Monarchs live primarily in North America. In Canada, Monarchs have been spotted coast to coast but have been primarily observed in southern and eastern Ontario and in southern Quebec. Monarchs have a worldwide distribution: from North America down to Argentina, Bermuda; out to the Canary Islands, the Azores, Hawaii, India, Australia and New Zealand. It is only the North American population of Monarchs that migrates.
Monarchs live primarily in North America. In Canada, Monarchs have been spotted coast to coast but have been primarily observed in southern and eastern Ontario and in southern Quebec. Monarchs have a worldwide distribution: from North America down to Argentina, Bermuda; out to the Canary Islands, the Azores, Hawaii, India, Australia and New Zealand. It is only the North American population of Monarchs that migrates.

© 1999, CHIN. All Rights Reserved.

Monarchs are migratory and live in various habitats at different stages in their lives. In late August, shorter days and chilly temperatures signal Monarchs that it’s time to abandon their summer breeding grounds in the northern United States and southern Canada and head south for the winter. Monarchs migrate as far as 4000 km.

Monarchs east of the Rocky Mountains will fly to tiny patches of Oyamel fir forest high in the Transvolcanic mountains that cross central Mexico. About 100 million will likely survive the journey. The combination of high altitude (2900 to 3300 metres), tropical latitude and the protective cover of the fir forest provides Monarchs with a special microclimate which allows them to survive. A smaller Monarch population (about 10 million ) west of the Rockies migrates to wintering sites along the California coast from north of San Francisco south to San Diego. Here, groves of Monterey Pines, Monterey Cypress and Eucalyptus serve as winter homes. In their summer and spring breeding grounds further north, Monarchs need milkweed and other flowers. In the spring, Monarchs leave their overwintering sites to breed in the fields of the southern United Read More
Monarchs are migratory and live in various habitats at different stages in their lives. In late August, shorter days and chilly temperatures signal Monarchs that it’s time to abandon their summer breeding grounds in the northern United States and southern Canada and head south for the winter. Monarchs migrate as far as 4000 km.

Monarchs east of the Rocky Mountains will fly to tiny patches of Oyamel fir forest high in the Transvolcanic mountains that cross central Mexico. About 100 million will likely survive the journey. The combination of high altitude (2900 to 3300 metres), tropical latitude and the protective cover of the fir forest provides Monarchs with a special microclimate which allows them to survive. A smaller Monarch population (about 10 million ) west of the Rockies migrates to wintering sites along the California coast from north of San Francisco south to San Diego. Here, groves of Monterey Pines, Monterey Cypress and Eucalyptus serve as winter homes. In their summer and spring breeding grounds further north, Monarchs need milkweed and other flowers. In the spring, Monarchs leave their overwintering sites to breed in the fields of the southern United States. By mid-May, the offspring of these early-breeders have left the southern states. During the summer months, Monarchs reproduce in the fields, roadside cuts, and abandoned farmers’ fields in southern Canada and the northern United States, extending as far as the northern limit of milkweed.

© 1999, CHIN. All Rights Reserved.

Monarch Winter Habitat

Monarchs overwinter in the Oyamel fir forests of Mexico.

B. Peers

MEXICO
© B. Peers


Mexico:

The pressures on the Monarch’s winter home are enormous: butterflies are not the only ones that depend on the forest. With skyrocketing population growth in Mexico, arable land and wood are in great demand. Local farmers are moving further and further up the mountainsides into Monarch habitat, cutting trees for fuel and construction as well as to provide land for their crops. Meanwhile, commercial logging is also on the increase, destroying Monarch habitat through selective cutting and some clear cutting. Selective cutting or thinning can be just as detrimental to butterflies as clearcutting. In a thinned forest, nights are colder and days are warmer, reducing a Monarch’s chances of survival.

California:

Unfortunately, Monarchs have the same tastes as developers and in many cases Monarchs are squatters on privately owned land. The wind-free frost-free environments that the Monarchs need to survive the winter are threatened as these coastal oases vanish under development, turned into condominiums, golf courses, trailer parks, and hotels. Even in Pacific Grove, also known as "Butterfly Town U.S.A.", where the town has Read More
Mexico:

The pressures on the Monarch’s winter home are enormous: butterflies are not the only ones that depend on the forest. With skyrocketing population growth in Mexico, arable land and wood are in great demand. Local farmers are moving further and further up the mountainsides into Monarch habitat, cutting trees for fuel and construction as well as to provide land for their crops. Meanwhile, commercial logging is also on the increase, destroying Monarch habitat through selective cutting and some clear cutting. Selective cutting or thinning can be just as detrimental to butterflies as clearcutting. In a thinned forest, nights are colder and days are warmer, reducing a Monarch’s chances of survival.

California:

Unfortunately, Monarchs have the same tastes as developers and in many cases Monarchs are squatters on privately owned land. The wind-free frost-free environments that the Monarchs need to survive the winter are threatened as these coastal oases vanish under development, turned into condominiums, golf courses, trailer parks, and hotels. Even in Pacific Grove, also known as "Butterfly Town U.S.A.", where the town has instituted a Monarch protection program, only two overwintering sites remain. In at least one case, the butterflies fell victim to their own popularity when the construction of a hotel to accommodate butterfly-loving tourists altered the habitat on which the butterflies depend to the extent that they did not return.

Canada:

Today, the best soils all across the Monarch’s breeding range have become bleak places for butterflies. Modern agricultural practices in the United States and Canada have greatly reduced nectar sources and milkweed-- the staff of life for Monarchs. The diversity and numbers of wildflowers and milkweed growing along the edges of cultivated fields and among crops have been drastically reduced as industrial agricultural practices transform land into monoculture deserts.

© 1999, CHIN. All Rights Reserved.

The Monarch’s migration is unique in the insect world. Most temperate insects spend the winter in a life stage that is adapted to the cold. But if Monarchs didn’t migrate they would inevitably freeze to death during the cold winter. Monarchs east of the Rocky Mountains spend the winter clustered in mountain-top enclaves of Oyamel firs in Mexico, while those west of the Rockies do the same in groves of pines and eucalyptus along the coast of central and southern California. But come the first warm sunny days of early spring, eastern and western Monarchs alike are summoned by the instinct to reproduce. After five months of relative inactivity they begin to stir --they are ready to re-colonize the north. Female Monarchs carrying fertilized eggs will push north in search of milkweed, the only plant that Monarch larvae will eat. Her offspring will also continue on to the northern limit of milkweed. The last generation born in August is special; they will live eight or nine months and travel thousands of kilometres to Mexico and California -- places they have never been before.
The Monarch’s migration is unique in the insect world. Most temperate insects spend the winter in a life stage that is adapted to the cold. But if Monarchs didn’t migrate they would inevitably freeze to death during the cold winter. Monarchs east of the Rocky Mountains spend the winter clustered in mountain-top enclaves of Oyamel firs in Mexico, while those west of the Rockies do the same in groves of pines and eucalyptus along the coast of central and southern California. But come the first warm sunny days of early spring, eastern and western Monarchs alike are summoned by the instinct to reproduce. After five months of relative inactivity they begin to stir --they are ready to re-colonize the north. Female Monarchs carrying fertilized eggs will push north in search of milkweed, the only plant that Monarch larvae will eat. Her offspring will also continue on to the northern limit of milkweed. The last generation born in August is special; they will live eight or nine months and travel thousands of kilometres to Mexico and California -- places they have never been before.

© 1999, CHIN. All Rights Reserved.

Throughout their journey, Monarchs make use of favorable winds, and thermal updrafts (ascending masses of warm air) soaring as high as 2100 metres above the ground. At this height they are able to catch a ride on the strong high-altitude winds and glide along. Fixed-wing gliding permits Monarchs to conserve a lot of energy compared to regular wing-powered flight. Monarchs have also been observed angling their wings in order to take advantage of crosswinds, thus making the best of available conditions. Monarchs average 13 km/hr and travel as many as 200 km in a day. Nectar is essential to fuel their flight; so during the day Monarchs alternate intervals of soaring, gliding and flying with nectaring. A critical stage of the journey south occurs in Texas and northern Mexico. Here, butterflies gorge themselves on nectar from an abundance of fall-flowering plants. This enables them to build up their fat reserves for the long winter ahead. By the time they arrive at their Mexican over wintering sites in mid-November, Monarchs are five times fatter than when they left!
Throughout their journey, Monarchs make use of favorable winds, and thermal updrafts (ascending masses of warm air) soaring as high as 2100 metres above the ground. At this height they are able to catch a ride on the strong high-altitude winds and glide along. Fixed-wing gliding permits Monarchs to conserve a lot of energy compared to regular wing-powered flight. Monarchs have also been observed angling their wings in order to take advantage of crosswinds, thus making the best of available conditions. Monarchs average 13 km/hr and travel as many as 200 km in a day. Nectar is essential to fuel their flight; so during the day Monarchs alternate intervals of soaring, gliding and flying with nectaring. A critical stage of the journey south occurs in Texas and northern Mexico. Here, butterflies gorge themselves on nectar from an abundance of fall-flowering plants. This enables them to build up their fat reserves for the long winter ahead. By the time they arrive at their Mexican over wintering sites in mid-November, Monarchs are five times fatter than when they left!

© 1999, CHIN. All Rights Reserved.

Every year, millions of Monarchs journey south to a place they’ve never been before. How do they do it? There is no experienced leader to guide the way. Navigation by landmarks is out of the question because they’ve never flown the route before. The sun perhaps? Monarchs fly even on the cloudiest of days. All that scientists can say for sure is that it is an inherited behavior. Somewhere in the Monarch’s primitive nervous system is a genetic program that leads them to their overwintering sites. Nobody knows how Monarchs navigate, but scientists have a theory. They speculate that Monarchs find their way by sensing changes in the earth’s magnetic field. The magnetic field is weakest at the equator and strongest at the poles. Monarchs may be able to tell how far north or south they are by detecting the strength of the magnetic field.
Every year, millions of Monarchs journey south to a place they’ve never been before. How do they do it? There is no experienced leader to guide the way. Navigation by landmarks is out of the question because they’ve never flown the route before. The sun perhaps? Monarchs fly even on the cloudiest of days. All that scientists can say for sure is that it is an inherited behavior. Somewhere in the Monarch’s primitive nervous system is a genetic program that leads them to their overwintering sites. Nobody knows how Monarchs navigate, but scientists have a theory. They speculate that Monarchs find their way by sensing changes in the earth’s magnetic field. The magnetic field is weakest at the equator and strongest at the poles. Monarchs may be able to tell how far north or south they are by detecting the strength of the magnetic field.

© 1999, CHIN. All Rights Reserved.

Milkweed and wildflowers are the staff of life for Monarchs. Although milkweed is poisonous to most creatures, Monarch caterpillars happily gobble it up. In fact, it’s all they eat. Caterpillars eat so much that they grow to about 3000 times their original weight. Milkweed contains cardenolides (cardiac glycosides) -- a type of poison. When Monarch caterpillars eat milkweed they are unharmed by the toxin, but become poisonous themselves. Adult butterflies retain the poison and are distasteful to would-be predators such as birds. Not all milkweed is created equal; there are over 100 different species of milkweed in North America, each with different toxicities. Much of the milkweed eaten by the larvae of Monarchs migrating to Mexico contains small amounts of cardenolides. As a result Monarchs arriving in Mexico are less toxic than their Californian counterparts and thus are more susceptible to bird predation. While caterpillars munch milkweed, adult Monarchs sip nectar. Monarchs depend on wildflowers to fuel breeding activities and migration, and to build up reserves of fat for the winter. Adult butterflies drink nectar from a variety of wildflowers including asters and golde Read More
Milkweed and wildflowers are the staff of life for Monarchs. Although milkweed is poisonous to most creatures, Monarch caterpillars happily gobble it up. In fact, it’s all they eat. Caterpillars eat so much that they grow to about 3000 times their original weight. Milkweed contains cardenolides (cardiac glycosides) -- a type of poison. When Monarch caterpillars eat milkweed they are unharmed by the toxin, but become poisonous themselves. Adult butterflies retain the poison and are distasteful to would-be predators such as birds. Not all milkweed is created equal; there are over 100 different species of milkweed in North America, each with different toxicities. Much of the milkweed eaten by the larvae of Monarchs migrating to Mexico contains small amounts of cardenolides. As a result Monarchs arriving in Mexico are less toxic than their Californian counterparts and thus are more susceptible to bird predation. While caterpillars munch milkweed, adult Monarchs sip nectar. Monarchs depend on wildflowers to fuel breeding activities and migration, and to build up reserves of fat for the winter. Adult butterflies drink nectar from a variety of wildflowers including asters and goldenrods. In the fall, Monarchs feast furiously from flowers to fatten up for the winter ahead. They increase their fat reserves by 500 percent, doubling their weight and tripling their waistline! During the winter, there are not enough wildflowers to feed the millions of overwintering Monarchs. From December through March, Monarchs must live off their reserves of fat. If a Monarch does not succeed in storing enough fat during the fall, or if it uses up its reserves too quickly, it may not survive the winter.

© 1999, CHIN. All Rights Reserved.

Squirrels, birds (black-backed oriole, black-headed grosbeak), mice, shrews, and ground dwelling invertebrates (black and orange garden spiders, praying mantis) are known to prey on Monarch butterflies. The bird and mouse predation has mostly been documented in Mexico, where the Monarchs’ toxicity has been found to be lower than in Monarchs overwintering in California. Cattle and domestic turkeys have also occasionally been seen eating fallen butterflies on the ground. Frogs, toads, lizards and snakes have been observed eating Monarch larvae. Parasites such as tachinid flies, parasitic wasps and disease organisms such as the polyhedrosis virus can also cause mortality among Monarch populations. During their winter stay in Mexico, Monarchs exploit a very narrow climatic window; any unusual disturbance such as extreme cold and snow storms can be very dangerous to the hibernating Monarchs. In 1992 a sustained snowstorm and cold snap may have resulted in a 90 percent decline of Monarch sightings in eastern North America the following summer.

Perhaps the most serious threat to Monarchs is habitat destruction by humans. Logging, pesticide application, real-estate devel Read More
Squirrels, birds (black-backed oriole, black-headed grosbeak), mice, shrews, and ground dwelling invertebrates (black and orange garden spiders, praying mantis) are known to prey on Monarch butterflies. The bird and mouse predation has mostly been documented in Mexico, where the Monarchs’ toxicity has been found to be lower than in Monarchs overwintering in California. Cattle and domestic turkeys have also occasionally been seen eating fallen butterflies on the ground. Frogs, toads, lizards and snakes have been observed eating Monarch larvae. Parasites such as tachinid flies, parasitic wasps and disease organisms such as the polyhedrosis virus can also cause mortality among Monarch populations. During their winter stay in Mexico, Monarchs exploit a very narrow climatic window; any unusual disturbance such as extreme cold and snow storms can be very dangerous to the hibernating Monarchs. In 1992 a sustained snowstorm and cold snap may have resulted in a 90 percent decline of Monarch sightings in eastern North America the following summer.

Perhaps the most serious threat to Monarchs is habitat destruction by humans. Logging, pesticide application, real-estate development and lack of legal protection for Monarch habitat have led to the Monarch’s annual North American migration being deemed a threatened phenomenon.

© 1999, CHIN. All Rights Reserved.

Male Monarchs have a sex patch on their hind wing. This appears as a wider area of black scales just below the centre of the back set of wings. This patch is absent in female Monarchs. The rear tip of a Monarch’s abdomen is also indicative of sex. In females it is cone shaped, in males it is forked.
Male Monarchs have a sex patch on their hind wing. This appears as a wider area of black scales just below the centre of the back set of wings. This patch is absent in female Monarchs. The rear tip of a Monarch’s abdomen is also indicative of sex. In females it is cone shaped, in males it is forked.

© 1999, CHIN. All Rights Reserved.

Learning Objectives

The learner will:
  •  relate a species of animal to its habitat
  • describe the migration of the monarch butterfly
  •  describe adaptations of the monarch butterfly
  •  understand that habitat destruction is a major environmental issue, with widespread impacts
  • recognize that single species, such as the monarch, are indicators of the health of ecosystems

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