Horses are sociable animals that have evolved to live in stable, tight-knit groups that we call herds. In a stable group, all relationships are well established and there is little to no conflict over resources, which makes it an ideal environment for horses to thrive in. For this reason, from a horse’s point of view, maintaining the integrity of the social group is an important survival strategy.
When a new horse arrives at a yard, the social structure of the established herd is changed, and this leads to an initial period of increased conflict and potential for aggression. While this is a normal and natural process, it carries with it the risk of injury and can be stressful for both horses and owners. With any new arrival, ensure biosecurity procedures have been followed before introducing them to other horses on the yard.
Aggressive encounters within feral horse populations are extremely low in comparison to that seen in the domesticated horse population. This is largely because domesticated do not have the same opportunities for unrestricted movement, socialisation and foraging, as feral horses do. The constraints on space, limited access to resources such as forage and lack of socialisation with other horses are all compounding factors that can lead to initial introductions being high stress situations.
Thankfully, there are ways to make the introduction of a new horse to an established herd easier – and yes, even two horses living together are an established herd!
- If possible, allow the new horse to interact with the established herd over a barrier for a day or two. This can be an adjacent stable or field, for example. If the fence is made of electric rope or tape, make sure there is enough distance between the two fields so that the horses cannot reach over and sniff or touch each other, as there is high risk of them getting their legs caught in the fence if they should strike out. You may also want to swap droppings, putting droppings from the new horse in with the herd and droppings from the herd in with the new horse. This helps each horse find out about each other through the scents in the droppings.
- For the first day or two, feed any supplementary hay or haylage to the new horse and the established herd on opposite sides of the fence so that they can eat close to each other without conflict over resources. Eating in proximity is something only horses in the same social group do, so providing such opportunities may facilitate the process of integrating the new horse into the established herd.
- If possible, remove their shoes, ideally on all four feet but at the very least on the hind feet. Studies have shown that the risk of fractures following a kick is much lower with barefoot than shod hooves.
- Once you decide that it’s time to put the new horse in the same field as the established herd, make sure all horses have eaten plenty of forage and had an opportunity to drink water before, as hunger can make aggression worse. If you don’t wish to put the new horse in with the whole herd initially, you can introduce a calm, established herd member in the new horse’s paddock first and if all is well after a few days, they can go back into the herd together. The new horse will have made a social connection and feel supported by their friend there when meeting the rest of the herd. Alternatively, if you know a member of the herd is likely to be antagonistic, they could be removed for a few hours to allow the new horse to start establishing social bonds with the other members of the herd before they are reintroduced.
- Allow as much space as possible so they can choose to stay apart if they want to. This will help them avoid conflicts and allow them to integrate on their own terms. Ideally, select a field that has grass so that they can keep themselves busy by grazing, as well as visual barriers such as trees, field shelters etc. so that they can choose to stay out of each other’s sight.
- When you first introduce the new horse, it may be beneficial to remove all limited resources such as hay and water (if in small buckets) at first, to minimize the risk of conflict, or to provide a surplus of resources (at least one but ideally several more hay nets/pile and one water bucket more than the number of horses) and spread them out evenly and far enough apart so that everyone can have access without having to get too close to each other and risking conflict, yet not so far apart that they will choose to try to graze at the same pile rather than go to the other piles.
- Allow at least two weeks for the new group member to settle in. You may see some initial aggressive behaviours, which can be a normal part of establishing a new social group. This should gradually diminish over the course of the first three days to two weeks but can take longer based on the individuals in the herd. Ideally, do as little as possible during this time to allow the horses to get to know each other and work out their relationships undisturbed. Remember, it can take several months for a new group to stabilise, so patience will be your most important tool!
Space and conflict over resources such as forage and water are two of the biggest considerations when introducing a new horse to an established herd. Herds may be kept in smaller than ideal pastures for weight management or simply because there are more horses than is suitable for the amount of space available. Ensuring that you are following stocking density guidelines (minimum of 1 acre per horse plus 1 acre) should avoid over-grazing and alleviate pressure for resources. Equally, sheltering opportunities for all horses need to be considered, so that they can avoid inclement or hot weather without conflict for space.