The owner of a tame animal however is liable only if he knows that the animal has a “mischievous propensity
” to do the damage complained of. However in the case of a dog, the owner will be strictly liable under Section 21 of the 1986 Act
if the dog bites a person. Tame animals include dogs, cats, horses, cattle but there are exceptions to this class of supposed tame animals. For example some dogs are automatically deemed dangerous, in circumstances where they are clearly used as guard dogs for security purposes. So, different rules apply depending upon whether you are the victim of a dog attack or a dog bite.
The knowledge of mischievous propensity which an animal owner must have is actual knowledge, although it does not matter whether it is acquired from personal observation, from hearsay, or through another person.
The injured Plaintiff who argues that the young foal has a tendancy to frolic and jump around people or that a dog that bounds enthusiastically at strangers will not have demonstrated a mischievous propensity to prove liability on the part of the animal owner. However it is sufficient for an injured Plaintiff to show that a dog “was always growling at children” (case of Duggan –v- Armstrong 1992)ie proof of a mischievous propensity is not that the dog will bite someone but that having displayed a vicious or fierce nature it may do so.