Many species of animals move seasonally from a breeding location to a wintering ground. The breeding location is often in a cooler climate. In the northern hemisphere this means flying south in winter and north in spring for many bird species. Large mammals often migrate as well, but due to human predation and fencing of land most mammal migrations have been curtailed. Flying animals have a somewhat easier time because man-made terrestrial objects do not tend to obstruct flight paths. However, the disappearance of favored rest stops along the migratory route, wintering grounds, and breeding grounds can reek havoc with the survival of a migratory species.
Example: Insects as a migrant in trouble.
Monarch Butterflies are one of the best publicized
examples of a species in danger because of disappearing wintering grounds.
They are some of the most common insects to be found in classrooms
studies each fall. Protection of the butterflies habitat by the Mexican
and United States governments has improved their situation, but more remains
to be done. Some people living in areas were the butterflies over winter
are still without resources for survival so they cut down parts of
the forest, despite the governments protections. It is not that these people
do not know or care about what they are doing, it is just when people have
to chose between the butterflies survival and their own warmth and food,
they tend to chose their own survival.
Monarch
Butterfly Facts
The Florida Monarch
Butterfly WebSite
Monarch Watch : Dedicated
to Education, Conservation and Research
Birds
Birds are the most commonly seen, and probably best known, migrants.
In the northern hemisphere most waterfowl and many songbirds migrate south
to winter near the equator, or in warm parts of the southern hemisphere,
for the winter. In the summer they come back to breed and rear young. Sometimes
these young travel without their parents for the trip south.
One experiment on young that migrate without parental direction was done on the European Stork (White Stork) around the Mediterranean. There are two migratory populations of these birds one flies around towards the east the other towards the west to fly south for the winter. Each population flies the shortest route along the coast. Eggs from birds nesting on the east side were switched with eggs from the west side and the young birds were reared in the new location. When it came time to migrate the birds flew the direction programmed in their heads which meant they had much longer flights. (Susan Smith 1998) Birds are completely unaware of political boundaries and are following their instincts for survival despite human intervention.
Mammals
Terrestrial migration is made difficult for caribou
by roads and other human structures which they are afraid
to cross or get killed crossing. Fore more information
on the biology of caribou and the difficulties they face
during migration go to Arctic
Refuge: Caribou Conversations.
One of the problems facing wildlife in the oceans is that governments
can only dictate the waters allocated to them. Most governments have
policies such as the Australian Whales
are Protected policy. However as whales are migratory animals
they run into dangers from whalers outside of the protected waters.
Wales and other aquatic animals often run into difficulties with pollutants
even when in protected areas. Wetlands
are crucial for absorption of pollutants, and migration of birds
and aquatic animals.
Discovery
Online, Expeditions -- Humpbacks of Madagascar, Today With the Whales