Other edge-of-the-desert life of the Northern Territory
While exploring the edge of the desert of the Northern Territory of Australia, you can’t help but notice the massive variety of reptiles and other animals. Here are a few that I have seen on desert adventures but don’t quite fit into the other articles. This showcases some of the species found on the edge of the desert region, northwards of Tennant Creek and up to about Daly Waters.
Reptiles of the desert’s edge
First of all are the dragons we see running about. One of the most common around the Tennant Creek area on the verge of the desert is the Yellow-sided Dragon, Diporiphora magna. This lizard is very nondescript during the Dry season, in fact hardly noticed at all. But come the start of the Wet season, all of the sudden away goes the winter fashions that includes only shades of brown and in comes the summer-wear. Males sit on prominent perches and exhibit a wide range of colours. A light brown head, yellow sides, two yellow racing stripes and a bright red tail.
This outfit is topped off with a dark under-arm patch that can be switched on and off at will. During the morning when it’s time to warm up (semi desert regions get very cold at night), the males are very drab indeed- mostly verging on black. These dark colours absorb heat from the sun rapidly, but do not get the female’s attention, so as soon as they are warm enough the colours come back on. So this begs the question, how do the colours attract the females? What advantages is a male showing with bright colours as he sits high up for all to see? Well, predators also see the colours and if a male is to be both colourful and dodge birds of prey he must be smart and quick-witted or he will die. This trait alone would be attractive to the ladies, but bright colours also display health and the ability to look after his well-being by being a good hunter and not getting diseases. So bright colours do say a lot about a male Dragon, even though the females might not know the reason they like the most colourful males.
Very often overlooked but exceedingly common in the northern half of the NT is Australia’s most famous lizard, the Frill Neck (Chlamydosaurus kingii). A large and brightly coloured Dragon, they spend much of their lives clinging to the tree trunks, coming to the ground to feed and fight. Males are seen far more commonly seen than females as they are bigger, brighter and will often fight rivals on the ground. Sometimes the only indication of their presence is the frill of a male as he extends it and rustles it at a rival. Otherwise they sit in a position that makes them easy to mistake for a tree stump. During the cool dry parts of the year, say from May to October these lizards are rarely seen as they ascend to the tree tops. But from October onwards their presence is well known in woodlands and even city gardens as they actively forage on the ground, especially right before a thunderstorm. It is about this time of year that females are said to lay eggs. A nest hole is dug at the base of a tree and the eggs are buried there. When they hatch later in the season when food is abundant, they will dash up the nearest tree, complete with a tiny frill around their necks. The frill is only used as a defense against predators, normally it is folded tightly against their body. When upset and unable to escape, they hiss loudly, extend the frill and make snapping lunges at the attacker, before turning the other way and dashing for safety.
But what are Australian desert lizards without at least a mention of the biggest, smartest and nastiest of them all? Yep, Monitors or Goannas are very well represented here with over half of the world’s species in Australia and most of them in the Northern Territory. Many are small, like the elusive (I have seen them but never through the camera!) Pigmy and Spiny monitors which look like medium sized skinks right up to the 2.5m long Perentie, the second largest in the world next to the Komodo Dragon.
The most frequently seen of the monitors in Central Australia’s deserts and on the edge of them are the Gould’s or Sand monitor and the Black Headed Monitor. The Gould’s (Varanus gouldii) takes on a lovely orange/yellow colour scheme in the central desert sandy regions as this picture shows. These are burrowers, digging temporary homes for the night in a couple of minutes and having more elaborate semi-permanent ‘warrens’ they use more regularly. Like their larger cousins, the Gould’s is every bit an opportunist. I have witnessed them locating spider burrows by smell (like snakes they have forked tongues) and digging them up for the juicy spider or scorpion. They will also tear bits off road-kill and dead mice that fall out of unpacked swags. Like all monitors they have superb intelligence and are a challenge to approach in the wild, and even harder to film as they go about daily life.
The Black Headed Goanna (Varanus tristis) is also very often seen in and around the desert, although they tend to occupy the trees and rocky cliffs. Commonly seen on the sides of Uluru (Ayer’s Rock) and the Devil’s Marbles they feed on the eggs of birds as well as any other items they can catch on the rock faces, including other monitors. On warm days they are frequently seen on the roads and may get run over as they run straight into the path of cars as the drivers swerve to miss them. Despite the name, go further east and this species has no trace of a black head.
Snakes are also common on the desert’s edge, though in the heat are rarely seen. Driving the roads at night may very well put you in the path of this lovely little snake, the Unbanded Shovel Nosed Snake (Brachyurophis incinctus). Not at all likely to bite, it is a close cousin of all of our dangerous snakes, the Front Fanged snakes, or Elapids. Like the unrelated Scaly Foot lizard, they imitate the young of the extremely dangerous Western Brown Snake with near identical head markings. An unusual feature of all Shovel Nosed Snakes is the upturned snout, like the underside of a snow-ski. This is likely a burrowing aid, as they burrow under loose sand and gravel so common on the desert’s edge in search of the food they specialise in- lizard eggs. This is pretty much all they eat, going for bigger food items would not be such a good idea – they only grow to 40cm or less.
Finally, the last common species I will mention that is found throughout the NT, in desert and forest is a gecko that is in the running for Australia’s most widespread, competing with a type of legless lizard. The Bynoe’s Gecko (Heteronotia binoei) has no pads on the feet, instead having claws. Totally adapted for life on the ground, they behave much like a skink, although nocturnal. When a light is shone on them they race for cover rapidly, unlike most geckos which either freeze or slide slowly behind an object. This makes them easy to find at night. By day they can be found in their dozens under almost any object on the ground, especially in the desert. Some populations are female only, with females laying eggs that contain clones of themselves in a process known as parthenogenesis. This has its advantages as a single female can rapidly populate a new area, but as there is no genetic diversity, bad mutations are passed down as is lack of resistance to new diseases. Many lizards and a couple of snake species do this.
Psychedelic desert Scorpions
At night on desert’s edge, other hunters emerge. All business and no pleasure is a great way to describe the battle-tank-like scorpions. Two major types are found around the near-desert of Tennant Creek, the large brown and small mottled species. The large is very bulky and measures around 120mm from the mouthparts to the tip of the sting. Apparently the sting is painful but not deadly. I would not like to test that theory… The small mottled desert species is much more lively and measures only 50mm. It has very thin claws which in many species indicates a more powerful sting. I would also not like to test this.
Either way, the life of a scorpion is mostly violence. By day they rest in their burrow (or shoes left outside) and emerge at night to sit on the sand and ambush passing prey. They are covered in fine hairs that are almost like radar in that they can sense the movement of most prey and danger by disruptions in the air. When prey gets near, they grab it with their claws and drive the sting into it, killing it in seconds. We witnessed a fast, buzzing Hawkmoth get grabbed by a scorpion and stung. It was totally still within three seconds.
As I said, life for a scorpion is violent. Even mating is a non-contact sport, other than a grasp of claws and the pair trying to sting each other. The male deposits his package on the ground, and pulls the female over it, then makes his escape. The exception is that the mother does care for her young on her back until they are big enough to leave.
But, there is one thing about them that I do like. Scorpions, not just the desert varieties are highly fluorescent. All species have proteins in their exoskeleton that reflect UV light very brightly. Scanning the ground with a UV Blacklight makes finding them very easy as they glow green or yellow. The reason for this is unclear. It may just be a bi-product of the chemical makeup of the shell or something else. One theory is that UV light bounced off the moon and onto the scorpion will cause it to glow bright enough to attract moths, but not bright enough for us to see. Whether this is true or not remains unclear, but one thing is certain, shining the UV Blacklight on them did attract the moths in large numbers.