Search

The Endangered Mediterranean monk seal Monachus monachus is one of the most threatened marine mammals. Across Cyprus, suitable habitat and presence of monk seals is well documented and, recently, camera-trap surveys in Southern Cyprus found there to be pupping. We present results of the first camera-trap surveys in Northern Cyprus spanning the pupping period. Four adult/subadults and three pups were identified in three of eight caves monitored with camera traps. One site on the north-west of the island supported at least three adult/subadult seals and pupping occurred there in 3 consecutive years. The breeding and resting sites identified require urgent conservation to manage threats of disturbance, coastal development and fisheries bycatch. To determine the size of this population, a long-term survey with greater and more continuous coverage is required.

[Extract] Why do sea turtles garner such intense interest? The answer is visceral: they are widely loved! A cryptic life cycle spent mostly out of view lends a sense of mystery that makes them special. Yet, these large animals are highly accessible at an extremely vulnerable time, when females emerge on sandy beaches at night to lay eggs, before disappearing again into the oceans. Being nocturnal, they provide us the adventure of going out in the dark on secluded beaches to find them. Plus, the hatchlings are cute, and releasing them into the sea must be one of the most engaging activities that people can do with a protected species. To mark World Sea Turtle Day on 16 June, we—conservation scientists working across the oceans on this small yet well-studied group of seven species—reflect on their conservation. Sea turtles have lived in the oceans, largely unchanged, for millions of years. They play important roles in their ecosystems, possibly even as ecosystem engineers, and serve as prey for other protected species (Verissimo et al., 2012). They have been a source of sustenance and useful products for people for millennia, and these needs persist (Hancock et al., 2017; Humber et al., 2017; Delisle et al., 2018; Sardeshpande & MacMillan, 2019). Consequently, sea turtles are culturally important and the subject of myths and lore. They have also become economically important to many coastal communities through tourism (Waylen et al., 2009), although this can affect turtles or their habitats, if not correctly managed (Katselidis et al., 2013).

Madagascar is an important foraging ground for marine turtles in the Western Indian Ocean, yet the status of the country's nesting aggregations remains poorly documented. We assess the current status and trend in nesting throughout Madagascar, including data recorded by a community-based monitoring project in the Barren Isles (western Madagascar). We contextualize the findings in comparison with data from Madagascar's closest neighbouring states. Reports indicate that nesting levels have declined at many coastal sites, with no known recordings since 2000 at > 40 nesting sites. We estimate there are a minimum of 1,200 nests per year in Madagascar, with the largest recorded nesting aggregation (< 1,000 nests per year) found on islands off the west and northern coasts. The majority of nesting aggregations, including those recorded by the community-based monitoring project in the Barren Isles, are relatively small, in the order of < 50 nests per year, yet they are potentially important sources of regional genetic diversity. Nesting on many of the islands (e.g. Tromelin, Europa) around Madagascar has increased over the last 20 years, despite the fact that thousands of turtles probably originating from these sites are taken by fishers in the waters of Madagascar annually. We discuss the importance of protecting small nesting populations, and how community-based monitoring could be an important tool for conserving remote and vulnerable populations and building capacity for natural resource management.

Ascension Island in the South Atlantic Ocean is renowned for its globally-important nesting population of green turtles (Chelonia mydas) that has been the subject of long-term research. By comparison, very little is known about the apparently small population of hawksbill turtles (Eretmochelys imbricata) that have been recorded in its waters, thousands of kilometres from known nesting beaches. Here, we collate 10 years of in-water tagging data, opportunistic public sighting records and underwater observations to provide a baseline for future research, and present preliminary data on habitat use derived from two individuals fitted with GPS transmitters. Although public sightings were inevitably biased towards popular recreation areas, the resulting distribution suggests that hawksbill turtles occur year round in Ascension Island's waters along the entire 65 km of coastline. Hawksbills were observed feeding on benthic algae and encrusting sponges, and were frequently seen scavenging on fish discards around the Island's pier at night aided by anthropogenic lighting. Between 2003 and 2013, 35 turtles were captured, measured, tagged and then released. Curved carapace lengths ranged from 33.5 to 85 cm (mean = 48.8 cm) indicating that most (if not all) individuals encountered around Ascension are post-pelagic juveniles. Four individuals were recaptured at least once giving a mean minimum residence time of 4.2 yr (range: 2.8–7.3 yr) and a mean growth rate of 2.8 cm yr−1. Turtles fitted with Fastloc™ GPS devices remained at Ascension Island for the duration of the study (>90 days) and occupied restricted home ranges with an average area of 2.5 km2 and an average ‘core use area’ (50% utilization distribution) of 0.05 km2. Together, these results suggest that Ascension Island serves as a mid-Atlantic developmental habitat for benthic-feeding, juvenile hawksbill turtles on extended oceanic migrations before recruiting to their adult foraging grounds, likely to be located in Brazil or tropical West Africa.

The beaches of Jaragua National Park in the Dominican Republic are the country's last known major nesting site for the leatherback marine turtle Dermochelys coriacea. This nesting aggregation is threatened by widespread illegal egg take, and clutch relocation and artificial incubation have been carried out as protection measures since 1974. We assess the efficacy of such efforts and investigate how artificial incubation may be influencing the success and sex ratios of clutches. We compare hatching success, incubation duration and embryo mortality in in-situ clutches (n = 43) with those incubated artificially at sites in the east and west of the Park (n = 35 and n = 31, respectively). Our results show that in the west, artificial incubation significantly decreases hatching success in clutches. In the east the duration of incubation is increased, which we predict would result in an increase in the number of males from these clutches. Clutch relocation is currently the only viable conservation option for clutches on eastern beaches because of illegal egg take but action is needed to ensure that the natural sex ratio is not distorted. However, on the western beaches in situ clutch incubation seems possible through beach protection. Further community engagement and enforcement are required to improve conservation measures at eastern beaches if long-term, less sustainable intervention is to be avoided.

We document patterns of distribution and relative abundance of marine megavertebrate fauna around Cornwall and the Isles of Scilly from a combination of aerial and boat-based surveying. Between January 2006 and November 2007, 20 aerial surveys were undertaken, comprising over 40 hours of on-effort flying time. In April to October of these years, 27 effort-corrected ferry surveys were also conducted from a passenger ferry travelling between Cornwall and the Isles of Scilly. Opportunistic sightings were also logged by the crew members of the ferry and another vessel travelling regularly along the same route on 155 days. Ten megavertebrate species were sighted: basking sharks Cetorhinus maximus, sunfish Mola mola, common dolphins Delphinus delphis, harbour porpoise Phocoena phocoena, grey seals Halichoerus grypus, Risso's dolphins Grampus griseus, bottlenose dolphins Tursiops truncatus, minke whales Balaenoptera acutorostrata, long-finned pilot whales Globicephala melas and killer whale Orcinus orca. During aerial surveys, 206 sighting events of seven species were made, compared with 145 sighting events of eight species during ferry surveys and 293 sighting events of 10 species from opportunistic ship-board data collection efforts. Seasonal and spatial patterns in species occurrence were evident. Basking sharks were the most commonly-sighted species in the region and were relatively abundant throughout the estimated 5 km-wide strip of coastal waters covered by the aerial surveys, during spring and summer. Ferry surveys and opportunistic vessel-based sightings data confirmed that the distribution of surface-feeding aggregations of this species was largely around the coasts. Despite the limited scope of this study, it has provided valuable baseline data, and possible insights into the marine biodiversity of the region.

This study investigated the phenology, patterns of haul-out habitat use and distribution of the grey seal around Cornwall and the Isles of Scilly. A full census of the coast was carried out by boat over 4 days, in order to make a full count of seals hauled out and close to the coast, and to document all haul-out sites. Regular land-based surveys were made of three haul-out sites in Cornwall, to investigate the effects of spatial, temporal and environmental factors on seal haul-out behaviour. Data from 2004 to 2007 were analysed to describe long-term temporal variation in seal abundance at two haul-out sites. A total of 592 sightings were made along the coast of Cornwall and the Isles of Scilly over the four-day census period; 476 of these sightings (80.4%) were recorded at six main haul-out sites. The highest proportion of seals was observed at three haul-out areas on the Isles of Scilly. In Cornwall, seals were observed in higher numbers on the north coast, where the three largest mainland haul-out sites were documented, than on the south coast. At one key haul-out site in Cornwall, a distinct seasonal pattern was evident in data collected between 2004 and 2007, with higher numbers of seals present during the moulting and breeding seasons than over the summer months. There was considerable inter-annual variability in peak seal abundance, during the moulting season, at this site. There was no significant variation in haul-out behaviour with tidal state at this site, although haul-out counts were generally highest at mid-ebb tides. Data on seal abundance, distribution and haul-out behaviour may aid the designation of Special Areas of Conservation for the protection of grey seals in Cornwall and the Isles of Scilly.

A 24-year set of data from monitoring of a nesting beach at Bald Head Island, North Carolina, USA, was analysed in parallel with limited data from nearby rookeries to investigate trends in loggerhead turtle Caretta caretta nesting numbers. There was no statistical evidence of an increasing or decreasing trend in numbers of clutches laid per year, although a significant decrease in the number of turtles nesting and number of clutches laid per year was found from 1991. Remigrating turtles were larger and had larger annual clutch frequencies than neophyte turtles. Annual levels of nesting at beaches within the Cape Fear area were significantly correlated. The stable trend in number of clutches laid across more than two decades is discussed in relation to other factors affecting marine turtles in North American waters.

A comparison of body size and flipper size was carried out on green turtle (Chelonia mydas) hatchlings produced from natural nests at two beaches on Ascension Island, South Atlantic and one beach in northern Cyprus in the Mediterranean (N=18 nests; N=180 hatchlings). Hatchlings from Ascension Island were significantly larger and heavier than hatchlings in Cyprus, a likely consequence of maternal size effects. Incubation temperature appeared to influence body size of hatchlings on Ascension Island with higher temperatures producing smaller hatchlings. Both hind and fore-flipper area scaled positively with body size. In proportion to body size, hind-flipper area appears relatively consistent among the Atlantic populations but is smaller than hatchlings measured in Hawaii.

Most species of marine turtle breed every two or more years and it is the norm for females to lay more than one clutch of eggs within a nesting season. Knowing the interval between breeding seasons and the clutch frequency (number of clutches laid by an individual in a breeding season) of females allows us to assess the status of a nesting population. At Alagadi Beach, Northern Cyprus, over a period of 6 years (1995–2000), we attributed 96% of green Chelonia mydas and 80% of loggerhead Caretta caretta turtle clutches to known individual females. This intensive level of monitoring enabled us to estimate the clutch frequency for both species. Using four different methods we estimated clutch frequency to be 2.9–3.1 clutches per female for green turtles and 1.8–2.2 clutches per female for loggerhead turtles. The median interval between nesting seasons for green turtles was 3 years, and for loggerhead turtles it was 2 years. Utilizing these parameters and available data from other beaches that are monitored regularly, we estimate that there are 2,280–2,787 logger-head and 339–360 green turtles nesting annually at these sites in the Mediterranean. This highlights the Critically Endangered status of this population of green turtles. Furthermore, as conventional beach patrols underestimate clutch frequency, these population estimates are likely to be optimistic.

Albatrosses and sea turtles are known to perform extremely long-distance journeys between disparate feeding areas and breeding sites located on small, isolated, oceanic islands or at specific coastal sites. These oceanic journeys, performed mainly over or through apparently featureless mediums, indicate impressive navigational abilities, and the sensory mechanisms used are still largely unknown. This research used three different approaches to investigate whether bi-coordinate navigation based on magnetic field gradients is likely to explain the navigational performance of wandering albatrosses in the South Atlantic and Indian Oceans and of green turtles breeding on Ascension Island in the South Atlantic Ocean. The possibility that magnetic field parameters can potentially be used in a bi-coordinate magnetic map by wandering albatrosses in their foraging area was investigated by analysing satellite telemetry data published in the literature. The possibilities for using bi-coordinate magnetic navigation varied widely between different areas of the Southern Oceans, indicating that a common mechanism, based on a bi-coordinate geomagnetic map alone, was unlikely for navigation in these areas. In the second approach, satellite telemetry was used to investigate whether Ascension Island green turtles use magnetic information for navigation during migration from their breeding island to foraging areas in Brazilian coastal waters. Disturbing magnets were applied to the heads and carapaces of the turtles, but these appeared to have little effect on their ability to navigate. The only possible effect observed was that some of the turtles with magnets attached were heading for foraging areas slightly south of the control turtles along the Brazilian coast. In the third approach, breeding female green turtles were deliberately displaced in the waters around Ascension Island to investigate which cues these turtles might use to locate and return to the island; the results suggested that cues transported by wind might be involved in the final stages of navigation.

The depth and swim speed of a green turtle (Chelonia mydas) were measured during the internesting period in Cyprus. For dives to the seabed (U-dives) we used these data to determine dive angles. Typically the turtle initially descended at a steep angle (∼60°) but as the dive continued this angle lessened until the turtle approached the seabed at an average angle of ∼15°. This systematic change in descent angle is consistent with the prediction that the energetic implications of dive angle are most important at the start of the dive when the turtle is fighting to overcome its positive buoyancy. On leaving the seabed, the turtle often seemed to rise passively.

Large populations of marine turtles breeding in the Cayman Islands were drastically reduced in the early 1800s. However, marine turtle nesting still occurs in the islands. The present-day status of this nesting population provides insight into the conservation of marine turtles, a long-lived species. In 1998 and 1999, the first systematic survey of marine turtle nesting in the Cayman Islands found 38 nests on 22 beaches scattered through the three islands. Three species were found: the green Chelonia mydas, hawksbill Eretmochelys imbricata and loggerhead Caretta caretta turtles. Comparison with other rookeries suggests that the small number of sexually mature adults surviving Cayman's huge perturbations may be impeding population recovery. This shows the need to implement conservation measures prior to massive reductions in population size.

The globally distributed leatherback turtle Der- mochelys coriacea is subject to fisheries bycatch throughout its range. Protection from fisheries within pelagic foraging habitats is difficult to achieve but may be more tractable when populations are concentrated near neritic breeding and nesting grounds. We used satellite telemetry to de- scribe patterns of habitat utilization during the inter- nesting period for seven leatherback turtles nesting at Mayumba National Park in Gabon on the equatorial West African coast. The National Park includes critical nesting grounds and a marine protected area to 15 km offshore. Turtles dispersed widely from the nesting beach spending a mean of 62 - SD 26% of tracking time outside the confines of the National Park. This propensity to disperse is likely to increase the chance of deleterious interactions with fisheries in the region. Patterns of habitat utilization indicate the need for wider spatial scale planning on the West African continental shelf to enhance protection of leatherback turtles when they are seasonally occupying these habitats in great numbers for breeding and nesting.