Why are porcupine quills hollow

MF : Okay, but back to quills. But they are. African brush tailed porcupine. The crested porcupine shown here living in captivity can grow as large as 60 pounds. They live pretty much all over the world, all different species. One of the biggest ones in Africa is like something pounds. But also, that kind of porcupine makes noise with its quills. CS : Right, when they hit each other, and then they are other quills among them that will act like a clapper and make a lot of noise.

Figure 3. Hedgehog tenrecs can roll into spiny, nearly impenetrable balls. Photo credit: Link E. Hedgehog tenrec spines are rather short and stout compared to species like the porcupine, are uniformly sized across the dorsum, and are not barbed.

At birth, the spines are already visible and protruding slightly from the skin, although they are initially soft and hair-like. The spines do not fall out easily, as the fibers of the subcutaneous muscle m.

On the microscopic level, the core of each spine consists of a series of septa, similar to true hedgehogs. However, unlike hedgehogs, the septa of hedgehog tenrecs are more closely spaced, the external walls of the spines are thinner, and there are no longitudinal stringers. During courtship and marking behaviors, Echinops often moves its body muscles rhythmically, causing its dorsolateral quills to rub against each other and produce a low sound. Figure 4. Three rows of specialized spines, as seen in the center, make up the stridulating organ in the streaked tenrecs Hemicentetes.

Tenrecs are the only mammals in the world that are known to communicate with one another through sound produced by spines. This behavior is most extensively developed in relatives of the hedgehog tenrecs called the streaked tenrecs genus Hemicentetes. Stridulation, the rubbing together of spines, produces pulses of sound between 2 and KHz humans generally hear within a range of 12 to 20 KHz.

While streaked tenrecs also produce noise from their mouths, stridulation appears to be an important form of communication because it occurs while feeding, during social contact, during courtship, during exploration, and when fighting or fleeing. Figure 5a. The tip of a juvenile common tailless tenrec spine Tenrec ecaudatus magnified x. Everson Figure 5b. Figure 5b. The shaft of a juvenile common tailless tenrec spine Tenrec ecaudatus magnified x. The common or tailless tenrec Tenrec ecaudatus has a structure similar to the stridulating organ of Hemicentetes , although it is only present in juveniles.

In the common tenrec, spines Fig. The stridulating organ is not as active in the common tenrec as it is in streaked tenrecs; the common tenrec vibrates its spines only when it is frightened, often in conjunction with the erection of quills on its neck and back, and the sound it produces occurs at a reduced frequency range 12 to 15 KHz.

In adult common tenrecs, even after the stridulating organ disappears, the fur on that area of the back vibrates rapidly when individuals are threatened or scared.

The stridulation sounds produced by tenrecs appear to be used solely for intra-species communication and not for warning predators, but the bright yellow and black stripes of spines in streaked tenrecs and juvenile common tenrecs may be aposematic -- a message to enemies to stay away! Indeed, streaked tenrecs are the only tenrecs with barbed, detachable spines for active defense. When threatened, streaked tenrecs erect a circle of menacing spines around their heads and, if necessary, buck at attackers to drive spines deep into their skin.

Although they superficially resemble a cross between the anteaters of South America and the hedgehogs of Eurasia and Africa, they are not closely related to either. In reality, they are in the order Monotremata , an ancient lineage of egg-laying mammals that contains only five living species: four species of echidna and the platypus. Of all of the spiny mammals, the quills of the echidna are perhaps the least studied. While they resemble hedgehog quills in shape — they are short, thick, and unbarbed — their structure is more akin to porcupines — the core of the quill is filled with a foam-like material.

The quills have very robust walls relative to their diameters 2 mm in diameter with 0. This and the relatively blunt tips on each quill suggest that they function as tough body armor, but future research may reveal whether echidna quills are also used in anointing, shock absorption, or one of the many other functions associated with the spiny mammals. Brockie, R.

Self-anointing by wild hedgehogs, Erinaceus europaeus , in New Zealand. Animal Behaviour, 24 1 , Caro, T. Antipredator defenses in birds and mammals. University of Chicago Press: Chicago. Contrasting coloration in terrestrial mammals. B Biol. Chapman, R. Biology of the Integument 2: Vertebrates. Like all hairs, quills do shed, and when the porcupine shakes, loose quills can fly off but without deadly force. Still, the quills can cause problems, and puncture wounds inflicted by porcupines are serious.

Having quills does not mean that the porcupine's life is trouble free. Large cats, especially lions, and human hunters bushmeat trade threaten Old World porcupines. One porcupine predator, the fisher, is able to flip the North American porcupine onto its back, exposing its unprotected belly.

In fact, the fisher has been reintroduced to some areas of North America in hopes of bringing destructive porcupine populations under control. There are still many myths and misunderstandings about porcupines, just as there were in ancient times. The philosopher Aristotle warned of the dangers of getting too close to a porcupine: the quilled beast could "shoot its deadly needlelike darts" over great distances at hunters and dogs alike.

After reading this far, you know that is not true! Old World porcupines spend their life on the ground. They are somewhat social, sometimes traveling in pairs. They find shelter in caves, rock crevices, holes, or burrows that they may have dug. They sometimes rest in abandoned aardvark holes, which they may change to suit their own needs.

Old World porcupines do not climb or jump well, but they are excellent swimmers. New World porcupines spend most of their time alone or in pairs moving through the trees. They may den in tree nests, rock crevices, brush, logs, or in tangled tree roots. All New World porcupines have long, curved claws that are excellent for climbing.

Prehensile-tailed porcupines have tails that curl around branches, anchoring them to a tree. All porcupines have a great sense of smell. To make quick work of available food, these herbivores have sharp, chisel-like front teeth. Planet Earth. A porcupine quill.

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