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Monarch butterfly numbers could be at historic lows this year, study suggests

Date:
March 19, 2014
Source:
Texas A&M University
Summary:
Monarch butterflies may be named for their large size and majestic beauty, but once again their numbers are anything but king-sized. In fact, 2014 may go down as one of the worst years ever for the colorful insects, says a Monarch watcher. It's been a disturbing trend that has been going for most of the past decade, he points out. This year, Monarchs face a triple whammy: a lingering southern drought, unusually cold winter temperatures and lack of milkweed, their primary food source.

Monarch resting in the central Texas area.
Credit: Texas A&M University

Monarch butterflies may be named for their large size and majestic beauty, but once again their numbers are anything but king-sized. In fact, 2014 may go down as one of the worst years ever for the colorful insects, says a Texas A&M Monarch watcher who is proposing a national effort to help feed Monarchs.

Craig Wilson, a senior research associate in the Center for Mathematics and Science Education and a longtime butterfly enthusiast, says reports coming from Mexico where the Monarchs have their overwintering grounds show their numbers are significantly down yet again -- so much so that this year might be one of the lowest yet for the butterfly.

It's been a disturbing trend that has been going for most of the past decade, he points out. This year, Monarchs face a triple whammy: a lingering drought, unusually cold winter temperatures and lack of milkweed, their primary food source.

Citing figures from the Mexican government and the World Wildlife Fund, Wilson says, "In 1996, the Monarch breeding grounds in Mexico covered about 45 acres, and so far this year, it looks like only about 1.65 acres. That means fewer Monarchs will likely reach Texas to lay eggs, perhaps the lowest numbers ever of returning butterflies."

Wilson says the colder-than-usual winter, which set record lows in many parts of Texas and even Mexico, has had a chilling effect on Monarchs.

"Unfortunately, the harsh and lingering cold conditions mean that the milkweed plants that Monarch caterpillars must have to live have yet to start growing, and these are the only plants on which they can lay eggs to provide food for their caterpillars," he adds.

Wilson says that last fall, the number of Monarchs that were netted and tagged in the College Station area was one-fifth the number tagged in 2012.

The dry conditions during the past decade and changing farming practices are hampering the growth of milkweed, the only type of plant the Monarch caterpillars will digest as the multiple generational migration heads north.

Texas also has had dozens of wildfires in the past few years that have hampered milkweed growth, and even though there are more than 30 types of milkweed in the state, the numbers are not there to sustain the Monarchs as they start their 2,000-mile migration trip to Canada. Increased use of pesticides is also adversely affecting milkweed production in a huge way, he notes.

"The severe drought in Texas and much of the Southwest continues to wreak havoc with the number of Monarchs," Wilson explains, adding that the wintering sites in the Mexican state of Michoacαn are at near-historic lows.

"The conditions have been dry both here and in Mexico in recent years. It takes four generations of the insects to make it all of the way up to Canada, and because of lack of milkweed along the way, a lot of them just don't make it.

"But if people want to help, they can pick up some milkweed plants right now at local farmer's cooperative stores," he says, "and this would be a small but helpful step to aid in their migration journey and to raise awareness of the plight."

Wilson says there has to be a national effort to save Monarchs or their declining numbers will reach the critical stage.

"We need a national priority of planting milkweed to assure that this magical migration of Monarchs will continue for future generations," he says.

"If we could get several states to collaborate, we might be able to promote a program where the north-south interstates were planted with milkweed, such as Lady Bird Johnson's program to plant native seeds along Texas highways 35-40 years ago. This would provide a 'feeding' corridor right up to Canada for the Monarchs."

Wilson is currently adding a variety of milkweed plants to the existing Cynthia Woods Mitchell Garden on the Texas A&M campus. He recommends the following sites for Monarch followers: Journey North, Texas Monarch Watch and Monarch Watch.


Story Source:

The above story is based on materials provided by Texas A&M University. Note: Materials may be edited for content and length.


Cite This Page:

Texas A&M University. "Monarch butterfly numbers could be at historic lows this year, study suggests." ScienceDaily. ScienceDaily, 19 March 2014. <www.sciencedaily.com/releases/2014/03/140319114608.htm>.
Texas A&M University. (2014, March 19). Monarch butterfly numbers could be at historic lows this year, study suggests. ScienceDaily. Retrieved September 17, 2014 from www.sciencedaily.com/releases/2014/03/140319114608.htm
Texas A&M University. "Monarch butterfly numbers could be at historic lows this year, study suggests." ScienceDaily. www.sciencedaily.com/releases/2014/03/140319114608.htm (accessed September 17, 2014).

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