Here is a selection of awesome animals I saw around Pulau Weh, an island just north of Sumatra, Indonesia:
• A flying lizard with a yellow skin flap on it’s neck and fan-like wings tucked away under its body. No known lizards have powered flight, so this flying lizard like all others was a glider, but some can travel hundreds of metres while losing only a couple of metres in height. The male had a blueish head and yellow neck which it was extending, possibly to display to the less impressive, but very well camouflaged, female that was slightly lower on the tree. A similar lizard from Bogor Zoological Museum
• Millions and millions of baby, translucent crabs migrating up the river, where we walked to find a waterfall on Pulau Weh. I’m not entirely sure why they were migrating, but we followed them as they crawled across the rocks (and each other) on either side of the river. Occasionally the stream of crabs hopped into the water and swam for a short while before clambering back onto a rock as the water became too fast and choppy.
• Monitor lizards swimming in the clear, aqua-marine ocean in front of our hut and basking in the sun. Then one chasing a rival off the rocks and into the sea as it asserted its authority over a territory. Monitor lizard showdown
• Fruit bats flying between islands during and just following a storm. From our kayaks we saw around a dozen over a couple of hours. Soaring above us with a wingspan of around a metre, they flew between trees and then started munching on some fruit as they hung beneath the branches. With over 12,000 different species discovered so far, bats make up a fifth of the total number of mammal species on Earth! This they owe to their almost exclusive access to the large, nocturnal-flying niche.
The last common ancestor of all living mammals* was a nocturnal insectivore that looked something like a shrew and lived alongside the dinosaurs around 140 million years ago. Maybe it looked a little like this shrew I saw in West Java
This mammalian ancestor scraped by, living in the shadows, at a time when dinosaurs – reptiles – ruled the planet. But the Cretaceous-Tertiary (K-T) mass extinction 65 million years ago wiped out all of the dinosaurs, except the ancestors of modern birds. This allowed the mammalian clade to undergo massive diversification and to dominate the planet as it does today.
The bat lineage separated from the rest of the mammals around 80 million years ago and, with the aid of flight and echolocation, has enjoyed huge success in colonising the world. Most bats use echolocation to navigate in the dark – they emit high-frequency sound which bounces off the environment and is detected by their ears, giving them a sound scape, a mental ‘image’ of the scene. Despite the saying, most bats are not blind, and many have very large eyes which they use instead of echolocation. Our fruit bats on Pulau Weh were frequently spotted in the late afternoon navigating by sight, which they exclusively use.
Unfortunately, I’ve since learnt that some local Indonesians fly barbed wire kites to bring down these majestic fliers to put them in a soup. Across Asia, many bat species have been pushed close to extinction through human hunting activity, though smoking out caves is a more common method of capture. This illustrates one of the biggest difficulties in conservation biology – educating and convincing local people to care for the long-term survival of a species, rather than over-exploiting it to extinction (as we’ve done time and time again across the continents).
*excluding the five species of monotremes, the egg laying mammals (echidnas and platypus of Australia), which diverged earlier, maintaining their reptilian oviparity.
• Moray eels, lobsters, octopus, barracuda, sting rays and more on two scuba dives off Pulau Weh. Plus countless numbers of other fish swimming in every conceivable direction around us. And the occasional tiny sting of a jellyfish, barely visible to the naked eye.
Domestic animals reach remote islands by deliberate and accidental introduction. And domestic cats are one of the most harmful alien species you can take to a remote island, especially in places that have no large mammals of their own. This is because the native community of species are not used to living alongside such predators. Without the strong selective pressure of mammalian predators, endemic island species are able to thrive while being relatively defenceless. But throw in a handful of cats and they can quickly eat their way through a huge proportion of the naive local species.
Other invasive species that typically do serious damage to island fauna are rats, snakes, rabbits and toads. Not to mention the foreign parasites and diseases they bring with them, to which the local species have no immunity. It requires huge operations to try to rid an island of an invasive species, and often the efforts are in vain. Hence why there are such strict customs regulations in countries like Australia, where Johnny Depp recently took two un-quarantined, illegal-immigrant Yorkshire Terriers.
All pictures from this article were taken by me, except the crab photo, which was taken by my travelling companion Samuel Holdway.