by: Tiego Vazquez
Seasonal movement of animals from one region to another.
Monarch butterflies are not able to survive the cold winters of most of the United States so they migrate south and west each autumn to escape the cold weather. The monarch migration usually starts in about October of each year, but can start earlier if the weather turns cold sooner than that. Monarch butterflies will spend their winter hibernating in Mexico and some parts of Southern California where it is warm all year long.
Each spring thousands of elk in 6-8 populations migrate from far-flung winter ranges in Wyoming, Montana, and Idaho, to high-elevation summer ranges nearer to the core of Yellowstone National Park. These migratory elk link the ecosystem’s outermost foothills to its deepest, mountain wilderness. Their abundance sustains diverse carnivores and scavengers, attracts tens of millions of dollars to gateway communities, and inspires national and global conceptions of the beloved YNP wilderness. These migrations define and unify the GYE, both ecologically and culturally.
The salmon run is the time when salmon, which have migrated from the ocean, swim to the upper reaches of rivers where they spawn on gravel beds. After spawning, all Pacific salmon and most Atlantic Salmon die, and the salmon life cycle starts over again. The annual run can be a major event for grizzly bears, bald eagles and sport fishermen. Migration between fresh and saltwater occurs during every season of the year, depending on latitude and genetic characteristics of the fish. Groups of fish that migrate together are called runs or stocks. Salmon spawn in virtually all types of freshwater habitat, from intertidal areas to high mountain streams. Pacific salmon may swim hundreds, even thousands, of miles to get back to the stream where they hatched.
The timber rattlesnake, critically endangered, once inhabited the entire East Coast and Midwest. Timber rattlesnakes spend their winters hibernating in communal dens. In the spring, those not pregnant migrate to feeding and breeding ranges. Timber rattlers spend their winters hibernating in multiple-species dens. The same dens serve for generations. Pregnant females stay near their winter dens in spring while males, females who aren't pregnant travel to find food and mates. They migrate up to five miles to their summer ranges, then return when winter rolls around again. Both trips are extremely treacherous for the snakes. They must stave off starvation, evade predators and navigate human developments. Humans kill these migrating snakes out of fear or malice, or by accident. Once they reach their summer ranges, they travel within them to find prey and mates.