island refuge

Usually we think of islands as delicate ecosystems, sensitive to change because of the few numbers of species there and their complex interactions that can be upset by the loss (extinction) or addition (invasion) of a species.  However, through the introduction of a couple of milkweed plant species, Maui, as well as Oahu and the big island of Hawaii, seem to have become a refuge for Monarch butterflies, whose populations are crashing in various parts of mainland North America.

In the town of Kapalua on the northwest shoreline of Maui, a very hilly and abandoned golf course has become a refuge for all sorts of exotic plants and animals like the Monarch butterfly.

Kapalua golf course-Maui

It hardly seems possible that there could have been fairways and greens here once. A forest of Norfolk Island pines and other exotics have completely overgrown everything but the golf cart paths, which now make wonderful hiking trails.  That’s the island of Molokai in the distance.

Kapalua golf course-Norfolk Island pine

These lofty Norfolk Island pine forests make welcome cool, shade on a hot, humid day.

Kapalua golf course-balloon milkweed

Along the edge of the golf cart path, balloon milkweed, introduced from southeast Asia, grows in dense patches. Both flowers and seed pods were present, and dozens of Monarch butterflies flitted in and about the vegetation.

Kapalua golf course, Maui-balloon milkweed

The flower head points downward (unlike other milkweeds) below reflexed petals, so the butterflies have to hang from the flower rather than perch on it. This might make it more likely they will catch their feet on the pollen sacs, removing them and helping the plant outcross its pollen to another plant.

Kapalua golf course-Monarch butterfly on balloon milkweed

A female Monarch butterfly feeding on the nectar of balloon milkweed attracted the attention of a few males, but fluttered her wings vigorously and drove them off.

Kapalua golf course, Maui-balloon milkweed

Unlike Asclepias species of milkweed we have in North America, this species (Gomphocarpus phytocarpus) sports inflated pods surrounding the tender seeds within.  The air space between pod wall and seeds must make it difficult for seed predators to feed on the next season’s crop of milkweed plants.

Dozens of Monarchs flitted about us as we walked.  I don’t think I have seen this many Monarchs in an entire summer (or two) in Minnesota, but here they are thriving with plenty of the balloon milkweed leaves for the caterpillars to feed on and the nectar of this and other flowering plants in the overgrown golf course to sustain the adults.

Kapalua golf course-Monarch butterfly on balloon milkweed

It’s possible that Monarchs have become established on the Hawaiian islands by founding individuals from California, but that is a 2400 mile journey, and the wind generally blows from west to east, not the reverse.  Unlike the California population, island Monarch butterflies are not migratory, so once they have found isolated patches of milkweed, populations thrive and increase.  In addition, several butterfly “farmers” in Hawaii market their Monarchs for weddings, with additional individuals being released to the island as the couple pronounce their vows.

So here’s a rare story of how an introduced plant species benefits the survival of a species that is threatened in other parts of its range.  It’s a wonder how the butterflies find their milkweed hosts (needle in a haystack?), but impressive when they do.

5 thoughts on “island refuge

  1. Hi, Sue-how great to find a local colony (or whatever you call a group of Monarchs) on a refurbished golf course. Thought I would pass on that in today’s Strib, it was reported that Monarchs made a big comeback in their wintering Mexico wintering grounds. Area covered by them was more than 3 1/2 times greater than last winter!They covered 10 acres vs. 2.8 acres in 2014. Of course, they covered 44 acres 20 years ago, but nevertheless! Plant more milkweed!

  2. Really enjoyed your post. Spring flowers are beginning here in the Sonoran Desert, where we’ve had an unusually warm February. 2015 was warm too, but the last really warm spring was back in 1957. El Nino is the strongest in many, many years so we’re having “interesting” weather!

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