The marine turtles visit the Canary Islands on their migration from the US coasts to Africa. Although they visit these islands all year, the peak is in the summer.
There are 8 species known of the marine turtles that are found in the subtropical and tropical seas. These species originated from about 60-10 million years ago and developed from a much more ancient ancestor, some 200 million years ago. Some 130 million years ago, they were abundant and managed to survive cataclysmic events, unlike the dinosaurs. But since then, they have not changed significantly. They have a characteristic shape due to their bone shell that covers the viscera and efficiently protects them.
Turtles are classified as reptiles and although they are well adapted to their marine environment, they have to surface to breathe and the females have to go on land to nest their eggs. They can live for about 100 years, but are now an endangered species due to the fact that their way of reproduction and their food habits make them vulnerable to the changed environment. Marine turtles like to eat jelly fish and they eat plastics that float in the sea because of the similar appearance. Also the need for nesting their eggs on a sandy beach is causing them problems as many beaches now are being occupied by tourists. All this, added with accidental captures in fishing nets, is putting a severe strain on the survival of this species.
There are four species that are regularly visiting the Canary Islands:
The Leatherback Sea Turtle: the oldest of the 8 species. It does not have a hard shell like the other ones, but is covered with a leather-like skin. Its predominant colour is black. Can measure up to 2 metres long and weight up to 500kg. Mainly eats jelly fish.
The Green Sea Turtle: the shell can measure up to 1,4m and the weight can reach up to 250kg. The predominant colour is greenish or brownish. The carapace has 5 vertebral and 4 costal elements. It feeds on jelly fish and algae.
The Hawksbill Sea Turtle: the shell can measure up to 1m and the weight can reach 150kg. The predominant colour is dark greenish brown. The head is pointed (like a hawk). The carapace has 5 vertebral and 4 costal elements.
The Loggerhead Sea Turtle: this is the most common turtle for the Canary Islands. The shell can measure up to 1m and the weight can reach more than100kg. The predominant colour is brownish orange. The carapace has 5 vertebral and 5 costal elements and is more oval. The diet consists of crabs, fish and jelly fish.
Mating is in the ocean and can be multiple with fertilisation of the eggs being delayed, if necessary for years. The mating period is April-October.
Sexual maturity is between 15-30 years. Nesting is done during autumn-winter and the females select each time the same beach, namely where they were born. Males await the females close to the shore where fertilisation takes place. At night the females land on the beach where they excavate on the boundary between the dry and wet sand, lay their eggs (40-190), cover them up and return to the sea. In one season, a turtle can lay up to 600 eggs. Nest building, egg laying and closing the nest takes up to 2 hours.
After about 60 days of incubation the turtles hatch. Chromosomes for males and females are equal and sex is determined by the temperature during incubation. Higher temperatures lead to more females. Lower to males. Incubation temperature is between 26 and 32ºC. The baby turtles hatch at night and immediately run to the shore from where they swim into the open sea.
The nests can be plundered and/or destroyed by crabs and the hatchlings, on their way to the sea, can be captured by birds. Once in the sea, they can be eaten by fish. This all result in a high mortality number when they are young. Once adult, a turtle barely has predators, unless one exception... man.
Capture of female turtles for human consumption, egg robbery, degradation of breeding areas due to the tourist industry, incidental capture by fishing nets and lines result into only 1 or 2 turtles reaching adulthood from 1000 eggs. Another threat is the transparent plastic garbage that floats in the oceans as turtles cannot distinguish it from jelly fish.
If you encounter a turtle in good condition and swimming freely, then enjoy the view. But if it is wounded, entangled or ill (slow behaviour) then evaluate the help you might give. Beware of the fact that turtles can act slowly when they are on the surface as they might be thermo-regulating (warming up). If the turtle still needs help after your intervention, take it slowly out of the water, keep it in the shade and rinse constantly with seawater to keep it cool. Call the local police or Guardia Civil (Emergency Tel. number: 112)
Marine turtles are included in the National Catalogue of Endangered Species (RD439/1990) as animals with "special interest". Their capture, the capture of their eggs, the maintenance in captivity and any activity that might result in damage or death to the species is illegal and is considered as a crime.
The Government of Canarias, through its Viceconsejería de Medio Ambiente, is actively supporting the local initiatives to improve the conditions for survival of the turtle species and to guarantee their conservation for future generations. You can visit the Fuerteventura breeding and conservation station at the harbour in Morro Jable.
Michel
