Main "Tour to Neocene"

Dragons of Eyre Gulf

We re on the Australian coast, to be more exact its the coast of Eyre Gulf. Its July, and were lucky to watch the spectacular scene from the past not from Holocene, but from the times even more distant Triassic era when reptiles have just started to establish their dominance in the seas. Two almost 3-metres long lizards are engaging in the fierce battle at the beach of Eyre gulf. To speak frankly, a great deal of those 3 meters is made of their tail and long neck where sits relatively small head with powerful jaws. Lizards are coloured dark green (the back has darker colour), and theyre rather aggressive: reptiles wave their tails, throwing around lots of wet sand, and are hissing at each other. They stretch their long necks and open their mouths, full of large teeth. All of that is done in honour of their hearts desires who are lying on the sand not far away, watching the tournament just like ladies should and dont intervene into the battles of raging males.
Those are beach goannas (Varanus semimaritimus), sea lizards inhabiting the coasts of Australia and Australasia. Compared to the mighty sharkodile (Carcharosuchus deinodontus) theyre like sea otter compared to valrus, but despite that theyre the main predators and consumers of small fish, crustaceans and mollusks in the shallow waters and among reefs. But now they have much more important task than eating breeding and producing future generation. The battle comes to its end: one of the fighting males finally got tired and left the battlefield to recover from his defeat, leaving the females to the winner. The winning one slowly goes to the females to impregnate them.
Its not the last of such battles to happen on the coast of Eyre Gulf till the end of mating season which is the beginning or middle of Australian August beach goannas arent the smartest reptiles around, but their males are very active animals, and mating rituals last until theyre exhausted. For the recreation theyre heading back to the ocean to hunt small animals. There are more than enough prey for goannas there as during the mating period the reptiles were starving their appetite decreases at that time. Also theres the fact of their life being less dangerous now despite males are heading to the ocean to feast, females are going their own way now. They go east, heading for the Pacific Ocean and Tasmania. There they will lay their eggs after having to travel for several long weeks. Its not that much if you compare it to the legendary travels sea turtles perform, but then its no small feat for goannas who are not of very marine origin to make such a travel under close watch of attentive cold eyes, looking at them from oceanic abyss. Those eyes belong not to rays but to their close relatives sea angels or rasp sharks (Squatina sp.). Theyre not the most active predators... if you compare them to other sharks.
But despite the presence of oceanic predators, the female beach goannas rather successfully crossed the waters separating Tasmania from the rest of Australia, and now are heading up the multiple Tasmanian rivers. Some of them are coming there to lay eggs not for the first and not even for second time in their lives.
Its nice, warm and rather dark around specifically for goannas, who are used to sunny beaches. Suddenly troubled bird cries are heard above the swimming females, and a few feathers covered in blood drop into the water. If it were another time, goannas would have searched for the source of blood in the water, but now their aim is to lay eggs and then slowly return home until next mating season comes. But we can stay and watch long whickered snouts, sometimes covered in blood or with small pieces of feathers and fur on their teeth appear in the tops of the trees. Those are marsupial civets (Pseudoviverra marsupialis), the descendants of eastern marsupial cat and one of the major Tasmanian predators. They are hunting both on earth and in the trees. Unlike stupid goannas, they have rather good brains and memory a positive result of competition with introduced placental predators. Theyll memorize the travel of the giant lizards up the river and it will surely come in handy later...
But not only marsupial civets are interested in the travel of giant lizards up the river towards their goal. The swimming lizards have scared a flock of hare kangaroos (Lagobettongia timida) who descend from some species of Tasmanian kangaroo rats, most likely from Tasmanian bettong. Timid marsupials dont understand that goannas arent interested in them so they run into the bushes. In a few minutes their terrified cries are heard from the bush one small animal is eaten by the animals looking like cross between extinct South American bush dogs and overgrown dachshunds. The later is closer to the truth as in reality were looking at descendants of domestic dog introduced to Tasmania by people and surviving their extinction there. They got used to the wild life and separated into the few species. One of them is water dog or mink dog (Potamocanis speothicus), a canid living along rivers and springs who got used to living near water. Their love for the water isnt that strong when it comes to the biggest and deepest rivers, but that's not the thing to disturb mink dogs. And goannas continue their journey.
But the journey is coming to the end or has already come for some of them- in search of their motherland goannas have left the bigger Tasmanian rivers and now are heading up smaller and smaller rivers. Goannas have swam in the big group before for the reason of safety, but now we can see them divided into the small groups of 2-4 lizards swimming up the river. Swimming? Every few meters one or even two goannas are leaving the water and crawl to their desired strip or to the one thats left without host for some reason. Once they reach that place, they dont waste any time and immediately start digging ground or throwing away dry branches. Then goannas lay eggs in those pits, cover them with dirt and branches and leave the place forever! Thats right decision cause in a few hours after the eggs are laid the appetite of goanna females recovers to the full force so they eat whatever they can see and can eat even the frogs! Goannas regain lost weight on they way back to the Australian coast they swallow and eat frogs, fishes, small mammals, birds and everything they can catch on their way home.
But whats about eggs? They lay buried in the ground, and the small lizards will hatch from them only in a few months. But will they hatch at all? Bushes are moving and a pack of mink dogs is appearing in the clearing. They head to the hidden eggs and start digging them from the ground with very determinate look. They lack the experience of their ancestors in such tacks but nevertheless eggs soon appear on the surface. Sometimes you can see the birds the size of daws near the dogs. Those birds have thin tail, dark green feathers and bright red head. Its redheaded nocturnal bee eater (Nyctyornis purpurea), a descendant of bearded nocturnal bee eater who moved to Tasmania from New Guinea during the Ice Age, leaving lots of descendants in its way. Redheaded bee eater is typically forest bird, who hunts invertebrates and small vertebrates. It doesnt refuse to eat eggs be it the eggs of other birds or those of goannas. But its rare delicacies for it the nest of one goanna contains about 20-30 eggs in it and mink dogs have good appetite, not to mention them having to share their meal with marsupial civets. Unlike dogs civets hunt the birds such as bee eaters, so the later have to keep away from them.
But nothing in the world lasts forever. Both avian and mammalian predators are full up and leave goannas eggs alone. Not to mention that not all the nests are found by them. The youth of goannas hatch from remaining eggs approximately in the end of October beginning of November. They immediately rush for the water. But directly into the water of small rivers they get not immediately but in a few months when they grow 30-50 cm in length. Till that theyre hiding in the tangle near the river and act timidly. But when they grow two feet in length, they finally become brave enough to resemble their parents in character. The goannas of that size attack even hare kangaroos that come down to the river to drink. But if young goanna meets mink dog or some marsupial predator, its lizard that becomes a prey. But the most interesting is yet to come it happens when goannas reach maturity and start their travel to their ancestors motherland
And the rasp sharks rise from the depth... Adult rasp shark is a flat fish roughly the size of adult goanna male 2.5 meters in length and weights up to 70 kg. Despite they resemble rays in their way of life, sometimes, especially in dark moonless nights they remember that theyre sharks... and the horror begins.
Usually sea angels attack in the night, when especially stupid young goannas try to swim alone (most goannas have learnt to keep in group for the reasons of safety so that happens rarely), or in the day when goannas have to swim through the strait separating Tasmania from the rest of Australia. Then the horde of rasp sharks attacks. It usually happens near the Australian coast when goannas are tired from the long swim and too weak to defend themselves properly. Its especially important for sharks, as goannas while relatively young, have teeth strong enough to seriously wound any rasp shark or even bite through their cartilaginous skeletons. That makes wounded rasp shark a good dinner for goannas or even for their own species.
In a few days survived young goannas reach their motherland. It happens approximately two years after their pregnant mothers left their coasts. Right now adult females are ready for the next long journey and absolutely dont care about the arrival of their young kids or siblings. Even worse adult males are so hungry after the end of mating season, that they can eat the youth of their own species. But that works both way a pack of juvenile goannas can kill and eat old or wounded mature male as they are almost as hungry as the adults and have the same level of cruelty. But goanna wont mature fully until it reaches 2 meters in length, and that mean that juvenile ones have to survive for at least few years to join the adults.
Thats the brief insight in the life of Eyre Gulf dragons.

Translated by Charles


Hosted by uCoz