Milkweed is Key for Monarchs

Leier Doug
Doug Leier

By Doug Leier, NDG&F Dept.

It’s the middle of July and all over North Dakota, milkweed plants are working toward full bloom.

While not everyone appreciates the bright pinkish-purple flower pods everywhere they grow, for the monarch butterfly, one of the more well-known representatives of the insect world, this is prime time for continuation of the species and milkweed is the life cycle hub.

Monarchs need milkweed like human infants need milk. And while in places it might seem there is a lot of milkweed, across the central part of the United States it’s not quite as prevalent as it once was, and because of that and perhaps other reasons, scientists are saying that the overall monarch population is much lower than it once was.

So much so, in fact, that just about two years from now, the U.S. Fish and Wildlife Service is scheduled to determine whether the monarch butterfly warrants listing as an endangered species.

In an article in the July issue of North Dakota OUTDOORS magazineGreg Link, State Game and Fish Department conservation and communications chief, said the monarch butterfly population has fallen from an estimated high of almost 1 billion in 1996 to a low of 35 million in 2013.

Because of that, the U.S. Fish and Wildlife Service has received petitions to list the monarch, and several other pollinator species that may occur in North Dakota as well, under the Endangered Species Act.

“A threatened and endangered species listing is essentially the emergency room ‘code blue’ for critters and plants,” Link said. “Therefore, we want to avoid the need for a trip to the emergency room with wildlife species.”

Sandra Johnson, Game and Fish Department conservation biologist, said that while there are a number of potential reasons for the decline in monarch numbers, disease and predation among them, loss of milkweed habitat on summer grounds figures near the top of the list.

“Without milkweed, there are no more monarchs,” Johnson said.

North Dakota has roughly 10 species of milkweed, all of which are native. Common milkweed and showy milkweed are likely the most familiar.

At this time of year when the milkweed plants are reaching full growth, the female monarch typically lays one egg per plant, on perhaps hundreds of plants. Once hatched, monarch larvae feed exclusively on the plant.

“The young depend on the milkweed, primarily the leaves, as a food source,” Johnson said. “They eat constantly. They eat and grow, eat and grow…just devouring the plant.”

Eggs hatch in about four days and the larvae go through five stages as they grow. The larvae then transform into a chrysalis and after 10-14 days, an adult monarch emerges.

While the early life stages of the monarch is tied to milkweed, adult butterflies do feed on a variety of nectar producing plants found in the wild and in backyard gardens, which helps them prepare for what’s ahead – a long flight to wintering grounds in Mexico.

Leier is a biologist with the Game and Fish Department.

(Featured Photo: In order to make it to the butterfly stage, monarch caterpillars require a supply of milkweed plants, stands of which are dwindling in number in recent years.  NDG&F Photo)

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