Here is an excerpt from an interesting article another BYCer provided that should become a sticky. This could explain why so many "pet", hand-raised roos become aggressive.
How is it possible for a tame pet to turn on its caretaker or other humans? First off, all avian and mammalian neonates are born with a preprogrammed drive to imprint onto their mother. Imprinting refers to a critical period of time early in the animals life when it forms attachments and develops a concept of its own species identity. Imprinting provides animals with information about who they are and for males it determines specifically who they will find attractive when they reach sexual maturity. Only a few species like cow birds and cuckoos, that are essentially parasites in another birds nest, can be reared by surrogate parents and get things right when they reach sexual maturity. The famous German ethologist, Konrad Lorenz demonstrated the imprinting process in goslings and ducklings and showed that in the absence of their real mothers these precocial birds would imprint onto their human care taker.
Imprinting has long lasting and important biological and psychological effects on adult sexual behaviour, which is often irreversible. Males that have been imprinted onto another species tend to court the surrogate species that raised them. For example, ram lambs that are raised on nanny goats will court and try to breed female goats when they reach sexual maturity and they show very little interest in ewes. The same pattern unfolds in birds. Some farm families have the embarrassing pet tom turkey who spends his entire life courting and pestering the family members that raised him. That is why in captive breeding programs for endangered species like the whooping crane or the California condor the hatchlings are raised and fed by bird puppets. The human caretakers must stay hidden from the young birds in order to ensure they are properly imprinted onto the correct species and not imprinted onto humans. Fortunately young females that imprint onto the wrong species are usually not affected and will remain attracted to the courtship displays from males of their own species. That is why ewe lambs that are raised on nanny goats will breed to rams even though their surrogate mother was a goat.
The point to remember is that orphan males of most species will imprint onto their surrogate mothers and then later in life will direct their sexual behaviour towards the surrogate species. If humans become the surrogate species it creates a potentially dangerous situation. When the male reaches sexual maturity, in addition to his misdirected attraction, he will have bouts of male aggression that he will direct against his human competition. Male aggression is a normal part of sexual behaviour. In nearly all our livestock and wild species (horses, dogs and cats may be the exception)
bottle raised intact males will show aggression towards humans when they reach sexual maturity.
Most people mistakenly believe that dairy bulls are dangerous because of their genetics. It is true that most dairy bulls are dangerous, but it has more to do with their rearing conditions then their genetics. Most dairy bulls are hand reared in isolation which contributes to their behaviour towards humans when they become adults. Dr. Ed Price, a behaviour researcher from the University of California at Davis, has shown that Hereford bull calves raised in isolation and hand fed by humans became dangerous to people when they reached adulthood, whereas their group raised counterparts where not mean towards people.
There are numerous examples of intact male animals that were wonderful pets as young animals, but grew up to become killers or potential killers of their human caretakers. When I was a child one of my neighbors was forced to shoot and kill their pet whitetail buck they had bottle raised, after it had attacked them during rut. This story is not uncommon. There were 15 deer related human fatalities over a 5 year period in the United States (Langley and Hunter, 2001); many of these were likely the result of bottle raised males. During the same time period another 142 humans were killed by cattle. Though the statistics did not state the exact circumstances, some of these fatalities were certain to have been caused by hand reared bulls. The berserk male syndrome, talked about in llama circles, whereby a male llama suddenly becomes aggressive towards people is not a syndrome per se, but the result of bottle raising the male llama. Even bottle raised ram lambs that seem so friendly and docile while growing up have been known to inflict severe injury onto their caretakers or an unsuspecting visitor (who turns their back towards them) when the ram becomes mature.
What should you do with orphan newborns? The best option is to look for other lactating females in the herd or flock who may have lost their own offspring or who have additional milk. Such females can be excellent candidates provided that they can be tricked into accepting the orphan as their own. How to get a surrogate mother to accept the newborn as her own is a story in itself. However, assuming the adoption or cross fostering is successful, this offers the best possible method for rearing the orphan since a surrogate mother will likely have the right milk composition, plus she is willing to remain on call for 24 hours a day.
The take home message is that newborn male orphans of deer, elk, bison, cattle, sheep, goats and llamas should never be bottle raised or at the very least should be castrated before reaching sexual maturity in order to avoid a dangerous and potentially lethal future situation. Please spread the word.
References,
Langley,