Australian Wildlife Episode 3 Ocean Life
Australian Wildlife Episode 3 Ocean Life
I’m sure a lot of you are keen to head to the beach while you’re in Australia. A nice relaxing trip with friends, cooling off in the water on a hot Aussie Summer’s day sounds pretty inviting. But before you go, let’s take a look at some of the fascinating animals that call Australian Waters home.
Leafy Sea Dragon
There are three known species of sea dragon, leafy, weedy and the recently discovered ruby. But today we are going to focus on the Leafy Sea Dragon.
Affectionately known as “Leafies”, many people don’t realise that they are actually a species of fish, closely related to seahorses and pipefish. Their long, delicate, leafy flaps of skin make them perfectly adapted for hiding in kelp and seaweed.
These leafy appendages are useless for movement, so they must rely on their dorsal fins, found on their backs, as well as pectoral fins, which are found behind their heads (which look a bit like ears).
They are exclusively found in the waters of south and east Australia.
They feed on plankton, small crustaceans and even other fish (but only juveniles small enough to eat) or their eggs.
The way they consume and digest food is very interesting. They have no teeth or stomach and must eat almost-constantly throughout the day. They suck in their food whole, through their snout.
They also have interesting breeding adaptations. Like seahorses, the male sea dragons are the ones who care for the eggs. But they don’t have a pouch, instead they have a spongy “brood patch” on the underside of their tails. The females deposit their eggs on this patch, the male fertilizes the eggs and the skin hardens around the eggs, securing them in place and providing them with a source of oxygen. Around 250-300 bright pink eggs will remain attached to their father for approximately 100 days until they hatch.
They have quite small territories, usually no larger than ten square metres. They stay within their territories because although their appearance is perfectly adapted for camouflage, in the open water they would stand out, particularly to humans who often seek to take them home as pets.
This is in fact, the biggest risk to their survival. In the early 90s, so many were taken as pets that their numbers became critically low, the Australian Government had to place a complete protection on them. Other threats include pollution and habitat loss.
Perhaps surprisingly, Manta Rays are classified as fish, just like the Sea Dragons.
Their name comes from the Spanish word “Manta” meaning blanket, coat or shawl, referencing their unique, flat, diamond-shaped bodies. They are sometimes known as “devil fish” due to the horn-shaped fins on their heads.
They are highly intelligent and possess the largest brain-to-size ratio of any ectothermic fish. And research indicates that they have highly developed, long-term memory.
Until recently, it was believed that there was only one extant species of manta ray. Then in 2008, DNA testing revealed that there are in fact two distinct species, the larger Giant Oceanic Manta Ray and the smaller Reef Manta Ray.
The Giant Oeanic Manta Ray spends most of its time away from land and can be found across all of the major oceans. They can grow up to eight metres (from the tip of one wing to the other) and weigh over 1500kg. They have a widespread distribution and are found worldwide in tropical and temperate waters.
The Reef Manta Ray is found in the Indo-Pacific and tropical east Atlantic Ocean and is found primarily in coastal regions, staying within the proximity of coasts, reefs or islands. They can grow up to five metres but are usually between three and three and a half metres, (from wing tip to wing tip).
They take around ten years to reach sexual maturity but that’s alright, as they live up to fifty years. The female is pregnant for 12-13 months, giving birth to just one (or occasionally two) offspring. The babies are born self-sufficient and can survive without their parents.
They are filter feeders, meaning they swim with their large mouths wide open, sifting food through tiny “gill plates” which line their mouths. They feed on plankton as well as small fish and squid.
Fun fact: a group of manta rays are called a squadron.
They are very difficult to keep alive in captivity, only a few aquariums have managed it. Often, when held in captivity they will refuse to eat and eventually die.
Both species are classified as vulnerable. This is largely due to overfishing and further hindered by their slow rates of maturation and reproduction.
Grey Nurse Shark
There are many species of shark that thrive in Australian waters. More than fifty species live in the Coral Sea, off the coast of Queensland alone.
But don’t worry! Not all sharks are scary! This particular shark is the Grey Nurse Shark but sometimes goes by the name sand tiger shark. It may look ferocious and until fairly recently, it had a fearful reputation. However, this was unwarranted. Research has found that it is only a threat to humans if provoked.
They are grey or greyish-brown in colour with a much lighter underbelly and can grow to over 3 metres long, with the largest recorded at 3.2 metres. They have small eyes and a long mouth, full of long sharp teeth.
They live in relatively close proximity to land, such as tropical reefs, coastal waters, estuaries and shallow bays. They live in all Australian waters, except around Tasmania. But are also found in other parts of the world, such as the USA, South Africa and Argentina. They prefer sub-tropical to cool temperate waters.
Their diet is made up of fish (including other sharks), squids and crustaceans. They are slow-moving and do most of their hunting on the ocean floor.
Due to their previous reputation, they were hunted for a time. As a result, their numbers have reduced and they’re now protected by both Queensland and NSW law.
Males reach sexual maturity at 4-6 years of age and females at 6-8 years. The females usually give birth to two, one metre-long, fully-independent “Pups” (or occasionally just one). They are ovoviviparous, meaning they hatch out of their eggs whilst still inside their mother. They display intrauterine cannibalism, where the young pups will eat their less-developed siblings while still in the womb, as well as unfertilized eggs.
They have one of the lowest reproductive rates of any shark, as they only give birth every 2-3 years. They are classified as vulnerable.
Blue Ringed Octopus
The Blue Ringed Octopus is a name collectively given to a group of four highly venomous species of octopus. We’re going to talk about the Greater Blue-Ringed Octopus today. They are not exclusive to Australian waters and can be found anywhere in the Pacific Ocean, from here to Japan.
Despite their name, they are actually quite small. About the size of a golf ball. Like most octopus, they have the ability to change their skin colour to camouflage into their surroundings. The “Blue Ring” in the name, refers to the 60 or so, circular shaped rings that cover their bodies. When threatened, these rings flash bright blue, warning potential predators of the octopus’ toxicity. They produces a paralysing neurotoxin which it releases through its salivary glands.
Luckily, they are not an aggressive species and will generally only bite a human if they are picked up or stepped on. So, no matter how cute and innocent they might look, if you happen across one in a rock pool, do not touch it!
Their venom is generally used for hunting prey, they pierce the exoskeleton or scales of crustaceans and small fish with their beak, inserting the venom. They then consumed the helpless, paralysed prey.
Our next ocean creature isn’t actually too distantly related to the blue ringed octopus, as they are all part of a phylum (a taxonomic category or “group” of animals) called Mollusks.
Cone shell refers to approximately 500 different species of predatory sea snails distributed throughout the Pacific and Indian oceans. You can find many of these in the waters surrounding the northern half of Australia, with 133 living in the waters of the Great Barrier Reef. National Geographic describes them as an “underwater tank”.
As the name suggests, these snails have cone shaped shells, which are brightly coloured or patterned. Some people see these pretty shells and think it’s a good idea to take them home. It’s not. It’s a bad idea.
They possess a specialized tube, known as a proboscis which they use to shoot tiny harpoons, coated in venom, into their victims. They have over 500 different components to their venom, which they mix in different combinations depending on what they need it for, for example, in defense against a predator, or for paralysing their own prey.
While there is no antivenom available, the last reported human death in Australia resulting from a coneshell sting was in 1935. Symptoms often include intense pain, numbness or tingling and in extreme cases double vision, fainting and respiratory paralysis.
Remember: If it’s a cone, leave it alone.
Australian Box Jellyfish
There are over 50 species of box jellyfish but the largest is the Australian Box Jellyfish. Their name comes from the distinctive cube shape they possess in their Medusae (Adult) life stages. They have 60 tentacles, each equipped with millions of stinging cells known as nematocysts. These are tiny harpoons attached to a bulb filled with venom that attacks the heart, nervous system and skin cells. They can grow to 38cm wide across the “Bell” and the tentacles can extend up to three metres.
They are found in Northern Australian waters, around the top three states. Specifically north of Bundaberg, Queensland and Exmouth, Western Australia.
Australian Box jellyfish are often considered to be the most venomous marine animal. The tentacles leave whip-like marks which may lead to significant scarring and victims may experience strong pain for weeks after a run in with one of these Jellyfish.
Again, it’s not as bad as it sounds. There’s only a death in Australia every 3-4 years from a box jellyfish sting. But other countries such as the Phillipines report between 20-50. So you still need to be careful.
If you do decide to head to the beach, there are a couple of rules to follow to keep you as safe as possible. Look out for red and yellow flags and always swim between them. These are set up to help you avoid dangerous currents, known as rips in addition to dangerous animals and other risks. And if you do get in trouble, swimming at a beach with lifeguards and lifesavers means they can come to your aid, if you need.
Be sure to read any and all safety signs, never swim at night, alone, after drinking or at unpatrolled beaches and if you do get into trouble, stick your hand up in the air and call for help. For further information on beach and water safety, as well as general information visit Australia.com.
As a bonus tip, remember that the sun in Australia can be quite harsh, especially in the summer months. So be sure to use SPF 50+ sunscreen and wear appropriate protection such as hat, sunglasses and long-sleeved shirts. You might be surprised about how quickly you can get sunburnt. Also, be sure to bring plenty of water with you, stay hydrated!
Thank you so much for joining me today. As always, it’s been a pleasure. We’ll see you in the next episode, bye for now!