By Stacey Venzel
Compared to other animals, turtles take their time making ticks on the growth chart. Humans can reach sexual maturity in their teenage years, but some turtles take twice as long to mature.
With differences among both species and individuals, including influences by age and the environment, average turtle growth rates are all over the board.
AVERAGE GROWTH RATES
Smaller species tend to grow slower than larger species. This makes sense when you realize all hatchlings are close in size but some only grow to a few ounces while others reach hundreds of pounds. Juvenile red-eared sliders can grow at an annual rate of half an inch whereas larger hawksbill sea turtles have a rate of nearly 4 inches per year.
GROWTH WITH AGE
Throughout its life cycle, a turtle can designate its energy sources for specific functions. In its younger years, a turtle grows faster because it is channeling most of its food toward getting big and strong to avoid predators. As it matures, an adult turtle will dedicate its energy consumption less toward growth and more toward reproduction and overall health. This explains the shift in an aging green sea turtle’s diet from protein-rich carnivore to vitamin-fused herbivore.
ENVIRONMENTAL GROWTH RATE
Increased growth rates occur during optimal environmental conditions. Species grow faster in warmer climates and seasons, as evidenced by a group of sliders in a warmed pond that grew two times faster than individuals in an unheated pond in the same region. Diet can also affect growing speed among individuals, as referenced with the food change in developing green sea turtles.
Annette C Broderick, Brendan J Godley, Shannon Gore, Et. Al., “High rates of growth recorded for hawksbill sea turtles in Anegada, British Virgin Islands,” Ecology and Evolution, March 14, 2013, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4020687/.
Karen Eckert, David Gulko, Sea Turtles: An Ecological Guide (Honolulu, Mutual Publishing, 2004), 44, 75.
Carl J Franklin, Turtles: An Extraordinary Natural History 245 Million Years in the Making (St. Paul, Voyageur Press, 2007), 44-45.
Whit Gibbons, Judy Greene, Turtle: The Animal Answer Guide (Baltimore, The John Hopkins University Press, 2009), 70.