![]() Pica is the ingestion of non-nutritive substances and has so far been poorly documented. Similar effects have been observed in overcrowded situations in jack rabbits and deer. Male beetles lose interest in the females and although there is plenty of water and food, there is no population growth. When overcrowding occurs, female beetles destroy their eggs and turn cannibalistic, eating each other. Similar effects have also been observed in dense populations of beetles. Even though there was plenty of water and food, the rats stopped eating and reproducing. The population reached a number of individuals and did not grow thereafter overcrowding produced stress and psychopathologies. Studies on the effects of overcrowding were conducted in the 1940s by placing pregnant Norway rats in a room with plenty of water and food and observing the population growth. Affected sows have poor appetite but often show pica, excessive water intake (polydipsia) and are anemic. It is also likely that two subordinate sows make up part of the group who actively avoid competitive feeding situations and are bullied by the dominant sow. When placed into groups they fight vigorously, with one dominant sow emerging that eats voraciously. ![]() However, increased movement and freedom is also stressful for adult sows, which is usually the case after weaning. The sows that experience the most restraining conditions are those lactating or pregnant as they have very little room to move around because they are kept in barred gestation crates or tethered for the 16 weeks of pregnancy which prevents natural and social behaviors. Stress in stalled sows is often perceived as the consequence of the restraint of animals that happens in intensive production units. The syndrome may mainly be related to social and environmental stressors. They experience emaciation, hypothermia, a depraved appetite, restlessness, and hyperactivity. Thin sow syndrome (TSS) is a behavior observed in stalled sows that is similar to AA where some sows after early pregnancy are extremely active, eat little, and waste away, resulting very often in death. Rhesus macaque males become hyperactive in response to long-term chronic food restriction. The effect of semi- starvation on activity has also been studied in primates. Laboratory rats therefore run (forage) more in response to food shortages. One theory is that running simulates foraging, a natural behavior in wild rats. Results support the notion that the running interferes with adaptation to the new feeding schedule and is associated with the reward system in the brain. In fact, if rats are first trained to the feeding schedule and then given unrestricted access to a running wheel, they will not develop AA behavior. Also, if rats are restricted both in food intake and wheel access, they will adjust accordingly. Unrestricted food access and restricted wheel access will not cause any significant change in either feeding or exercise routine. In other conditions, AA does not develop. The running cycles shift so that most of the running is done in hours before feeding is scheduled. However, if food intake is restricted and wheel access is unrestricted, rats begin to exercise more and eat less, resulting in excessive weight loss and, ultimately, death. When given free access to food and an exercise wheel, rats normally develop a balanced routine between exercise and food intake, which turns them into fit rats. The expectation is that farm animals also display this behavior, but questions arise if the same principles apply to laboratory and pet animals.Īctivity anorexia (AA) is a condition where rats begin to exercise excessively while simultaneously cutting down on their food intake, similar to human anorexia nervosa or hypergymnasia. Evolutionary fitness drives feeding behavior in wild animals. However, domesticated animals including farm, laboratory, and pet animals are prone to disorders. This article provides a non-exhaustive list of animal psychopathologies.Īnimals in the wild appear to be relatively free from eating disorders although their body composition fluctuates depending on seasonal and reproductive cycles. But animal psychopathologies can, from an evolutionary point of view, be more properly regarded as non-adaptive behaviors due to some sort of a cognitive disability, emotional impairment or distress. Historically, there has been an anthropocentric tendency to emphasize the study of animal psychopathologies as models for human mental illnesses. Animal psychopathology is the study of mental or behavioral disorders in non-human animals.
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