Rage Disorders in Animals
A number of genetic, physiological or psychological condition can cause animals to become severely aggressive and potentially dangerous. The conditions generally fall into a few categories.
1) Extreme but functional aggression such as territorial defence (e.g. Africanised honey bees).
2) Abnormal aggression cause by early life experiences when animals are not habituated to stimuli or not taught appropriate behavior (e.g. hand-raised animals).
3) Abnormal aggression cause by genetic factors such as those causing seizures, or causing hyper-reactivity to stimuli (e.g. Springer Rage).
4) Abnormal aggression cause by disease, toxins or other vestors (e.g. Rabies).
A few of the more common or prominent examples of conditions that cause extreme aggression in animals are discussed below. Many of the most studied and discussed rage conditions are found in purebred domestic dogs.
Genetically Influenced Conditions
is a popular name for a genetically influence behavior problem that occurs in Springer spaniels (a.k.a. Rage Syndrome, Sudden Onset Aggression, Avalanche of Rage Syndrome). It's a very rare condition shown in Springers and sometimes in other dog breeds including the Cocker Spaniel, Bernese Mountain Dog, Dobermans, Bull Terriers, German Shepherds, Golden Retriever and Papillon.
The effected animal will experience bouts of sudden and uncharacteristic aggression. This syndrome is distinguished from normal aggression in that it occurs sudden, for no apparent reason, is difficult to interrupt and during and afterwards the dog my seem confused and disoriented. At this point the basis for the problem is not known but it shows patterns of inheritance that suggest a genetic cause. It is speculatively considered to be a form of seizure disorder similar to epilepsy.
Red Coat Cockers
It was initially noticed that red-coated Cocker Spaniels were disproportionately involved in aggressive incidents. It has been suggested that Cocker Spaniels are somewhat more prone to impulsive and spontaneous aggression, especially those that are red-coated. However most people still find them to be a good breed to keep as a family pet. The basis for the color / temperament correlation is not known, but may relate to the production of melanin which effects both coat color and the brain.
Killer bees are hybrids of the African Honey Bee that are known for their aggressiveness. The African Bee was first released in Brazil and has since been spreading around the world and former more aggressive hybrids in many different countries, leading to increased and more sever attacks by bees on humans.
While the stings of these bees are no more toxic than of other types, their behavior means that humans and other animals are more likely to be attacked more rapidly and stung more times when the bees attack. This can lead to serious and even lethal responses such as kidney failure.
Thee African bees are not really abnormal, they are simply an completely undomesticated lines of bees. By breeding with tamer bees they bring the species back closer to its more aggressive wild type. Bees in other areas have not only been eradicated when the became a nuisance, but intermittently kept in beehives where only the tamer bees will survive--thus changing the temperament of the species.
The following examples all seem to share hand-raising by humans as a causal factor. The hand-rearing may either cause these animal to lose all their fear or people, or to categorized humans differently so they start to be seen as direct rivals for resources such as food and mates.
Llama Berserk Male Syndrome
Also known as "Aberrant Behavior Syndrome", Berserk Male Syndrome described a behavioral problem that been known to cause in male llama, making them very aggressive. Some animals have been euthanized as a result. Treatment can be carried out, generally in the form of gelding and corrective training. This condition may be associated with animals who have been hand reared and handled by people not familiar with large livestock. Despite this recognized problem llamas only very rarely cause serious injury.
Another species where hand-reared animals are known to sometimes become very aggressive is the common domestic cat. It is thought this had to do with missing maternal experiences, such as during weaning--so these animals may react aggressive even to slight frustrations.
Other types of animals where hand-raising has been associated with heightened aggression includes parrots, deer (especially bucks) and cattle (especially bulls).
One suggested cause of this problem is that the males are raised with a blurred idea of species boundaries. Thus when they become mature, humans are seen as sexual rivals. For this reason it is often recommended that males of large species that are hand-raised should be castrated or gelded.
It is also considered a good idea to raise orphans with others of their own species rather than in isolation.
Natural Biological States
Males of many species with become extremely aggressive during mating season when they are competing with other males for the attention of females. This includs stags is rut and elephants in musth. While these behaviors can be extreme it mustbe remembered that they are part of a normal process. Animals in rut should be avoided whenever possible.
Rabies is a virus that can in fact a wide range of mammals including dogs and humans. Rabies is often detected in wild animals because they become unusually aggressive. The virus changes the animals behavior in order to be transmitted to new hosts via the bite.
Without immediate and extensive treatment Rabies is usually fatal. For this reason there are ongoing campaigns to encourgae vaccination of anials and other preventative measures (e.g. World Rabies Day)
The Effect of Substances
A number of toxins are known to increase aggression including lead. In some animals such as squid, female pheromones can spark extreme aggression in males.
Other substance may cause aggression when their levels are too low, such as glucocorticoid.
Outside of recognized disorders there are genes being discovered that are associated with families prone to impulsively aggressive and/or criminal behavior, such as a variant of the HTR2B gene identified by a study in Finland.
General aggression is seen as being largely a letter of temperament or upbringing, but there is also a genetic aspect even to the normal range of aggressivity.