Peculiar partnerships and a walking sausage

 The Lord Howe Island Stick Insect and the Melaleuca Howeana.

There are some bizarre, wonderful and often disturbing partnerships that occur within the natural world. Symbiosis is when different organisms share a relationship that benefits the pair throughout their lives. But these relationships are not always terribly straightforward and can be broken into further categories and distinctions.

Over the next little while I’m going to be blogging and posting about these partnerships as there has been a lot of discussion lately in the media about the significance of one species becoming extinct. This may start to highlight why each living organism has a bigger role to play in our environment.

 One of my favourite animals in the flashcard series is the Lord Howe Island [LHI] Stick Insect. [Dryococelus australis]. One of the Earth’s most rare insects! Boy am I looking forward to going to LHI that tiny place is a hot spot for critically endangered diversity.

This six legged ‘tree lobster’, ‘land lobster’ or ‘walking sausage’ grows up to 12 cm and survives solely on the Melaleuca Howeana. This particular species of tea tree is only found on Ball’s Pyramid – a tiny extinct volcano off the east coast of Port Macquarie NSW.

Claimed to be the tallest volcanic stack in the world, Ball’s Pyramid is about 550m high, around 300m wide and 1km long. It’s so narrow that no one can land a boat on it. Instead, you have to anchor your boat in the ocean, and proceed to launch yourself onto the vertical pyramid wall and climb your way up! Many a reckless explorers risked life and limb to find a Lorde Howe Island phasmid here and bring the species ‘back from the dead.’

The leaves and sticks of the Melaleuca Howeana provide not only food but perfect camouflage from predation and without it our walking sausage would be extinct. Nocturnal, it feeds at night so it’s not taken by birds. It is still unknown how the Lord Howe Island Stick Insect managed to get to Balls Pyramid – 23 km away - as it’s flightless.

In fact!

It was thought to be extinct and is considered a “Lazarus species”

When shipwrecked rats arrived to Lord Howe Island in 1918 they totally wiped out the population. By 1960 they were officially proclaimed extinct.

However, when a couple of scientists went over to LHI in 2001 to confirm the extinction – they found a Melaleuca, on the volcanic remnant of Ball’s Pyramid and discovered what they thought no longer existed – a Lord Howe Island stick insect. It turned out that this one bush sustained the entire population – between 24 and 40 individuals. It gained the reputation of being the rarest insect on Earth, supported by a single bush.

Just how they made it from Lord Howe Island to the safety of Ball’s Pyramid is still a mystery - they might have been carried over as nesting material by the common noddy bird.

This type of partnership is called Commensalism – the stick insect benefits from the relationship and the tea tree is unaffected.

Lord Howe Island Stick Insect Flashcard