Jackson ratio

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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.

Tortoise family of turtles that live on land

Tortoises are reptile species of the family Testudinidae of the order Testudines. They are particularly distinguished from other turtles by being land-dwelling, while many other turtle species are at least partly aquatic. However, like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like other members of the suborder Cryptodira, they retract their necks and heads directly backwards into the shell to protect them.

Hibernation Process in which an organism enters a dormant and inactive state in order to pass winter

Hibernation is a state of inactivity and metabolic depression in endotherms. Hibernation refers to a season of heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most commonly occurs during winter months.

Carapace part of exoskeleton in some animals

A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.

Tortoise Protection Group organization

The Tortoise Protection Group (TPG) is a British non-profit organisation founded in January 2007 with the aim of stopping the importation of tortoises into the UK for the commercial pet trade, and to promote high standards of husbandry in tortoise keeping. The mission of the Tortoise Protection Group is to help ensure the survival of tortoises in the wild and to promote high standards of husbandry for tortoise keepers in the UK. Over the last year, it has been working closely with members of Parliament and various charities to bring about a change in legislation, with a petition enlisting thousands of signatures.

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