing into distinct ecotypes perfectly adapted to the environments they found themselves in. They would soon be found across almost the entire continent, with only Tasmania, isolated earlier than most, remaining free of the wild dogs. As they continued to spread out, thrive and diversify, the ecology of Australia developed around them and soon inserted them as the apex predators of the continent alongside the humans with which they would still associate. Although having descended from an introduced species, the Dingo was now vital to the health of ecosystems across the continent and fit comfortably into the landscapes they inhabited just like any other native animal.

Things would not go as smoothly for dingoes following the arrival of Australia's second human invasion. As European settlers crept out across the land they brought with them cattle, sheep and other livestock, animals that proved to be tempting occasion targets for the local apex predators. It would not be long until the Dingo would be villainised as a cowardly and devious predator of livestock, with farmers welling up fear among the people in order to encourage their persecution. A war against the wild dogs began, one fought with guns, poison and steel-jawed traps, reducing Dingo numbers in some places and completely wiping them out in others. However, such actions would result in consequences those early settlers could not have predicted. As a top order predator, the Dingo was responsible for maintaining balance in many ecosystems, and its removal would change everything from the abundance of invasive species to the makeup of the vegetation and the composition of the soil. Areas in which dingoes remained prominent maintained a higher biodiversity, especially regarding small animals, and many of the small native mammals vulnerable to predation by invasive predators lasted the longest where dingoes were left alone. Such a thing was even beneficial to the farmers, with the presence of dingoes greatly improving the quality of grazing land by keeping the ecosystem in balance. Furthermore, the removal of many adults from dingo society destroyed the structure of packs, and with no one to teach them how to hunt more challenging wild prey like kangaroos or invasive species, the young delinquents focused on the easiest prey around - in areas where dingoes were culled, predation on livestock actually increased. Despite all of this, dingoes would remain in the firing line for many centuries after colonisation, their extermination justified with misinformation and fear mongering.

However the wild dogs were more tenacious than they might appear, and even in areas with intense culling (such as those south of the immense Dingo Fence, which, despite its name, is not actually very good at stopping dingoes) they managed to survive in reduced numbers, living on the periphery of the farmland man had fought so hard to rid them from. Here they met their distant relatives, domestic dogs, from which they were now nearly as genetically distinct as both were from wolves but also managed to interbreed with very easily. The majority of the resulting hybrids were identical to pure dingoes both physically and ecologically (the dingo's characteristics were both genetically dominant and favoured through natural selection), to the point where making a distinction between the two was almost pointless. Nonetheless, the decrease in "pure" dingo numbers as a result of interbreeding was frequently used in arguing for the extermination of dogs in Australia as a whole.

Fortunately, such a thing never came to pass. When the great purge of invasive species began, dingoes, dingo-dog hybrids as well as domestic dogs were the only large placental mammals or carnivorans on the continent to be spared - not only were they the only ones not to result in any detriment to Australian ecosystems, but their vital role in maintaining the health of such ecologies was finally recognized. By the time man had disappeared and the great ice age had returned, domestic dogs had been completely absorbed into the dingo gene pool and howls of wild dogs could once again be heard right across the continent, with the lowered sea levels even allowing them to finally colonise Tasmania. In the wake of man's extinction canids worldwide would prove to be among the most successful of radiators, and in Australia it would be no different. The Dingo, Australia's only canid after the extermination of the Red Fox, would give rise to the continent's greatest radiation of carnivorans. While viverrids are only recent arrivals and cats remain fairly conservative, the canids have garnered a diversity of five genera ranging everything from semi-arboreal burrowers to lithe sprinters and powerful bone-crushers, all descended from some lucky mutt that made its way into Melanesia many millions of years ago.

Not all canids are so derived of course, a fact best exemplified by the continued success of members of the genus Canis, of which Australian species are still referred to generally as dingoes. By the time European settlers arrived in the Holocene dingoes had already evolved into different ecotypes that somewhat mirrored the traits of other canids elsewhere - the inland or desert dingoes resembled jackals or coyotes, the alpine or eastern dingoes appeared closer to wolves while those in the jungles of New Guinea developed more squat forms that could perhaps be comparable to other rainforest canids such as the Short-eared Dog. The generic and opportunistic bodyplan that all Canis species possessed allowed for this amount of variation to appear in dingoes in such a short period of time, and it was also what allowed the genus to derive into all the more specialised genera we see in Australia today. Recurocene dingo species have taken a similar path to their Holocene ancestors, developing into forms that resemble those of Canis species on other continents. The Sabled Dingo (C. apemelas), Sandy Dingo (C. xanthos) and Papuan Dingo (C. nonxanthos) are all medium-sized mesopredators of the same caliber as jackals, while the Greater Dingowolf (C. densuthrix) and Western Dingowolf (C. xanthos giganteus) are larger and more powerful predators that bring down big game in packs, just like their ancestor and namesake.

The only other Australian members of the genus are the Southern and Northern Gudaga (C. hylerepens and C. gudaga), endemic to the rainforests of New Guinea and the north-east coast. Unusually small and short in stature for a Canis, they are exclusively nocturnal and specialized in the predation of small mammals such as possums, bandicoots and rodents. They would likely be classed in a separate genus if not for the fact that, even though gudagas and other dingoes cannot interbreed naturally due to size differences, they can still produce fertile offspring with other species in Canis, which are well known for hybridising with one another.

To the inexperienced eye, it could easily be mistake a Gudaga as one of the austral foxes, but this is not so. The supergenus Avendavulpes is of course not related to true foxes, but instead consists of two genera of small canids descended from the Dingo. The Red Fox, while wildly successful in Australia for several centuries after its introduction by man, was completely wiped out in the continent's invasive purge and unlike the other carnivoran invader, the cat, it had no population in New Guinea. "Foxes" is by no means a monophyletic group - indeed, there were several completely distinct groups of canids referred to as foxes during the Holocene, including the Vulpini ("true" foxes), Lycalopex/Cerdocyon (South American foxes) and Urocyon (Grey and Island Fox). In truth, the fox seems to be the base canine condition, with the larger and more specialised forms having been derived from them. This does not mean that a larger species cannot evolve back however, with the lack of small canids in Australia encouraging dingoes to take such a path. From there they split into two separate genera, adapted for living in different environments - the tree foxes (Arborocyon) and the sand foxes (Gracilicyon).

As their name suggests, the four species of tree fox are tied to the trees and therefore are confined to the forested regions of the east and north. Dingoes displayed remarkable hypermobility which gave them double-jointed limbs, human-like wrist rotation and dexterous paws, and this made them adept climbers able to shimmy up trees with ease. The tree foxes have expanded on this ability and all are semi-arboreal in one way or another, although how much time they spend up in the trees varies from one species to another. For example, the Bush Fox (Arborocyon variegatus), the largest of the austral foxes and the most widespread member of its genus, spends as little as 20% of its time up in the trees, often less, and usually prefers to hunt in the forest undergrowth instead. Meanwhile, the Jungle Fox (A. petuarus) and Cuscus Fox (A. flavioculus) of the continent's tropical north will spend up to 70% of their time in the rainforest canopy in pursuit of possums, birds, geckos and similar animals, gaining very little of their prey from hunting on the ground. The Black-backed Fox (A. orientalis) of the eastern seaboard sits somewhere between these two extremes. Although largely predators of small animals, fruit also constitutes a large part of their diet. Despite their arboreal tendencies all still rest and raise their young in underground burrows and no species is completely arboreal, a lifestyle taken up by the marsupial arborgales instead.

While the tree foxes adapted to life in the forest, the small canids in the harsher lands to the west instead evolved to cope with dry, fickle conditions of the Australian inland. Sand foxes only constitute two species, but both are quite widespread. The Scrub Fox (Gracilicyon fulvus) is the larger of the two, about the size of a Swift Fox (which it also resembles rather closely in appearance), and may be found in most dry environments excluding the harshest of deserts, including scrublands, dry woodlands, arid and semi-arid plains and desert rangelands. They extend into some wetter habitats in the south-west due to the absence of other foxes. Meanwhile the smallest of all Australian canids, and indeed one of the smallest in the world, is the diminutive Pophole Fox (G. minimus), which inhabit arid grasslands, sandplains and gibber flats including some of the continent's driest deserts. They have unusually large ears, a common adaption among tiny desert-dwelling canids that makes it easier to dissipate the desert heat while also boosting their hearing. They get their name from their habit of making dozens if not hundreds of different boltholes across their territory, which ensures they are always close to sanctuary if danger arises. Being exclusively nocturnal these boltholes also double up as shelters away from the fierce desert heat during the day. Pophole Fox territories overlap and different individuals will make use of the same boltholes, although given the abundance of them it is rare for two foxes to be in the same hole at the same time. When raising young they will modify an already existing bolthole into a more specialized nursery burrow. They are the most carnivorous of all austral foxes, rarely if ever eating plant matter, and get all of their moisture from food.

Dingoes and austral foxes constitute the majority of Australian canid species, a testament to their generalization and adaptable bodyplans. The three remaining species are much more specialised by comparison, but nonetheless they remain successful and widespread. An obvious area for such a predator to specialise in would be macropods, which dingoes have been locked in a predator prey relationship with ever since they first arrived in Australia. Only after a few thousand years of contact the two had already developed various strategies against one another, dingoes often using teamwork to funnel macropods into debris, dense vegetation or uneven terrain to trip them up, meanwhile kangaroos will instinctively leap into the water if the chance arises to drown any dogs that follow them in. One of the main issues dingoes had with hunting kangaroos was that they couldn't simply run them into exhaustion as a wolf would with an ungulate, as of course such a technique is practically useless on macropods given their hyperefficient locomotion. Pack hunting and clever strategizing was instead used to combat this, and indeed such a technique is still common among the Recurocene's dingoes, but one species has developed a much more simple solution. If you can't exhaust them, why not outrun them?

The Vivveren (Velocicurrus melaslatus) has evolved to do just that. Its adaptions for running are immediately obvious given its muscular but light body, remarkably flexible spine, enlarged nasal passages and lungs, extremely powerful heart, and a lengthy tail and legs. Many of these adaptions are similar to those possessed by sprinting carnivorans of the Holocene like the Cheetah or the selectively bred Greyhound, and this too is an animal highly specialised in extreme bursts of speed over short distances. They can accelerate from a standstill extremely rapidly, reaching speeds up to 98 km/h in a matter of seconds, although when hunting they usually sprint only around 60-70 km/h. For their incredible bursts of speed they have had to sacrifice the great endurance they once possessed, now only chasing after prey for up to half a kilometre but usually no more than two hundred metres before they give up the pursuit. Nonetheless, this is often more than enough to allow them to catch up to their quarry.

Vivverens prefer the wide open environments which are most prominent in the drier regions of the continent, and hence they have a wide distribution across the Australian interior. However, they may also be found in scattered populations east and south of the Great Dividing Range, occurring in wet open woodland, prairie and swampy grassland areas. The Vivverens here are darker than their inland counterparts, but are otherwise identical. Their occurrence in open environments is not just because of the lack of dense vegetation impeding on their sprinting, but also because this is also the preferred habitat of their favourite prey, macropods. There is no predator more specialised or more efficient at preying on these most successful of herbivores than the Vivveren, but to have any chance of catching one it must first get as close as it can. A Vivveren may spend hours carefully approaching a mob of kangaroos before it is finally within chasing range, usually locking onto a single individual early on. It will then launch from cover, often giving its quarry little time to react as it pummels towards the marsupial at speeds no other land animal in Australia can reach. Their long tails and large claws allow them to make sharp turns even at such high speeds as they dodge and weave after desperate prey, before tripping it at the legs and killing it with a strong bite to the neck. While macropods, especially the larger kangaroos, constitute the majority of their diet, they will also prey on smaller animals like rodents, young deer, birds and lizards.

Although solitary in nature, a Vivveren will often be happy to share its kill with another of its kind as long as conditions are plentiful enough, and given that the abundance of macropods in any given area often fluctuates across the year according to the availability of food and water they do not set up territories of any kind. During the breeding season males and females will raise the pups together, and this will be the only time when Vivverens will hunt cooperatively in a pair. Once the young get a little older the father will leave but the mother will continue to care for them until they are mature enough to fend for themselves. Understandably, the presence of such a specialised and efficient predator has had an effect on the evolution of macropods, with many species now being significantly faster than their Holocene ancestors.

The final group of Australian canids are the bone-crushing dogs (Gaiyacyon), which today constitute two quite different species. Such a name brings to mind the Borophaginae of pre-Quarternary North America, and indeed the similarities between the two groups could be cited as a case of convergent evolution. However, while the decline of the borophagines is suggested to have been triggered by competition from both felids and canines, Australia's bone-crushers evolved in an ecosystem where both were already very prominent. The genus first appeared about 3 million years ago and originally consisted mostly of medium-sized generalists, just as happy to scavenge as they were to hunt, their bulky frames and powerful jaws allowing them to easily dominate a carcass or bring down an animal as big as a deer without assistance from other individuals. Over time as the bone-crushing dogs spread out across the continent some species began to become more specialised, with the most extreme case of this being the lineage that led to today's Scrap Dog (G. minor). Already being equipped with powerful jaws easily capable of crunching through bone, the development of dedicated scavengers was an obvious path for the bone-crushers to take.

In many ways, the Scrap Dog could be said to be the canid version of the Hyaena hyenas or the Tasmanian Devil, a sturdy and powerfully built animal with immensely strong jaws that only hunts its own food when an easy opportunity presents itself. Seemingly replacing the devils after the extinction of the scavenging marsupials 2 million years prior (caused by a combination of climatic shifts and competition from other carnivores), they can be found everywhere but the driest of deserts and past the tree line on New Guinea's immense mountains, usually roaming around in small bands of three to seven individuals. On occasion they form much larger groups of ten to eighteen animals, but such "megapacks" are rare and generally only occur in extremely productive grassland ecosystems. The wolf-sized predators keep in contact through deep moans, yips and yells, as well as howling over long distances.

Canids are equipped with an impressive sense of smell from the get go, but that of the Scrap Dog is even more advanced and they can sniff out carrion many kilometres away. Upon arrival they easily gain control over a kill from other scavengers and even from predators as large as Woodcats - only their larger congeneric cousin is invulnerable to their assaults, and instead at a Gaiyacyon kill they will wait on the periphery hoping to get a few scraps once the powerful predator is done feeding. Their snouts are short, deep and backed up by powerful jaw muscles in the neck, giving them the strongest bite for their body size of any canid and allowing them to eat everything on a carcass, even the hooves and horns. Their only real competitor over a corpse is that other scavenging specialist, the three metre-long Carrion Goanna, but the huge lizards usually only eat the meatier cuts of a carcass and leave the bonier parts to the dogs.

The only other surviving member of the genus is quite a different creature in both behaviour and appearance, and is undoubtedly one of the Recurocene's most impressive animals. It is nonother than Gaiyacyon (Gaiyacyon major) itself, the largest mammalian predator Australia has ever seen and the biggest canid of all time. Weighing in at 160 to 340 kilograms, these huge dogs are as big as tigers and more than twice the size of any canid that has come before, making them the continent's undisputed apex predators. The species gets its name from the "giant devil dingo" of Cape York mythology, Gaiya, and indeed such a nickname is a fair description of this most remarkable of canids.

Their origins once again lie in the isolation of the Australian south-west, with the bone-crushers first arriving in this remote corner of the continent just over 2 million years ago. At this time Gaiyacyon was in its prime in terms of species diversity, attaining an Australia-wide distribution and splitting off into many distinct species in the process. Those in the south-west entered an ecosystem completely unlike that found elsewhere on the continent, especially when it came to prey. It would not be long until the bone-crushers became locked in an evolutionary battle with the south-west's most influential herbivores - the brutes, which were still in their infancy when it came to growing truly large. Before the arrival of Gaiyacyon the region's predators were not very big or threatening, and therefore no species grew larger than the now relatively diminutive Southern Brute. The bone-crushing dogs presented a predator unlike any they had faced before, and it was this that triggered their increase in size to the giants we know today. In due response, the canines also increased radically in size, resulting in the evolution of Gaiyacyon major. Sciurutherines would remain endemics of the south-west until the brutes finally colonised the Australian interior only a million years ago, and sure enough their greatest predator was quick to follow. Once the enormous dogs had colonised the inland they then spread across the Great Dividing Range to the east coast, marched north across the floodplains and into New Guinea's rainforest, until their distribution was essentially continent-wide. It was this expansion that was responsible the decline of species diversity in Gaiyacyon, for G. major was a powerful competitive force from which only the Scrap Dog was immune due to its specialisation in scavenging.

Like its much smaller cousin, only the highest and driest of Australia's environments, too extreme to support large herbivores, are free of these huge canids, and they otherwise maintain a continent-wide distribution. As can be expected for an animal distributed across such a vast area and great variety of climates they display considerable variation across their range when it comes to size and colouration. Gaiyacyons in the forested regions of the east and north tend to be smaller (often no larger than 230 kilograms) and usually tawny grey or black in colour, while at the other extreme those of the inland are significantly larger, their increased body mass resulting in a lower metabolic rate (an adaption to the desert's sparser abundance of prey), and are mostly beige, fawn, tan or other sandy colours. The New Guinean population is unique in that a large percentage of individuals have a black hood and back while the rest of their body remains tawny grey, a type of patterning not found in Gaiyacyons elsewhere. All colour morphs have a significantly lighter underbelly. Given their size maintaining a good sized social group is no longer a viable option in most instances and instead they are either solitary or live in a close knit pair or trio. This is more beneficial to protecting productive territory than anything else, as even when in a pack they only hunt cooperatively for the largest and most dangerous of prey items and usually spend most of their time out of each other's line of sight. Even so they continue to maintain knowledge on other pack member's whereabouts through deep, slow and eerie howls which can travel for more than a dozen kilometres. Contrastingly, Gaiyacyon of the floodplains and savannahs of the tropical north will often form larger groups of four to seven animals as the immense herds of Northern Brute and Australian Buffalo make such a social unit necessary if they are to stand any chance of making a kill.

Gaiyacyon are the only natural predators of many of the continent's largest herbivores, including brutes, brachiotheres, junglehorns and ohkaries, and these are the animals they are specifically adapted to hunt. Although not as strong in comparison to their body size, the biteforce of a Gaiyacyon significantly outclasses even a Scrap Dog allowing them to easily shatter bone, and their jaws are longer than those of previous species of bone-crushers to increase their reach after fleeing prey. Although they are not fast runners they have an immense amount of stamina and may spend hours loping after a herbivore in the hopes of wearing it down. In most circumstances their prey consists of younger animals, either through panicking a herd to separate it or chasing down a recently independent individual. Adults are much more dangerous and they will only hunt one if it is particularly sickly, old, or during times of extreme pressure like an extended drought or particularly harsh dry season. This is most necessary for the Gaiyacyon that live in the interior, where droughts are frequent enough that hunting adult Inland Brutes, the meanest, toughest and heaviest of Australia's giant herbivores, is a relatively regular affair. In their old age a desert-dwelling Gaiyacyon will often possess many ancient scars which mark where the claws of brutes once raked their flesh. If the opportunity arises they will also prey on smaller animals like wombats, emus, smaller ungulates or particularly slow kangaroos.

Most of the time Gaiyacyon reproduce only with their packmates, so if they are solitary or part of a group consisting only of animals of the same sex then they may never reproduce. Alternatively, some seek out other packs or individuals in which to mate with during particularly good times, which are what usually triggers breeding in Gaiyacyons rather than a seasonal cycle. Such conditions result in a massive increase in the numbers of young herbivores and therefore prey for the dogs, making this the perfect time to rear young. They have small litters of one to four pups, but usually only one or two of them will survive their first year. Gaiyacyons are slower growing than other canines and they finally gain independence from their mothers at around a year and a half in age, invariably being driven out of her territory. Upon eviction groups of teenage dogs will band together to form packs of two to five individuals to increase their chances of survival, but most will succumb to injuries obtained through hunting or the whims of the harsh environment before they reach sexual maturity. They may be the most impressive mammalian predator that Australia has ever seen, but the life of a Gaiyacyon is certainly far from easy.