Animal Psychopathology - Eating Disorders - Pica

Pica is the ingestion of non-nutritive substances and has so far been poorly documented. In non-human animals in the laboratory it has been examined through the ingestion of kaolin (a clay mineral) by rats. Rats were induced to intake kaolin by administering various emetic stimuli such as copper sulfate, apomorphine, cisplatin, and motion. Rats are unable to vomit when they ingest a substance that is harmful thus pica in rats is analogous to vomiting in other species; it is a way for rats to relieve digestive distress. In some animals pica seems to be an adaptive trait but in others it seems to be a true psychopathology like in the case of some chickens. Chickens can display a type of pica when they are feed-deprived (feeding restriction has been adopted by the egg industry to induce molting). They increase their non-nutritive pecking, such as pecking structural features of their environment like wood or wire on fences or the feathers of other birds. It is a typical response that occurs when feeding is restricted or is completely withdrawn. Some of the non-nutritive pecking may be due to a redirection of foraging related behavior. Another animal that has displayed a more complex pica example are cattle. Cattle eat bones when they have a phosphorus deficiency. However, in some cases they persist on eating bones even after their phosphorus levels have stabilized and they are getting adequate doses of phosphorus in their diet. In this case evidence supports both a physical and psychological adaptive response. Cattle that continue to eat bones after their phosphorus levels are adequate do it because of a psychological reinforcer. "The persistence of pica in the seeming absence of a physiological cause might be due to the fortuitous acquisition of a conditioned illness during the period of physiological insult."

Cats also display pica behavior in their natural environments and there is evidence to support that this behavior has a psychological aspect to it. Some breeds (such as the Siamese cat) are more predisposed to showing this type of behavior than other breeds, but several types of breeds have been documented to show pica. Cats have been observed to start by chewing and sucking on non-nutritive substances like wool, cotton, rubber, plastic and even cardboard and then progress into ingestion of these substances. This type of behavior occurs through the first four years of a cat's life but it is primarily observed during the first two months of life when cats are introduced into new homes is most common. Theories explaining why this behavior becomes active during this time suggest that early weaning and stress as a consequence of separation from the mother and litter-mates and exposure to a new environment are to blame. Eating wool or other substances may be a soothing mechanism that cats develops to cope with the changes. pica is also observed predominately during 6–8 months of a cat's life when territorial and sexual behaviors emerge. pica may be induced by these social stressors. Other theories contemplated include pica as a redirection of prey-catching/ ingestion behavior as a result of indoor confinement, especially common among oriental breeds due to risk of theft. In natural environments pica has been observed in Parrots, Macaws and other birds and mammals. Charles Munn has been studying Amazon Macaws lick clay from riverbeds in the Amazon to detoxify the seeds they eat. Amazon Macaws spend two to three hours a day licking clay. Munn has found that clay helps counter the tannin and alkaloid in the seeds the Macaws ingest, a strategy that is also used by Indians in the Andes Mountains in Peru.

Pica also affects domesticated animals. While drugs like Prozac are often able to diminish troublesome behaviors in pet dogs, they don't seem to help with this eating disorder. The following story about Bumbley, a wirehaired fox terrier who appeared on 20/20 as a result of his eating disorder, is taken from a book by Dr. Nicholas Dodman.

"This dog's presenting problem was light chasing (otherwise known as shadow chasing). It chased shadows for hours on end, even excavating through plasterboard walls to pursue its will-o'-the-wisp illusions...The one thing that didn't come across clearly in the show was that Bumbley ate everything in sight and the house had to be "Bumbley-proofed" against his relentless ingestion of anything his owners left around...He had already had surgery to relieve intestinal obstructions resulting from his habit and, each day, his owners reentered their house with trepidation after work, fearing that Bumbley might have eaten something else."

Dodman talks about new research relating bulimia and compulsive eating to seizural behavior in human patients. He suggests that anti-epileptic medication might be a possible treatment for some cases of pica in animals.

Read more about this topic:  Animal Psychopathology, Eating Disorders

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