Animal welfare

The issue of rearing livestock for human benefit raises the issue of the relationship between humans and animals, in terms of the status of animals and obligations of people. Animal welfare is the viewpoint that animals under human care should be treated in such a way that they do not suffer unnecessarily. What is ‘unnecessary’ suffering may vary. Generally though, the animal welfare perspective is based on an interpretation of scientific research on farming practices. By contrast, Animal rights is the viewpoint that using animals for human benefit is, by its nature, generally exploitation regardless of the farming practice used. It is a position based on anthropomorphism, in which individuals seek to place themselves in the position of an animal. Animal rights activists would generally be vegan or vegetarian, whereas it is consistent with the animal welfare perspective to eat meat depending on production processes.

Animal welfare groups generally seek to generate public discussion on livestock rearing practices and secure greater regulation and scrutiny of livestock industry practices. Animal rights groups usually seek the abolition of livestock farming, although some groups may recognise the necessity of achieving more stringent regulation first. Animal welfare groups, such as the RSPCA, are often – in first world countries - given a voice at governmental level in the development of policy. Animal rights groups find it harder to find methods of input, and may go further and advocate civil disobedience or violence.

A number of animal husbandry practices that have led to legislation in some countries have been the subject of campaigns in the 1990s and 2000s. Confinement of livestock in small and unnatural spaces is often done for economic or health reasons. Animals may be kept in the minimum size of cage or pen with little or no space to exercise or engage in normal actions or grooming. Close confinement is most common with chickens, pigs, and calves raised for veal. Unnatural living environments may be used for some animals. Even when allowed to move, animals may be denied a natural environment. For example, ducks may be kept in free-range barns but have no access to water in which to swim. Cattle may be kept in barns with no chance to graze. Overuse of pharmaceuticals and hormones is also an issue in large agricultural operations. Intensive raising of livestock may lead to a health problems and the necessity to use antibiotics to prevent disease. In some cases antibiotics and hormones are also fed to livestock to produce rapid weight gain.

Overwork and exhaustion of animals: Where livestock are used as a source of power they may be pushed beyond their limits to the point of exhaustion. The public visibility of this abuse meant it was one of the first areas to receive legislation in the nineteenth century in European countries but it still goes on in parts of Asia. Modification to the bodies of living animals: Broiler hens may be de-beaked, pigs have deciduous teeth pulled, cattle de-horned and branded, dairy cows and sheep have tails cropped, merino sheep mulesed, many types of male animals castrated. Long distance transportation of livestock: Animals may be transported long distances to market and slaughter. Overcrowded conditions, heat from tropical-area shipping and lack of food, water and rest breaks have been subject to legislation and protest. (See Live Export) Slaughter of livestock: Slaughter was an early target for legislation. Campaigns continue to target Halal and Kosher religious ritual slaughter.

Lizards

Lizards are a large and widespread group of reptiles of the order Squamata, with nearly 5,000 species and ranging across all continents except Antarctica. Most lizards have four limbs, external ears, and a tail. Many lizards can shed their tails in order to escape from predators, although this trait is not universal. Vision, including color vision, is particularly well developed in lizards, and most communicate with body language or bright colors on their bodies as well as via pheromones. The adult length of species within the order range from a few centimeters for some Caribbean geckos to nearly three meters in Komodo Dragons

Any generic description of lizards is often complicated by the fact that many typical lizard traits are either retentions from their evolutionary ancestors (such as the basic, 4-limbed, tetrapod body form) or are either lost or changed in some species (loss of limbs, loss of external ears, loss of the tail, etc.)

Common chamaeleon Chamaeleo chamaeleon

Lizards are reptiles, and universally possess scaly skin and a skull with many fused or reduced bones. Most lizards retain the typical tetrapod body plan of a short neck, four limbs of roughly equal size ending in five toes each, a moderately long body, and a long tail. Most lizards possess external ears and have movable eyelids. Encompassing forty families, there is tremendous variety in colour, appearance and size. Most lizards are oviparous, though a few species are viviparous. Many are also capable of regeneration of lost limbs or tails. Almost all lizards are carnivorous, though most are so small that insects are their primary prey. About 120 species (3%) are known to be herbivorous.[1] A few species are omnivorous, and others have reached sizes where they can prey on other vertebrates. Many lizards are good climbers or fast sprinters. Some can run bipedally, such as the collared lizard, and some can even run across the surface of water to escape, namely the basilisk. Many lizards can change colour in response to their environments or in times of stress. The most familiar example is the chameleon, but more subtle colour changes occur in other lizard species as well, such as the anole, also known as the "American chameleon," "house chameleon" or "chamele".
Argus monitor (Varanus panoptes) at the New England Aquarium.


Some lizard species, including the glass lizard and flap-footed lizards, have lost their legs or reduced them to the point they are non-functional. However, some vestigial structures remain. Snakes, which evolved from the ancestors of monitor lizards, are characterized by lack of eyelids, lack of an external ear, a forked tongue, and having a highly elongate body (as opposed to a normal body but extremely long tail). While any given legless lizard species (of which there are many) may match on one or two of these characteristics, they invariably differ from snakes in others. For example, flap-footed lizards lack eyelids as do true snakes, but can be distinguished by their external ears.

Lizards are part of the reptile family, meaning that they have no inner means of achieving homeostatis. As a result, they must keep careful watch of their body temperature. This need requires lizards to live in areas with consistently high temperatures. Lizards are rarely seen in the upper half of the United States and most European countries.

Senses and communication
Green iguanas (Iguana iguana), are popular exotic pets.


Lizards employ many diverse methods of communication. Like many other animals, they have an acute sense of smell, detecting scents of their prey or pheromones from other lizards. The primary organ of scent in lizards is a vomeronasal organ in the roof of the mouth, and lizards gather scents by flicking out their tongues, then retracting them and delivering the captured odor molecules to this organ. Some large carnivorous lizards, such as tegus and monitor lizards, have forked tongues like snakes, to take advantage of this organ better. As a result, many male lizards possess enlarged pores on the underside of their thighs, which they rub against objects to mark their territory.

While most lizards can hear well, few are capable of vocalizations or otherwise making noise. The exception to this rule is the geckos, which communicate through a wide variety of barks, chirps and whistles, with each species having specific patterns and sounds.

Sight is quite important for most lizards, both for locating prey and for communication, and as such, many lizards have highly acute color vision. Most lizards rely heavily on body language, using specific postures, gestures and movements to define territory, resolve disputes, and entice mates. Some species of lizard also utilize bright colors, such as the iridescent patches on the belly of Sceloporus. These colors would be highly visible to predators, so are often hidden on the underside or between scales and only revealed when necessary.

A particular innovation in this respect is the dewlap, a brightly colored patch of skin on the throat, usually hidden between scales. When a display is needed, the lizards erect the hyoid bone of their throat, resulting in a large vertical flap of brightly colored skin beneath the head which can be then used for communication. Anoles are particularly famous for this display, with each species having specific colors, including patterns only visible under ultraviolet light, as lizards can often see UV.

Evolution and relationships

Frill-necked lizard Chlamydosaurus kingii

The retention of the basic tetrapod body form by lizards makes it tempting to assume any similar animal, alive or extinct, is also a lizard. However, this is not the case, and lizards are part of a well-defined group.

The first reptile was superficially lizard-like, but had a solid, box-like skull, with openings only for eyes, nostrils, etc (termed Anapsid).[citation needed] These organisms later gave rise to two new groups with additional holes in the skull to make room for and anchor larger jaw muscles.[citation needed] Those with a single hole, the Synapsids, became modern mammals.[citation needed] The Diapsids, possessing two holes, continued to diversify.[citation needed] The Archosaurs retained the basic Diapsid skull, and gave rise to a bewildering array of animals, most famous being the dinosaurs and their descendants, birds.[citation needed] The Lepidosaurs began to reduce the skull bones, making the skull lighter and more flexible.[citation needed] Modern tuataras retain the basic Lepidosaur skull, distinguishing them from true lizards in spite of superficial similarities.[citation needed] Squamates, including snakes and all true lizards, further lightened the skull by eliminating the lower margin of the lower skull opening

Relationship to humans

Most lizard species are harmless to humans. Only the very largest lizard species pose threat of death; the Komodo dragon, for example, has been known to stalk, attack, and kill humans. The venom of the Gila monster and beaded lizard is not usually deadly but they can inflict extremely painful bites due to powerful jaws. The chief impact of lizards on humans is positive as they are significant predators of pest species; numerous species are prominent in the pet trade; some are eaten as food (for example, Green Iguanas in Central America); and lizard symbolism plays important, though rarely predominant roles in some cultures (e.g. Tarrotarro in Australian mythology). The Moche people of ancient Peru worshiped animals and often depicted lizards in their art According to a popular legend in Maharashtra, a Common Indian Monitor, with ropes attached, was used to scale the walls of the Sinhagad fort in the Battle of Sinhagad.