Jackson ratio

Researched and devised by Dr. Oliphant Jackson, the Jackson ratio is a method of determining whether a member of the tortoise species Testudo graeca or Testudo hermanni is maintaining its optimum bodyweight, which is necessary for a successful hibernation. The Jackson Ratio is calculated by taking the weight of the tortoise in grams and dividing it by the cube of the length of the tortoise's carapace in centimeters. This is essentially a value of the density of the tortoise in g/cm^3. The optimal value for this ratio is 0.21 with a range of 0.18 - 0.22 being acceptable for hibernation. Values significantly less than this indicate an underweight tortoise and larger values are indicative of overweight tortoises. The Jackson Ratio is expressed as a graph of minimum and optimum weights for a given carapace length. This exhibits the same principle without the maths.

External links

• http://www.tortoisetrust.org/articles/jackson.html
• http://www.tortoisetrust.org/articles/measuring.htm
• http://www.tortoise-protection-group.org.uk/site/169.asp
• http://www.slowcoach.org.uk/care/jackson/jackson.html
• http://www.heosemys.org/Jackson.php

Tortoise family of turtles (Testudinidae)
Genus	Species of the tortoise family
Aldabrachelys	Aldabra giant tortoise
Astrochelys	Angonoka tortoise Radiated tortoise
Chelonoidis	Yellow-footed tortoise Chaco tortoise Galápagos tortoise Red-footed tortoise
Chersina	Angulate tortoise
Centrochelys	African spurred tortoise
Cylindraspis†	Domed Mauritius giant tortoise† Domed Rodrigues giant tortoise† Réunion giant tortoise† Saddle-backed Mauritius giant tortoise† Saddle-backed Rodrigues giant tortoise†
Geochelone	Burmese star tortoise Indian star tortoise
Gopherus	Bolson tortoise Desert tortoise Gopher tortoise Sonoran Desert tortoise Texas tortoise
Homopus	Common padloper Nama padloper Karoo padloper Greater padloper Speckled padloper
Indotestudo	Elongated tortoise Forsten's tortoise Travancore tortoise
Kinixys	Bell's hinge-back tortoise Forest hinge-back tortoise Home's hinge-back tortoise Lobatse hinge-back tortoise Natal hinge-back tortoise Speke's hinge-back tortoise
Malacochersus	Pancake tortoise
Manouria	Asian forest tortoise Impressed tortoise
Psammobates	Geometric tortoise Serrated tortoise Tent tortoise
Pyxis	Flat-backed spider tortoise Spider tortoise
Stigmochelys	Leopard tortoise
Testudo	Hermann's tortoise Kleinmann's tortoise Marginated tortoise Russian tortoise Spur-thighed tortoise
Phylogenetic arrangement based on turtles of the world 2012 update: annotated checklist. Key: †=extinct.