Walking along the tracks of Lord Howe Island’s palm forests was a strange experience. All I could hear was the wind through the palm leaves, the sea and the occasional rustle. At home when I hear rustling, it’ll be a brush turkey, a goanna, a snake, maybe a frog or three, or one of many, many birds. In the same month (November) at home, there’s also the ear-splitting stridulations (love that word) of cicadas en masse.
On daytime Lord Howe, the rustle might be one of half a dozen birds or a feral black rat, but that’s about it. Apparently the cicadas (the one endemic species) set in later in the year, but when I was there was very little animal noise.
A friend who’s been to Tahiti says it’s the same in the forests there. It’s a real lesson in how few species make it to isolated islands and, if they survive and breed, what happens to them when introduced predators (people, pigs, rats, cats, goats) turn up.
Studies have been done on newly emerged volcanic islands where there is virtually nothing but cooled lava – the first thing that arrives is spiders, tiny ones who have been floating around in the upper atmosphere and then settle on the island. Seeds wash up or are deposited by birds. Lizards wash up on bits of floating vegetation. A bit of soil appears, and, if everything gels, island life is off and running. (Of course, this is a very simplified version of events.) Birds may fly in or be blown in by storms. Seabird species may find that breeding on islands protects their eggs and chicks from predators. Some birds are able to evolve from mainland species into their own species, as I mentioned here. You can see a species list of LHI birds here. The more variety of species of everything (biodiversity), the more is able to live on the island – up to a certain point. Physical factors, weather, food availability, breeding success or otherwise, competition and cooperation continually interact to form a dynamic whole.
So it may have been with volcanic Lord Howe. The small size of the island does not allow for a large biodiversity compared to the mainland, but it’s doing pretty well, considering. Yet the silence is telling.
For instance, on Lord Howe, there are only two native lizards: the Lord Howe Island southern gecko (Christinus guentheri, also found on Norfolk Island) and the Lord Howe Island skink (Oligosoma lichenigera). Both as listed as ‘vulnerable’ due to predation by introduced black rats.
There’s only one native mammal there – the large forest bat (Eptesicus sagittula). Another bat was identified from a lone skull (Nyctophilus howensis), but no living ones have been found.
There are about 50 species of land snails, but they are pretty quiet even when alive (although if you’ve ever heard the magnified sound of a land snail munching a lettuce, like here, you’ll know it probably terrifies any plants around).
… and especially when extinct …
You can find out more about Lord Howe land snails here.
Lord Howe Island phasmids (see my previous post here) used to come out to feed at night before introduced black rats exterminated them. The phasmids still do come out on nearby Ball’s Pyramid, but they are pretty quiet both day and night.
The Lord Howe Island woodhen (Gallirallus sylvestris) was almost exterminated by rats, but due to last-minute conservation efforts their numbers are healthy. You can often hear them scratching around in the forest.
According to the document here, nine species of birds are presumed extinct, due to rats.
There are no snakes or dangerous spiders except the imported red back (Latrodectus hasseltii).
Most unexpectedly from my point of view, there are no native frogs (but the bleating tree frog, Litoria dentata, is a pest introduced from the mainland in the imported fruit and veggies – bleaters are common at home).
According to this document, about 100 species of spider have been identified. The golden orb weaver (Nephila plumipes) is easy to see in its large, strong webs (see this photo taken on the island) and I saw only one other species …
So if you go out in those woods today, you’re in for a big surprise. It’s quiet in there.