Adult: A member of the population that has reached sexual maturity. Sea turtles may reach sexual maturity at different sizes rather than after a certain number of years; hence, the age at sexual maturity may be quite variable and dependent on a number of factors, such as amount and quality of food sources.

Anthropogenic: Effects or processes that are derived from human activities, as opposed to natural effects or processes that occur in the environment without human influences.

Aquaculture: The process of raising aquatic organisms in a controlled environment for commercial purposes.

Arribada: The emergence of and aggregation of ridley turtles onto nesting beaches. Copulating pairs congregate in large numbers followed by mass nesting of females, generally over a period of several days. Olive ridley turtles exhibit mass nesting behaviour in India along the coast of Orissa.

Axillary notch: The notch in the front part of the shell into which the front leg fits.

Basking: A behaviour that exposes the body, or a portion of the body, to the warmth of the sun.

Biodiversity: In an ecosystem, variability among living organisms from all sources, sometimes measured by the total number of species or other taxonomic groupings, and their relative abundances.

Body pit: The depression dug by the female turtle during nesting. Body pits are characteristic of different species and range from shallow (ridleys) to rather deep (greens and leatherbacks) and may persist for months under certain conditions. The center of the body pit usually does not indicate the location of the egg chamber.

Bycatch: Organisms caught incidentally, or by accident, during fishing operations for which the organism is not a target. Bycatch can be fish with no commercial value, juveniles of marketable species, sea turtles and birds, marine mammals such as seals, dolphins and whales, and many other forms of ocean life. See also: Incidental capture.

Carapace: A bony shield or shell covering all or part of the dorsal (top) side of an animal.

Carnivore: An organism that primarily eats other animals. See also: Herbivore.

Caruncle: A temporary egg tooth. The horny tubercle on the snout of a hatchling is used to cut through the eggshell.

Caudal: Pertaining to the tail.

Cheloniid: Cheloniids are hard-shelled sea turtle species (green, loggerhead, olive ridley, Kemp’s ridley, flatback and hawksbill) that are members of the Cheloniidae Family. The leatherback it is the sole living member of the Dermochelyidae Family. See also: Dermochelyid.

Cloaca: The common cavity into which the intestinal, urinary, and reproductive tracts open in reptiles and other animals; the opening through which sea turtle eggs are laid.

Clutch: A group of eggs laid at the same time. Clutch size refers to the number of eggs produced by a turtle/deposited in a nest at one time.

Conservation: The preservation and careful management of the environment and of natural resources.

Costal bones: The bones of the carapace lying between the neural and the peripheral bones. The lateral (also called pleural or costal) scutes roughly overlie these bones.

Crawl: The tracks of a turtle on the beach. “Track” is used synonymously with crawl. See also: False crawl.

Curved carapace length: Length of the turtle’s carapace measured with a flexible tape measure. CCL can be measured in one of two ways; (i) CCL minimum – from the notch at the anterior of the carapace to the notch at the posterior end of the carapace where the last two marginal scutes meet, and (ii) CCL n-t –from the notch at the anterior of the carapace to the tip of the last posterior marginal scute. See also: Carapace.

Curved carapace width: Width of the turtle’s carapace measured with a flexible tape measure. A variety of start and stop points are used by different research groups, but the maximum widest measurement is usually taken. See also: Carapace.

Data Deficient: An IUCN category for listing endangered species. A taxon is Data Deficient when there is inadequate information to make a direct, or indirect, assessment of its risk of extinction based on its distribution and/or population status. (For precise criteria, visit:

Dermochelyid: Leathery-shelled sea turtle species (the leatherback turtle is the only Dermochelyid sea turtle). All other sea turtle species are Cheloniids. See also: Cheloniids.

Disorientation: The lack of directed movement towards a specific area or goal. Sea turtle hatchlings on the beach can be disoriented at night when confronted by bright lights on a nesting beach. Also called: Misorientation. See also: Orientation.

Dorsal: On the upper or top side or surface.

Drift lines: Elongated masses of seaweed, debris and other floating objects that often form where ocean currents converge. Hatchling sea turtles take refuge in drift lines.

Ectothermic: An animal, including most reptiles, whose body temperature is determined largely by ambient (outside) temperature, as opposed to generating heat within its own body. With the arguable exception of the leatherback, sea turtles are ectothermic.

Egg chamber: A hole dug by an adult female turtle using her rear flippers, into which she lays her eggs.

Embryo: This stage of development spans the period from the time of first cell division until hatching.

Emergence success: The relative number of eggs in a clutch that produce live hatchlings that leave the nest chamber.

Emergence: (a) Female: The action of the female turtle leaving the water and coming onto land to nest. (b) Hatchling: The emergence of hatchlings on the beach surface above the nest cavity (emergence occurs a variable number of hours or days after hatching from the egg).

Endangered: An IUCN category for listing endangered species. A taxon is Endangered when it is considered to be facing a very high risk of extinction in the wild. (For precise criteria, visit:

Environmental sex determination: Environmental sex determination (ESD) is the phenomenon when the sex of the offspring is determined by the environment. TSD (temperature-dependent sex determination) is a special case of ESD. See also: Temperature-dependent sex determination.

Ex situ: Meaning “out of place” and the opposite of in situ. Ex situ conservation is the practice of protecting wild animals/plants outside of their native habitat. In sea turtle conservation, an example of ex situ conservation is the practice of relocating nests to a hatchery.

False crawl: The track left by a sea turtle that has ascended a beach but returned to the sea without laying eggs.

Foraging: The process of looking for food. Areas where turtles feed are referred to as foraging/feeding habitat or foraging/feeding grounds.

Feral: Animals (typically pets or livestock) that have reverted to a wild condition after escape or release from captivity. Feral dogs, for example, are important predators of sea turtles along some parts of the Indian coastline and in the Andaman and Nicobar Islands.

Fibropapillomas: Lobulated tumors that grow on the skin, eyes, in the oral cavity, and on the viscera of sea turtles. This disease is life-threatening as these lesions can impair the turtle’s ability to swim, eat, see, and even breathe.

Fidelity: In sea turtles, nest site fidelity refers to adult females returning to the same beach to lay their eggs clutch after clutch, year after year.

Genus (or genera): A taxonomic division that generally refers to a group of animals which are similar in structure and descent but are not all able to breed amongst themselves. For the seven species of sea turtles, there are six different genera: Genus Caretta – Loggerhead turtle; Genus Chelonia – Green turtle; Genus Dermochelys – Leatherback turtle; Genus Eretmochelys – Hawksbill turtle; Genus Lepidochelys – Kemps ridley and olive ridley turtle; Genus Natator – Flatback turtle.

Gill net: A fishing net set vertically in the water so that fish swimming into it are entangled by the gills in its mesh.

Habitat: The specific place in the natural environment where an animal or plant lives.

Hatchery: A man-made structure or enclosed (e.g., fenced) area constructed for the incubation of eggs.

Hatching success: The relative percentage of eggs in a nest that produce live hatchlings. See also: Emergence success.

Hatching: The process of leaving the egg after development is completed.

Hatchling: A turtle that has recently emerged from the egg.

Head-starting: The experimental practice of raising hatchling turtles in captivity for the first several weeks or months of life.

Herbivore: An animal that eats mainly plants or parts of plants. Green sea turtles are primarily herbivores. See also: Carnivore.

Home range: The area in which an animal normally lives, whether or not it defends the area from other animals; the area that an animal learns thoroughly and habitually patrols.

Immature: An animal that has not reached sexual maturity. See also: Juvenile.

Imprint: Impress on or fix in the mind memory of a thing or person. In the case of sea turtles, hatchling turtles are thought to imprint on the beach or coastal area from where they hatched, enabling them to return to this site to breed. See also: Natal homing.

In situ: Latin term meaning “in place” or “not removed”. With sea turtles in situ is often used to refer to nests that are left in place as opposed to nests that are relocated or moved to a hatchery. See also: Ex situ; Relocation; Hatchery.

Incidental capture: The unintended capture of non-target species during fishing activity. For example, sometimes sea turtles are incidentally captured during fishing activities for shrimp or swordfish. Also called: Incidental catch; Incidental take. See also: Bycatch; Take.

Incubation: The process of development between egg-laying and hatching. In sea turtles, incubation typically lasts 50-75 days depending on the ambient temperature and the species involved.

Inframarginal pores: Pores located near the rear of the inframarginal scutes. These pores are only found in the ridleys (Lepidochelys sp.).

Internesting (interval or period): The period of time between a successful nest and the next nesting attempt (sea turtles of all species lay several clutches of eggs during a nesting season). Typically this is 10-18 days in most species and up to 28 days for ridleys.

Juvenile: Not at full size or strength; a sexually immature sea turtle. Inasmuch as wild sea turtles may take up to 50 years to reach sexual maturity, and that different species and even populations within a species have different growth rates, the distinction between a juvenile and subadult is not well defined. This distinction is further complicated in that there is little or no correlation between size and age in sea turtles. See also: Immature; Subadult.

Laparoscopy: Surgical procedure to examine and/or treat abdominal and pelvic organs through a small surgical viewing instrument (laparoscope) inserted into the abdomen.

Management: The science of working with the characteristics and interactions of habitats, wild animal populations, and humans to achieve specific goals.

Marginals: The scutes lying around the margins of the carapace. These more or less overlie the peripheral bones.

Migration: The directed movement of animals from one place to another. Sea turtle migrations usually involve feeding and nesting activities.

Misorientation: See: Disorientation.

Natal homing: The behaviour by which an animal returns to the place where it was born. For sea turtles, adult females return to lay eggs in the general region where they were born.

Navigation: The method by which an animal orientates and finds a location.

Necropsy: Dissection of a dead body to determine the cause of death. Also called: Postmortem; Autopsy.

Nest: A container or shelter in which birds, reptiles, fish, insects, or other animals deposit eggs or keep their young.

Nesting population: A group of adult female turtles that tends to nest in a specific and defined region or beach.

Nesting: The process of depositing eggs in a nest cavity on a beach. This is often used interchangeably with breeding.

Oceanic: The open ocean where depths are greater than 200m.

Orientation: A specie’s ability to be aware of its environment and its position within that environment with reference to time and space. A species cannot navigate unless it is oriented.

Oviposition: The process of depositing eggs.

Papillae: The esophagus of sea turtles is lined with keratinised projections that point inward towards the stomach. The papillae end where the esophagus joins the stomach and are presumed to trap food while excess water is expelled prior to swallowing.

Pelagic: An organism, such as a young sea turtle, living in the open ocean. Organisms are pelagic if they occupy the water column, but not the sea floor, in either the neritic zone or oceanic zone. Leatherbacks are considered to be the most pelagic species of sea turtle.

Peripheral bones: The bones around the edge of a turtle’s carapace that lie beneath the marginal scutes.

Phalanges: The elongate finger or toe bones in the flippers.

Philopatry: Derived from the Greek for “home loving”, philopatry refers to the drive or tendency of an individual to return to, or stay in, its home area. Sea turtles display philopatry by migrating from a feeding area to a breeding area and then back again.

Phylogeny: The evolutionary history or genealogy of a group of organisms.

Pivotal temperature: Pivotal temperature is the constant incubation temperature of eggs that will produce equal numbers of males and females. The pivotal temperature is a characteristic of TSD (Temperature-dependent Sex Determination). Also called: Threshold temperature. See also: Temperature-dependent sex determination.

Plastron: The ventral shell covering the underside of a turtle.

Pollution: The presence of a substance in the environment that because of its chemical or biological composition or quantity prevents the functioning of natural processes and produces undesirable environmental and health effects.

Population: A group of organisms belonging to the same species that occupy a fairly well defined locality and exhibit reproductive continuity from generation to generation. Genetic and ecological interactions are generally more common between members of a population than between members of different populations of the same species. See also: species.

Predation: When one species feeds on another species. The predator species feeds on the prey species. See also: Predator.

Predator: An animal that hunts and eats other animals. Sea turtles are important predators in the ocean food web.

Prefrontal scales: Thin, flattened, plate-like structures between the eyes that can be used to help distinguish sea turtle species.

Relocation: The removal of an organism from one site and placing it in another. Sea turtle nests that are laid too close to the ocean or in a dangerous section of beach are often relocated to safer areas (either on the beach or into a hatchery). See also: Ex situ.

Remigrant: In sea turtles, this term refers to a nesting female turtle that has been recorded nesting at a particular nesting beach before and has returned, or remigrated, to the nesting beach in a different subsequent year to nest again.

Remigration: The return of adult sea turtles to a particular breeding area in succeeding years. Depending on the species involved, remigration usually occurs on a one (ridley), two, three, or four (most other species) year cycle.

Rookery: The nesting location of populations of sea turtles. Rookery may refer to one species or to a general area of sea turtle nesting.

Scale: Thin, flattened, plate-like structures that form the covering of certain animals, including turtles and other reptiles.

Scutes: The horny scales covering the bony carapace and plastron, except in the leatherback sea turtle. The shape of the scutes does not mirror the shape of the underlying bones and they are named differently from the bones. Both are of taxonomic importance.

Sex ratio: The number of males divided by the number of females (sometimes expressed in percent). It can be specified as “Primary sex ratio” that is the sex ratio of the hatchlings, “Secondary sex ratio” that is the sex ratio of adults, or “operational sex ratio” that is the ratio of reproductive males to females.

Site fidelity: Being faithful to a particular location. Many sea turtles show nest site fidelity, returning to the same beach to lay their eggs clutch after clutch, year after year.

Species: A taxonomic term to describe a type of plant or animal which can interbreed successfully with members of the same type; these are reproductively isolated from members of all other types (or species). They may mate with similar organisms which are in the same genus and bear considerable resemblance to them but either cannot produce offspring as a result, or the offspring are sterile, or the offspring have distinct survival disadvantages. In some cases, they simply cannot mate because of morphological, behavioural, or physiological differences.

Stock: A management term which refers to a harvestable portion of a species living within a certain geographical area. A stock may include a portion of a biological population or several populations.

Straight carapace length: Length of the turtle’s carapace measured with a pair of large calipers. SCL can be measured in three ways; (i) SCL minimum – from the notch at the anterior of the carapace to the notch at the posterior end of the carapace where the last two marginal scutes meet, (ii) SCL n-t – from the notch at the anterior of the carapace to the tip of the last posterior marginal scute, and (iii) SCL maximum – from the anterior edge of the carapace to the tip of the last posterior marginal scute. Usually measured to whichever scute is longer. See also: Carapace.

Straight carapace width: Width of the turtle’s carapace measured with a large pair of calipers. There is no standard point to measure to, but the maximum widest measurement is usually taken. See also: Carapace.

Subadult: A turtle approaching sexual maturity. See also: Juvenile.

Survival rate: The percentage of individuals surviving from one developmental stage, year class, or life stage to the next stage, or succeeding period.

Sustainable use: The use of components of biological diversity in a way and at a rate that does not lead to the long-term decline of biological diversity, thereby maintaining its potential to meet the needs and aspirations of present and future generations.

Take: Refers to any activity that might result in the following actions that impact a protected species: harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect. When a species is accorded protection under law (for e.g., all species of sea turtle are listed under Schedule I of the Indian Wildlife (Protection) Act of 1972), the listed species is protected from “take.” See also: Incidental capture.

Taxonomy: Referring to the science of hierarchically classifying animals by groups (e.g., genus and species) which share common features and are thought to have a common descent.

Telemetry: The use of electronic equipment to monitor the movements of animals. With regard to sea turtles, sonar, radio telemetry and satellite telemetry are most often used. Typically, an electronic device which emits a signal at a characteristic frequency is attached to the turtle’s carapace.

Temperature profile: Refers to the various temperatures encountered on a beach at different times of the day. Temperature profiles of the sand may be considered in both horizontal and vertical dimensions. The temperature profile may influence nest site selection and surely affects sex ratios and duration of incubation of eggs.

Temperature-dependent sex determination: Temperature-dependent sex determination (TSD) is the condition where the sex of the offspring is influenced by the prevailing temperatures during embryonic development. In sea turtles, warmer temperatures produce more or all females, cool temperatures produce more or all males, and the pivotal temperature is the constant incubation temperature that produces equal numbers of males and females. TSD also occurs in other reptiles (crocodilians, some freshwater and land turtles, some lizards), some types of fish, some types of invertebrates, etc. See also: Pivotal temperature; Environmental sex determination.

Threatened: The term is used in the 1994 IUCN Red List of Threatened Animals to refer collectively to species categorised as “Endangered” (E), “Vulnerable” (V), “Rare” (R), “Indeterminate” (I), or “Insufficiently Known” (K) and in the 1996 IUCN Red List of Threatened Animals to refer collectively to species categorised as “Critically Endangered” (CR), “Endangered” (EN), or “Vulnerable” (VU). (For precise criteria, visit:

Tracking: Following the spatial movements of an animal. Typical tracking methods employ satellite, radio, sonic or passive (i.e. flipper or PIT tags) telemetry. See also: Telemetry.

Trawl: A large tapered fishing net that is towed along the sea bottom to catch benthic animals (shrimp, prawn, squid, etc.).

Turtle Excluder Device: A gear modification used in shrimp trawls for the purpose of excluding sea turtles caught in the trawl net before they drown.

Ventral: On the lower or bottom side or surface. In several species of sea turtles, the ventral side (plastron) is lighter in color than that dorsal side (carapace). See also: Plastron; Dorsal.

Vertebrals: The scutes of the carapace which overlie the backbone of the turtle (absent in the leatherback). Also called: central or neural scutes.

Vulnerable: A species or population that is considered to be facing a high risk of extinction in the wild (for precise criteria, visit:

Year class: All the animals in a population that hatched during a particular nesting season. The sizes of a particular year class can vary substantially after a few years depending on quantity and quality of food sources.

Yearling: A turtle that has survived one year from the time of hatching. Depending on amount and quality of food, and the species involved, yearlings may vary in size.

Yolk sac: The residual yolk that remains inside a hatchling turtle is contained within the yolk sac.