Strong site fidelity and longer internesting interval for solitary nesting olive ridley sea turtles in Brazil

Olive ridley sea turtles display two different types of nesting behavior: in arribada (synchronous mass nesting) or solitarily. Contrarily to arribadas, little has been published about solitary nesters. This study aimed to expand the knowledge on internesting interval and site fidelity of solitary nesting olive ridleys and to test a possible development of arribada nesting behavior. Data were collected in Sergipe (Brazil) over 125 km of beach from 10°30′S/36o23′W to 11°26′S/37o19′W, between nesting seasons 2004/2005 and 2006/2007. From 962 tagged females, 173 were seen renesting. The average internesting interval found was longer (22.35 ± 7.01 days) than previously described, which might relate to lower water temperatures during the internesting period. Olive ridleys at Sergipe showed high nesting site fidelity, with consecutive nesting events occurring in close proximity, non-randomly and dependently of previous events. Most of the consecutive nests were separated by 4.06–5.59 km. Development of arribada nesting behavior was not confirmed.     

Satellite telemetry reveals behavioural plasticity in a green turtle population nesting in Sri Lanka

Satellite transmitters were deployed on ten green turtles (Chelonia mydas) nesting in Rekawa Sanctuary (RS-80.851°E 6.045°N), Sri Lanka, during 2006 and 2007 to determine inter-nesting and migratory behaviours and foraging habitats. Nine turtles subsequently nested at RS and demonstrated two inter-nesting strategies linked to the location of their residence sites. Three turtles used local shallow coastal sites within 60 km of RS during some or all of their inter-nesting periods and then returned to and settled at these sites on completion of their breeding seasons. In contrast, five individuals spent inter-nesting periods proximate to RS and then migrated to and settled at distant (>350 km) shallow coastal residence sites. Another turtle also spent inter-nesting periods proximate to RS and then migrated to a distant oceanic atoll and made forays into oceanic waters for 42 days before transmissions ceased. This behavioural plasticity informs conservation management beyond protection at the nesting beach.     

Regional and annual variation in plasma steroids and metabolic indicators in female green turtles, <Emphasis Type="Italic">Chelonia mydas</Emphasis>

Variation in environmental conditions at a foraging area or at a nesting rookery has the potential to impact reproductive output of green sea turtles (Chelonia mydas) by affecting food resources or the nesting substrate. In this paper we test whether turtles‘ physiological characteristics reflect variation in relevant environmental conditions. We did this by profiling metabolic and hormonal markers among (1) non-vitellogenic females from three different foraging areas and (2) nesting females from different rookeries and breeding seasons. Among the non-vitellogenic females, the highest plasma triglyceride concentrations (4.29 mmol/l) and the lowest plasma cholesterol concentrations (1.27 mmol/l) were found in non-vitellogenic females residing in Moreton Bay during the El Niño year of 1997. Furthermore, during 1997, these Moreton Bay females had higher plasma triglyceride and lower cholesterol concentrations than those recorded in non-vitellogenic females foraging at Heron Reef (triglyceride 1.22 mmol/l and cholesterol 4.53 mmol/l) and Shoalwater Bay (triglyceride 1.69 mmol/l and cholesterol 3.50 mmol/l) in the same year. Among nesting turtles, those nesting at Raine Island had low mean plasma triglyceride concentrations during the high density 1996 nesting season. For those nesting at Heron Island, the mean triglyceride concentrations were the lowest during the 1997 nesting season. This is the first time that hormone and metabolic markers have been used in concert to compare the physiological condition of nesting and foraging sea turtles and its relationship with the environment. Collectively, our data indicate that variation in the environmental conditions at both foraging and nesting areas are reflected at a physiological level. Moreover, our study indicates that turtles feeding during El Niño years are able to attain higher levels of body condition, and that physiological data combined with morphometric data is a useful proxy for assessing the condition of turtles in foraging areas.     

Interactions among endocrinology,seasonal reproductive cycles and the nesting biology of the female green sea turtle

We collected data on plasma levels of testosterone+5a-dihydrotestosterone (T+DHT) and corticosterone (CORT) from adult female green sea turtles (Chelonia mydas) from southern Queensland during distinct stages of their reproductive cycle. Those females capable of breeding in a given year had elevated plasma steroid levels (T+DHT 0.91ǂ.08; CORT 1.05ǂ.29 ng/ml), associated with follicular development, until courtship began in October. At the beginning of the nesting season in November plasma levels of CORT were related to when the female first nested (r²=0.06; F=10.45; P=0.01). However, they were not correlated with the number of clutches a female laid in that season (F=3.65; P=0.08). We repeatedly sampled 23 turtles over the nesting season and profiled changes in steroids immediately following oviposition of each clutch. Levels of T+DHT (range 0.41-0.58 ng/ml) and CORT (range 2.13-2.81 ng/ml) were similar through the early stages of the nesting season and inter-nesting period, and declined to near basal levels (T+DHT 0.37ǂ.03 and CORT 1.85-ng/ml) following the last clutch for the season. Steroid hormone levels were also low (T+DHT 0.38ǂ.16; CORT 0.46ǂ.21 ng/ml) in four independent post-breeding (atretic) females; samples for these females were taken at a time when body condition was presumably at the lowest for the season. Subtle changes in the nesting environment, such as variation in nesting habitat or the time of night that nesting occurred, were associated with a small and slow CORT increase. We suggest CORT is increased in nesting females to assist in lipid transfer to prepare the ovarian follicles and/or the reproductive organs for ovulation.     

Breeding biology of the green turtle, Chelonia mydas (Reptilia: Cheloniidae), on Wan-An Island, PengHu archipelago. II. Nest site selection

Nest site selection of the green turtles on Wan-An Island in the summer of 1996 was determined. Turtles (Chelonia mydas) laid on average one clutch for every three emergences. Even though the total track length was 115 m on average, individual lengths varied considerably depending on the nesting beach where the turtles emerged. Limited accessibility, i.e. adequate distance from the nearest village and a well-protected environment, make beaches A and D suitable nesting beaches for green turtles on Wan-An Island. Both total track and nesting track apexes were found clustered in the interface zone, and turtles preferred to reach the vegetation zone once they emerged from the sea. It is suggested that the turtles on Wan-An Island exhibit nest site selection behavior. Based on these results and the high nest site fidelity to their first nesting beach, conservation recommendations are proposed to the county and central governments for the preservation of nesting beaches in their natural state, by prohibiting illegal sand mining and properly controlling turtle watch groups on Wan-An Island. Received: 21 November 1997 / Accepted: 24 December 1998     

Migratory and reproductive movements of male leatherback turtles (<Emphasis Type="Italic">Dermochelys coriacea</Emphasis>)

The biology of the endangered leatherback turtle (Dermochelys coriacea) at sea is poorly understood. As research has been almost exclusively limited to studies of nesting females, the movements of male turtles and the timing and location of mating activity have remained unknown. We report on the first deployments of satellite tags on male leatherbacks. Male migration to and residency in waters adjacent low-latitude nesting beaches in the western Atlantic suggest that this is where mating occurs, and return migration to these areas reveals male fidelity for breeding sites. Rate of travel decreased markedly after arriving in coastal breeding areas, where males remained for up to 96 days before assuming northward migrations. The initiation of these northward migrations coincided with peak nesting activity in adjacent nesting colonies. Data from satellite-linked time-depth recorders attached to two males revealed diel dive patterns in breeding areas and marked differences in diving behaviour between migratory and breeding periods in one turtle. When male turtles were in waters adjacent nesting colonies, their movements differed from those reported for nesting females, with females ranging farther from shore. Our results suggest that male leatherbacks may be vulnerable to entanglement in coastal fishing gear in waters adjacent nesting beaches.Communicated by R.J. Thompson, St. Johns     

Migration of green turtles <Emphasis Type="Italic">Chelonia mydas</Emphasis> from Tortuguero,Costa Rica

During 1955–2003, flipper tags were attached to 46,983 green turtles and ten turtles were fitted with satellite transmitters at Tortuguero, Costa Rica. Eight satellite-tracked turtles stayed within 135 km of the beach and probably returned to nest after release. The internesting area is more extensive than previously documented. Post-nesting migration routes of satellite-tracked turtles varied. Seven turtles swam close to the coast and three turtles swam through oceanic waters before moving toward nearshore areas. Sea surface height anomaly maps indicate that oceanic movements were consistent with the southwestern Caribbean gyre. Circling and semi-circling turtles could have been disoriented but submergence and surface times suggest they may have been feeding in Sargassum sp. concentrations. Rapid post-nesting migrations (mean 2.2 km hr⁻¹) ended on benthic feeding grounds in shallow waters (<20 m) off Belize (n=1), Honduras (n=1) and Nicaragua (n=8). The spatial distribution of migration end points (n=10) and tag returns (n=4,669) are similar. Fishermen in Nicaragua target green turtles along migratory corridors and on foraging grounds. Management efforts are urgently needed in Nicaragua, particularly in the high-density feeding areas south and east of the Witties (N14°09 W82°45). The proximity of foraging grounds to the nesting beach (mean 512 km) may permit female turtles to invest more energy in reproduction and hence the Tortuguero population may have greater potential for recovery than other green turtle nesting populations. Recovery of the Tortuguero green turtle population will benefit countries and marine ecosystems throughout the Caribbean, especially Nicaragua.     

Migration,distribution, and diving behavior of adult male loggerhead sea turtles (<Emphasis Type="Italic">Caretta caretta</Emphasis>) following dispersal from a major breeding aggregation in the Western North Atlantic

Sixteen satellite-tagged adult male loggerhead sea turtles (Caretta caretta) dispersed widely from an aggregation near Port Canaveral, Florida, USA (28°23′N, −80°32′W) after breeding. Northbound males migrated further (990 ± 303 km) than southbound males (577 ± 168 km) and transited more rapidly (median initial dive duration = 6 (IQR = 4–16) versus 19 (IQR = 10–31) min, respectively).. Migration occurred along a depth corridor (20–40 m) except where constricted by a narrow continental shelf width. Males foraged in areas 27 ± 41 km² day⁻¹ at locations <1–80 km from shore for 100.1 ± 60.6 days, with variability in foraging patterns not explained by turtle size or geography. Post-breeding dispersal patterns were similar to patterns reported for adult female loggerhead sea turtles in this region and adult male loggerhead sea turtles elsewhere in the northern hemisphere; however, foraging ground distributions were most similar to adult female loggerhead sea turtles in this region.     

Effects of male removal on female foraging behavior in the Eurasian treecreeper

In old, spruce-dominated forests of central Finland, Eurasian treecreepers Certhia familiaris divide their territories spatially during the breeding season. Females forage primarily on the upper parts of the tree trunks, while males use the lower parts of the tree trunks. In this study we removed males from eight territories in the early nestling period to see if the mate's absence would change the foraging patterns of the resident female. Widowed females foraged at lower heights, thus behaving more like paired males. These females also spent less time on each tree and on each foraging bout than did paired females. We conclude that male removal facilitated the change in a female's foraging niche and foraging time at the trees. Females may re-optimize their foraging site selection owing to the absence of dominant males and a consequent need to increase their parental care. Behavioral plasticity may be the mechanism of niche partitioning between the sexes in this species. Received: 28 June 1996 / Accepted after revision: 27 March 1997     

Nest-Site Selection in Individual Loggerhead Turtles and Consequences for Doomed-Egg Relocation

Abstract:  Relocation of eggs is a common strategy for conservation of declining reptilian populations around the world. If individuals exhibit consistency in their nest-site selection and if nest-site selection is a heritable trait, relocating eggs deposited in vulnerable locations may impose artificial selection that would maintain traits favoring unsuccessful nest-site selection. Conversely, if most individuals scatter their nesting effort and individuals that consistently select unsuccessful nest sites are uncommon, then artificial selection would be less of a concern. During the 2005 nesting season of loggerhead turtles ( Caretta caretta ) at Mon Repos beach, Queensland, Australia, we measured the perpendicular distance from the original nest site to a stationary dune baseline for in situ (unrelocated) and relocated clutches of eggs. We observed the fate of in situ clutches and predicted what would have been the fate of relocated clutches if they had not been moved by mapping tidal inundation and storm erosion lines. In 2005 turtles deposited an average of 3.84 nests and did not consistently select nest sites at particular distances from the stationary dune baseline. Selection of unsuccessful nest sites was distributed across the nesting population; 80.3% of the turtles selected at least one unsuccessful nest site and when previous breeding seasons were included, 97% selected at least one unsuccessful nest site. Females with nesting experience selected more successful nest sites than females with little or no experience. Relocating eggs vulnerable to tidal inundation and erosion saves the progeny from a large percentage of the population and the progeny from individuals who may in subsequent years nest successfully. Our results suggest that doomed-egg relocation does not substantially distort the gene pool in the eastern Australian loggerhead stock and should not be abandoned as a strategy for the conservation of marine turtle populations.     

Seasonal variation in the duetting behaviour of rufous-and-white wrens (<Emphasis Type="Italic">Thryothorus rufalbus</Emphasis>)

Seasonal variation in animal signalling behaviour has been well documented and has contributed much to our understanding of male signals. In contrast, we know little about seasonal variation in female signals or signals produced jointly by males and females, such as the vocal duets of birds. Here, we examine how singing behaviour changes in relation to time of year and breeding stage in rufous-and-white wrens (Thryothorus rufalbus), neotropical songbirds where both males and females sing and where breeding partners coordinate songs to produce vocal duets. We recorded a colour-marked population of birds over an extended time period encompassing multiple breeding stages. Across all time frames and breeding stages, males sang at higher rates than females and male solos were more common than duets or female solos. Males and females showed divergent seasonal patterns of singing. Females sang more often early in the year, during the pre-breeding season, and female song tapered off as the breeding season progressed. Duetting followed a parallel pattern, which resulted from females showing less duet responsiveness to their partner’s songs later in the year. Male independent song rate peaked at the onset of the rainy season – a time when females become fertile – and males showed the highest level of duet responsiveness during this period. Our results suggest that early in the year, duets appear to be cooperative displays, functioning in joint territory defence and/or the coordination of breeding activities. When females are fertile, however, increased duet responsiveness by males is consistent with mate or paternity guarding.     

Satellite tracking experiments on the navigational ability and migratory behaviour of the loggerhead turtle Caretta caretta

Four loggerhead females (Caretta caretta) were caught when emerging at their nesting beach on the Natal coast, prevented from egg laying and displaced along the coast 38 to 70 km from the capture site. They were then released either on the shore or 37 km offshore. The successful journeys back to the capture area and the successive migrations were tracked by satellite. In compensating for the displacement, loggerheads showed a capability of true navigation. The 545 to 1000 km long migratory journeys of three turtles were followed along the Mozambique coast up to the feeding grounds. Migratory speed was similar at night and during the day. During the trip, submergences were shorter and more frequent than during the stay at the feeding grounds. Received: 17 March 1997 / Accepted: 21 April 1997     

Replacement males in the western bluebird: opportunity for paternity, chick-feeding rules, and fitness consequences of male parental care

In western bluebirds (Sialia mexicana), most pairs remain together for life and share equally in post-hatching parental care. We removed resident males of socially monogamous pairs during laying and after clutch completion to examine chick-feeding rules used by replacement males and current and future fitness consequences of paternal care. Replacement males were not infanticidal and 7 (47%) fed nestlings. Feeding replacement males and the females they joined fed at rates similar to controls. Females without a feeding replacement male compensated by feeding more themselves so that overall feeding rates were not compromised, but they reduced their brooding time. Unlike assisted females, unassisted females exhibited reduced nesting success and their 14-day-old chicks weighed less than controls. Field metabolic rates of unassisted females were 17% higher than those of control females, but the difference was not statistically significant. Older females were better able to raise young without the male's help than were yearling females. Female condition was not affected by male provisioning and unassisted females were as likely to survive to the next breeding season as assisted females. We found no future benefits of provisioning by replacement males; those that fed were no more likely to breed with the female on her subsequent attempt than were males that did not feed, and subsequent clutch sizes were not reduced for females rearing young without the male's help. These experiments suggest that male parental care increases nesting success in western bluebirds and that replacement males use an all-or-none rule to determine whether or not to feed chicks: if they are present during the fertile period they feed at typical rates; if they are not, they usually do not feed at all. Because chick-feeding by males is tied to opportunity for paternity, influences success in the current nest, and does not affect the male's future breeding success, it appears to be parental rather than mating effort. Received: 8 May 1998 / Accepted after revision: 23 July 1998     

Remigration and growth of loggerhead turtles (<Emphasis Type="Italic">Caretta caretta</Emphasis>) nesting on Senri Beach in Minabe,Japan: life-history polymorphism in a sea turtle population

There are size-related differences in the use of feeding habitats (planktonic or benthic; oceanic or neritic) by adult female loggerhead sea turtles (Caretta caretta) within Japanese populations. We thus hypothesized that the differences may be reflected in their remigration and growth patterns, and investigated the relationships between body size and remigration intervals, growth rates, and remigration percentages, for female loggerheads nesting on a Japanese beach between 1991 and 2001. Although remigration intervals, growth rates, and remigration percentages were not significantly different among females, there were trends for longer remigration intervals and lower remigration percentages in smaller females. All females grew little. Considering these results along with previous findings, we speculated on the life-history strategy of female Japanese loggerheads.Communicated by T. Ikeda, Hakodate     

Inter-seasonal maintenance of individual nest site preferences in hawksbill sea turtles

Within a single population of hawksbill sea turtles (Eretmochelys imbricata), we found a behavioral polymorphism for maternal nest site choice with respect to beach microhabitat characteristics. Some females preferred to nest in littoral forest and in places with overstory vegetation cover, and others preferred to nest in more open, deforested areas. Nest site choice was consistent within and between nesting seasons two years apart. This was not a result of females simply returning to the same location along the shoreline; beach sections used by individual turtles varied between seasons. Nest site choice was not influenced by changes in beach environment (e.g., beach width and foliage cover) or by changes in females' reproductive output (e.g., clutch size), suggesting that fidelity to particular microhabitats is a major determinant of the observed nesting patterns. Because hawksbills exhibit temperature-dependent sex determination, if the behavioral polymorphism in nest site choice has a genetic basis, as is plausible, then this would have implications for sex ratio evolution and offspring survival. By taking an individual-based approach to the study of maternal behavior we reveal previously overlooked individual variation and hope to provide some impetus for more detailed studies of nest site choice.     

Polygyny in the red-winged blackbird: do females prefer monogamy or polygamy?

Five hypotheses have been proposed to explain polygyny in the red-winged blackbird (Agelaius phoeniceus). We categorized the hypotheses into three groups based on female preference for unmated versus monogamously mated males: (1) the “polygyny threshold” model, “sexy son” hypothesis and the “asynchronous settlement” model, which assume that females prefer unmated males to mated males on breeding situations of homogeneous quality; (2) the “neutral mate choice” hypothesis, which assumes that females have no preference; and (3) the “cooperative female choice” model, which assumes that females prefer monogamously mated males to unmated males. We tested the direction of female preference in two field experiments. In both experiments, newly settling females were given a choice of two adjacent territories, one defended by an unmated male and the other by a monogamously mated male. Male mating status was randomized with respect to the variation in territory quality and male quality. Early in the breeding season, significantly more females settled with the unmated males than with the mated males. Although more females settled with the unmated males than with the mated males late in the breeding season, the difference was no longer significant. Female settlement late in the season appeared to be related to the tenure of the resident females: the new females avoided territories where the resident females were in early stages of their nesting, but settled on territories where the resident females were in late stages. The pattern of female settlement shows that females prefer unmated males to mated males. The preference is consistent with the polygyny threshold model, sexy son hypothesis and the asynchronous settlement model, and inconsistent with the neutral mate choice hypothesis and the cooperative female choice model. For this reason, the latter two hypotheses are unlikely to explain the occurrence of polygyny in our population of red-winged blackbirds. Received: 1 December 1994 / Accepted after revision: 28 October 1995     

Chemical aspects of mass spawning in corals. II. (-)-Epi-thunbergol,the sperm attractant in the eggs of the soft coral Lobophytum crassum (Cnidaria: Octocorallia)

Sea turtles migrate between feeding and nesting areas that are often geographically separated by hundreds or thousands of kilometers. Observations of their aggregations at sea and at nesting beaches have led to the hypothesis that sea turtles migrate in socially structured groups. While this migratory strategy is common to many marine vertebrates, socially facilitated behavior is not well documented in testudines. In 1990 and 1991, we attached satellite transmitters to olive ridleys (Lepidochelys olivacea Eschscholtz) found ovipositing together during a mass nesting at Nancite Beach, Costa Rica, to determine whether they migrate independently or in groups after they leave the nesting beach. Results showed that the turtles were not spatially associated during the internesting period, were capable of re-establishing themselves as a group during a subsequent nesting emergence, and were not spatially associated during their postnesting migrations to oceanic feeding areas. We suggested that what appear to be socially structured groups of L. olivacea are in fact individual turtles simultaneously using the same habitat.     

Breeding biology of the green turtle,Chelonia mydas, (Reptilia: Cheloniidae) on Wan-An Island,Peng-Hu Archipelago,Taiwan. I. Nesting ecology

The nesting season of the green turtle, Chelonia mydas on Wan-An Island, Peng-Hu Archipelago, Taiwan extended from early June to early October in both 1992 and 1993. Turtles nested on 9 of the 11 beaches on the island. The average inter-nesting interval was 14.9 d. A close relationship between the first reemergence time and the tidal cycle was found in the present study. The mean straight carapace length of the adult female was 96.6 cm. Female turtles produced from one to nine egg clutches; the average clutch size was 113 eggs. The mean egg size was 46.9 mm in diameter and 22.7 g in weight. The average incubation period was 49.3 d. The sediment characteristics of the beaches on the island are well within the incubation requirements for green turtle nesting. The average hatching success was 70%, but was lower in the artificial nest. The average size for hatchlings was 46.9 mm in straight carapace length and 22.7 g in body weight. The health of the hatchling is influenced by the adult female size, the nesting depth and the precipitation during incubation.     

Estimating demographic parameters for a critically endangered marine species with frequent reproductive omission: hawksbill turtles nesting at Varanus Island,Western Australia

The hawksbill marine turtle (Eretmochelys imbricata) is listed on the IUCN Red List as critically endangered but little is known about its demography to support robust diagnosis of population trends. Moreover, adult female hawksbills do not nest each year due to environmentally mediated physiological constraints and this skipped breeding behaviour presents a major challenge in data collection and for estimating demographic parameters from such data sets. We estimated demographic parameters such as survival and breeding probabilities for a major Indo-Pacific nesting hawksbill population using a capture-mark-recapture (CMR) study and a multistate open robust design statistical modelling approach, which accounts for breeding omission and the staggered arrival and departure of nesters during each season. Our study used CMR histories for 413 nesting hawksbills tagged on Varanus Island (Western Australia) over a 4-month sampling period each year for 20 austral summer nesting seasons between 1987 and 2007. The estimated annual survival probability for these nesting hawksbills was constant over the 20 years at ca. 0.947 (95% CI: 0.91–0.97), which is encouragingly high for a population associated with industry. The estimated annual conditional nesting (breeding) probability for female hawksbills that had skipped the previous nesting season was time-specific ranging from 0.07 to 0.29 (mean = 0.18, CV = 41.3%), which presumably reflects the interaction between turtle physiology and in-water habitat quality. The mean conditional probability of breeding again having skipped 2 prior consecutive nesting seasons was ca. 0.83 (95% CI: 0.73–0.89), indicating a high frequency of breeding season omission. The annual nesting probability for females that had nested the previous season was 0, reflecting known obligate skipped breeding (reproductive omission) that is characteristic of hawksbill populations in response to high energy demands of vitellogenesis and breeding migration. These are the first estimates of annual survival and state-dependent breeding probabilities for any Indo-Pacific hawksbill stock that provide a basis for developing a better understanding of regional population dynamics for this critically endangered species.     

Flipper beat frequency and amplitude changes in diving green turtles, <Emphasis Type="Italic">Chelonia mydas</Emphasis>

Using a turtle-borne camera system, changing flipper beat frequency and amplitude were measured in five diving green turtles (Chelonia mydas Linnaeus 1758) in the Bahía de los Angeles, Mexico (28°58′N, 113°33′W). These observations were made between June and August 2002. Turtles worked hardest (i.e., had the highest flipper beat frequency and amplitude) at the start of descents when positive buoyancy is predicted to oppose their forward motion. During the later part of descents, turtles worked less hard in line with opposing buoyancy forces being reduced. For example, flipper beat frequency declined from about 60–80 beats min⁻¹ at the start of descent to around 25–40 beats min⁻¹ after 30 s of the descent. At the start of ascents the flipper beat frequency was around 30 beats min⁻¹, lower than on descent, and declined as the ascent progressed with often passive gliding for the final few meters to the surface. This pattern of effort during diving appears to apply across a range of marine reptiles, birds and mammals suggesting that graded effort during descent and ascent is an optimum solution to minimising the cost of transport during diving.