The gopher tortoise, a long-lived reptile found across Florida, has been declining over the years due to a variety of factors, including habitat loss and fragmentation, predators, and human activity. As if it wasn't threatened enough, scientists have now found that gopher tortoises are now assaulted by a host of upper respiratory tract infections.
A recent study published in the journal Conservation Physiology by a team of wildlife biologists and conservationists found the tortoises are exposed to an outbreak of Mycoplasma agassizii, an infectious bacterium that causes upper respiratory tract diseases that are difficult to treat. As a result, these poor animals face reduced reproduction, abnormal growth and development, increased susceptibility to secondary infections, and even a shorter lifespan.
A tortoise that really likes to dig
Deep in the sandy terrain of the southeastern United States, a fascinating creature roams. At first glance, gopher tortoises (Gopherus polyphemus) may seem unremarkable, but upon closer inspection, their unique characteristics stand out. They have flattened, shovel-shaped front legs and are equipped with powerful claws, which they use to dig their burrows in the sandy soil. They're also known to live up to 80 years.
These burrows are a critical part of the gopher tortoise's survival. Not only do they provide shelter from predators, but they also serve as a refuge during harsh weather conditions. The burrows also help maintain the ecological balance of their habitat by providing a home for more than 350 species of animals, including snakes, mice, and even the rare Eastern indigo snake.
So even though the gopher tortoise may not be the most glamorous creature in the animal kingdom, its importance to the ecosystem cannot be overstated. But despite its key ecosystem role, gopher tortoises face great challenges.
In a new study, researchers from Florida Atlantic University (FAU) collected samples from 91 tortoises captured at two sites in Florida. Results showed that 42.9 percent of all tortoises tested had circulating antibodies to Mycoplasma agassizii. At one of the study sites, 70 percent of tortoises had antibodies to this bacterium, indicating that an outbreak is in full swing. On the upside, if you can call it that way, none of the tortoises tested positive for Ranavirus or Herpesvirus, two other concerning microorganisms that are known to cause upper respiratory tract disease in gopher tortoises.
The study also revealed that adult tortoises were more likely than juveniles to have clinical signs of upper respiratory tract disease, and larger tortoises were more likely to have antibodies to Mycoplasma agassizii. Furthermore, some tortoises displayed physical abnormalities, including nasal discharge, wheezing, eyelid and conjunctival swelling, and ocular discharge.
Respiratory tract infections aren't the only disease that gopher tortoises have to worry about. The Florida researchers also found that ticks and hemogregarine parasites were more common in adult tortoises than in juveniles. Tortoises with ticks were also more likely to have hemogregarine parasites. These findings are significant because hemogregarines in tortoises are believed to be transmitted by ticks.
"The full effect of chronic disease on a long-lived species such as the gopher tortoise may take months to years to manifest in a population," said Annie Page-Karjian, lead author of the new study and a clinical veterinarian and an assistant research professor at FAU Harbor Branch. "Because the gopher tortoise is one of the most commonly translocated species in North America, it is important to understand pathogen distributions within their populations and to monitor them using standardized techniques so that any changes associated with health problems may be detected over time."
The study provides important baseline data on the prevalence of Mycoplasma agassizii in wild tortoises and highlights the need for further research on the health of these threatened reptiles. The results also underscore the importance of protecting the habitat of the gopher tortoise, as habitat loss and fragmentation can increase the risk of disease outbreaks.
"Free-ranging animals typically have higher internal and external parasite burdens and are likely exposed to pathogens more frequently than captive animals, which often are regularly treated with parasiticides and also receive supportive care such as anti-microbials when they are sick," said Page-Karjian. "Long-term studies of these animals and other populations will help us to better understand the consequences of disease and various stressors that impact their behavior and reproductive potential. Additional health assessments and surveillance of pathogens in southeastern Florida's gopher tortoises are warranted."