Warm water and cool nests are best. How global warming might influence hatchling green turtle swimming performance

For sea turtles nesting on beaches surrounded by coral reefs, the most important element of hatchling recruitment is escaping predation by fish as they swim across the fringing reef, and as a consequence hatchlings that minimize their exposure to fish predation by minimizing the time spent crossing the fringing reef have a greater chance of surviving the reef crossing. One way to decrease the time required to cross the fringing reef is to maximize swimming speed. We found that both water temperature and nest temperature influence swimming performance of hatchling green turtles, but in opposite directions. Warm water increases swimming ability, with hatchling turtles swimming in warm water having a faster stroke rate, while an increase in nest temperature decreases swimming ability with hatchlings from warm nests producing less thrust per stroke.     

Exclusive predation of sea turtle hatchlings by juvenile blacktip reef sharks Carcharhinus melanopterus at a turtle nesting site in Malaysia

This study reports the discovery of the exclusive predation of sea turtle hatchlings by several juvenile blacktip reef sharks (Carcharhinus melanopterus) in Chagar Hutang bay on Redang Island, Malaysia, in the South China Sea. Three dead specimens of C. melanopterus were retrieved from ghost nets, and the entire digestive tracts of these sharks solely contained the partially digested bodies of sea turtle hatchlings, with no evidence of the remains of any other prey. Thus, juvenile C. melanopterus may opportunistically feed primarily on turtle hatchlings during times when hatchling abundance is high.     

Influence of sea turtle nesting on hunting behavior and movements of jaguars in the dry forest of northwest Costa Rica

Jaguars (Panthera onca) are opportunistic predators that prey on large profitable prey items, such as sea turtles at nesting beaches. Here, we use jaguar and sea turtle track-count surveys, combined with satellite telemetry of one jaguar, to evaluate whether jaguar hunting behavior and movements are influenced by seasonal sea turtle nesting in the Sector Santa Rosa of Área de Conservación Guanacaste in northwest Costa Rica. We used generalized linear models to evaluate the effect of moon phase and sea surface temperature on olive ridley (Lepidochelis olivacea) and green turtle (Chelonia mydas) nesting abundance, as well as the combination of these predictors on the frequency of jaguar predation activity (proximity to nesting beaches) and movements. For home-range size and location analyses, we calculated kernel density estimates for each season at three different temporal scales. Sea turtle nesting season influenced jaguar activity patterns, as well as sea turtle abundance was related to jaguar locations and predation events, but jaguar home-range size (88.8 km² overall) did not differ between nesting seasons or among temporal scales. Environmental conditions influenced sea turtle nesting and, as a consequence, also influenced jaguar movements and foraging activity. Our study defined the home range of a female jaguar in the tropical dry forest and its relationship to seasonally abundant turtles. Additional information related to the effect of tourism on jaguar–sea turtle interactions would improve conservation of these species at unique nesting beaches in the area.     

Sea Turtle Nesting as a Process Influencing a Sandy Beach Ecosystem

Sea turtle egg mortality, egg predation, and small organisms associated with turtle nests were studied at Playa Ostional, Costa Rica. Sites with concentrated sea turtle nesting were compared with solitary nesting sites as a function of place and time based on ANOVA, Akaike's Information Criterion, and Bayesian analyses. Results indicate that sea turtle egg mortality was significantly associated (P < 0.005) with flowing water that erodes or saturates nesting sites, and with overlapped nesting in which sea turtles disturb each other's nests. Sarcophagid and calliphorid fly larvae (Bayesian prior = 1.19; posterior = 2.27), fungi (prior = 1.14; posterior = 1.92), mites (prior = 0.51; posterior = 1.15), and several other types of small organisms increased in number after turtle egg laying (N= 303 nests; 34,451 turtle eggs). During peak sea turtle nesting periods, visitation to nesting sites by poachers and vertebrate predators was high, and relative number of nests disturbed by these predators was low (P < 0.02). In multimodel analysis, the three most parsimonious models were: (1) turtle egg mortality and distance from mean high tide; (2) turtle egg predation and distance from mean high tide; and (3) turtle egg mortality and nesting density, with Akaike weights of 0.224, 0.203, and 0.153 respectively. Intensive sea turtle nesting might result in upwelling and turnover of nesting debris and nest organisms, and may influence biotic community structure of sandy beach ecosystems.     

Energetics during hatchling dispersal of the olive ridley turtle Lepidochelys olivacea using doubly labeled water

Studies of metabolism are central to the understanding of the ecology, behavior, and evolution of reptiles. This study focuses on one phase of the sea turtle life cycle, hatchling dispersal, and gives insight into energetic constraints that dispersal imposes on hatchlings. Hatchling dispersal is an energetically expensive phase in the life cycle of the olive ridley turtle Lepidochelys olivacea. Field metabolic rates (FMRs), determined using the doubly labeled water (DLW) method, for L. olivacea hatchlings digging out of their nest chamber, crawling at the sand surface, and swimming were five, four, and seven times, respectively, the resting metabolic rate (RMR). The cost of swimming was 1.5 and 1.8 times the cost of the digging and crawling phases, respectively, and we estimated that if L. olivacea hatchlings swim at frenzy levels, they can rely on yolk reserves to supply energy for only 3-6 d once they reach the ocean. We compared our RMR and FMR values by establishing an interspecific RMR mass-scaling relationship for a wide range of species in the order Testudines and found a scaling exponent of 1.06. This study demonstrates the feasibility of using the DLW method to estimate energetic costs of free-living sea turtle hatchlings and emphasizes the need for metabolic studies in various life-history stages.     

Some analyses of artificially incubated eggs and hatchlings of Green and Loggerhead sea turtles

Eggs of the Green sea turtle ( Chelonia mydas ) and the Loggerhead sea turtle ( Caretta caretta ) were incubated in coral sand or silica sand moistened with distilled water. The eggs and hatchlings were analysed for calcium, magnesium and phosphorus. There was less magnesium but more calcium in the hatchlings than in the original egg contents but this was not influenced by the type of sand used during incubation. The results are interpreted as indicating that the eggshell is the major source of calcium for the developing embryos. The Logger-head sea turtle shows a greater efficiency in the incorporation of yolk magnesium and phosphorus into the embryo than does the Green sea turtle.     

Spawning timing of the cleaner wrasse, Labroides dimidiatus, on a warm temperate rocky shore

We observed spawning behaviors of the haremic cleaner wrasse Labroides dimidiatus at a rocky reef in southern Japan. Females released pelagic eggs daily from June to September after a spawning ascent by pairs. When the high tide occurred between noon and evening (quarter moon to new or full moon), they spawned around the time of the tide providing fast offshore currents. For the rest of the lunar cycle, spawnings occurred during late afternoon independent of the state of the tide at the time of day. This spawning pattern is quite different from that of conspecifics on coral reefs that always spawn around the high tide at all lunar stages to avoid potential egg predators. The wrasse ascended high in the water column, probably because of its predator-immune characters as a cleaner. The steep slope of the study site seemed to contribute to releasing gametes far above aggregating planktivores. Thus, gametes were not subject to heavy predation. Current direction might not always affect survival of spawned pelagic eggs on the temperate reefs so crucially as it does on coral reefs. We conclude that spawning during unfavorable tidal conditions during the daytime may be better than spawning during the best tidal condition in the crepuscular period when predation pressure on adults will be high. Intraspecific variation in the timing and location of spawning of the wrasse may result from different conditions for larval survival. Received: February 6, 2000 / Revised: June 16, 2000 / Accepted: July 17, 2000     

Effects of predation risk on the nocturnal activity budgets of thin-billed prions Pachyptila belcheri on New Island, Falkland Islands

Predation is a major ecological and evolutionary driver of natural populations, greatly influencing fitness and behaviour of prey species. Small, long-lived petrels are vulnerable to predation at the breeding colonies and are expected to evolve behavioural strategies to minimize predation risks. Using an automatic nest monitoring system and nightly aerial counts, we examined the effect of vegetation cover and moonlight on colony attendance patterns and levels of burrow activity of breeding thin-billed prions, Pachyptila belcheri, on New Island, Falkland Islands. We further investigated how these parameters were related to predation by Falkland skuas. We monitored up to 32 nests in two habitats, one with Tussock grass and one with low vegetation cover. Individuals in both areas were more active at the nest before hatching, and those breeding in the low cover habitat were more active and arrived at the colony earlier, which might reflect an effect of reaction time over predation risk. Nocturnal activity peaks shifted in time as the season progressed, indicating behavioural adjustments to sunrise hours. Moon phase did not affect attendance and activity levels of breeders in either habitat or overall aerial activity, but influenced arrival time at the colony during chick-rearing, individuals arriving later in periods of full moon. Skua capture rates were positively correlated with aerial and nest activity but not with overall breeder attendance and were unaffected by moon phase. Thin-billed prions activity budgets are influenced by environmental parameters that affect their likelihood of being predated.     

Mass spawning of Caesio teres (Pisces: Caesionidae) at Enewetak Atoll,Marshall Islands

Synopsis Mass spawning of Caesio teres occurred between March and August, 1983 on a reef emerging from deep water just inside the East Channel of Enewetak Atoll, Marshall Islands. Aggregations and spawning were observed from one day before until three days after the full moon. Spawning aggregations were not observed during the new or quarter moons. Spawning commenced after high tide, when the current began to flow out the pass from lagoon to ocean. The spawning aggregation of close to 1000 individuals migrated to the spawning site. Spawning occurred when the aggregate ascended to near the water's surface. Subgroups dashed horizontally within the aggregate, releasing a highly visible gamete cloud. Predation on spawning adults was not observed. Predation on spawned eggs was noted. The eggs of C. teres are described. Mid-Pacific Research Laboratory, Enewetak Atoll, Republic of the Marshall Islands Present address: Motupore Island Research Station, P.O. Box 320, University of Papua New Guinea, Papua New Guinea     

Temporal patterns in ambient noise of biological origin from a shallow water temperate reef

A systematic study of the ambient noise in the shallow coastal waters of north-eastern New Zealand shows large temporal variability in acoustic power levels between seasons, moon phase and the time of day. Ambient noise levels were highest during the new moon and the lowest during the full moon. Ambient noise levels were also significantly higher during summer and lower during winter. Bandpass filtering (700-2,000 Hz and 2-15 kHz), combined with snap counts and data from other studies show that the majority of the sound intensity increases could be attributed to two organisms: the sea urchin and the snapping shrimp. The increased intensity of biologically produced sound during dusk, new moon and summer could enhance the biological signature of a reef and transmit it further offshore. Ambient noise generated from the coast, especially reefs, has been implicated as playing a role in guiding pelagic post-larval fish and crustaceans to settlement habitats. Determining a causal link between temporal increases in ambient noise and higher rates of settlement of reef fish and crustaceans would provide support for the importance of ambient underwater sound in guiding the settlement of these organisms.     

Responses of hatchling sea turtles to rotational displacements

After emerging from underground nests, sea turtle hatchlings migrate through the surf zone and out to the open ocean. During this migration, both waves and water currents can disrupt hatchling orientation by unpredictably rotating the turtles away from their migratory headings. In addition, waves cause turtles to roll and pitch, temporarily impeding forward swimming by forcing the hatchlings into steeply inclined positions. To maintain seaward orientation and remain upright in the water column, hatchlings must continuously compensate for such displacements. As a first step toward determining how this is achieved, we studied the responses of loggerhead (Caretta caretta L.) sea turtle hatchlings to rotational displacements involving yaw, roll, and pitch. Hatchlings responded to rotations in the horizontal plane (yaw) by extending the rear flipper on the side opposite the direction of rotation. Thus, the flipper presumably acts as a rudder to help turn the turtle back toward its original heading. Turtles responded to rotations in the roll plane with stereotypic movements of the front flippers that act to right the hatchlings with respect to gravity. Finally, hatchlings responded to rotations in the pitch plane with movements of the hind flippers that appear likely to curtail or counteract the pitching motion. Thus, the results of these experiments imply that young sea turtles emerge from their nests possessing a suite of stereotypic behavioral responses that function to counteract rotational displacements, enable the animals to maintain equilibrium, and facilitate efficient movement toward the open sea.     

Feral cats (Felis catus) as predators of hatchling green turtles (Chelonia mydas)

In many parts of the world feral animals have been reported to have severe effects on marine turtle hatchling production. In this study, green turtle ( Chelonia mydas ) hatchlings were shown to be an important component of the diet of the feral cat ( Felis catus ) on Aldabra Atoll, Seychelles, and feral cat activity in the coastal areas was found to be concentrated on the beaches used most intensively by turtles for nesting. The impact of the feral cat's predation on green turtle recruitment could not be determined. However, despite cat predation, the size of the Aldabran green turtle nesting population has increased considerably since human exploitation ceased.     

The role of Steller sea lions in a large population decline of harbor seals

We provide the first direct evidence that Steller sea lions will prey on harbor seals. Direct observations of predation on marine mammals at sea are rare, but when observed rates of predation are extrapolated, predation mortality may be found to be significant. From 1992 to 2002, harbor seals in Glacier Bay declined steeply, from 6,200 to 2,500 (∼65%). After documenting that Steller sea lions were preying on seals in Glacier Bay, we investigated increased predation by sea lions as a potential explanation for the large decline. In five independent data sets spanning 21–25 yr and including 14,308 d of observations, 13 predation events were recorded. We conducted a fine-scale analysis for an intensively studied haul-out (Spider Island) and a broader analysis of all of Glacier Bay. At Spider Island, estimated predation by sea lions increased and could account for the entirety of annual pup production in 5 of 8 yr since 1995. The predation rate, however, was not proportional to the number of predators. Predation by Steller sea lions is a new source of mortality that contributed to the seal declines; however, life history modeling indicates that it is unlikely that sea lion predation is the sole factor responsible for the large declines.     

Multi‐temporal factors influence predation for polar bears in a changing climate

Predation is an ecological interaction influenced by abiotic and biotic factors acting on multiple temporal scales, yet multi‐temporal comparisons are rare in empirical studies. For polar bears Ursus maritimus, the physical configuration of the habitat and conditions in which seals are hunted may change on intra‐ and inter‐seasonal scales. Additionally, while the effects of climate change on polar bears have focused on linking reductions in sea ice to body condition and survival, the potential changes to on‐ice hunting conditions have not been examined. Employing observational counts of seals killed by polar bears between early‐April and late‐May 1985–2011 (n = 650), we modelled the likelihood of predation events in the Beaufort Sea, Canada at multi‐temporal scales. We used the top model to estimate the expected kill rate of seals in the springs of 1985–1986 and 2005–2006 and integrated the result with fasting rates derived from physiological markers in blood samples. A log‐likelihood ratio test suggested a multi‐temporal approach fit the seal kill data better than any single scale alone. Predation events were influenced by ringed seal Pusa hispida reproduction and haul‐out behaviour, regional sea ice concentration and the phase of climatic indices. The expected kill rate from the top predation model and the estimated mean biomass of seal kills were significant predictors of polar bear fasting rates. Results suggest that 50% less seal biomass was killed in 2005–2006 than in 1985–1986, which correlates with a significant increase in the frequency of polar bears in a fasting state. We propose that the documented changes in polar bear fasting rates between 1985–1986 and 2005–2006 are due to a complex set of abiotic and biotic factors including underlying prey dynamics, rather than a single‐scale environmental correlation.     

Aspects of the spawning of labrid and scarid fishes (Pisces: Labroidei) at Enewetak Atoll,Marshall Islands with notes on other families

Synopsis Spawning of 32 species of Labridae and 13 species of Scaridae was seen at Enewetak Atoll, Marshall Islands. Most spawned on a reef bisecting the main ocean-lagoon passage which had strong tidal currents. Others spawned on lagoon reefs and in Halimeda beds. Polygynous haremic, lek-like and promiscuous mating systems were found which were species specific. Data on reproductive patterns, sexual dichromatism, sexual dimorphism, seasonality and spawning behavior were determined. Many spawned during the day in a time-phase dependent pattern from near sunrise to sunset. Scarid spawning began at slack high water or after when currents were starting to move out of the lagoon. Labrid spawning usually started about 30 min later with some continuing up to 2 h after high tide. With high tide before sunrise, scarid spawning began 30–50 min after sunrise as the current started flowing over the reef. With high tide near sunset, spawning occurred with an incoming current. Most labroids spawned on all phases of the moon. Acanthuridae (6 spp), Caesionidae (1 sp.) and Zanclidae (1 sp.) spawned after high tide at the same time as labroids. Pomacanthidae (5 spp.) spawned only shortly before sunset without reference to tidal currents. Fishes producing pelagic eggs at the lagoon-ocean channel spawned (1) at or slightly after high tide (44spp.), (2) in late afternoon without reference to tide (6 spp.) or (3) after slack low water (1 sp. ). Spawning style can vary within a single species in different environments. Despite the presence of many piscivores, no successful predation on spawning adults was seen. Predation on newly released eggs was uncommon. Labrichthys unilineata and Anampses twistii attempted to defend their eggs for a few sec after release. Attacks by piscivores on spawning adults on tropical reefs occur once per 100–1000 spawnings. Most are wary when preparing to spawn and prespawning behavior is easily interrupted. The risk from piscivores goes down and spawning ascent speed decreases with increasing size of spawners. Egg predation by zooplanktivores is less for pair spawners than group spawners possibly due to less conspicuous gamete clouds and times of spawning. Increasing height of egg release, speed and length of the spawning ascent, and trajectory alteration of ascending adults are believed to make it more difficult for zooplanktivores to locate eggs after release. For labrids, permanent full sexual dichromatism was found among haremic, lek-like and promiscuous mating systems. Species with temporary full dichromatism, permanent and temporary partial dichromatism and monochromatism were haremic. Smaller scarids were believed to have lek-like, and larger species haremic, mating systems. Smaller scarids had male looping behavior and post spawning displays, plus faster spawning ascents and different locations for egg release than larger ones. Eggs of 21 labrids were spherical or nearly spherical, ranging from 0.55–0.80 mm in diameter, and most had one oil globule. Among 7 is scarids, 6 had spindle-shaped eggs ranging from 1.25 ×0.50 mm 2.14× 0.48 mm while one had a nearly spherical egg. One scarid egg lacked an oil globule.     

A retrospective analysis of sea turtle nest depredation patterns

Nest predation can significantly reduce hatchling recruitment in sea turtle populations. We examined 20 yr of data from Canaveral National Seashore, Florida, which has pristine and altered beaches. We used chi-squared test to determine if secondary predation events were related to the nests' primary predation events, and proportional hazard regression analysis to determine the relative risk of individual nest predation. To determine if human beach use and nest predation risk were spatially or temporally linked, we ranked human beach use and examined predation frequency across all screened and marked nests. We found that once a nest has experienced predation it has an increased likelihood of experiencing a subsequent predation event when compared to other nests on the beach. Primary and multiple predation events occurred with greater frequency in limited beach use areas and with lowest frequency in moderate use areas. Predation risk decreased by an average of 29.5% from 2000 to 2008, relative to the initial year of study. Nests deposited mid-season were 9.8% more likely to be predated than early or late season nests. We conclude that where anti-nest predator management efforts are required but restricted (e.g., by funds, available personnel, or multiple management goals) resources should be concentrated to protect mid-season nests and those in limited access areas, if enhancing hatchling numbers is a management goal. © 2012 The Wildlife Society.     

Metabolic heat estimation of the sea turtle Lepidochelys olivacea embryos

Several studies have reported the importance of metabolic heat on the increment of temperature in the sea turtle nests; however, the metabolic heat has not been calculated for sea turtle eggs. In this study, the metabolic heat generated by embryos of the sea turtle Lepidochelys olivacea was estimated from a thermal balance model by means of three measured temperatures—one in the center of the nest, and the others in the sand above and beside the nest. An experiment was conducted with a sample of 100 eggs from a Lepidochelys olivacea nest collected in the Baja Peninsula, Mexico. The results showed that during the incubation period, no metabolic heat was detected before day 19 but it increased from that day until a maximum of 0.84 W at day 34, when the incubation process was interrupted due to rain. This value corresponds to 31 emerged hatchlings. The novel model is a suitable framework to predict the temperature and metabolic heat within the nest.     

Timing and pattern of annual silver eel migration in two European watersheds are determined by similar cues

Many animals perform long‐distance migrations in order to maximize lifetime reproductive success. The European eel migrates several thousand kilometers between their feeding habitats in continental waters (fresh‐, brackish, and sea water) and their spawning area in the Sargasso Sea. Eels residing in freshwaters usually initiate their spawning migration as silver eels during autumn, triggered by diverse environmental cues. We analyzed the time series of silver eel downstream migration in Burrishoole, Ireland (1971–2015), and Imsa, Norway (1975–2015), to examine factors regulating the silver eel migration from freshwater to the sea. The migration season (90% of the run) generally lasted from 1 August to 30 November. Environmental factors acting in the months before migration impacted timing and duration of migration, likely through influencing the internal processes preparing the fish for migration. Once the migration had started, environmental factors impacted the day‐to‐day variation in number of migrants, apparently stimulating migration among those eels ready for migration. Both the day‐to‐day variation in the number of migrants and the onset of migration were described by nearly identical models in the two rivers. Variables explaining day‐to‐day variation were all associated with conditions that may minimize predation risk; number of migrants was reduced under a strong moon and short nights and increased during high and increasing water levels. Presence of other migrants stimulated migration, which further indicates that silver eel migration has evolved to minimize predation risk. The onset of migration was explained mainly by water levels in August. The models for duration of the migration season were less similar between the sites. Thus, the overall migration season seems governed by the need to reach the spawning areas in a synchronized manner, while during the actual seaward migration, antipredator behavior seems of overriding importance.     

Community regulation: the relative importance of recruitment and predation intensity of an intertidal community dominant in a seascape context

Predicting the strength and context-dependency of species interactions across multiple scales is a core area in ecology. This is especially challenging in the marine environment, where populations of most predators and prey are generally open, because of their pelagic larval phase, and recruitment of both is highly variable. In this study we use a comparative-experimental approach on small and large spatial scales to test the relationship between predation intensity and prey recruitment and their relative importance in shaping populations of a dominant rocky intertidal space occupier, mussels, in the context of seascape (availability of nearby subtidal reef habitat). Predation intensity on transplanted mussels was tested inside and outside cages and recruitment was measured with standard larval settlement collectors. We found that on intertidal rocky benches with contiguous subtidal reefs in New Zealand, mussel larval recruitment is usually low but predation on recruits by subtidal consumers (fish, crabs) is intense during high tide. On nearby intertidal rocky benches with adjacent sandy subtidal habitats, larval recruitment is usually greater but subtidal predators are typically rare and predation is weaker. Multiple regression analysis showed that predation intensity accounts for most of the variability in the abundance of adult mussels compared to recruitment. This seascape-dependent, predation-recruitment relationship could scale up to explain regional community variability. We argue that community ecology models should include seascape context-dependency and its effects on recruitment and species interactions for better predictions of coastal community dynamics and structure.     

Temporal coincidence of environmental stress events modulates predation rates

Climate warming experiments generally test the ecological effects of constant treatments while neglecting the influence of more realistic patterns of environmental fluctuations. Thus, little is known regarding how the temporal interaction between multiple episodes of thermal stress influences biotic interactions. We measured the sensitivity of predation rate in an intertidal sea star to changing levels of temporal coincidence of underwater and aerial thermal stress events. In laboratory trials, we controlled for intensity, variance and temporal patterning of both underwater and aerial body temperature. Predation rate decreased as underwater and aerial thermal stress episodes became temporally non-coincident, despite a similar intensity and variance among treatments. Experiments under constant conditions were a poor predictor of more complex environmental scenarios because of these strong temporal interactions. Such temporal interactions may be widespread in various ecosystems, suggesting a strong need for empirical studies and models that link environmental complexity, physiology, behaviour and species interactions.