The grassland rattleback is about the size of an otter. It is covered in an armor of thick protective plates used for defense which give it the appearance of an armadillo. The scales which form the plates are actually great mats of hollow hairs, similar to that of pangolins. The air trapped inside the hairs provides insulation against heat. Beneath the roof of scales, there is a layer of insulating pelt, and the animal has rows of spines along its flanks. The hairy plates are the rattleback's first line of defense against bushfires.In most cases hair is soft and fluffy, trapping air between its strands and acting as an insulator, to keep a mammal warm in cold climates and cool in hot climates. But hair can also be highly specialized. Porcupine quills have always been individual hairs, grown stiff, strong and pointed, while the horn of a rhino was made entirely of compacted hair. The basic protein in hair cells is keratin. In fact, it is not just hair cells which contain keratin: skin, nails, feathers, beaks, horns and hooves are also based on this one substance.
In the case of the rattleback, the keratin in its large plates has mineralized (minerals from the animal's diet have combined with the keratin to make it harder). In a fire, the grassland rattleback flattens its flameproof back plates, digging its fringe of long tough spines along its sides into the soil around its body. Hunkered down in this way, it can weather out the firestorm as it sweeps overhead.
Fireproof plating would be of little use if the grassland rattleback's eyes were not also protected, but it seems that this rodent has all bases covered. In a firestorm, it shields its eyes with a thick layer of hardened skin. When the fire has passed, the rattleback opens its eyes and surveys the damage. At worst, it will have suffered a scorched plate or two, and these are easily regrown. Of much greater interest are the charred corpses of other animals which litter the burnt ground.
Food is scarce on the Amazon Grassland and so the grassland rattleback is an opportunistic feeder. Its diet consists mainly of grass stems an buried tubers, which it digs out using its large front paws and strong claws. However, when a fire passes overhead, killing everything in its path, the rattleback is on hand to pick over the spoils. As the flames die down, the rodent helps itself to a barbecue of burnt carrion.
Another tasty protein supplement comes in the shape of carakiller eggs (as well as other kinds of eggs), laid on the ground during the wet season, when fires are less frequent. The grassland rattleback shows no fear as it approaches a nest. It simply breaks open an egg and eats it on the spot. Should the enraged mother carakiller return to the nest, the rattleback flattens itself into the soil, wedging itself into the ground with its sharp spines. Muscles at the base of the spines lock them in place, making it almost impossible for anything to dislodge it. The carakiller's beak is useless against this armor and no amount of scratching and clawing will pry the rattleback loose. Sometimes they might curl up in defense.
Rattlebacks are solitary animals, coming together only to mate. Competition for food makes them highly territorial and they defend their foraging areas by clattering their heavy back plates. The distinctive, aggressive noise warns off potential intruders. It is this rattle that gives the rattleback its name. In a territorial dispute, the loudest rattle wins and the loser retires gracefully.
The grassland rattlebacks are so highly successful in the dry grasslands that are spreading across the Amazon Basin. So much so, in fact, that they were able to migrate northwards, out of South America, into the North American Desert. There it evolved into yet another species, one adapted for life in the cold desert environment, the desert rattleback.