If you have read my Author Notes you will have noticed that I have decided to give my fictional echidnas, and Knuckles in particular, some true echidna attributes.
In overall appearance, Knuckles bears little resemblance to the creature he was based on. I personally believe he was based at least in part on the Tasmanian devil, with their aggressive personalities and obvious white markings. Appearances aside, Knuckles is actually very much an echidna. They are solitary, almost freakishly strong creatures, capable climbers, fantastic diggers and adept swimmers (a trait Knuckles picked up in Sonic Adventure 2). They are not, however, the slightest bit territorial.
Echidnas are a truly remarkable, and highly unusual species that have walked this earth, virtually unchanged, since the time of the dinosaurs. That's around one hundred million years! Kind of helps to explain why they've become the most advanced civilization on Mobius. They are one of only three monotremes (more on the other two later). Basically, these animals have a single body opening used for both the expulsion of waste and reproduction.
It is generally accepted that Knuckles was based on the Tachyglossus Aculeatus, or short-beaked echidna. The name, translated from the Latin, means "quick-tongued, provided with spines" (which I have always found a rather fitting description of Knuckles' overall character). This animal is native to Australia and the lowlands of Papua New Guinea, and can be found in just about every environment, from coastline to desert, though they prefer a more temperate climate.
The name 'echidna', which you must admit, rolls off the tongue far more easily than Tachyglossus Aculeatus, was inspired by a monster from classic Greek Mythology. Echidna (who has appeared in both Universal's Hercules - The Legendary Journeys and Disney's animated Hercules series (based on their animated film), though neither version is particularly accurate) was considered the mother of all monsters, and she was to many. Half nymph, half serpent, she was a beautiful ageless woman from the waist up, but bellow the navel, she was a snake. Due to the echidna's strange mesh of mammalian and reptilian traits, the name was chosen for the strange little creature.
It is roughly the size of a cat, with a long slender snout, small, almost beady eyes and a coat of thick, and very sharp, spines. Echidna spines are so strong and sharp that the Aboriginal people use to use them for removing thorns and splinters.
Each comes equipped with a set of 20 strong claws (yep, that means five on each foot), mostly used for digging, and tearing open termite nests (their favourite food...no grapes for these guys...), digging for ants and burrowing for worms.
The tongue is also quite remarkable. Measuring about fifteen to eighteen centimetres long, it is extremely sticky and flexible. When feeding, the tongue will flick in and out of the mouth about a hundred times a minute, the prey getting trapped in its sticky coating. The echidna then draws its tongue back into its tiny mouth (with a gape of about five millimetres), where the food is crushed against the roof of the mouth for digestion, due to the fact that echidnas have no teeth.
Males generally also have a wicked looking spur on each ankle. This is not an accurate way to determine the sex of an echidna, however. All echidnas are born with spurs, probably to help in their hatching, but females usually shed them, however, some ladies retain this nifty accessory. Unlike their cousin, the platypus, echidna spurs contain no venom and serve no real purpose.
In fact, it is almost impossible to differentiate between echidna genders. Even picking them up (which I wouldn't recommend) won't help, as the external anatomy is pretty much identical (not a "rude bit" in sight). Both males and females also possess the muscle ridges on their bellies which will develop into the pouch during the mating season. The echidnas themselves have no trouble in this particular area, which is a good thing for the continuation of the species.
They are also extremely strong, and it can be very hard to keep one captive. They'll tear through practically anything with their strong claws, or pry open the toughest door with their sturdy snouts, not even caring if they're injured in the process. They love their freedom that much. They are also very capable climbers, using both claws and spines to get a grip on their situation. Though they are easily imprisoned in a plastic garbage can or a simple sack tied with a rope where they can get no leverage. They are extremely shy and solitary creatures, and it is very hard to see one in the wild. Their primary sense is not vision like most mammals, even though their eyesight is quite good. They rely more on smell and, rather unusually, touch. They can feel vibrations in the ground, so they know when something's coming their way long before they're spotted. Their usual way of dealing with such occurrences is to dig straight down, and remove themselves from harm's way.