Grasslands have evolved with grazing; and even before European settlement, native herbivores such as deer, elk, pronghorn and bison applied grazing pressure. Many native grassland wildlife species have evolved with grazing. A prime example of this is the endangered Burrowing Owl which prefers shorter vegetation so it can see predators.
Livestock behaviour plays a key role in the relationship between grazing animals and plant communities. Key grazing behaviours that impact grassland management include grazing time, selective grazing and seasonal grazing.
Cattle that have access to abundant, good quality forage will graze for about nine hours during a 24-hour time period. The length of time for grazing can be lengthened under high stocking rates, high forage availability or when the quality of feed is reduced. This daily grazing period may also be extended when cattle graze vegetation of mixed quality and growth such as shrubs and grasses.
Livestock have inherent responses to natural phenomena, including their ability to seek out the best forage. This ability has developed from generations of natural selection under range grazing conditions; individuals that are capable of selecting superior forage and being able to utilize it efficiently were more likely to survive.
When left to natural habits, cattle graze readily accessible areas first and forage may be underutilized on less accessible range. Unless these habits can be overcome, preferred areas may be overused while other areas are passed up.
A definite response is demonstrated by all livestock during the changing of the seasons, particularly when grazing on range with variations in elevation and vegetation types. Cattle generally tend to graze immature versus mature plants, leaves versus stems and plants with fine versus coarse stems. Seasonal shifts from one preferred species to another often occur when plant species mature at different times throughout the grazing season. Grass regrowth is highly preferred and, when continuously grazed, may lead to overgrazing. Such seasonal preferences for forage and forage species tend to be associated with plants higher in protein and other nutritive parameters.
Photo: Larry Halverson (Big Horn Sheep)
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