Many animal species have specific mating (or breeding) periods . ( seasonal breeding ) so that offspring are born or hatch at an optimal time. In marine species with limited mobility and external fertilisation like corals , sea urchins and clams , the timing of the common spawning is the only externally visible form of sexual behaviour. In areas with continuously high primary production , some species have a series of breeding seasons throughout the year. This is the case with most primates (who are primarily tropical and subtropical animals). Some animals ( opportunistic breeders ) breed dependent upon other conditions in their environment aside from time of year.
New discoveries in a broad range of fields—gene therapy, epigenetics, neural prosthetics, pharmacotherapy, regenerative medicine—highlight the avenues by which animal studies contribute to our understanding and ability to improve human and animal health. It may be that the public ultimately decides that the benefits are not worth the cost of using animals in research. Our responsibility as scientists is to make sure that the decision is based on accurate information and thoughtful consideration of the full range of issues involved in this complex topic. Scientists engaged in animal research certainly cannot accomplish this alone. They are, however, among those who see the potential implications of the recent IOM and NIH actions concerning chimpanzee research. These actions are not a single, limited case of restricting animal research for which there is nearly universal agreement; rather they may be another step along a trajectory that leads to the end of all animal research.
Horses learn through both positive and negative reinforcement. Through negative reinforcement (still today a horse training standard) a horse performs an action in order to avoid something unpleasant, such as moving away from pressure. Through positive reinforcement, a horse learns to perform a behavior in order to receive something he desires, such as food, stroking, or praise. The horse becomes an active participant, eagerly seeking out the right answer. Dull horses brighten, sour horses turn sweet, and the underachiever suddenly moves to the head of the class.