LIONS VS HYENAS ENDLESS WAR NATIONAL GEOGRAPHIC – NAT GEO WILD

Regulations require that scientists use as few animals as possible, especially for terminal experiments.[136] However, while policy makers consider suffering to be the central issue and see animal euthanasia as a way to reduce suffering, others, such as the RSPCA, argue that the lives of laboratory animals have intrinsic value.[137] Regulations focus on whether particular methods cause pain and suffering, not whether their death is undesirable in itself.[138] The animals are euthanized at the end of studies for sample collection or post-mortem examination; during studies if their pain or suffering falls into certain categories regarded as unacceptable, such as depression, infection that is unresponsive to treatment, or the failure of large animals to eat for five days;[139] or when they are unsuitable for breeding or unwanted for some other reason.[140] Methods of euthanizing laboratory animals are chosen to induce rapid unconsciousness and death without pain or distress.[141] The methods that are preferred are those published by councils of veterinarians. The animal can be made to inhale a gas, such as carbon monoxide and carbon dioxide, by being placed in a chamber, or by use of a face mask, with or without prior sedation or anesthesia. Sedatives or anesthetics such as barbiturates can be given intravenously, or inhalant anesthetics may be used. Amphibians and fish may be immersed in water containing an anesthetic such as tricaine. Physical methods are also used, with or without sedation or anesthesia depending on the method. Recommended methods include decapitation (beheading) for small rodents or rabbits. Cervical dislocation (breaking the neck or spine) may be used for birds, mice, and immature rats and rabbits. Maceration (grinding into small pieces) is used on 1 day old chicks. High-intensity microwave irradiation of the brain can preserve brain tissue and induce death in less than 1 second, but this is currently only used on rodents. Captive bolts may be used, typically on dogs, ruminants, horses, pigs and rabbits. It causes death by a concussion to the brain. Gunshot may be used, but only in cases where a penetrating captive bolt may not be used. Some physical methods are only acceptable after the animal is unconscious. Electrocution may be used for cattle, sheep, swine, foxes, and mink after the animals are unconscious, often by a prior electrical stun. Pithing (inserting a tool into the base of the brain) is usable on animals already unconscious. Slow or rapid freezing, or inducing air embolism are acceptable only with prior anesthesia to induce unconsciousness.Basic or pure research investigates how organisms behave, develop, and function. Those opposed to animal testing object that pure research may have little or no practical purpose, but researchers argue that it forms the necessary basis for the development of applied research, rendering the distinction between pure and applied research—research that has a specific practical aim—unclear.[143] Pure research uses larger numbers and a greater variety of animals than applied research. Fruit flies, nematode worms, mice and rats together account for the vast majority, though small numbers of other species are used, ranging from sea slugs through to armadillos.[144] Examples of the types of animals and experiments used in basic research include: Studies on embryogenesis and developmental biology. Mutants are created by adding transposons into their genomes, or specific genes are deleted by gene targeting.[145][146] By studying the changes in development these changes produce, scientists aim to understand both how organisms normally develop, and what can go wrong in this process. These studies are particularly powerful since the basic controls of development, such as the homeobox genes, have similar functions in organisms as diverse as fruit flies and man.[147][148] Experiments into behavior, to understand how organisms detect and interact with each other and their environment, in which fruit flies, worms, mice, and rats are all widely used.[149][150] Studies of brain function, such as memory and social behavior, often use rats and birds.[151][152] For some species, behavioral research is combined with enrichment strategies for animals in captivity because it allows them to engage in a wider range of activities.[153] Breeding experiments to study evolution and genetics. Laboratory mice, flies, fish, and worms are inbred through many generations to create strains with defined characteristics.[154] These provide animals of a known genetic background, an important tool for genetic analyses. Larger mammals are rarely bred specifically for such studies due to their slow rate of reproduction, though some scientists take advantage of inbred domesticated animals, such as dog or cattle breeds, for comparative purposes. Scientists studying how animals evolve use many animal species to see how variations in where and how an organism lives (their niche) produce adaptations in their physiology and morphology. As an example, sticklebacks are now being used to study how many and which types of mutations are selected to produce adaptations in animals’ morphology during the evolution of new species.