Research associate Daniel checks tortoise hatchling pens.
As we begin the new year at the San Diego Zoo Desert Tortoise Conservation Center (DTCC), almost all the tortoises have gone down into their burrows for their winter brumation (reptilian hibernation). During the winter months, we shift our responsibilities from feeding and processing tortoises (giving health assessments to those brought in to the DTCC) to doing surveillance in our assigned areas. We walk each section of pens looking for sick or injured tortoises and for damage that needs to be repaired in the pens.
Daniel checks tortoise pens to make sure the animals are in their burrows.
At this time of year, with consistently cool weather, all the tortoises should be pretty well entrenched in their burrows. After we are comfortable that the tortoises are down for the winter, we create a wall of earth in the opening of each burrow to provide an extra layer of protection against the elements. At this point, any tortoise found outside of their burrow is cause for concern. When we find tortoises out in cool weather, we bring them in for a complete health assessment.
All sick or injured tortoises are kept in the medical center for treatment, and the tortoises that appear healthy are put back in their pen and checked more frequently to monitor any change in their condition. Typically, tortoises that are awake and out of a burrow during the cold winter months usually have a health issue causing them to come out of brumation. Doing pen surveillance is the only way we can monitor the condition of the tortoises during the winter. Since it is not healthy to disturb the tortoises in their burrows, we have to closely monitor the behavior and condition of the tortoises that are active outside their burrows.
Rachel Foster is a research associate at the San Diego Zoo Desert Tortoise Conservation Center. Read her previous post, Saving Tortoises, One Urolith at a Time.
Are the start and end hibernation dates dependent on the temperatures, age of the animal or the length of day or other factors?
also, does the total amount of time in hibernation have anything to do with age of the animal; for example, the babies spend more time hibernating?
The start and end dates of hibernation depend on a number of different factors including those you have mentioned. Temperature and photo period does influence when a tortoise goes down and comes up from hibernation. The warmer the temperatures are, the less likely it is that the tortoises will go under permanently for the winter. For example, this year has been unseasonably warm, and the tortoises went down much later than usual. For the past few weeks the afternoons have been in the mid to upper 60s and we still see some tortoises coming out to bask at the opening of their burrows. Also, tortoises will sometimes come out of hibernation when it rains to drink.
Age can also be a factor in the length or timing of hibernation. We have noticed here at the Center that the juveniles/hatchlings spend less time hibernating than the adults and will come out of their burrows sporadically through the winter. It is also not uncommon for a sick tortoises to either never go down for hibernation or to come up early to bask in an attempt to increase body temperature.
As with any animal behavior there will always be exceptions to the rules. It is very important to pay attention to the normal behavior of the animals you live with (regardless of species) so that you will quickly recognize any changes. As we know, behaviors can change for a variety of reasons, and it is important to recognize whether the changes are due to environmental factors or illness.
What is the difference between brumation and hibernation? Just the species it is being applied to? Thank you!
Moderator’s note: Yes, brumation refers to reptilian hibernation. Try that one out at your next family gathering.