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upper respiratory tract disease

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Desert Tortoises Step Closer to the Wild

Can you find the desert tortoise in this burrow?

We recently completed our inventory of all the tortoises on site at the San Diego Zoo Desert Tortoise Conservation Center (DTCC). It took us two full active tortoise seasons, but we did it! (See Pam’s previous post, Counting Tortoises). Although this task has occupied nearly all of our time, we have somehow also been able to move healthy tortoises into our newly designated 20-acre translocation enclosure. Healthy, ELISA-negative tortoises (see post Tortoise Science: Cooler than You Think about ELISA testing) that have remained free of upper respiratory tract disease (URTD) symptoms for at least 30 days will be moved to the translocation enclosure (we call it a “pen”), the final step before being relocated into the wild next spring!

We had to make sure that the translocation pen could accommodate the number of tortoises we wanted to put in it, so our four seasonal research assistants had the task of adding burrows to provide the tortoises with protection from the heat and cold and installing a water delivery system to this pen. Each burrow takes an hour or more for one person to dig, but we have successfully added 50 burrows to this pen over the course of 2 months while still conducting inventory!

We now have over 100 healthy tortoises waiting to be relocated to a U.S. Fish and Wildlife Service-approved translocation site here in southern Nevada! We plan to put radio transmitters and GPS data loggers on the healthy tortoises prior to the long-anticipated release in the spring of 2011. A team of experienced telemetry technicians will follow the signal from these transmitters, allowing us to track and study the movements and habit use of these animals.

Why is translocation into the wild so important? Wild populations of Mojave desert tortoises have reportedly declined by approximately 90 percent in the past 30 years; it is estimated that there are only about 150,000 wild Mojave desert tortoises remaining in critical habitat. The desert tortoise is a keystone species, meaning that it plays a critical role in its environment. How? Desert tortoise burrows serve to protect other desert species from predators and harsh weather conditions, and they disperse seeds from the native plants that they eat, repopulating the desert ecosystem with them.

Our mission is to play a significant role in the conservation of the Mojave Desert, including the recovery of the desert tortoise and its habitat. Through all of our work, including translocation, we are well on our way to fulfilling our mission!

Pamela Cicoria is a research associate at the San Diego Zoo Desert Tortoise Conservation Center.

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Tortoise Science: Cooler than You Think!

A desert tortoise enjoys the Mojave Desert.

At the San Diego Zoo Desert Tortoise Conservation Center (DTCC) in Las Vegas, we take a blood sample from every tortoise that enters the facility, and we send it out for an ELISA test, which will determine if the tortoise has been exposed to Mycoplasma agassizzi, the bacteria that causes upper respiratory tract disease (URTD). Part of my job is to make sure those blood samples are prepared, cataloged, and properly packaged for shipment to the appropriate lab for testing.

Drawing blood from a tortoise is not the easiest skill to master; in fact, when I was first learning I was so afraid of harming the tortoise that it must have taken me 15 minutes of talking to the tortoise to put myself at ease! Eventually I did get the hang of drawing blood after a lot of close supervision from my colleagues here, and I am now the newest member of the staff permitted by the U.S. Fish and Wildlife Service to draw blood from desert tortoises.

Larisa's tools of the trade.

An ELISA, which stands for enzyme-linked immunosorbent assay, is a test done in a molecular laboratory. It is used to detect particular antibodies in the blood; in this case, antibodies against Mycoplasma agassizzi. A positive, negative, or suspect result is based on the concentration of these antibodies (titers) present in a tortoise’s blood. When a tortoise tests positive, it means the tortoise has been exposed to the bacteria at some point in its life, but it does not necessarily mean that a tortoise is sick (this is a common misconception!). As a precaution, though, we never house tortoises that tested negative with those that tested positive, even if they show no symptoms, because there is always a chance that they ARE infected and could transmit the disease.

This is why it is very important to never release your pet desert tortoise back into the wild yourself: even if it doesn’t look sick, it could be carrying a pathogen and could infect an entire wild population of already threatened desert tortoises and put them at risk of disease and even death. The only legal means of surrendering a pet desert tortoise in Nevada is by calling our Hotline.

If you have a tortoise that doesn’t seem to be feeling well, look for symptoms that are somewhat similar to those we experience when we have a chest cold. Tortoises may have discharge from their eyes or nose, labored breathing, missing scales around the nares (nostrils), puffy eyelids and/or sunken eyes; these may be combined with lethargy and depressed behavior, much like the way we act when we don’t feel well (minus the missing scales around the nares!). Left untreated and without access to proper food, water, sunlight, and/or shelter (burrow), a desert tortoise can slowly succumb to the symptoms of URTD. If your tortoise does show upper respiratory symptoms, it is very important to get treatment from a veterinarian that specializes in desert tortoises (not just an exotics vet or a reptile vet!). And you can call our Hotline for more information as well.

Larisa Gokool is a research associate at the San Diego Zoo Desert Tortoise Conservation Center. Read her previous post, Feeding Frenzy.