The Predator in Your Pasture

No, I am not talking about lions, tigers, or bears. I am talking about the other ones, and you know the ones I mean; the four-legged, leaf-ripping, tiller-tearing, stem munching, crown stomping, and mobile manure spreading mammals known as herbivores.

Now I recognize that most people don’t view their little “Happy” the horse, “Lily” the lamb, or “Harriet” the Holstein in the same light as they do lions, tigers, or bears (and of course, the occasional “Oh My”) but that is because you are not a green plant.   If you were, your entire worldview concerning the likes of “Happy,” “Lily,” and “Harriet” would change with the first ripping tearing bite, the first sap crushing stomp, or the first light-robbing plop of poop that renders your solar collecting chloroplasts utterly useless.

Nor are you an herbivore that despite having foraged all day has not been able to break through a plant’s physical defense mechanisms to acquire enough nutrients to meet your base energy requirements let alone recover the additional energy costs for having spent an entire day on the move. Or worse yet, you are an herbivore that took a few bites of a plant that, the last time you ate it, was high in nutrients and low in toxins but now is high in toxins and low in nutrients, and now you are not feeling much like eating despite the fact that you have not yet met your intake requirements. Obviously this is good for the plant, but not so good for you.

The Battle Going On In Your Pasture

From a distance, the view of a herd or flock of livestock slowly grazing across a green sunlit pasture on a warm spring day is a peaceful sort of sight but, up close and personal, it is an entirely different story. Hidden away behind the outward view that speaks of peace and tranquility, there is a multi-millions of years old life and death struggle taking place between plants and the animals that eat them. And this relationship is best described as a predator-prey interaction.

Animals influence plants primarily through defoliation, trampling, and altering nutrient dynamics. Plants influence animals in positive ways through the provision of nutrients such as protein and energy, and by providing other dietary components such as vitamins and minerals.

However, plants do not give up their nutrients easily. Plants also influence animals in negative ways. Many plants have well-defined defense mechanisms consisting of such things as stickers, spines, toxins, and thorns, which serve to regulate or prohibit grazing. They also influence grazing animals through their growth form, spatial and temporal variations in forage quality, quantity, and availability. Thus, despite being rooted in place, with no place to run or hide, they represent a food source that is a qualitative and quantitative moving target for any predator trying to make a meal of them.

Plants and herbivores are coevolved species in that they evolved in the same place at the same time with each influencing the survival of the other. As stated by Stoddart, Smith, and Box, 1975. “The grazing animal is a part of the plant’s environment and the plant is a part of the animal’s. So long as the two live together, the welfare of each is dependent upon the other.”

And naturally, this “living together” has created a vast array of anatomical, morphological, physiological, and behavioral adaptations in both plants and herbivores that allow them to continue to exist each in the presence of the other.

One need only look at the tremendous amount of diversity found in the plant kingdom to observe this. Some plants are single celled and small, some are multi-celled and large. Some plants are short and creep along the soil surface, some plants are tall and erect. Some plants live in the water, some live in deserts. Some plants are single stemmed, some are multiple stemmed, and some are clonal. Some plants are cool-season (initiate growth during the cool weather of spring,) some are warm-season (initiate growth during the warm weather of summer). Some plants are more nutritious relative to toxin content; some are more toxic relative to nutrient content. Some plants grow slowly, some grow rapidly. Some plants are annual, some are biennial, and some are perennial. Some tolerate grazing, some avoid it, and some limit it by producing toxins and thorns. Some plants require deep, well-drained, or highly fertile soil to live, some do not. And these are just some of the adaptations that have allowed plants to survive in the face of herbivores for millions of years.

Herbivores are no less diverse in their adaptive characteristics than the plants they are trying to eat. They come in numerous sizes and shapes and include insects, reptiles, fish, snails, crabs, birds, and mammals such as “Happy,” “Lily,” and “Harriet.” All are likewise adapted to exploit various food sources and to survive in different environments. Herbivores vary in body size and shape, dentition, mouth size and shape, digestive tract specialization (some herbivores are ruminants, some are not, and some have well-developed rumens, while others do not), size and complexity of digestive system in relation to body weight, length of neck, dexterity of lips, and feet and leg architecture. And these are just a few of the many adaptations that differentiate one herbivore from the next, allow them to live in diverse environments, and to eat different things. Thus, despite the diversity in plants, there is likely a pasture predator out there adapted to eat it.

Managing the Combatants

Now that we have an idea of what’s going on out there, we’ll begin to look at what we can do to create a setting that works for both sides. Next up: Managing Your Pastures So Your Animals Like You.