Massive Migrations

Throughout the evolution of the animal kingdom, animals have needed to adapt to their environment in order to survive. Whether it be for food, reproduction, or weather, migration has become an essential part of animals’ lives. Here are some of the longest, largest, and most spectacular migrations of the world.


Caribou

caribou
Source: Nelly Degraeve

During the summer, female caribou head north with yearling calves, about 3 weeks before the males. They travel more than 965 kilometers (600 miles) in order to feed on richer grasses that grow in colder climates. Once they reach the tundra, the adults graze as much as possible — they can eat 5 kilograms (12 pounds) of plants a day! Caribou can swim well and walk in the deep snow because their hooves are shaped like shovels. In the winter, caribou travel back south to a warmer climate, where they eat lichens instead of grass.


Monarch Butterfly

monarch
Source: Owl Net Files

The Monarch Migration starts in September and October, when the butterflies move from Canada to the USA. They continue south — for low precipitation, warmer temperature, and nectar-rich plants — and arrive in Mexico in November. When it gets too dry and arid in Mexico because of droughts, the monarchs start to return to Canada in March. As they head north, the females lay eggs because of the large leafy plants for larvae located in the USA. The butterflies arrive in Canada in July after five generations passing in the annual migration cycle. The migration is longer than one butterfly’s lifespan, a total distance of 3,1000 kilometers (19,262.5 miles). In 2013, 300,000 butterflies were counted to be present in the migration. However, it is extremely hard to get an accurate population count of monarch butterflies.


Salmon

salmn
Source: Critfc

When salmon are born, they inhabit calm, freshwater rivers that pose few threats other than birds. After they mature, they head together to the open ocean where they eventually become solitary. Salmon are especially unique from other fish because they can adapt between fresh water and salt water in a chemical process, after which the salmon are called smolts. Smolts stay living in the ocean until they are ready to breed, gaining weight because of the abundance of food. Because their offspring will have a better chance of surviving in freshwater, the salmon return to same river where they were born. They have a sort of  “mental compass” that allows them to remember the right path back home. The salmon travel hundreds if not thousands of miles swimming upstream to the rivers of Northwest Canada and Alaska, where they face the threats of hungry grizzly bears. After reaching the nesting spot, the salmon lay their eggs on gravel beds and die after reproducing. The newborn salmon hatch and the 3,000 kilometer (1864 mile) journey starts over.


The Great Migration

wildebeest
Source: David Lazar Photo

The Great Migration is considered one of the “Seven New Wonders of the World” or one of the “Seven Natural Wonders of the World.” With either title, this migration is astonishing: it consists of two million animals, some species being wildebeest, zebras, and gazelle. 1.7 million animals of them are wildebeest. The giant amount herbivores attracts predators such as the lion, leopard, cheetah, and hyena to feast. The migration starts in the Serengeti National Park in Tanzania and goes to the Maasai Mara National Reserve in Kenya. In January and February, the wildebeest have synchronized births. In March, the climate becomes too dry in southernmost part of Tanzania, so they head west in search of water, following rain clouds to find lush greens. Once they have reached more nutritious fields, they stay put for April. Then, from May to June, they head far north, when the male animals fight for mates. As they head north, they have to cross the Mara River, which is teeming with crocodiles. For the rest of summer and the start of autumn, the wildebeests stay north in Kenya. Females now pregnant, they begin to head south again in October, and the whole process starts over again. Wildebeest travel 1,600 kilometers (994 miles) a year.


Fruit Bat

Source: Discover Wildlife

Straw-colored fruit bats, migrate to Kasanka National Park, Zambia, every November and December to feed on the abundant fruit trees. 8 million bats arrive each year, consuming twice their body-weight every night. By eating so many fruits, and therefore seeds as well, straw-colored fruit bats are responsible for at least 60 percent of seed dispersal of Africa’s rainforest trees. Their journey is estimated to be 3,8000 kilometers (2361 miles); however, nobody knows where they come from or were they go after the large feast.


Jellyfish

jelly-fish
Source: National Geographic

Unlike most species, jellyfish conduct daily migrations, following the sun. When the sun rises in the east, the jellyfish follow it in order to provide energy to the zooxanthellae algae living inside of their tissue. These organisms help the jellyfish survive by producing energy. Jellyfish propel jets of water with their appendages and swim just until they reach the shore. Although the length of the jellyfish migration is fairly small, the amount of jellyfish that congregate is breathtaking.


Christmas Island Red Crab

christmas
Source: Max Orchard

Christmas Island, the tropical home to 121 million Christmas Island red crabs, is located north of Australia. These crabs live in burrows in the forest and have evolved the inability to swim. Their babies, however, can only live in water, so the crabs are forced to migrate across the island to the shore. Annual monsoon rains, which usually occur in November and December, signal the crabs to make their migration. First, the males begin their 5 kilometers (3 miles) journey, trekking through hazardous, human territory — 1 million crabs are crushed by cars and trains in the process. The females soon follow and stay at the beach to lay eggs into ocean. Afterwards, they make their return trip in January as the eggs in the ocean hatch as larvae.


Horse-shoe Crab

horseshoe
Source: Beach Chair Scientist

Horse-shoe crab migration starts in the open ocean, where they travel to the beaches of the East Coast and Gulf Coast. The males come first and are followed by the females. Horse-shoe crabs prefer to breed at night during high tides. When they are ready to reproduce, females dig and lay eggs on the beach, and the thousands of eggs that are under ground become food for many different birds, reptiles, and fish. When the eggs hatch, the larvae move into the ocean and settle onto the ocean bottom. As the larvae mature, they swim further into the ocean and eat more food, molting and growing in the process. After they become adults, they return back to the beach to lay their own eggs.


Humpback Whale

Source: National Geographic

Humpback whales have one of the longest migrations of all mammals. They travel 5000 – 9,8000 kilometers (3107 – 6,090 miles) annually, moving from the cold Antarctic waters to the warmer, tropical areas of the Pacific. Adult humpback whales spend their summers feeding in Antarctica because krill is more abundant in colder temperatures. They then must swim north, towards the equator to breed and nurse their young.


Leatherback Sea Turtle

A male leatherback sea turtle
Source: The Guardian

Because the leatherback sea turtle is the largest turtle, it can withstand colder waters. This allows the turtle to be able to complete the longest migration of sea turtles. The journey from nesting to foraging grounds can take two to three years, a total length of 16,093 kilometers (10,000 miles). Leatherback sea turtles start at the nesting beaches of the Caribbean and follow the currents, traveling north as far as Canada to find food such as crabs and jelly fish. After feasting, they return to their birth place in warmer waters. One hypothesis on how they remember where to return to is that the turtles use the earth’s magnetic field and water chemistry.


Arctic Tern

arctic tern
Source: John Molloy

Basically flying from the top of the world in Iceland, Greenland, and the Netherlands to the bottom of the world in Antarctica, the arctic tern surpasses all animals because their migrations are 71,000 kilometers (44,117 miles) a year. Researchers estimate that the Arctic tern migrates about 2.4 million kilometers (1.5 million miles) in its lifetime. By traveling to the ends of the earth, the Arctic tern lives through two summers each year — they spend their first summer in the north, and after it begins to become winter, they go to the south and have another summer.  Once every one to three years, Arctic terns breed in north. After laying their eggs, they return to the south Antarctic coast for the summer. Throughout their journey, Arctic terns follow the patterns of the wind and constantly eat fish and crustaceans in the open ocean.


Dragon Fly

dragonfly
Source: BBC

Although very little is known about dragon flies’ migration patterns, researchers estimate that they travel about 18,000 kilometers (11,185 miles) each migration. Dragons flies’ migrations occur on every plant except Antarctica because they follow the seasonal monsoon rains from continent to continent. Because dragon flies have short lifespans, it takes more than one generation for a full migration to be completed — similar to the monarch butterfly.


Fur Seal

fur seal
Source: World Wildlife Fund

Fur seals’ journey starts at the Pribilof Islands, which are located near Alaska. Fur seals start migrating when they are just four months old, their main goal of migration being a large search for food. In November, the fur seals head south, past the Aleutian Islands and all the way to the southern California coast. They eat in the open ocean and on different beaches for 8 months. When summer comes, the seals head back north, covering over 9656 kilometers (6000 miles) and 1/4 of the way around the world.


One Comment

  1. Jetta Layden

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