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  Behavioral Education for Human, Animal,
Vegetation & Ecosystem Management

Stories of Applied Animal Behavior
Created by members of a graduate Foraging Ecology Class
     at the University of Idaho and Washington State University
     under the direction of Drs. Karen Launchbaugh and Lisa Shipley

Livestock Grazing Distribution Patterns: Does Animal Age Matter?   

By Tracy K. Brewer


Non-uniform grazing distribution by livestock on diverse landscapes and its effects on present vegetation has presented a challenge for livestock, grazing, and natural resource managers for an extended period of time. Many variables, such as water location, forage availability, and ruggedness of the terrain, which exist at a variety of scales, influence habitat selection and use behaviors by livestock. As a result, livestock tend to use some areas more than others, resulting in degradation of the plant communities that are used heavily throughout the grazing period.

Animal age, a variable that has been researched very little in relation to livestock distribution, is highly related to an animal’s physical, physiological, and morphological characteristics. Understanding how these factors may interact to influence the grazing behaviors of animals of different ages may help managers create tools to reduce the negative effects of heavy use in some areas and little or no use in other areas of a pasture.  One question still exists, “Can you teach an old cow, sheep, or goat new tricks?”.

How Does Vegetation Respond To Non-Uniform Livestock Grazing?

Large herbivores play a major role in the dynamics and function of ecosystems by selectively consuming some plants within certain plant communities in a pasture. A decline in range condition due to direct and indirect effects of heavy, prolonged grazing on certain sites within a landscape may cause a shift in forage production and/or species composition in these areas. It is important to keep in mind that some level of patchiness is good for increased biodiversity of plants and animals on a landscape level. However, excessive use or lack of use of plants and patches across the landscape may be unfavorable to the overall sustainability of plant communities. Therefore, knowledge and implementation of management practices, such as grazing with intraspecific age classes of livestock (i.e. various ages of the same kind of animals grazing together), that enhance some level of diversity but minimize excessive selection and degradation of resource patches is critical.

What Animal Characteristics Affect Distribution?

Little research to date has focused directly on intraspecific age differences related to landscape- or community-level resource selection patterns by livestock. All factors that influence livestock resource selection behaviors are highly interrelated. Therefore, it is important to understand how age relates to physical, physiological, and morphological characteristics of an animal and how they all relate to each other to influence animal grazing behaviors.

Physiology and Body Size. As age and body size are directly related, physiological differences between ages must also take into account differences in body size. Younger, smaller animals have greater energy and nutrient requirements per unit body weight, smaller rumen capacity, and, subsequently, lower absolute intakes of forage than larger, older animals. The combination of a smaller rumen capacity and greater nutritional requirements per unit body weight requires smaller, younger animals to consume higher quality diets within a foraging bout than larger, older animals. Additionally, lactating cows, those that are producing milk to feed their young, tend to consume more forage per unit body weight than non-lactating cows to satisfy greater energy and nutrient requirements.

Thermoregulation. Animals must maintain a constant body temperature, which is called thermoregulation, despite any challenges from their surrounding environment.  Winter grazing studies conducted in Montana, have documented young cattle, which have higher thermoregulatory needs than older cattle, using pastures less efficiently, spending more time in cold, windy, unprotected areas, and grazing longer and traveling farther per day than older animals. This difference may be due to a lack of grazing experience of young cattle in winter pastures and higher nutrient and energy demands when compared to experienced, mature cows.

Foraging Time and Efficiency. Under more moderate environmental conditions, young cattle and goats have been documented grazing longer than older animals each day and spending more time searching for forage of higher nutritional quality. Suckling calves may be at leisure to be more selective when they graze because a majority of their needs are met via milk consumption from their mother. Differences in forage harvesting efficiency between age classes of livestock may also contribute to variable resource selection and use patterns. For example, younger animals tend to have teeth that are in better condition for foraging than older animals.

Learned Behavior. Learned behaviors, both individually and socially, play a large role in livestock resource selection patterns throughout their lifetime. Animals are sensitive to social facilitation by different intraspecific classes at various ages and stages of their life. As a very young animal that is dependent upon mom’s milk and before its rumen is completely developed, calves tend to be the most influenced by their mother’s behavior. This effect weakens as calves become yearlings, or “cow-teenagers”, and peer influences become the strongest. Ultimately, as cattle mature, individual experiences become the strongest influence of behaviors that dictate foraging and resource use patterns.

Previous Grazing Experience. A factor that plays an incredible role in influencing livestock resource selection and use patterns that should not be considered independently of age is previous grazing experience. Many studies conducted that have documented livestock grazing distribution use patterns have attributed portions of their results to previous grazing experience. Animals that have previously grazed in a pasture or similar situation are like people who have eaten at a specific restaurant or similar kind of restaurant previously.  They probably know what is good to eat and what is not! 

How Can Livestock Behavior Be Modified To Improve Distribution?

Animal behavior is a reflection of a lifetime of individually and socially learned behaviors up to that point in the animal’s life. Therefore, grazing behavior modification to enhance utilization of various plant communities must be started at a young age and reinforced throughout the animal’s lifetime to persist, because it’s not easy to teach an old cow, sheep, or goat new tricks. As animals are the most receptive to learning from their mother at a young age, shaping young animal behavior to increase their distribution should begin by modifying mom’s behavior first. An example of this type of modification might be to herd mother animals away from preferred areas of a pasture, such as areas near a stream, into less preferred areas, such as upland slopes, influencing the young via their mother’s actions. Ideally, as generations of animals pass through the herd or flock, these early-learned behaviors exhibited by maturing animals may become more prominent and influential to young animals entering the herd or flock. 

Cattle have been documented utilizing working spatial memory to return to places for which preferences have been developed.  Preferences are generally formed for areas that animals perceive as having desirable and adequate forage. Animals, in general, also respond to various types of punishment and reinforcement. Perhaps a combination of these factors that influence animal behavior could be used to improve livestock distribution. An example of this might be to rotate pasture entrance points (e.g. use different gates) every time livestock are placed in a pasture. In addition to rotating entrances, managers could provide a source of positive reinforcement near the entrance and in surrounding areas, such as molasses blocks.  The blocks may cause the animals to create a place preference for that area of the pasture and influence livestock to return to the area during future use of the pasture. 

Additionally, this behavior modification, coupled with the previous idea of influencing animal behavior at a young age by modifying their mom’s behavior, by herding animals to areas that generally receive little use, may serve as an effective and efficient behavior modification and management tool.  Herding mother animals to new areas and rewarding them with something positive may facilitate the behavior of the animals returning to that area in the future, which may influence future behavior of young animals that observe their mother’s actions.


Intraspecific grazing of various age classes of livestock may be an effective tool managers can use to increase livestock distribution at a landscape level. Understanding the influence of physical, morphological, and physiological differences among age classes may have on distribution, the relation of each of those factors to each other, and the advantages and limitations potentially associated with each is a necessary first step in the development of such tools.  

Additional References:

Bailey, D.W., J.E. Gross, E.A. Laca, L.R. Rittenhouse, M.B. Coughenour,   D.M. Swift, and P.L. Sims. 1996. Mechanisms that result in large herbivore grazing distribution patterns. 49:386-400.

Howery, L.D., F.D. Provenza, R.E. Banner, and C.B. Scott. 1998. Social and environmental factors influence cattle distribution on rangeland. Appl. Anim. Behav. Sci. 55:231-244.

Pieper, R.D. 1994. Ecological implications of livestock grazing. p. 177-211. In: M. Vavra, W.A. Laycock, and R.D. Pieper (eds.) Ecological implications of livestock herbivory in the west. Society for Range Management, Denver, CO.

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Learn more about the Foraging Ecology Class by visiting http://www.cnr.uidaho.edu/range556/