Friday, August 6, 2010
Tuesday, July 27, 2010
We are so happy to greet the scores of sea turtle hatchlings emerging from their nests on beaches across Antigua. Between February and June, the giant leatherback turtles arrive to nest on our beaches, and throughout the summer, we wait in anticipation of the tiny hatchlings. But while there is great anticipation for the hatchlings, there are also great challenges that these hatchlings will face, particularly on beaches with bright lights.
In natural conditions, where beaches are dark throughout the night, turtle hatchlings will instinctively head towards the “glow” of the sea. However, on beaches with artificial lighting, this first step in a hatchling’s life is not so easy. On beaches with visible lighting from buildings, gardens, or streetlights, hatchlings will instinctively crawl towards the light, often converging under the light source. Lights can also attract hatchlings into thick vegetation, across roadways, into the path of predators, and unless rescued and returned to the sea, they can die within hours.
Fortunately, there is a lot that can be done to help minimize the risks for these hatchlings. Following these best practices for lighting can make a big difference for sea turtle survival:
§ Keep the Lights LOW – The most visible lights (from the beach) are lights mounted high on buildings or poles. In many cases, simply lowering the height of the light may solve the problem. Lowering and directing light to precisely where it is needed can also be more aesthetically pleasing, more functional, and more energy-efficient.
§ Turn Lights OFF in peak times – Restrict usage or extinguish lights during peak sea turtle nesting and hatching seasons, and especially during peak hatching hours (typically 7-11 PM) when hatchlings are most likely to emerge from their nests.
§ Use Directional Fixtures – Some lights, such as carriage lights or globe lights, disperse light in every direction. Be thoughtful about your lighting! Do you really need to illuminate (and pay for!) the entire night sky? Directional fixtures can focus the light downwards and away from areas visible from the beach.
§ Shield Lights – Shielding an open light source may reduce the amount of light directed onto the beach. Simple screens (such as the use of aluminum flashing) or planting vegetation (such as an ornamental hedge) can effectively shield lights. Be creative! Soften lights with locally-made basket shades. If shielding is impractical, then these lights may need to be substituted with lower, directional lighting.
§ Use Motion Sensitive Lights – When night-time lighting is indispensable, particularly from a
security standpoint, installing lights with motion detectors reduces their detrimental effect on sea turtles because of the relatively brief duration of their illumination. Moreover, motion sensitive lighting carries the element of surprise, conveying a distinct advantage to posted guards who remain in the shadows. Motion-lighting provides light only when necessary, and is ideal for lowtraffic areas.
§ Remove Unnecessary Lights – Lighting inspections may determine that some lights are unnecessary or redundant and can be removed or turned off, saving money and benefiting both ambiance and sea turtles. Try to avoid the use of purely decorative lighting, such as lights that highlight vegetation, in places that can be seen from the beach.
§ Invest in Alterative Light Sources – Sea turtles are less sensitive to certain types (and colors) of lights. All metal hyalites can have adverse effects on sea turtles and should be replaced as a priority. High pressure sodium vapor lights also strongly affect sea turtles, and should only be used in areas not visible on the beach. Incandescent lights have moderate effects on sea turtle behavior, except for “bug lights” which are tinted yellow. Low pressure sodium vapor lights (LPS) are the least detrimental to sea turtles. Monochromatic yellow in color, LPS lights have the longest wavelengths, which sea turtles do not detect as readily. The best choice, if light is necessary, is often LPS lighting.
The Antigua Sea Turtle Project is happy to assist anyone who is interested in making their beachfront lighting more turtle-friendly. This will ensure a better chance for dozens of hatchlings, especially on active turtle nesting beaches. If you should find hatchlings heading far away from the sea or disoriented (e.g. under a light, in a garden, in the road) please:
- Turn off or shield any sources of light and remove physical obstructions that may be distracting and allow them to naturally find the sea
- If hatchlings will not enter the water, or disoriented hatchlings are found in the day time, contain them in a bucket or box and contact the EAG Sea Turtle Project at 720 6955 immediately for assistance
Wednesday, May 19, 2010
Green sea turtles are known to be particularly loyal to their feeding grounds, often staying close to their chosen plot of sea grass. Beaks with finely serrated edges allow the green turtle to tear off grasses or algae from hard surfaces. Turtle grass or Thalassia, is the grass of choice of most greens, they can often be seen crawling on the sea bottom, “grazing” (almost like cows). But some might also call this “pruning”, for the sea turtles actually increase the productivity and nutrient content of the grass plot by removing the older upper portions of the grass and allowing the nutrient rich shoots to flourish. Older grasses are often overgrown with algae and fungus, and their accumulation on the sea bottom drains important nutrients from the food chain, resulting in less productive fisheries. Healthy grasses on the other hand, benefit the food chain and fish stocks. In Florida Bay, die off of sea grasses was directly linked to the local extinction of greens in the 1980s. The above photo is of a green sea turtle on a bed of turtle grass (courtesy WIDECAST).
A Diet of Glass?
Hawksbill turtles are known to take up residence in coral reefs that provide a rugged landscape for hiding out and a ready buffet of their favourite foods, especially sponges. Researcher Anne Meylan examined the stomach contents of 61 hawksbills caught by fishermen in the Caribbean and found that sponges accounted for almost 95% of the total digested food. The turtles also showed a strong preference for the most well defended sponges (demosponges), which are inedible and toxic to other species. The hardy skeletons of demosponges are made of spicules – tiny silica rich spines similar to glass needles! The above photo (courtesy CENSEAM) shows the glass like spicules. The strong beak-like mouth of the hawksbill allows them to rip through these sponges, and other animals then feed on the softer material that is left exposed once the turtle has moved on. Without hawksbills to keep them in check, sponges could easily take over from corals in the reef community. This would dramatically change the physical structure of the reef and diversity of species that it supports. Who would have thought that the small, shy hawksbills were such fearless guardians of the reef?
Leatherbacks are the largest of all sea turtle species and even those that nest in the Caribbean will often circumnavigate the Atlantic in between nesting seasons. Leatherbacks have a varied habitat, but are usually in the open ocean following the cooler currents that carry their food – jellyfish. Whatever the jellyfish lacks in substance and appeal the leatherback makes up for by consuming great amounts of it - up to 440 pounds in one day! That’s the same weight as an adult lion! As one of the largest jellyfish consumers in the world, leatherbacks evidently play a key role in keeping jellyfish populations in check. Without leatherbacks and other top predators it is possible that jellyfish could become more plentiful than commercially important fish species, which are currently on the decline. This could have a devastating effect on already stressed fish stocks. It is also worth considering what our beaches would be like without the great appetite of the leatherbacks, with just one single turtle removing hundreds of pounds of jellyfish from our waters each day.
Though out of sight much of the time, our sea turtles are working hard each day to keep the oceans in check. If we can conserve the local nesting beaches and feeding areas of these endangered species, it seems that they will also do a lot in return. It is even possible that we might be saved from a painful jellyfish sting or two! The Antigua Sea Turtle Project collects information on sea turtle nesting on beaches throughout Antigua. To report sightings of nesting turtles, fresh turtle tracks, or nest hatchings on beaches around the island telephone 720 6955.
Thursday, February 25, 2010
Based on observations of video footage aired on ABS Television on Saturday, the "rare turtle" found in Blackman Bay, Parham is most likely an Atlantic Loggerhead (Caretta caretta). The turtle had been found by villagers in about 3 feet of water on Saturday, brought to shore, and later released alive. Loggerheads are indeed rarely seen around Antigua and Barbuda, although there are occasional sightings of the species at sea. Unlike other turtle species including Hawksbills, Green, and Leatherback turtles, Loggerheads are not known to nest on Antigua's beaches. Loggerheads do use the area however for feeding, and the large and powerful jaws allow them to feed on hard shelled animals such as whelks and conch. Typically, loggerheads reach sexual maturity at 35 years old, when they average about 250 lbs. This suggests that the turtle found on Saturday was in the pre-adult stage. Once maturity is reached the turtles will usually make migrations, often crossing the open ocean to reach nesting beaches (often the same beach they were born on). Loggerheads nest mainly in the northern Caribbean (Bahamas, Cuba) and north eastern coast of the United States.
All species of sea turtles found in the Caribbean are endangered, due to serious threats from pollution, entanglement in fishing gear, over-harvesting and loss of nesting and feeding habitats. The actions of Robert Young (aka Bubbler) and others in the Parham community on Saturday to protect and release the rare sea turtle are exemplary and absolutely essential for the survival of turtle populations. If all communities around the island adopted the attitude of Bubbler to "look after these animals", then sea turtles may be around for years to come.