In the natural world, a surprising number of animals have developed the ability to swell up — whether to ward off predators, squeeze into tight spaces, attract a mate or amplify their calls. These creatures show that getting bigger is sometimes the best way to survive.
Animals that swell up or inflate
Pufferfish
One of the deadliest animals in the ocean, pufferfish contain tetrodotoxin (TTX), a lethal poison found in some bacteria in their diet. Nevertheless, they are threatened by predators like any other sea creature – and they aren’t able to escape predators as quickly as other species due to their small fins, which make them slow swimmers. Instead, they rely on puffing themselves up to make themselves too big to eat.
They do this by sucking water or air into their elastic stomachs, which – thanks to their modified gill muscles and lack of ribs – helps them swell like a balloon. This allows them to grow up to four times their usual size.
Swell shark
The swell shark’s name is a bit of a giveaway, as it is indeed a master of self-inflation. Usually a slender bottom-dweller, the swell shark will slip into a small hole or crevice if it’s threatened. Here, it will inflate its body to twice its original size and become wedged in place, making it almost impossible for the predator to reach. In open water, it can grab its tail in its mouth and expand like a rubber ring, making it difficult for the predator to negotiate.
Understandably we named it one of the weirdest sharks in the ocean!
Hooded seal
Hooded seals take their name from the inflatable hood on the head of the adult male. They also have a balloon-like sac which they can inflate from inside one of their nostrils, by shutting off a nostril valve and inflating a membrane so a bright red balloon appears from the other nostril. When shaken, this membrane is able to produce sounds and calls. It develops for acoustic signalling, so seals can attempt to warn off competing species while swimming, and is also used to attract a mate.
Twig snakes
When twig snakes are under threat, they can inflate their throat as a warning gesture – and it may then strike, delivering its highly toxic venom.
- 13 deadliest snakes: Meet the world's most venomous snakes whose lethal bites can kill a human...
- Which deadly snakes are able to crush and eat people?
Porcupinefish
Though easily confused, porcupinefish and pufferfish are distinct species, belonging to different families. Like pufferfish, porcupinefish can inflate – but they look markedly different when they do so, due to their well-developed spines.
Painted tree frog
The painted tree frog is able to produce its trademark piercing screech by inflating its vocal sac – a flexible membrane that most male frogs and toads possess. Air is released from the lungs and into the larynx, the vibrations of which emit a sound. This resonates on the membrane of the vocal sac, which helps amplify the sounds of their mating call.
Great frigatebird
During breeding season, the male great frigatebird – one of the weirdest birds in the world – will inflate their gular sac – the area of featherless skin that joins their beak to their neck. These are bright red in colour, so the courtship display of the great frigatebird is particularly eye-catching. The males will shake their heads and quiver their wings as they call out to the females.
- Meet the 10 bonkers birds that break the rules of nature
- 8 weirdest bird beaks: Discover some avian oddballs
- The 8 weirdest eyes in the animal kingdom: From creepy to cute, here are the eyes that take ordinary to extraordinary
- Nature's most bizarre creatures: These are the 10 weirdest mammals on the planet