Yellowstone National Park (USA) is the oldest national park in the world. Its territory covers three neighbouring states - Wyoming (96% of the area), Montana and Idaho. This ground, cut by the canyon of the Yellowstone river, for 11 thousand years was inhabited by indigenous people of Americas (native Americans). Then, founded in 1872, became a UNESCO World Heritage Site (1978) as a national park. The biosphere reserve established there joint the ecosystem considered as
almost the last remaining untouched in the temperate climate of the northern hemisphere.
Any information about scientific experiments and researches conducted there (prior agreement obligatory) is an extremely valuable source of knowledge. Consequences of such researches reach far beyond the borders of that place. One of them is a detailed analysis and observation as part of the study of population ecology regarding mammals living in Yellowstone. Among the many animals (i.e. bird species, scavengers and predators) inhabiting the park there are also larger herbivores (ungulates, i.e. bison, moose, elk, deer), the smaller ones (i.e. rodents), typical carnivores (Canada lynx, coyote, wolverine) together with the omnivorous grizzly bear (as a large predator). In 1995 the wolf species was reintroduced, what - regardless of the controversies and doubts - resulted in a success (in January 2016 their population reached 99). Wolf permanently joined the ranks of active predators belonging to the Yellowstone ecosystem.
According to history, the last remaining wolf of the Yellowstone territory was killed in 1926 (those animals lived there since the beginning). In 1975 - after the wolf has been listed as an endangered species - a laborious returning process of that core animal to the fauna of the park has been started. The elk population at that time was on a level directly threatening the plant population (not mentioning about reduced food supply for other herbivorous species), what enforced population control management by shooting (ineffective). Besides, coyotes - due to the lack of competition coming from similar but larger sized predator - dominated in quantity lynxes, predatory birds and other smaller carnivores. The wolf reintroduction to the Yellowstone has been named the "experimental population". Currently, the ungulates - potential wolf prey - population went back to an appropriate range (and doesn't fall below the range causing population endangerment) as well as in the ecosystem biodiversity succeeded. To the terrains which elk withdrew, other species returned (i.e. beaver). The coyote population was naturally constrained in action and quantity, especially within the border of territories where wolf packs reside. Scavengers can count on sufficient food supply remaining after wolf hunts, and the bears on an adequate competitor.
Wolf influence on the trophic cascade - as a hierarchical structure where specific levels relate to each other - is still under discussion, though their appearance clearly influenced the elk behavior, as a typical prey of that species. Elk herds do not graze on open plains living in close neighborhood (on hunting grounds) of wolves, it causes them to remain alert in harmony with their instinct. In consequence, they don't eat to be full in benefit for other herbivorous animals and the flora of the park (i.e. aspen or willow). Present Yellowstone reports are available on the internet up to date. After wolf reintroduction, elk populations decreased, but both beaver (Caster canadensis) and bison (Bison bison) numbers increased, possibly due to the increase in available woody plants and herbaceous forage resulting from less competition with elk. - the research provided in Yellowstone park ecosystem (2011) proves, 15 years after wolf reintroduction.
Without a doubt, the "experimental population" of Yellowstone is the most thoroughly researched and most often studied wolf population in the world. The Wolf Project continues their research project till today. For ethologists and canine scientists Yellowstone wolves made it possible to compare "live" behavior sequences between a wild wolf - living free, not in the sanctuary - and a domestic dog, for which certain behaviors have been suppressed and others reinforced during the breeding process (and previous creation of specialized breeds); with the final links of the predatory drive vanished for the purpose of domestication. As a complex structural model of numerous, free from human interference population, Yellowstone wolves helped to tip the scale in controversy about the theory of domination, notorious hierarchy conflicts in the pack and the alpha male status definition (or rather its nonexistance), in turn making them permanently leave the area of dogwise and dog training. The wild wolf pack is a family pack (parents, siblings) initiated by the leading pair (self-picked for life) and is composed of generations of their offspring (puppies, youngsters) helping to educate younger ones and retaining full freedom in leaving the pack in order to create their own or to join an existing one (gene pool diversity). All internal conflicts are settled usually thanks to communication (facial expressions, body language, growling), external ones are prevented by laying out borders with scent. McIntyre has spent 20 years watching and studying wolves in Yellowstone for the National Park Service. He rises early, uses radio telemetry to pinpoint the location of a pack via a radio-collared pack member, then heads out with his spotting scope to observe the animals, keeping careful notes of their activities. In all that time, he has rarely seen an alpha male act aggressively toward the pack’s other members. They are his family - his mate, offspring (both biological and adopted), and maybe a siblings.
The Yellowstone National Park is officially available to visitors since 1918 when the US Army transferred oversight to the National Park Service. The sight of many people waiting for a chance to spot a wolf, even only from afar, is not rare phenomenon. A large percentage of them arrived there exactly to see that animal. Wolves of Yellowstone allowed both the scientists and ecologists, together with wildlife admirers (including professional photographers), to observe a wild predator in its natural habitat.
 Trophic cascades in Yellowstone: The first 15 years after wolf reintroduction (2012); research by William J.RippleRobert L.Beschta
 Rick McIntyre - half-time employee of the Yellowstone Wolf Project, Yellowstone worker since 1994 - has observed and collected data on Yellowstone wolves for over ten years, two times a day, seven days a week.
 citation after Think You Know What “Alpha Male” Means? These Wolves Will Prove You Wrong by Carl Safina (Stony Brook University professor, ecologist, writer), via The New York Times