Spur (zoology)
A spur is an outgrowth of bone covered in a sheath of horn found in various anatomical locations in some animals.
[2] Unlike claws, spurs are normally straight or only slightly curved, making them suited to striking or stabbing.
These spurs have a high degree of mobility and can be moved by appropriate musculature from their normal position lying along and against the body, into a perpendicular plane to resemble miniature legs.
[5][6] In at least one species, the Madagascan boa (Sanzinia madagascariensis), the spurs are also used in combat where they are erected perpendicular to the body and flexed vigorously against the scales of the opponent.
[10] In the striped legless lizard, the males can be distinguished externally from the females by spurs under each hind-limb flap.
A number of birds have spurs on their feet or legs, usually formed from the lower portion of the tarsometatarsus bone.
Contrary to this, the western sub-species, like the Merriam's, often live in rocky areas which usually means even very old birds will have spurs that have been worn off to less than 2.5 cm long.
[14] During mating in domesticated hens and turkeys, the claws and spurs of the male may often scratch and injure the back and shoulders of the female.
[15] The spur-winged goose (Plectropterus gambensis), the largest of Africa's waterfowl, has prominent carpal spurs[16] which are not visible when the wings are folded.
It is a stout, conical structure that is typically oval in cross-section, but sharp keels are present on the spur in some individuals.
It has been claimed that the spur is used in defence against predators[17] although they have also been described as "especially effective weapons" making this species "the most dangerous of all waterfowl".
This behaviour brings into view the spurs and white wing patches, and may possibly function as a simple threat display.
It has also been claimed that a number of other bird species are known to fight by hitting each other with their wings; some, including screamers, lapwings and spur-winged geese, "have evolved spurs to increase the damage they can wreak".
The larger one emerges from the extensor process, and a more distally located spur grows from near the end of the major metacarpal.
Nesting pairs defend their territory against all intruders by calling loudly, spreading their wings, and then swooping fast and low, and where necessary, striking at interlopers with their feet and attacking animals on the ground with the conspicuous yellow spurs.
The spurs are hollow and connected to a venom gland, allowing the platypus to deliver a very painful kick both in mating competitions and as a defense.
[25] The spur grows with age and seems to be developed from the secretions of the underlying gland, which may have up to 1,000 tiny ducts connecting through the skin.
