Ecology of Everglades Alligator Holes


Frank J. Mazzotti, Mark R. Campbell, Michelle L. Palmer, Jocie A. Graham, Karen Minkowski, Laura A. Brandt, Kenneth G. Rice


The American alligator (Alligator mississippiensis) creates small ponds, called alligator holes, by excavating substrate and vegetation. These holes are common in the Everglades and Frank Craighead in 1968 characterized alligator holes by these three components:

  1. A depression in the muck or limestone bedrock;
  2. Water to fill the resulting basin; and,
  3. Alligators to create and maintain the hole.


  • Provide water necessary for mating
  • Act as dry season refugia for aquatic organisms
  • Provide concentrated area for birds and mammals to forage
  • Provide disturbance site for plant establishment through soil enrichment and removal of vegetation
  • Increase overall diversity of Everglades
Hydroperiod Flow


  1. Where are alligator holes?
  2. What do alligator holes look like?
  3. How are alligator holes arranged in space?

Methodology Flow Chart


Mapping Summary

  1. Holes are classified into three categories by vegetation type.
  2. Color, infrared aerials (1:24,000) are adequate to map alligator holes.
  3. Minimum 5 m across, 20 cm deep
  4. Spatial accuracy 60 m
  5. Commission accuracy depends on size, location, and vegetation. Holes in sloughs are more difficult to identify than in wet prairies and sawgrass.

Surveying Alligator Holes

Surveying Surveying

Ecological Characterization

Enlarged Alligator Hole

The image above is a digital enlargement of an alligator hole at 1 meter resolution. These field maps assist in classifying vegetation types, identifying alligator holes, and mapping vegetation. Yellow dot indicates location of picture on right.

  1. Small holes are structurally and vegetatively distinct from larger holes.
  2. Larger holes surrounded by woody vegetation provide upland habitat and increase the diversity and richness of the surrounding vegetation (Figure 4).
  3. Larger alligators (and hatchlings) are found in larger holes, while juveniles are found in surrounding smaller ponds - holes act as social refugia (Table 1).

General Vegetation Zones

  1. Type 1 Vegetation Zone: Woody
  2. Type 2 Vegetation Zone: Marsh
  3. Type 3 Vegetation Zone: Artificia
#Active-Spring #Active-Fall Trails Adult Hatch. Juven. Nest Other*
Type 1 5 (56%) 7 (78%) 9 9 7 0 1 3
Type 2 5 (55%) 8 (73%) 11 0 0 5 0 3
Type 3 7 (78%) 8 (89%) 9 3 5 1 2 6
Total 18 (62%) 23 (79%) 29 5 12 6 3 12
*Other signs include: tail drags, footprints, sunning spots or gator dens.

Table 1. Number of Alligators Observed at Different Hole Types

Compostion of Vegetation

Figure 4. Composition of Vegetation in Three Meter Rings from Edge of Open Water.

Transect Data

Figure 5. Example of transect data for an alligator hole showing water and muck depths in the North to South direction. Note vertical scale exaggeration.

Spatial Analysis

  • Holes are clustered, but clusters are not.
  • Clusters are 3 km apart.
  • Vegetation and canals have an effect on overall hole distribution.
  • Fewer holes than expected are found within 1 km of a canal.
Density Map

Figure 6. Density Map: All Holes

Number of Alligator Holes

Figure 7. Number of Alligator Holes as compared to distance from canal.

Canal Influence

Figure 8. Canal Influence. Number of Alligator Holes as Compared to Distance from Canal at 1 km increments.


This research was supported in significant part by the Everglades Agricultural Area Environmental Protection District and the National Fish and Wildlife Foundation.


Pearlstine, L.G., F.J. Mazzotti, E.V. Pearlstine and G. Mann. (2004, December). Integrating Urban Growth Models and Habitat Models for Ecological Evaluation of Landscape Impacts. Poster presented at the National Conference on Ecosystem Restoration, Orlando, Florida.

More About This Project

Mapping and Characterizing Aquatic Refugia in Everglades National Park and Arthur R. Marshall Loxahatchee National Wildlife Refuge