The pufferfish balloons and extends spikes to discourage predators. The pufferfish stretches and spikes to look bigger than its prey. Air and water can triple their size.
Pufferfish
Sea urchins have quills. Their spines repel predators. Some sea urchins are venomous and can harm humans and animals.
Sea Urchin
The thorny devil dwells in Australian deserts. Mostly ants. Their protecting spikes serve two purposes. First, it discourages. Spikes prevent birds from devouring them.
Thorny Devil
Echnida is a shy, fearful species. They behave like hedgehogs by curling up when threatened. Their muscular front legs let them dig swiftly.
Echidnas
Their soft underside is covered with quills. Hedgehog quills are flat, like porcupine quills. They're barbless like porcupines. When threatened, a hedgehog's quills rise as it rolls into a ball.
Hedgehogs
The African spiked porcupine resembles the old world porcupine and has 12 to 13-inch quills. Its quills are mostly on its back.
Crested Porcupine
Pigtails have two applications. Commonly flattened quills. Porcupine muscles contract and raise quills when threatened. Assailants are pricked by their tails.