Aggression by mares towards people is normal during the first few days after parturition. Moderate aggression directed towards the foal is also a part of normal maternal behaviour. This behaviour is hormonally driven and usually wanes with time. The most common agonistic behaviours are bite threats and biting. Aggressive maternal behaviour may also include head threats with ears pinned, squealing, swishing of the tail, pushing the foal with the head, kick threats and kicking.
In most instances’ foals do not respond to maternal aggression, moderate aggression during suckling is usually associated with pain in the udder. Mares may be aggressive towards other horses and humans during the first few days after foaling even if they are normally gentle. The aim of this behaviour is to keep a foal away from other horses during the period in which the foal learns to recognize its dam.
Aggression toward humans or other animals, especially in confinement, can lead to foal injury. While rushing to interpose herself between the foal and perceived threat, the mare may trample or push the foal into an obstacle. Management aimed at avoiding evoking protectiveness when the foal is in a position where it might be trampled, coupled with deliberate training of the mare to accept necessary intruders usually are adequate solutions.
Because each mare is an individual, it is difficult to forecast maternal behaviour unless the mare has foaled previously. What might be normal and consistent behaviour for one mare might be abnormal for another. Mares should be familiarized with their caretakers before delivery and should have minimal contact with other strange people in the first few days post-delivery. The intensity of protectiveness typically subsides over the first few days, but some mares may persist for weeks. Injuries to the foal may be less likely in a large stall or paddock free of obstacles. In open spaces, mares are usually less inclined to accidentally injure the foal.