tle was endemic to 17 million acres in California alone. I can only imagine how much greater that area might be today, and it presents as an invasive infestation in and around forested areas.
Now, with this basis, if we analyze the earlier question “do wild horses change the fire regime of the area by consuming the natural grasses and allowing the invasive species to become dominate and increase fire spread rates?” using our understanding of animal/plant physiology, we can arrive at a simple conclusion:
Imagine for the moment a native pasture full of ripe yellow star-thistle (Centaurea solstitialisL.) nearing seed stage /w-spikes and native grasses/plants beginning to seed. And then cattle come through and graze this area of mixed yellow star-thistle and other native plants. The cows of course avoid the yellow star-thistle (due to spikes) and instead consume the other fruited grasses and plants. This leaves all of the yellow star-thistle seed in-place and unaffected by the grazing.
As a result of the cow’s complex (complete) digestive system, few grass and plant seeds are redeposited back onto the pasture in their manure. This results in a severe limitation of reseeding by the native grasses and plants of that area, and presents as a huge advantage to the yellow star-thistle as it can then reseed the area with a huge numeric advantage since the seeds from native grasses and plants have been largely digested by the cattle.
However, on the other hand, when wild horses graze that same area, they are incomplete in their digestion and thus they pass most seeds they consume back onto the pasture intact in their droppings, which can then germinate in soil conditions enhanced by the horse droppings which become a seed bed of sorts.
Basically, wild horses reseed the areas where they graze with the seeds from the local native plants.
This allows the grasses and plants to remain established in enhanced conditions and compete more effectively with the likes of the yellow star-thistle.
This naturally evolved mutualism between wild horses and plants offers the native seeds thus distributed an advantage due to the high-level of hummus and nutrients in the horse droppings aggregated with the native plant seeds. This unique mutualism between native north American plants and wild horses is of great value in rebuilding soils that have been devastated by catastrophic wildfire through abnormally extreme heat caused by excess ground fuels. The heat generated by these newly evolved super-hot wildfires is sufficient to pasteurize soils to a depth of many inches and volatilize nutrients, which leaves soils permanently damaged and altered in some cases, as we read here.
Of all the large native herbivores that currently roam the American rangelands, horses are the only large grazing herbivores that have a single-stomach simple digestive system. And as we have learned this is very important. This is in stark contrast to herbivores that are ruminants (such as cows), which have very effective digestion as a function of complex stomachs capable of fermentation, which breaks down and digests a greater percentage of grass and plant seeds.
“Ruminants are mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The process typically requires the fermented ingesta (known as cud) to be regurgitated and chewed again. The process of rechewing the cud to further break down plant matter and stimulate digestion is called rumination. The word “ruminant” comes from the Latin ruminare, which means “to chew over again”. The roughly 150 species of ruminants include both domestic and wild species. Ruminating mammals include cattle, goats, sheep, giraffes, yaks, deer, antelope, and some macropods.” – (from Wikipedia)
Clearly, the relationship between the ecosystems of North America and native wild horses is one that is mutually beneficial and is a true mutualism resulting from co-evolution over many millennia. The wild horses are nourished by the native plants, 