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HERPS OF THE SOUTHEAST VIRTUAL WALK
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Stop #14: Key Largo and Everglades National Park, FL
Featured Herp: American Crocodile (Crocodylus acutus)

mud flats
Coastal mud flats in Florida Bay
sawgrass
Many visitors are surprised on their first visit to the Everglades. Rather than the tropical jungle that some expect, much of the Park is a vast expanse of sawgrass. For more info on the ENP, visit the Park web site.

The East Aiken classes made it to the Key Largo/Everglades National Park region on December 14, 1999. The area had much to offer, both in terms of winter wildlife viewing and environmental education opportunities, so the school spent most of the next month "virtually" exploring the area (with a few weeks off for Christmas)

Everglades National Park (ENP) is huge, encompassing more than 1.5 million acres (greater than 600,000 hectares). Yet the ENP comprises less than one-fifth of the historic Everglades. Within the boundaries of the Park a visitor can see habitats ranging from red and black mangrove communities to freshwater cypress sloughs, and sawgrass prairies to limestone ridge pinelands. The sub-tropical climate, slight changes in elevation, and water—yes, the water is the key—combine to create a landscape of great beauty and rich biological diversity.

The tropical influence on South Florida means that the Everglades is a very seasonal place, not so much in terms of temperature as it is seasonal in rainfall. There is a wet season from May until November, and a dry season from December through April, with a lot of slop (variability) thrown in. The seasonal variation of wet and dry, wet and dry, wet and dry, shapes the entire ecosystem. Spring thunderstorms flood the sawgrass and cover much of the area in shallow water. Historically the flow of water southward from Lake Okeechobee created the River of Grass through which water flowed at a rate of about 100 feet (30 meters) per day. As more area was flooded during the wet season, fish and other animals dispersed to newly flooded, nutrient rich parts of the glades. Occasionally lightning would start fires that would burn until stopped by rainfall or a water body. With the onset of the winter dry season, shallow areas dried and only the deeper pools retained water. Plant and animal species were well adapted to these predictable seasonal changes.

coastal prairie
Coastal prairie near Cape Sable

The tropical influence on South Florida means that the Everglades is a very seasonal place, not so much in terms of temperature as it is seasonal in rainfall. There is a wet season from May until November, and a dry season from December through April, with a lot of slop (variability) thrown in. The seasonal variation of wet and dry, wet and dry, wet and dry, shapes the entire ecosystem. Spring thunderstorms flood the sawgrass and cover much of the area in shallow water.

Historically the flow of water southward from Lake Okeechobee created the River of Grass through which water flowed at a rate of about 100 feet (30 meters) per day. As more area was flooded during the wet season, fish and other animals dispersed to newly flooded, nutrient rich parts of the glades. Occasionally lightning would start fires that would burn until stopped by rainfall or a water body. With the onset of the winter dry season, shallow areas dried and only the deeper pools retained water. Plant and animal species were well adapted to these predictable seasonal changes.

juvenile crocodile

The population growth of South Florida, with its accompanying construction of canals and conversion to agriculture, has profoundly influenced the quantity, quality, and seasonal availability of water in the Everglades. The changes, in human terms, may have been somewhat gradual, but in evolutionary terms the changes are abrupt. Species with reproductive seasons adapted to the ‘old’ seasonal patterns of hydrology have not adjusted to the ‘new,’ which entail lesser amounts of more polluted water at unpredictable times. Most species will not be able to cope with these rapid changes. Unless old flow patterns can be restored (see current issues, Everglades National Park), the Everglades and its vast array of species will be lost.

 
 

American Crocodile (Crocodylus acutus) and Unsustainable Use

adult crocodile
Adult American crocodile in the Florida Keys

Twenty-three species of crocodilians occur throughout the world, primarily in tropical and subtropical habitats. Humans have affected populations of all species, from American crocs in South Florida to saltwater crocs in Australia, the smaller caimans of Central and South America, and everything in between. The two primary threats to crocodilians from humans are habitat loss and unsustainable use. "Unsustainable Use" is another of the six threats to herp species that have been identified by PARC.

juvenile crocodile
Juvenile American crocodile

Humans are consumers, and the consumption of wildlife in one form or another is a common characteristic that all cultures share. In a world currently supporting more than six billion people, much of our consumption has become unsustainable, however. At its simplest, an action is sustainable if it can be continued indefinitely. Crocodilians provide excellent examples of both unsustainable and sustainable use.

crocodile on patio
Backyard wildlife

Of the 23 species of crocodilians in the world, almost all were seriously threatened by human activities at one point or another—some still are. Decades of commercial overexploitation, combined with the destruction of wetland habitats, brought several species to the brink of extinction. The "success stories" — cases where populations and species have recovered — have been due to a combination of improved protection and tightly controlled exploitation. Although a great deal of research still needs to be conducted on sustainable use of crocs and other herps, many biologists believe that the commercial use of some species can be compatible with healthy, sustainable populations. For example, the commercial use of some crocodile species provides financial incentives for people to ensure that both the crocodile population and the habitat it depends on remain in good condition.

southeastern distribution
 

>American Crocodile Fact Sheet

For more information on crocodilians, including the American crocodile, and the concept of sustainable use, see:
American Crocodile Species Account
Differences between alligators and crocodiles
SREL's American Alligator brochure

 
 
 
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