It has come to our attention that some veterinary surgeons and keepers are relying upon data provided by the 'Jackson Ratio' graph in circumstances which are not appropriate.
The 'Jackson Ratio' graph may only be used with tortoises of 'average' body morphology, e.g. Testudo graeca and Testudo hermanni. This graph MUST NOT be used with Testudo horsfieldii or Testudo marginata, as it will invariably produce incorrect results. The body shape of these species is such that T. horsfieldii, being 'short and square' will tend to read 'overweight' even if it is actually underweight. T. marginata, being 'long and narrow' will, on the other hand, read 'underweight' even if it is of a perfectly average and safe weight for its size.
We also take this opportunity to point out that the 'Jackson Ratio' graph is of no use whatsoever for assessing the health of Hinge-back, Leopard, Sulcata or any other tropical, non-hibernating species. Neither is it of value in determining the suitability of Box turtles to hibernate.
This graph must ONLY be applied to Testudo graeca and Testudo hermanni and to no other species. When measuring for the Jackson Ratio graph, use the straight line carapace method, and do not measure 'over the curve'.The correct way to take these measurements is SHOWN HERE.
The Jackson Ratio graph can be downloaded as a PDF file HERE
More useful hibernation information on this site: