Migratory Animals Honor

Nature Study

Requirements

1. What is the difference between migration, immigration, and emigration?

   Answer: Migration: the movement of animals between seasonal habitats (general term). Immigration: the arrival of the animal in a new place (from the destination's perspective). Emigration: the departure of the animal from its place of origin (from the origin's perspective). In humans, all 3 are used for the same concept seen from different points of view. — Etymology: to migrate (to move), to immigrate (to enter), to emigrate (to leave); in zoology, the term migration is used more (without distinguishing origin/destination), whereas human demography distinguishes them strictly. Migration can be annual (birds), biannual (whales), generational (monarch butterfly), or one-time (lemmings during overpopulation).

2. For what reasons do animals migrate?

   Answer: Animals migrate due to: (1) the search for more abundant food (dry/cold seasons reduce food); (2) reproduction in safe places (birds, whales, salmon); (3) favorable climate (escaping a harsh winter); (4) avoiding predators or competition; (5) genetic instinct inherited over generations. A combination of factors. — Migration consumes a great deal of energy, so it is only worthwhile if the advantage is large — most migrations are forced by seasonal scarcity (tropical dry season, temperate winter). Some species have two migrations per year (round-trip journeys), others only one (lemmings, during overpopulation). It is a behavior encoded in DNA.

3. What dangers are encountered along the course of migration?

   Answer: Dangers of migration: human hunting (legal and illegal), storms and headwinds, exhaustion and hunger along the way, crossing highways and cities, predators along known routes, climate change altering the routes, pollution (artificial light confuses birds), and habitat loss due to deforestation. — Birds migrating at night become disoriented by urban lights (which attract and kill thousands each year on skyscrapers); whale routes cross oil-tanker routes; salmon face hydroelectric dams (without fish ladders, many die); forest fragmentation forces wildebeest and elephants onto longer, more dangerous routes.

4. Give an example of a migratory animal for each of the following classes:
   • Mammals;
   • Insects;
   • Fish;
   • Birds.

   Answer: 1) Mammals: the wildebeest, which migrates in large herds across the Serengeti in Africa, or the humpback whale, which travels from Antarctica to the coast of Brazil. 2) Insects: the monarch butterfly, which migrates from Canada to Mexico, traveling about 4,500 km. 3) Fish: the salmon, which returns to the river where it was born to reproduce. 4) Birds: the swallow, the stork, or the Canada goose, which migrate from Europe to Africa or from the Arctic to the tropics during winter. — The most spectacular mammal migration: 1.5 million wildebeest in the Serengeti (Tanzania/Kenya) following the rains; South Atlantic humpback whales leave Antarctica and reach the coast of Bahia (Abrolhos) to give birth between July and November; the monarch crosses 4,500 km over 4 successive generations of butterflies.

5. For each animal in requirement 4, describe the entire migration process, the reason for the migration, the dangers encountered, etc.

   Answer: Monarch butterfly: travels 4,500 km (Canada → Mexico) over 4 generations for reproduction and warmth. Salmon: born in a river, goes to the sea, and returns to the same river to spawn. Wildebeest: travels 1,800 km across the Serengeti following the rains. Swallow: Europe → Africa in winter; dangers: cold, hunting, predators, and winds. — Salmon use olfactory memory (the scent of their native river) to return — after 1-5 years in the ocean! Monarch butterflies do not return — they complete the cycle over 4 successive generations, and each one lives only 4-5 weeks (except the 4th, which lives 8 months in order to hibernate). The wildebeest follows the rains; the swallow follows the photoperiod and warmth (sun and heat).

6. What is the largest and the smallest species of migratory animals?

   Answer: Largest migratory animal: the blue whale (up to 30 m, 200 tons) — it migrates between the poles and the tropics. Smallest: the rufous hummingbird (Selasphorus rufus, less than 4 g) — it travels 6,500 km from Alaska to Mexico. Among insects, the monarch butterfly (0.5 g) is the smallest migratory one, traveling 4,500 km along the Canada-Mexico route annually. — The blue whale is the largest animal ever recorded in Earth's history (larger than dinosaurs); the rufous hummingbird beats its wings 60 times per second and loses 25-50% of its weight during migration; the monarch butterfly is considered the migratory insect par excellence. The difference in mass between the blue whale and the rufous hummingbird is 50 million times!

7. Which species travels the longest migration distance?

   Answer: The longest migration distance is that of the Arctic tern (Sterna paradisaea), a small seabird that flies about 70,900 km per year between the Arctic and Antarctica — a distance equivalent to nearly 2 trips around the Earth. It lives up to 30 years, migrating 2 million km over its lifetime (3 times the Earth-Moon distance). — The discovery was made using miniaturized geolocators in 2010 (Nature Communications) — previously it was estimated at 40,000 km, but the actual route is 70,000 km with strategic stopovers. The Arctic tern sees two summer seasons per year (boreal and austral), experiencing more daylight than any other living animal in the world.

8. Make a short study about the animal that gathers the greatest number of individuals during migration.

   Answer: Study an animal that migrates in enormous concentrations: monarch butterfly (200 million in 1 area in Mexico); wildebeest (1.5 million in the Serengeti); Mexican free-tailed bat (20 million in Bracken Cave, Texas); Antarctic krill (billions in swarms); birds such as the Canada goose (hundreds of thousands). Present the study in writing. — Bracken Cave (Texas) is home to 20 million Tadarida brasiliensis in the largest colony of mammals in the world; the Serengeti has the 'Great Migration' of 1.5 million wildebeest following the rains (an 1,800 km circuit); the monarch butterfly gathers 200 million in an area of 100 hectares in the Biosphere Reserve in Mexico.