ESTIMATING TORTOISE AGE: DID YOU KNOW?
August 27, 2024
Did you know that there is no precise method of visually determining a tortoise’s age? Some use growth rings on the scutes of the carapace (top shell) to indicate age, but just like growth rings on a tree, a tortoise can develop no rings, or up to several growth rings per season. Others use forelimb size or shell length by measuring the midline carapace length (MCL) to estimate age, but these methods can still be inaccurate, as growth rates and length can vary year to year depending on food availability and environmental conditions. Upon hatching, tortoises emerge at around 45 mm (< 2 inches), and can grow up to 360mm (14.17 inches)! Our biologists estimate age in the field using carapace length at the midline (MCL) paired with other visible sexual characteristics. Tortoises around 180mm (7 inches) or more in carapace length are considered adults and are likely 15 or more years old, and have reached sexual maturity. Adult tortoises that present significant wear on the vertebral scutes are likely older adults, and may appear sunken in as they near the end of their lifespan.
Want to know more? See the sources from the USFWS and academic papers below and stay tuned for our next “Did You Know?” segment!
https://www.fws.gov/species/desert-tortoise-gopherus-agassizii
https://deserttortoise.org/wp-content/uploads/2019_Berry-and-Murphy_CRM_5_109_agassizii.pdf
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