Hawai'i is home to a vast number of species found nowhere else on Earth, many of them endangered or threatened. The reason for both its richness and its fragility is the same: isolation.
The Hawaiian archipelago sits over 2,000 miles from the nearest landmass, meaning every species that lives here arrived by wind, wave or wing – and then evolved entirely on its own terms, cut off from the rest of the world. Geese lost their webbing and started mooing. Bats crossed an ocean no bat had ever crossed. Squid learned to project moonlight.
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These are some of the most unusual animals the islands have to offer.
Weirdest animals in Hawai'i
Reef triggerfish (Rhinecanthus rectangulus)
This colourful fish is also known as humuhumunukunukuapua’a, meaning ‘triggerfish with a snout like a pig’ in Hawaiian. When threatened, it uses its dorsal spine to lock itself into small crevices in the reef, a behaviour known as wedging. This is both a defence against predators and something the fish uses to rest at night. The spine locks upright and can’t be pushed down unless a second smaller ‘trigger’ spine is pushed down first.
When faced with a predator, reef triggerfish produce pig-like grunting sounds. The grunts aren’t just noise; they’re thought to warn nearby triggerfish that danger is close.
Hawaiian happy face spider (Theridion grallator)
This spider gets its name from the smiley face pattern on its abdomen – although the patterns differ across the Hawaiian Islands. The happy-face spider is polymorphic, meaning it exhibits different characteristics across the same species. Some of those spiders even lack the markings altogether.
This species not only comes in many variations of patterns, but they also change colour depending on the spider’s diet, which is a rare behaviour.
Its varying appearance and colouring are thought to be a survival tactic to avoid predators like birds, who will use a particularly abundant colour to identify possible prey.
Brahminy blind snake (Indotyphlops braminus)
The Brahminy blind snake is one of the smallest snakes in the world. It’s non-venomous and looks a lot like an earthworm. It’s usually about 2-4 inches long, with a head and tail that look almost identical. Its eyes are tiny dots hidden under scales, making it almost completely blind.
These snakes are also called ‘flowerpot snakes’ due to their habit of hitching a ride in flowerpots with the plant trade. That’s how they might have arrived in Hawai'i in 1927.
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All Brahminy blind snakes are female. The species is parthenogenetic, meaning they reproduce by laying eggs that hatch without fertilisation. It only takes one snake to produce countless generations.
While most snakes devour prey headfirst and whole, the Brahminy blind snake demonstrates an interesting tendency to decapitate termites before eating them.
Hawaiian Hoary Bat (Lasiurus semotus)
Hawai'i has no native snakes, land reptiles or land amphibians. But it does have a native mammal. Also known as ʻōpeʻapeʻa, this species of bat is the only extant and native terrestrial animal there.
It first landed in the islands 10,000 years ago, and to do that, it had to travel over 2,000 miles of ocean. Unlike birds, bats don’t usually fly such long distances – but scientists think the bat was aided by strong trade winds. Among the over 1,300 bat species, this is the single longest overwater flight followed by a founding of a new population.
It’s a small bat, about 30 per cent smaller than its North American relatives, with brown and grey fur tipped with white, giving it a frosted appearance. This is where both its names come from: ‘hoary’ means frosted, while ʻōpeʻapeʻa refers to the shape of its wing, resembling a half taro leaf – or the sail of a traditional Hawaiian canoe.
Oriental flying gurnard (Dactyloptena orientalis)
The flying gurnard owes its name to its winglike fins, although it’s completely misleading – flying gurnards don’t fly, but walk. On its undercarriage, pelvic fins with finger-like spines hold the fish off the bottom, moving like legs, allowing it to stroll around the ocean floor.
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During this stroll, it keeps the giant pectoral fins folded at its sides. When alarmed, it spreads them wide, going from three to 14 inches wide, and walks in circles – a bluffing display complete with false eyes to confuse predators. If that fails, it bolts.
Trumpetfish (Aulostomus chinensis)
In Hawai’i, the trumpetfish is known as nūnū. It has a tubular snout and an elongated body growing up to 80cm in length.
This fish is a clever hunter, employing two techniques to catch prey. The first is ambush – lying in wait for potential prey to get close. The second is more cunning and involves discreet tracking of bigger fish, waiting for an opportunity to strike. And when it does, it attacks with a short darting movement, sucking up the prey with an expansion of its tubular snout.
Hawaiian bobtail squid (Euprymna scolopes)
The Hawaiian bobtail squid is a small cephalopod, reaching a mantle length of about 3.5 centimetres – roughly the size of a golf ball.
It’s found in shallow coastal waters off Hawai'i. During daylight hours, it remains hidden by burying itself in the sediment and going as far as gluing sand grains to its body to form camouflage.
Also for the purposes of camouflage, this squid creates an extraordinary light show. It’s able to become ‘invisible’ thanks to a symbiosis with bioluminescent marine bacteria called Vibrio fischeri, which lives inside its light organ, located in the mantle.
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Predators will often use shadows cast by prey to locate them. Sensors on the squid’s mantle measure the intensity of moonlight and project an equal beam from their light organ. The brightness below is matched to that above – so all the predator sees is what looks like a single unbroken moonbeam. And the squid is left in peace.
Hawaiian goose (Branta sandvicensis)
Also known as the nēnē, this is the famous official state bird of Hawai’i, exclusively found on the islands of Maui, Kaua’i, Moloka’i, and Hawai’i.
Based on fossil DNA, the nēnē is closely related to the Canada goose, which is thought to have arrived on the archipelago over 500,000 years ago. With no need to migrate and no large predators to flee, the goose gradually lost much of its toe webbing, replacing the paddle-like feet of a water bird with toughened, gripping toes better suited to walking on hardened lava fields.
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It stopped breeding in summer like its North American relatives and switched to winter instead. It became semi-terrestrial, spending most of its life on land.
Today the nēnē is one of the rarest goose species in the world – the sole survivor of at least five goose species that once lived on the islands. Its Hawaiian name comes from its soft call, which sounds less like a goose and more like a cow.
Top image: a lava covered seashore and palm trees on a tropical island. Credit: James Keith/Getty Images
