Aquatic animal

From Wikipedia, the free encyclopedia

Animal environments are classified as either aquatic (water), terrestrial (land), or amphibious (water and land). Aquatic animals require a watery habitat, but do not necessarily have to live entirely in water. This term can be applied to aquatic or sea mammals such as those in the order Cetacea (whales), which cannot survive on land, as well as four-footed mammals like the river otter (Lutra canadensis) and beavers (family Castoridae). It also includes aquatic birds that either swim, wade or dive on the water itself and live outside the water. These include the seabirds, such as gulls (family Laridae), pelicans (family Pelecanidae), and albatrosses (family Diomedeidae), and the anseriforms, such as ducks, swans, and geese (family Anatidae).Aquatic animals can release nitrongenous wastes as ammonia.

Amphibious and amphibiotic animals, like frogs (the order Anura), while they do require water, are separated into their own environmental classification. The majority of amphibians (class Amphibia) have an aquatic larval stage, like a tadpole, but then live as terrestrial adults, and may return to the water to mate.

Aquatic animals are often of special concern to conservationists because of the delicacy of their environments.

Unwanted catches

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A side-effect of trapping is the catching of non-target animals. Skilled trappers and the use of exclusion devices such as pan-tension devices for leg hold traps and deer or rabbit stops for snares can limit this problem. One UK report stated that researchers using 1.65 mm smooth wire, instead of the larger 2 mm standard wire equipped with rabbit stops, had brown hares caught about as frequently as foxes with about half of those rabbits being released unharmed. ([9], section 2.7) The UK report goes on to say that using the larger wire and equipping the snares with rabbit stops eliminated the unwanted catch of brown hares. The catching of non-target animals can be minimized through the use of devices that exclude animals larger than the target animal. Guidelines can also advise against setting traps where domestic pets or protected animals are likely to be.[10]

Trap (O. Eng. treppe or traeppe, properly a step, as that or which an animal places its foot and is caught, cf. Ger. Treppe flight of stairs), a mechanical device for the snaring or catching anything, and especially wild animals. Traps for animals are of great antiquity, and no savage people has ever been discovered, whatever its culture scale, that did not possess some variety of snare. In the most primitive form of trap no mechanism need be present, e.g. a cavity into which the animal walks, as the pitfall of the Arabs and Africans or the snow-hole of the Inuit. Dr O. T. Mason has divided traps into three classes: enclosing traps, which imprison the victim without injury; arresting traps, which seize the victim without killing it, unless it be caught by the neck or round the lungs; and killing traps, which crush, pierce or cut to death.

Enclosing traps include the pen, cage, pit and door-traps. Pentraps are represented by the fences built in Africa into which antelopes and other animals are driven: and by fish-seines and poundnets. Among cage-traps may be mentioned bird-cones filled with cern and smeared with bird-lime, which adhere to the bird's head, blinding it and rendering its capture easy; the fish-trap and lobster-pot; and the coop-traps, of which the turkey-trap is an example. This consists of a roofed ditch ending in a cul-de-sac into which the bird is led by a row of corn-kernels. Over the further end a kind of coop is built; the bird, instead of endeavouring to retrace its steps, always seeks to escape upward and remains cooped. Pitfalls include not only those dug in the earth, at the bottom of which knives and spears are often fixed, but also several kinds of traps for small animals. One of these consists of a box near the top of which a platform is hung, in such a way that, when the animal leaps upon it to secure the bait, it is precipitated into the bottom of the box, while the platform swings back into place. Another kind of pitfall is formed of a sort of funnel of long poles, into which birds fall upon alighting on a perfectly balanced bar, to which a dish of corn is made fast. The door-traps form a large and varied class, ranging in size from the immense cage with sliding door in which such beasts as tigers are caught, to the common box-trap for mice or squirrels, the door of which falls when the spindle upon which the bait is fixed is moved. The box-trap with a simple ratchet door, allowing the animal or bird to push under the door or wires which fall back and imprison them, is alike an enclosing and an arresting trap.

There are four general classes of arresting traps, the mesh, the set-hook, the noose and the clutch.

The mesh-traps include the mesh and thong toils used of old for the capture of the lion and other large game, and the gill-net in the meshes of which fish are caught by the gills.

To the set-hook division are reckoned the set-lines of the angler, several kinds of trawls and the toggle or gorge attached to a line, which the animal, bird or fish swallows only to be held prisoner.

The noose-trap class is a very extensive one. The simplest examples are the common slip-noose snares of twine, wire or horsehair, set for birds or small mammals either on their feeding grounds or runways, the victim being caught by the neck, body or foot as it tries to push through the noose.

When the noose is used with bait it is generally attached to a stout sapling, which is bent over and kept from springing back by some device of the "figure-4" kind. This is constructed of three pieces of wood, one of the horizontal spindle on which the bait is placed, one of the upright driven into the ground, and the third the connecting cross-piece, fitted to the others so loosely that only the strain of the elastic sapling keeps the trap together. When the victim tries to secure the bait he dislodges the cross-piece and is caught by the noose, which is spread on the ground under the bait.