Invasive Species and Anole Microhabitats

October 8, 2016

A chubby little green anole glances nervously over its shoulder at my camera.

Protected since 1974, the Pascagoula River is the largest free-flowing river in the lower 48-- free of man-made damming. However, it is certainly not free of other human influences. Inevitably, invasive species, introduced by mankind, have made their mark and changed the way the Pascagoula presents itself.

Captain McCoy, of McCoy's River Tours, informed me that, when he was a budding nature nut among the buttressed roots, tall reeds, and humid summers of the swamp, there were far more snakes. Now, there are far fewer snakes on the river, in part because alligators, which eat snakes, have been protected and have increased exponentially, but also because wild hogs are new arrivals that are not phased by striking snakes. The hogs also root up the banks, which increases erosion and makes the river vulnerable to hurricanes. In essence, the invasive hogs have degraded the natural buffer between hurricane-caused tidal waves human residences. Yikes.

However, not all invasive species are totally evil like the hogs. Water hyacinths are pretty and add a tropical layer of green to the swamp's channels. Sure, they clog boating routs and choke out some of the native plants, but for this year's river tour, I noticed an interesting twist to the invasive hyacinth story.

Having been a Pascagoula resident practically all his life, Captain McCoy is a very knowledgeable of the nature in the river. As we puttered up a channel in the swamp, he pointed out a clustering of water hyacinth in the shallows and shoved the nose of his boat into the crowded, clumping mass of vegetation. He was eager to point out to us the interesting relationship that the hyacinths had struck up with a native lizard species.

A water hyacinth blooms on the Pascagoula River, Mississippi.

The green anole has been a Florida resident for a long time. Sometime after the ice age made way for reptile diversification and spread into North America, the green anole adapted to a variety of newly available habitats. Unfortunately, good times don't last forever and, when humans arrived with artificial ways to cross seas and bridge geographic gaps, the brown anoles were inadvertent benefactors. In the 1970s, the brown anoles hitched a ride to America from Cuba and the Bahamas with the intent of being sold as pets. Their well-meaning captors ultimately released them into the wild where they began competing the meek-and-mild green anoles. The greens had to adapt (which is one of their great strengths), or else be outcompeted. So they started frequenting new areas that the larger, more aggressive brown anoles couldn't occupy. Such as higher in trees, the tops of shrubs, or even on floating mats of swamp vegetation. Which is where the hyacinths come in.

Another invasive species is incidentally helping the green anoles cope. The browns are too large and heavy for a water-boat lifestyle and, as Captain McCoy pointed out, the invasive water hyacinths are the perfect refuge for juvenile green anoles. There were dozens of them enjoying the sunshine and water from their secure abode and we caught a few for a closer look before returning them back to what had become the new Pascagoula normal. Who could have guessed that an invasive plant could provide a valuable microhabitat!

The green anole has experience population declines since the invasive brown anole was introduced in the 1970s. However, another introduced species, the water hyacinth, provides a refuge for the native green anole.

As habitats change from various forces, some well within our control and others too far gone, there are bound to be some fairly startling changes in animal behavior, distribution, and ecology. Sometimes, it pays to keep an open mind about this strange and precarious balance of invasive and native species. Change, extinction, and adaptation are all part of life and I prefer to enjoy the intrigue it affords. There's no point in being glum over things that were.