How fat is obese for a tortoise?

[GeoTerraTestudo]

Many years ago, one of my box turtles was ill and looked "fat." I took her to the vet, and it turned out she had a respiratory infection (due to chilling), and so her "chubby" appearance was in fact edema, which is basically retention of excess fluid, as opposed to actual adipose tissue. So, I have never had a fat turtle. However, I was told that a turtle is considered obese if it is too chubby to withdraw itself into its shell, which can be dangerous when faced with a predator or another aggressive turtle.

When we first got our Russians a couple months ago, after a short period of adjustment, they began to eat like champions, just like Russians are supposed to (they eat a lot during the growing season because they have a long dormancy period). Now, looking at Mork and Mindy, they seem rather fat. Not so chubby that they can't withdraw into their shells, but chubby enough that it looks like they may be carrying excess weight under their shell. So, I decided to use the Susan Donoghue equation for calculating the minimum healthy weight for a tortoise (Mike Pingleton, 2001):

CL^3 * 0.191 = Minimum weight (g)

Both of my tortoises measure a little over 4 inches long, and weigh a little more than 300 g. Based on the Donoghue equation, they both have a weight that is about 160% of the minimum weight for their carapace length. They look like they have become chubbier over the past month, but strangely, based on weighing them on a kitchen scale (which is admittedly not very accurate), they appear to have lost a little weight instead.

So, my question for the wise members of TFO is, Are my tortoises fat? If they are, should I feed them a bit less than I feed them now (which is "to satiation" every morning). If so, then how much should I feed them? Should I reduce their servings by a little or a lot? Should I feed them nothing for a day, or feed them only every other day to get them to lose weight? Or, if they are overweight now, will they simply return to a normal weight by brumating (hibernating) over the winter? Looking forward to reading your thoughts and advice.

 

[dmmj]

I would say when they can no longer withdraw you might have a problem.

 

[Maggie Cummings]

I have a Russian that is so fat she is bigger then her shell, her butt is out and her carapace looks like a hat. I'll post a picture of her later. Her name has gone from Natasha to Fat Nat...I am feeding her twice a week just enough to stave off starvation...

 

[Yvonne G]

Hi Gaddy:

Yes, your tortoises are fat! Russians are hard-wired to do a lot of eating because in the wild their awake season is quite short. BUT in the wild, they also do a lot of wandering. We make a huge mistake with Russians by keeping them in habitats that are too small for them to get enough exercise.

 

[GeoTerraTestudo]

I have a Russian that is so fat she is bigger then her shell, her butt is out and her carapace looks like a hat. I'll post a picture of her later. Her name has gone from Natasha to Fat Nat...I am feeding her twice a week just enough to stave off starvation...

Is she obese, or does she have MBD? I sure hope your Russian tortoise doesn't look like this one:

Note: That poor tortoise is not one of mine. She is under the care of the Tortoise Trust, and I found her photo here:
http://www.tortoisetrust.org/articles/webdiet.htm

---

Yes, your tortoises are fat! Russians are hard-wired to do a lot of eating because in the wild their awake season is quite short. BUT in the wild, they also do a lot of wandering. We make a huge mistake with Russians by keeping them in habitats that are too small for them to get enough exercise.

Do you mean mine or Maggie3Fan's? Anyway, your right about the link between weight gain in tortoises, and too much food and/or not enough exercise; it's as true for them as it is for us. I do try to give my Russians as much exercise as possible by letting them explore the grounds or the porch outside, and even the house when it's not "turtle weather" out there. However, they still seem to be a bit chubby. I guess it could be much worse; they could be in a condition where they don't feed at all, so I guess I can't complain.

It's interesting to note that when they are outdoors and feeding on grass and weeds, not only are they burning calories by walking around, but they also seem to eat less. Not sure if that's because the environment (temperature, available plants, etc.) encourage that, or if it's just because when they are in their pens they eat out of boredom. I sure hope it's not the latter. If I don't give them enough in the morning, then they start tromping around their pens looking for food later in the day. So, sometimes I give them a little in the morning, and a little in the afternoon. At any rate, I am cutting back on how much I give them.

One other question: how quickly does a tortoise's weight change in response to diet, assuming they are getting what they need? On the one hand they are "cold-blooded," so their metabolisms are only about 1/10th of what a comparably sized mammal's would be. On the other hand, they do eat a heckuva lot, so I'm wondering how quickly they drop excess weight when on a diet, and how quickly they gain weight if they have been too thin. I'm sure growing, young tortoises respond faster than older tortoises whose growth has plateaued. But on average, how quickly will a tortoise go down to its normal weight if it is overweight and is being offered less food?