As Cayman’s turtle-nesting season gets under way, a new research paper prepared by the Cayman Islands Department of Environment and the University of Exeter in the UK has tracked a major increase in the sea turtle-nesting population over 22 years.
During the decades-long monitoring programme, the researchers found the number of nests of both green sea and loggerhead turtles has grown significantly across all three Cayman Islands since 1998.
“Comparing the first 5 years of nest numbers to the most recent 5 years, the greatest percentage increase in green turtle nests was in Grand Cayman from 82 to 1,005 nests (1,126%), whereas the greatest percentage increase for loggerhead turtle nests was in Little Cayman from 10 to 290 nests (3,800%),” the research paper, which deals with population numbers between 1998 and 2019, noted.
It stated that while the Cayman Turtle Centre’s captive breeding operation contributed to the increase in the Grand Cayman green turtle population, loggerhead turtles were never captive-bred, and these populations began to increase after a legal traditional turtle fishery became inactive in 2008.
The first turtle nests of the 2021 season have already been found on Cayman Brac, according to the Department of Environment. Three loggerhead turtle nests were found on a beach on the island late last month. Those monitoring the nests can tell what kind of turtle has dug the nest by the tracks – known as ‘batabano’ – left in the sand.
During last year’s turtle-nesting season, a record 557 nests were found on Grand Cayman and Cayman Brac. At the time, the DoE stated that the high 2020 nest numbers may have been aided by the COVID-19 lockdown early in the year which left beaches deserted for long periods of time, giving turtles the opportunity to lay their eggs unhindered.
Despite the upward-trending population numbers, the DoE and University of Exeter researchers, in their report published on 3 May, warned against complacency regarding the endangered turtle species. “Although both species have shown significant signs of recovery, populations remain at a fragment of their historical level and are vulnerable to threats. Illegal harvesting occurs to this day, with multiple females taken from nesting beaches each year,” they said.
From 1999 to 2019, 71 turtles were known to have been illegally harvested from the wild around the Cayman Islands, the report stated. Of those, at least 21 were mature females and 72% of the cases happened on Grand Cayman.
Some of the turtles captured by poachers were saved, however. DoE enforcement officers and police intercepted the illegal take of 37 turtles and released the animals back into the water.
The researchers pointed out that apart from poaching, there are a number of other threats facing the nests and hatchlings, including artificial lighting on nesting beaches that can cause the baby turtles to misorient away from the sea, and inundation of nests by seawater.
While the numbers of green sea and loggerhead turtles are on the rise, the number of hawksbill nests being found on local beaches has remained low, with a maximum of 13 nests recorded in a season during that 22-year period, the report noted.
Once extremely abundant in local waters, the overharvesting of turtles over many years led to a massive drop in numbers. It is estimated that in the 1600s, the local turtle-nesting population was 2.5 million, according to a 1997 report titled ‘Reefs since Columbus’, by Jeremy BC Jackson of the Smithsonian Institution.
The DoE and University of Exeter report states that although the Cayman Islands were not permanently settled until the 1700s, visiting ships were estimated to have harvested more than 10,000 green turtles per year from 1688 onward.
In Cayman, between 1971 and 1991, 78 sea turtle nests (17 green, 43 loggerhead, one leatherback, six hawksbill, and 11 unidentified) were recorded in ad hoc surveys, according to a chapter by James Woods and Fern Woods on sea turtle populations in the 1994 book ‘The Cayman Islands: Natural History and Biogeography’.
The first systematic survey of Cayman Islands sea turtle nesting was undertaken from 1998 to 1999, during which 38 nests were recorded on the three islands. Then, in 2002, 75 nests were found in Grand Cayman and Little Cayman.
Despite the small size of the nesting population, a small-scale local traditional turtle fishery continued until 2008, the researchers noted. “During this time, fishermen were permitted to capture juvenile and adult green and loggerhead turtles over 54.5 kg/120 lb. in an open season between October and April each year. In 2008, the closed season was extended to include May and November and a maximum size limit of 60cm curved carapace length was introduced. While captures by licensed fishermen are still permissible within these restrictions, no legal take of turtles has occurred since 2008.”
The report notes that, in Grand Cayman, it is likely that the Cayman Turtle Farm, now called the Cayman Turtle Centre, “re-seeded” the nearly extirpated green turtle population. “The number of hatchlings and yearlings released each year by the farm has varied but was highest in the early years of the programme (1980–1989), when more than 10,000 yearling and 15,000 hatchling turtles were released,” it stated.
Since 1998, ‘turtle patrols’, made up of DoE staff and volunteers, have been monitoring all of Cayman’s known nesting beaches. The patrols walk the beaches early in the morning about twice a week during nesting season, recording all turtle activities and taking GPS locations.
Turtle-nesting season typically lasts from May to November, but nests have been found as as early as April and as late as February.
Turtle eggs incubate in the nest, dug in the sand by the mother turtle, for about 44 days before the hatchlings emerge.
Funding over the years for Cayman’s turtle-nest monitoring has been provided by the Department of Environment, with assistance from the Foreign and Commonwealth Office, the Turtles in the UK Overseas Territories Project, the Cayman Islands Governor’s Fund, and the Darwin Initiative.