A sea pen may look like an underwater quill, but it's actually a colony of individual polyps — one polyp becomes the stalk of the sea pen and the bulb that attaches it to the sea floor, while the rest form feathery branches. Some sea pens have only a few polyps, while others have as many as 35,000.

The large-billed tern uses its disproportionately long and thick beak to catch fish — either by plunge-diving into the water or skimming the surface with its beak as it flies. It has a commensal relationship with the tucuxi river dolphin, which often flushes fish towards the surface while hunting.

A female Pacific blackdragon is ~60 cm (2 ft) long and uses a bioluminescent lure on her chin to attract prey. Her skin is 'ultra-black', among the darkest in nature, and her teeth are anti-reflective, so as not to reflect light from her lure and alert her prey. The male is only ~8 cm (3 in) long.

The common reed frog exhibits extreme variation in colour patterns — with some 50 recognised subspecies. Additionally, this frog changes the colour of its skin according to weather and temperature, turning pure white in the heat of the dry season.

Endemic to Fiji, the golden fruit dove exhibits remarkable sexual dimorphism — the female is forest green while the male is a brilliant golden yellow. This dove lives in the canopy and is more often heard than seen, producing dog-like barking, low growling, and snoring noises.

Endemic to Japan, the Japanese badger — like other badgers — lives in underground dens called "setts". However, the Japanese badger is known to be more solitary, with even mated pairs often living in separate setts. It is currently unknown why this is the case.

The palm-nut vulture is unusual among vultures, in that about 70% of its diet is vegetarian — mostly consisting of palm nut fruits. It was once called the "vulturine fish eagle”, because of its eagle-like appearance and the way in which it hunts; swooping to the water's surface to grab fish.

The giant otter shrew is named for its resemblance to both an otter and a shrew, despite not actually being either. It hunts nocturnally in forest pools and streams, swimming with a laterally flattened tail, like that of a fish or crocodile — an unusual swimming method among mammals.

A remora uses the sucking disk on top of its head to attach itself to larger marine animals like sharks, rays, and sea turtles — where it can stay for 3 months. The host provides the remora with protection, food, and a fast flow of water over its gills, which the remora needs in order to survive.

A silkworm wraps itself in a fluid substance from its silk glands that hardens to become a cocoon — this cocoon can be unravelled to a single strand reaching lengths of 1.5 km (1 mile). Inside, it "digests" its own larval body (called histolysis) before building up the body of a silkworm moth.

The coconut octopus carries seashells or coconut shells beneath its arms as it travels — using a few of its arms to hold the shells and the others to walk awkwardly along the sea floor. If this octopus encounters danger, it assembles the shells around itself, forming a kind of armour.

The Titicaca water frog lives solely in the depths of Lake Titicaca in the Andes mountains at elevations of 3,810 metres (12,500 feet). Its copious skin folds allow it to breathe — through cutaneous respiration (skin breathing) — at such high altitudes, its lungs are only 1/3 the size they should be.

The dwarf mongoose — Africa's smallest carnivore — uses old termite mounds as shelter, living with a family of up to 30 individuals. When foraging for insects, these mongooses work together with hornbills; the mongooses flush out insects and the hornbills watch for aerial dangers.

The common cockchafer spends its first 3 to 5 years below ground, growing as a larva. Then, all at once, these beetles emerge as adults in great numbers during spring. They clumsily buzz about, using their frilly antennae to find mates and reproduce — they live for only 6 weeks in this form.

The Amazon milk frog isn't named for its milky white appearance, instead, its name refers to a poisonous milky substance that it secretes when threatened. It also uses the fluid as "sunscreen" — lathering it over its body to prevent itself from drying out in the sun.

The common snake-necked turtle has a serpentine neck that can grow to more than half the length of its 28 cm (11 inch) long shell. It uses this neck to snatch prey underwater. When it strikes, it quickly lowers a bottom jawbone, creating a vacuum that sucks the prey into its mouth.

The snowy sheathbill is an Antarctic scavenger. It eats anything it can find or pilfer; from faeces to regurgitated penguin chick food and even elephant seal milk straight from the teat. It often stands on one foot to reduce heat loss — a technique that also makes it quite clumsy.

The pancake tortoise's shell is uniquely flat and flexible. While this lightweight armouring doesn't offer much defence, it does make it the fastest of all tortoise species. When in danger, it will swiftly wedge itself in between rocks.

The Devils Hole pupfish is perhaps the rarest fish in the world. It lives in the desert; its entire population is found in one 33.8°C (93°F) pool — mostly on a 3.5 by 5 m (11 by 16 ft) rock shelf — inside a cave in Death Valley, Nevada.

The white-tailed tropicbird performs noisy, aerial displays — swaying its tail streamer from side to side while gliding through the sky. A male courts a mate by flying above her and touching his tail to hers, they then glide away together in synchronized zigzag flight to find a nesting spot.