Monarch butterfly

Monarchs need milkweed like human infants need milk.

North Dakota Game and Fish Department

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, for the monarch butterfly, one of the more well-known representatives of the insect world, this is prime time for continuation of the species.

Monarchs need milkweed like human infants need milk. And while it might seem as if 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 scientists are saying that the overall monarch population is much lower than it once was.

In about two years, the U.S. Fish and Wildlife Service is scheduled to determine whether the monarch butterfly warrants listing as an endangered species.

Greg Link, State Game and Fish Department's 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 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 figures near the top of the list.

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

North Dakota has about 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 to 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.

Doug Leier is a biologist with the North Dakota Game and Fish Department.