Body weight and measurements
Weight trends can be a helpful indicator of hydration and nutritional status. Upon presentation of a sea turtle, obtain body weight and standardized measurements, including maximum and minimum curved and straightline carapace length (SCL) and width (Fig 1) (Table 1). If possible, a maximum depth or body depth, measured after the animal inhales, is also useful. Take the depth measurement three times; the average is a good measure with which to track change.
|Table 1. Adult female sea turtle body weight and estimated age at maturity (Wyneken 2007, Wyneken 2006)|
|Species||Adult female weight (kg)||Female age at maturity (years)|
|Kemp's ridley (Lepidochelys kempii)||32-49||10-12|
|Olive ridley (Lepidochelys olivacea)||35-45||13|
|Hawksbill (Eretmochelys imbricata)||78-91||---|
|Green turtle (Chelonia mydas)||96-186||28-40|
|Loggerhead (Caretta caretta)||170-182||29-30|
|Leatherback (Dermochelys coriacea)||200-916||11-14|
Subjective body condition scoring
At the Georgia Sea Turtle Center (GSTC), a body condition scale based on a 1-5 scoring system is used. A turtle that is emaciated with sunken eyes, that has a loss of shoulder and neck musculature as well as poor muscle tone would score a 1 on the scale. There is also loss of inguinal fat in the inguinal space, prominent skeletal elements on the skull and plastron, as well as loss of soft tissue between the carapace and plastron (Fig 2). The plastron may be slightly sunken in or concave (Fig 3). A body condition score (BCS) of 2 indicates that the turtle is thin (Fig 4). The neck muscles are pronounced and the shoulders are thin and wrinkled. A BCS 3 is normal (Fig 5), while 4 is robust (Fig 6) and 5 is obese.
Body condition scoring should be based on physical examination and not just observation. Edema of the subcutaneous tissue is not uncommon in debilitated turtles with hypoalbuminemia and can make the turtle falsely appear more robust.
Objective body condition scoring
An objective assessment of body condition uses a standard formula. To calculate a body condition index (BCI) requires two measurements where BCI = [weight (kg)/straight carapace length (cm3)] X 10,000 (Table 2).
|Table 2. Relationship between body condition index (BCI) and interpretation of body condition scoring in the sea turtle|
|Condition Index Code||BCI||Subjective Visual Interpretation|
Carapace length and sexual maturity
Age of sexual maturity varies among sea turtle species and within different populations of the same species. For example, loggerhead sea turtles (Caretta caretta) reach sexually maturity between 25 to 35 years of age, whereas the more recent research on leatherback sea turtles (Dermochelys coriacea) indicate they become sexually mature at approximately 11 to 25 years of age (Connet 2009, TEWG 2007, Snover 2002).
Onset of sexual maturity is related to carapace size. The turtle enters puberty when carapace length is approximately 75% of adult carapace length. Although there is considerable variability, approximate carapace size for mature turtles ranges from greater than 55 cm curved carapace length (CCL) in Kemp’s ridley (Lepidochelys kempii) and olive ridley turtles (Lepidochelys olivacea) to more than 130 cm CCL for leatherbacks (Table 3, Table 4).
|Table 3. Straight carapace length (SCL) in adult sea turtles (Wyneken 2007, Wyneken 2006)|
|Species||Adult SCL (cm)||Adult female SCL (cm)|
|Olive ridley (Lepidochelys olivacea)||56-78||60|
|Kemp's ridley (Lepidochelys kempii)||58-75||60|
|Green turtle (Chelonia mydas)||59-117||83-113 (average 97)|
|Hawksbill (Eretmochelys imbricata)||63-94||---|
|Loggerhead (Caretta caretta)||70-125||75-104 (average 92)|
|Table 4. Curved carapace length (CCL) in adult leatherback sea turtles (Dermochelys coriacea) (Wyneken 2007, Wyneken 2006)|
|Adult CCL (cm)||Adult female CCL (cm)|
|*The average value for Pacific Central American populations|
|**The average value for Caribbean populations|
For additional information on physical evaluation of the sea turtle, visit Sea Turtle Physical Examination Part 1: Eyes-Ears-Nose-Throat and Sea Turtle Physical Examination Part 2.
**Login to view references**
Conant TA, Dutton PH, Eguchi T, et al. Loggerhead sea turtle 2009 status review under the U.S. Endangered Species Act. NOAA Fisheries website. August 2009. Available at http://www.nmfs.noaa.gov/pr/pdfs/statusreviews/loggerheadturtle2009.pdf. Accessed on May 16, 2014.
Miller JD, Limpus CJ. Ontogeny of marine turtles gonads. In: Lutz PL, Muzick JA, Wyneken J (eds). The Biology of Sea Turtles. Boca Raton, FL; CRC Press: 199–224
Norton TM. Sea turtle rehabilitation. In: Miller RE, Fowler M (eds). Fowler’s Zoo and Wild Animal Medicine Current Therapy Volume 7. St. Louis, MO:Elsevier Saunders;2012:239.
Snover ML. Growth and ontogeny of sea turtles using skeletochronology: methods, validation and application to conservation. Ph.D dissertation, Duke University, Durham, North Carolina. 2002.
Stewart JR, Johnson C, Godfrey MH. The minimum size of leatherbacks at reproductive maturity, with a review of sizes for nesting females from the Indian, Atlantic and Pacific Ocean basins. Herpetological Journal 17(2):123-128, 2007.
Wyneken J, Godfrey MH, Bels V (eds.). Biology of Turtles: From Structures to Strategies of Life. Boca Raton, FL: CRC Press; 2007: 1-408.
Wyneken J, Mader DR, Weber III ES, et al. 2006. Medical care of sea turtles. In: Mader DR (ed). Reptile Medicine and Surgery, 2nd ed. St. Louis, MO: Elsevier Saunders; 2012: 972-1007.
Wyneken J. The Anatomy of Sea Turtles. US Department of Commerce NOAA Technical Memorandum. NMFS-SEFSC-470, 1-172, 2001.
Visit Widecast.org for more information on standardized sea turtle measurements.
Norton T, Wyneken J. Body condition scoring the sea turtle. January 27, 2015. LafeberVet Web site. Available at https://lafeber.com/vet/body-condition-scoring-the-sea-turtle/