Strong season for monarch butterflies passing through Cape May

Image courtesy of Mark Garland

Image courtesy of Mark Garland

It was a strong season for monarch butterflies in Cape May, a strategic stopover for a 3,000 mile migration from Canada to Mexico.

The migrating season, which begins on September 1 and generally ends around October 31, continued through last week, when 40 were tagged at Cape May Point, according to the organization.

The season featured the highest monarch counts in four years, with warm weather resulting in a late season influx.

[Related: Why Cape May’s monarch butterfly migration population varies so much]

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“Will monarchs lingering this late make it to Mexico? We really don’t know, so that’s why we continue to tag,” a Monarch Monitoring Project wrote in a blog post. “If one of these late monarchs makes it to Mexico and the tag is found, we will then be able to answer that question.”

In 2014, Sarina Jepsen of the Xerces Society, one of the three conservation groups petitioning the federal government for protected status, told WHYY that the monarch populations counted at wintering sites in Mexico have declined by about 90 percent in 20 years.

The causes, she says, are a loss of habitat and the decrease in available milkweed, the monarch caterpillar’s only food.

At the time, Cape May Bird Association’s Chris Tonkinson hypothesized that is because a main factor hurting monarchs worldwide isn’t as big of an issue here: the killing of milkweed plants by herbicides in Midwestern farm country.

“The monarchs that have made their way to the upper Northeast, as they come down the East coast they’re not as exposed to that big agriculture phenomenon,” Tonkinson said, “So there’s a lot more habitat and milkweed for them comparatively.”

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