Hawksbill

Juvenile hawksbill in a mound of sargassum shows its ornate shell.
Juvenile hawksbill in a mound of seaweed. Hawksbills were once hunted for their beautiful shells. NPS Photo.
The Hawksbill Sea Turtle
Species: Hawksbill (Eretmochelys imbricata)
Size: Adult carapace (upper shell) length = 25-36 inches (65-100 cm) (National Marine Fisheries Service 2015, U.S. Fish and Wildlife Service 2015)
Adult weight = 100-200 pounds (45-90 kg) (National Marine Fisheries Service 2015, U.S. Fish and Wildlife Service 2015)
Coloration: Hatchlings are dark brown; adults are brown above and yellow below; the carapace (upper shell) has a serrated back and overlapping scutes (plates) that are dark amber with radiating streaks of orange, red, and/or black
Range: Nesting – Worldwide, most nesting occurs in Australia, Mexico, Cuba, Indonesia, the Republic of Seychelles, and Puerto Rico; in the U.S., nesting occurs in Puerto Rico, the Virgin Islands, Hawaii, American Samoa, Guam, and Florida (National Marine Fisheries Service 2015)
Non-nesting – Found in subtropical and tropical waters of the Atlantic, Pacific, and Indian oceans and associated bodies of water from 30° North to 30° South latitude worldwide; widely distributed throughout the Caribbean Sea and western Atlantic Ocean, regularly occurring in southern Florida and the Gulf of Mexico, especially Texas (National Marine Fisheries Service 2015)
Diet: Primarily sponges, also other invertebrates and algae (National Marine Fisheries Service 2015, National Marine Fisheries Service and U.S. Fish and Wildlife Service 1993)
Lifespan: Unknown; reach sexual maturity at 27 inches (70 cm) in length for males and 30 inches (80 cm) in length for females; age at that length is unknown (National Marine Fisheries Service 2015)
Status: Federally endangered
Nesting season: April to November in most locations; females nest every 2-3 years and lay 3-5 clutches (nests) in one nesting season; each nest contains an average of 130 eggs that take about 2 months to hatch (National Marine Fisheries Service 2015)
Historic population: Unknown
Lowest population: Unknown
Current population: Current estimates include 8,000 to 10,000 females nesting annually in Australia; 2,800 females nesting annually in Mexico; 2,000 females nesting annually in Indonesia; and 1,000 females nesting annually in the Republic of Seychelles. In the U.S., 500-1,000 nests are found annually in Puerto Rico (National Marine Fisheries Service 2015)
Population trends: Undetermined; the solitary, low-density nesting behavior of hawksbills makes it difficult to determine population trends (National Marine Fisheries Service 2015)
Reasons for decline: Historic and ongoing direct harvest of juveniles and adults for their shells; historic and ongoing direct harvest of eggs, juveniles, and adults for other purposes; loss and degradation of coral reef habitat (National Marine Fisheries Service 2015, National Marine Fisheries Service and U.S. Fish and Wildlife Service 1993)
Current threats: Loss and degradation of coral reef habitat; direct harvest of eggs, juveniles, and adults; increased recreational and commercial use of Pacific nesting beaches; incidental capture in fishing gear; degradation of marine and nesting habitat (National Marine Fisheries Service 2015).

FUN AND FASCINATING FACTS about the Hawksbill:
  • A bill that fits the bill! The hawksbill’s name comes from its mouth. Its head is longer than other sea turtles and tapers to a pointed, resembling a beak or bill of a hawk. This unusual shape enables hawksbills to reach into the holes and crevices of the coral reefs where they live to find sponges and other invertebrates to eat.
  • Extra protection… The scutes (plates) on the hawksbill’s carapace (upper shell) are thicker than those of other sea turtles, and they overlap like shingles on a roof. This helps protect the hawksbill from getting injured by sharp coral and rocks, especially during storms (U.S. Fish and Wildlife Service 2015).
  • Too pretty for your own good… The beautiful, ornate shell of the hawksbill sea turtle has been its downfall. Many thousands were killed, and some still are, to make “tortoise shell” combs, mirrors, jewelry, and other items. This practice is illegal but still occurs in some countries.
  • To each their own… Most sea turtles nest individually (rather than all at the same time), at night, and in concentrated, defined areas or colonies that can be monitored. Hawksbill sea turtles nest individually and at night, but not in concentrated, well defined areas or colonies. This makes it much more difficult to estimate numbers or determine if hawksbill populations are increasing or decreasing.
  • A turtle with an iron stomach! Sponges may look like plants, but they are actually animals. These marine invertebrates are toxic to some animals and avoided by most others as food. Why? A large part of the sponge’s body is made up of spicules, tiny particles that resemble glass needles. Few creatures are able to feed on sponges, and most that do have special adaptations that protect them from the sharp spicules. Hawksbills, on the other hand, have no such protection. How they survive eating the needle-like spicules and sponge toxins is a mystery. Consumption of sponge toxins may be the reason hawksbills may be poisonous, even fatal, if eaten (Meylan and Whiting 2015, Meylan 1988).
  • There’s something about Padre! In the early hours of an August morning in 1998, Dr. Shaver and the sea turtle team were set to release a clutch of newborn turtles that hatched during the night. No one had seen the female when she laid the eggs weeks earlier, and it was thought the nest was that of a Kemp’s ridley. As the team transported the tiny hatchlings to the release site, Dr. Shaver realized the hatchlings were different. She examined closely and began to suspect they might be hawksbills! No hawksbill nest had ever been documented nesting in Texas before. Hawksbills typically nest in forested areas in the Caribbean. The team took hundreds of photographs of the hatchlings before releasing them to help document and confirm the species. Using the photos, measurements, and tissue samples from unhatched eggs, Dr. Shaver confirmed the nest was indeed a hawksbill nest! It was and remains the first and only hawksbill nest ever documented in Texas (Shaver 1998).
Literature Cited:
Meylan, A. 1988. Spongivory in Hawksbill Turtles: A Diet of Glass. Science 239:393-395.
Meylan, A. and S. Whiting. 2015. The Hawksbill’s Distinctive Diet. Retrieved from http://seaturtlestatus.org/pdf/r3_hawksbills-diet.pdf
National Marine Fisheries Service. 2015. Hawksbill Sea Turtle (Eretmochelys imbricata) species page. Retrieved from http://www.nmfs.noaa.gov/pr/species/turtles/hawksbill.htm
National Marine Fisheries Service and U.S. Fish and Wildlife Service. 1993. Recovery Plan for Hawksbill Turtles in the U.S. Caribbean Sea, Atlantic Ocean, and Gulf of Mexico. National Marine Fisheries Service, St. Petersburg, Florida.
Shaver, D.J. 1998. Padre Island National Seashore Kemp's Ridley Sea Turtle Project and Texas Sea Turtle Strandings 1998 Report. U.S. Department of the Interior, National Park Service. 58pp.
U.S. Fish and Wildlife Service. 2015. Hawksbill Sea Turtle (Eretmochelys imbricata) species page. Retrieved from http://www.ecos.fws.gov/speciesProfile/profile/speciesProfile?spcode=C00E

Last updated: December 6, 2018

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