The Jackson Ratio is a graph used by many tortoise keepers to correctly assess the body weight of their tortoise(s) at the time of hibernation or in the event that the tortoise may become ill. The Late Dr Oliphant Jackson MRCVS, studied and recorded the data of many Mediterranean tortoises, Such as the Spur- thighed tortoise (Testudo Graeca) and the Hermann’s tortoise (Testudo Hermanni). It was at this time in Dr Jackson’s studies he observed that there was such a thing as an optimum body weight amongst these tortoises, thus producing a weight to length ratio graph, now known as The Jackson Ratio. Using the Jackson Ratio Measuring your tortoise to record on the graph will involve the use of measuring scales (weight is measured in grams) and either a ruler or tape measure (length is measured in millimetres). When measuring your tortoise the full length of the Carapace is to be measured.
We find that measuring a tortoise between two solid ends will help to get accurate measurements. Please note that measuring over the top of the shell is the incorrect way to measure the Carapace of a tortoise.