When we think of a traditional farm, we often visualize a red barn flanked by rolling hills of golden wheat or green corn stalks. A flock of chickens peck the ground in front of a small pen of pigs while a mama cow and her calf munch happily on hay in the shade. This agrarian image of a rural farmstead may still exist, but today, animals are typically housed in larger groups and farms tend to specialize in only one species. Given the intensive management and high stocking densities of modern livestock systems, understanding the dynamics and value of group living in different species is essential for responsible management of food animals. It is our desire to assess the importance of sociality, specifically multi-level social interactions, among livestock species.

Despite the potential for overcrowding-induced stress in livestock, companionship can be one of the benefits of living in large groups. Participating in pro-social behaviors like grooming, play behavior, and spending time in close spatial proximity greatly increases welfare in a variety of livestock species. For example, horses of all ages groom each other and play behavior is common in young animals of this species¹. In a small study from Moulton College in the UK, cows had lower heart rates when isolated from the group and housed with a cow they had established a social bond with versus being housed with an unfamiliar cow². The researchers concluded that cows were less stressed when the cow they were paired with was familiar compared to when they were paired with a strange cow. Similar conclusions can be made about increased distress calling by chicks when housed with unfamiliar chicks³. An animal’s social environment is incredibly salient during development. Prior to being housed in groups for their adult lives, dairy calves are frequently isolated for the first few weeks of life to prevent disease transmission. However, calves housed with conspecifics are less fearful and more likely to engage in pro-social behavior than isolated calves⁴. Given that cattle, both dairy and beef, are frequently housed in large herds as adults, socializing calves is important for forming social bonds and discouraging competitive, agonistic interactions. While not yet studied in livestock, the ability to form social bonds may be lost when group size becomes so large that recognition of “friends” becomes challenging. When determining optimal group size, careful consideration should be given to the importance of forming affiliative relationships for a given species. This is especially important to take into consideration if frequent regrouping occurs, as is common for beef and dairy cattle.

In addition to social bonding between individuals, group living provides benefits that extend up to larger scale, population-wide levels. For species that have been adapted to exist in a group with their conspecifics, it is generally accepted that the benefits of living in that group are greater than those of living in social isolation. In species where this is the case, a combination of ultimate motivations, social factors, and the desire to be near conspecifics will give rise to a collectively structured social group. Though livestock species may not receive all the direct benefits that their wild counterparts do when living in a group, there are certainly advantages to acting collectively.

Flocking, for example, has been shown to be an affiliative behavior that poultry⁵ and sheep will participate in to enhance overall group fitness by effectively serving as a defense mechanism against predators. Even in the absence of a predator, herding behavior in ungulates can decrease the amount of energy costs associated with foraging for food patches⁶. Moreover, poultry will still display behavioral synchronization and clustering under non-threatening situations. Laying hens will often feed in bouts and nest and lay together under appropriate lighting regimens⁵. Thermoregulatory benefits are also realized as ‘rafts’ of hens accumulate in close proximity to each other during times of reduced ambient temperature⁵. Additionally, the influence of movement from nearby conspecifics can allow all individuals of the group to locate resources that may have not been discovered alone. This information transfer may not even require recognition, knowledge of which animals have information about resources, or a need for complex signaling between individuals⁷, which may otherwise be difficult in large groups of livestock.

Many livestock species will form pro-social relationships and preform behaviors collectively when given the opportunity. With this said, these behaviors are necessary and of intrinsic value to the animal individually and at the systematic level. Literature supports the importance of sociality and the positive effects it has on physiological health, emotional valence and group success⁵. It is worth mentioning that factors contributing to behavioral collectivism and synchrony, such as species evolution, should be considered with stocking animals in sub-optimal group sizes. Densities that exceed natural population densities have the potential to disturb group social behavior from small pair-wise bond interactions to large cohesive communities, which may have further consequences for maintaining good animal welfare. Conclusively, evidence supports domestic livestock motivation for sociality, and should be considered for the responsible management of animals in large groups.

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Kaleiah Schiller is a first year PhD student in the Animal Biology Graduate Group, working under Dr. Kristina Horback in the Animal Behavior and Cognition lab. The lab focuses on optimizing animal welfare by assessing behavioral expression and coping style in a variety of livestock species. Kaleiah’s researching personality as a driver for spatial positioning in flocks of sheep, and the consequential environmental interaction experienced by individuals given their differential spatial preferences.

Rachael Coon is a first year PhD student in the Animal Biology Graduate Group. She studies the intersection of feeding behavior and rumen health in beef cattle in order to promote nutritional management practices that improve animal health and welfare.

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Sources:

¹ Vandierendonck, M. C. and B. M. Spruijt. 2012. Coping in groups of domestic horses – Review from a social and neurobiological perspective. Applied Animal Behaviour Science 138(3-4):194-202.

²McLennan, K. 2012. Farmyard friends. Biologist 59(4):18-22.

³Mamiko, K., S. Yuka, M. Koki, S. Aya, K. Genta, and N. Shun. 2013. Familiarity perception call elicited under restricted sensory cues in peer-social interactions of the domestic chick. PLoS ONE 8(3):e58847.

⁴Bolt, S.L., N.K. Boyland, D.T. Mlynski, J. Richard, and D.P. Croft. Pair housing of dairy calves and age at pairing: Effects on weaning stress, health, production and social networks. PLoS ONE. 12(1): e0166926. doi:10.1371/journal. pone.016692

⁵Appleby, M. C., Mench, J. A., & Hughes, B. O. 2004. Poultry behaviour and welfare. Wallingford: CABI Publ

⁶Couzin, I.D., Krause, J. 2003. Self-Organization and Collective Behavior in Vertebrates. Advances in the study of Behavior, vol. 32.

⁷ Couzin, I.D., Krause, J., Franks, N.R., Levin, S.A. 2005. Effective leadership and decision making in animal groups on the move. Nature 433: 513-516

Featured image: socially-living cattle [Source]