01/03/1996

Hurricane Opal Takes its Toll on Beach Mouse Populations: Illustrates Importance of Deep Dune Systems on Gulf Coast Beaches

AUBURN, Ala.- When Hurricane Opal blew through the Gulf Coast regions of Alabama and Florida, it wiped out a lot of human habitat. But the storm's impact on wildlife habitat also was severe, especially for endangered beach mice.

According to Nick Holler, leader of the Alabama Cooperative Fish and Wildlife Research Unit (ACFWRU) and professor in Auburn's Department of Zoology and Wildlife Science, Hurricane Opal flattened sand dunes along the Gulf Coast, thus severely reducing the native habitat of several subspecies of beach mice.

Holler, who has been studying several endangered subspecies of beach mice since 1986, explained that these mice are the only small mammals that reside year-round along the beach dune habitat of Alabama and Florida. Beach mice belong to the oldfield mouse species, which includes 16 subspecies, eight of which live among the dunes.

Holler became involved in studying these mice after the U.S. Fish and Wildlife Service listed three of these subspecies as endangered in 1985. Those three subspecies included the Choctawhatchee beach mouse, which lives in Florida; the Perdido Key beach mouse, which occurs in Florida and Alabama; and the Alabama beach mouse, which resides along Alabama's coast.

One of the three missions of the ACFWRU is to do research on endangered species so, at the request of various federal and state fish and wildlife organizations, Holler and other scientists began assisting in search and recovery projects in 1986. Other researchers involved in the study include Mike Wooten, associate professor in Auburn's Zoology and Wildlife Science Department; Research Scientist Jim Moyers with AU; and five graduate students. The U.S. Fish and Wildlife Service has been instrumental in the initiation and support of the studies and the research is supported in part by the Alabama Agricultural Experiment Station System.

"Our first interest was in trying to reestablish the Perdido Key beach mouse in Florida," he recalled. "At that time, the only population of that subspecies that remained was on Perdido Key at Florida Point in Alabama. The Florida Game and Fresh Water Fish Commission requested that we relocate mice from there to Johnson Beach on Gulf Islands National Seashore in Florida and also reestablish the Choctawhatchee beach mouse at Grayton Beach State Recreation Area. At the same time, there was interest in assessing populations of the Alabama beach mouse near Fort Morgan and the Bon Secour National Wildlife Refuge along Alabama's coast."

The reasons for population declines of these beach mouse subspecies are multiple. Predation of the mice by other animals (particularly domestic cats), competition from house mice, loss of genetic diversity in the mouse populations and disease all affect the survival of beach mice.

It is habitat loss from real estate development and tropical storms, however, that have been the greatest threat to these animals. Holler noted that a great deal of habitat has been lost from real estate development. The small populations of beach mice remaining on isolated fragments of habitat between developed areas are very susceptible to loss during storms, he explained.

In fact, hurricane damage was the catalyst for Auburn University's research. The Alabama beach mouse populations had been reduced by Hurricane Elena in 1985 with losses most severe at Fort Morgan Historical Park at the extreme western end of Fort Morgan Peninsula. The Perdido Key beach mouse population at Gulf Islands had been wiped out by Hurricane Frederic in the 1970s.

When Holler and Wooten began their research, there were two remaining Choctawhatchee beach mouse populations -- one at Topsail Hill near Destin, Fla., and another on Shell Island just east of Panama City Beach. The Perdido Key beach mouse could be found only at the Gulf State Park on Perdido Key in Alabama and the Alabama beach mouse still had small populations at Fort Morgan and at Bon Secour National Wildlife Refuge, but the Fort Morgan population was very low.

Both the beach dune habitats and the mice were able to quickly recover from previous storm damage and within three years after the ACFWRU projects were initiated, substantial populations of all three subspecies were established along the coast.

Now, nearly a decade after these studies began, Hurricane Opal has again threatened populations. Holler said that Opal's storm surges (the waves of water that hit the beaches as Opal came ashore) washed away a large portion of the primary dune system in Alabama and Florida with extensive damage of some secondary dune fields in Florida. The storm itself likely drowned some mice, and others have died or may yet die from a lack of food and shelter now that the dune system has been damaged. The research team is currently trying to determine just how severe the damage has been to populations of these three subspecies. Early results indicate that the impact has been great.

"We totally lost the frontal dune system, which is the habitat that usually has the densest populations of mice," he said. "I'm sure some mice died outright, but some mice survived the surge. The question now is, can those surviving mice reestablish their populations in the damaged dune areas? If you have a tremendous loss of habitat, even the mice that don't drown may die because there is not enough habitat left to support them," Holler said.

He noted a lot of flooding occurred behind the frontal dune system, which may have cut surviving mice off from a food supply immediately after the storm. Some of those mice may have died soon after the storm.

"Hurricane Opal really demonstrated the importance of the secondary and scrub dune systems," he said. In several areas, these secondary dunes survived the storm, providing some habitat for beach mice and other animals that live along the coast.

Holler noted that most of the habitat at Fort Morgan Historical Park was wiped out, both frontal and secondary dunes. He explained that the Fort Morgan Park dune system was very shallow, or did not extend far into the secondary dune area. He estimates about 80 percent of the habitat there was wiped out, with only a few remnant dunes left. Dune restoration can be done, but it will take several years for the dune system to be reestablished.

While more than 100 mice had been captured during a previous five-night trapping in the beach dunes at Fort Morgan Park, only nine mice were captured during five nights of trapping early this November.

"I'm sure the Fort Morgan population is at a low level and right now we are at a crisis stage," he said. "Hopefully the mice will hang on until we get some habitat recovery and the populations can come back. But it is certainly in a much more precarious position now than it has been in the last eight years."

Trapping during the last week of November has determined that mice remain in scrub dunes north of Highway 180 and in undamaged dune habitat at the extreme western tip of the park. As the main dune systems recover, mice may reinvade from these areas.

At Florida Point, the situation is similar to Fort Morgan. Holler said the eastern half of that beach has a shallow dune system, which was virtually destroyed. However, the western half has a deeper dune system that may provide habitat for the surviving mice. At Gulf Islands Seashore, the habitat area was large and the researchers are hopeful that enough habitat remains there to support the mouse populations despite widespread damage to the dunes. Still, the population there was small before the storm and there is concern that the remaining mice may not be able to hang on. "It's at a stage right now where it could be lost, but if it hangs on for another year while the habitat reestablishes, it might survive," he said.

The researchers, who usually hesitate to intervene in these natural occurrences, are assisting the U.S. Fish and Wildlife Service and the National Park Service in spreading sunflower seeds at Fort Morgan, Florida Point and Gulf Island National Seashore to sustain the remaining mice.

The Bon Secour population probably came through the storm in the best shape. The habitat at the Bon Secour National Wildlife Refuge, which has a deep dune system, seems to be one of the best remaining dune systems left on the Gulf Coast.

"What we lost there as a result of Hurricane Opal was all of the frontal dune system, but we had the secondary and scrub dune systems remaining there. Despite the habitat reduction, trapping in October revealed good numbers of mice remaining immediately after the hurricane."

"If we don't have another storm in the next three years, the frontal dune system will redevelop and we will probably have a nice line of frontal dunes with a good stand of sea oats that will support the mice," he continued. The secondary and scrub dunes should support the mice until the frontal system is reestablished.

Wooten, a geneticist, and Holler have been investigating the genetics of several populations. He and Holler hope to compare pre- and post-hurricane genetic attributes of the mice to determine whether the populations have suffered a loss of genetic material that might reduce their potential for long-term survival.

So why do we care if they survive? Protecting beach mice from extinction is important, said Holler, for a variety of reasons. The first is simply the aesthetic value of all life, which many people would consider reason enough. Beach mice also are important to the coastal ecosystem and Holler said that studies of the beach mouse provides scientific information that can benefit humanity.

Holler noted that the most obvious lesson learned from Hurricane Opal is just how important the entire sand dune system is to the wildlife along the Gulf Coast and how vital it is to preserve entire dune systems, not just the frontal systems.

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January 3, 1996