Gopher Tortoise Ecology in Pine Rockland

with Steven Whitfield PhD, Dr. Steven Whitfield is a wildlife biologist and Conservation and Research Specialist at Zoo Miami

The gopher tortoise (Gopherus polyphemus) is the only species of tortoise native to Florida, and is a threatened species within the state. Gopher tortoises were formerly more widespread in Miami-Dade County, but early settlers hunted them for food and dramatically impacted populations. In recent decades and even today, gopher tortoise populations are dramatically impacted by habitat loss from urban development. The Pine Rockland reserve surrounding Zoo Miami supports a population of gopher tortoises - one of the southern-most populations within its range, and a population entirely surrounded by urban environments. Miami is the warmest and most urban part of the range of the gopher tortoises, but all of Florida is warming because of greenhouse gases and many parts of Florida are becoming more developed as the human population expands. Consequently, Miami’s gopher tortoises offer insight into conservation of tortoises of the future.

Our gopher tortoise program at Zoo Miami is focused on the biology and conservation of gopher tortoises in Miami-Dade County, and is focused on education of zoo guests about the biology and conservation of tortoises.

Gopher Tortoises in the Pine Rocklands

Population recovery, babies, and growing up!

Our most basic research with tortoises is trying to understand how many there are in Miami-Dade County, and how quickly they reproduce and grow. We’ve been conducting surveys of tortoise habitats for several years in county preserves throughout Miami-Dade. During the breeding season, we take x-rays of female tortoises, which allows us to count the number of eggs they produce each year. We mark each tortoise individually and measure our tortoises regularly so we can estimate growth rates. There are probably less than 200 tortoises in all of Miami-Dade County, but because of our warm weather, we’re learning that tortoises here lay more eggs than usual, and growth rates appear to be higher than normal - which is a good sign for the tortoise’s potential to recover.

Measuring a baby gopher tortoise

X-rays showing eggs

How Much Space do Tortoises Need?

Understanding how much space an animal needs is one of the most basic requirements for conservation. We’re conducting a study using radio telemetry to understand the movement patterns and home range size for gopher tortoises in the pine rocklands. This will allow us to better understand how much space each tortoise needs, what types of habitats tortoises like best, and helps us understand how tortoises are interacting socially.

Making a happy home

Pine rocklands are a rather unusual habitat for tortoises, since most pine rockland areas have very little soil for tortoises to dig in for their burrows. Further, the tortoises need habitats where sunlight hits the ground so they can bask in the sun. Yet in the pine rocklands, sunlight only penetrates to the ground when the ecosystem burns regularly, and one of the management challenges for pine rocklands is that humans have long suppressed the wildfires that are part of the natural ecology of the rocklands. We’re conducting a study of habitat associations of gopher tortoises where we sample dozens of habitat variables of sites where tortoises have made burrows so that we can better plan for habitat management for the tortoises.

Getting some sun!

We use small temperature recorders attached directly to the tortoises’ shells to record fine-scale temperature data on the tortoises. Information collected in this study will help us understand the temperature preferences of tortoises in different habitats, how they respond to record-breaking heat waves, and how they deal with cold weather. The whole process for the tortoises takes just a few minutes, and then they’re released back into their homes in the pine rocklands.

Why are gopher tortoises important?

Burrows Buddies

Gopher Tortoises are very important for their ecosystems. They create deep burrows that are used by many other species of wildlife - including mammals, reptiles, amphibians, and insects. Camera trap videos show interaction among tortoises - including frequency of foraging away from burrows, courtship and mating, and aggressive interactions among tortoises. Camera trap videos also show that many other species of animals in the pine rocklands use tortoise burrows, including snakes like black racers and coachwhips, and small mammals like hispid cotton rats, black rats, and eastern cottontails.

Forest Gardeners

Gopher tortoises are important not only for animal communities in the ecosystems where they live, but are important to the plants as well. Adrian Figueroa from Florida International University began conducting a research study of seed dispersal by gopher tortoises while a conservation intern at Zoo Miami, and is now continuing his research as a PhD student. We’re learning that tortoises eat a range of native and non-native plant species, and can affect germination rates of these plants as well as their distribution in the ecosystem. Adrian has been identifying seeds that tortoises eat, and is now beginning germination trials to determine how a tortoise digestive system impacts survival of the seeds.

Saving Urban Tortoises

A Safe Haven for Lost Tortoises

In 2019, Zoo Miami partnered with Miami-Dade County’s Natural Areas Management and Environmentally Endangered Land program and FWC to create a home for tortoises that were displaced by people and can’t return to their own homes. This site for “waif tortoises” allows us to monitor tortoises to make sure that they are adjusting well to their new homes. Because tortoises are so important for the ecosystem and the species, protecting the tortoises will help protect the entire community of animals that use tortoise burrows.

Tortoise Health

One of the major threats to tortoise populations in the southeast is an emerging disease called Upper Respiratory Tract Disease (URTD), caused by two species of bacteria in the genus Mycoplasma. We’re conducting tests of tortoises found throughout Miami-Dade County to determine if they’re healthy, and if they’ve been exposed to the bacteria that can cause the URTD.

New research by Zoo Miami studies Miami's last endangered gopher tortoises

Gopher Tortoises are a threatened species that lives throughout pine forests of Florida, where th...

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