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1.
The South Florida subpopulation of loggerhead sea turtles (Caretta caretta L.) nests with great fidelity on either the southeast or the southwest coast of Florida, USA. The hatchlings that emerge from those nests must swim in opposite directions and search for different surface currents to migrate away from continental shelf waters. In this laboratory study, we compared the pattern of swimming activity shown by the hatchlings from each coast over the first 6 days of migration. Turtles from both coasts were equally active during their “frenzy” period (the first 24 h of swimming) and during the daylight hours of the 5 days that followed (the “postfrenzy” period). However, the west coast turtles were significantly more active than the east coast turtles during the nocturnal portion of the postfrenzy period. This difference may be related to the greater distance southwest coast turtles must negotiate to locate surface currents for transport out of the Gulf of Mexico and into the Atlantic Ocean basin. These differing behavioral strategies may be genetically determined, as similar correspondence between activity and distance is well known among migratory populations of birds and fish and is often based upon inherited programs of endogenously driven activity. Alternatively, behavioral differences between the two nesting groups could be a manifestation of phenotypic plasticity that arises as the hatchlings respond to unique environmental cues on each coast. 相似文献
2.
Loggerhead sea turtle hatchlings emerge from nests on either the east or west coast of the South Florida peninsula and then
migrate offshore in opposite directions. Under laboratory conditions, magnetic cues induce east coast hatchlings to swim in
directions that promote their transport by oceanic surface currents, such as the North Atlantic gyre. However, the surface
currents used by west coast hatchlings are unknown. We examined the responses of west (Sarasota) hatchlings to magnetic cues
in the Gulf of Mexico, the Florida Straits, and the Gulf Stream to determine their (1) likely migratory routes (2) orientation
where currents lead into the Atlantic Ocean, and (3) orientation adjacent to Florida’s east coast. The results suggest that
migration inside Gulf waters may be circuitous, that the turtles respond appropriately to enter Atlantic waters, and that
orientation along Florida’s east coast probably promotes transport by the Gulf Stream into the North Atlantic gyre. 相似文献
3.
Locomotion performance plays a vital role in determining hatchling green turtle Chelonia mydas survival in the first few hours after emerging from their nests as hatchlings crawl and swim the gauntlet of predators before
reaching the relative safety of the open ocean. Previous laboratory based constant incubation experiments found incubation
temperature to influence the size and swimming performance of hatchling green turtles. Here we examine the morphology and
crawling and swimming performance of hatchling green turtles as they emerge from nests on Heron Island rookery in the southern
Great Barrier Reef to test the hypothesis that nest temperature in the field can influence these attributes. We found inter-nest
differences in hatchling mass and dimensions, and that hatchling mass was not correlated with nest temperature. However, hatchlings
from warmer nests had smaller carapace dimensions than hatchlings from cool nests suggesting that more yolk was converted
to hatchling tissue during embryonic development in cool nests. There was considerable intra- and inter-nest variation in
both crawling and swimming performance of hatchlings. Hatchlings from cool nests tended to be faster crawlers than hatchlings
from warm nests, but the thrust produced during swimming was not correlated with nest temperature. During the 4 h swimming
trial, hatchlings swimming effort decreased significantly during the first 3 h but swimming effort remained relatively constant
for the last 1 h. Individual hatchling crawling and swimming performances were not correlated with each other.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
4.
At the beginning of their offshore migration, hatchling sea turtles orient directly into oceanic waves as they swim away
from land. Recent experiments have demonstrated that hatchlings swimming underwater can determine the propagation direction
of waves by monitoring the circular movements they experience as waves pass above. During July and August 1993, we studied
how loggerhead sea turtle hatchlings (Caretta caretta L.) from the east coast of Florida, USA, responded to a range of wave parameters. We constructed a wave simulator to reproduce
in air the circular movements that normally occur beneath small ocean waves. Hatchlings suspended in air and subjected to
these orbital movements attempted to orient into simulated waves when periods and amplitudes were similar to those found near
the Florida coast. Orbital movements with longer periods (greater than 10 s), however, failed to elicit responses. The results
demonstrate that hatchling loggerheads can distinguish between waves with different periods and amplitudes, and that Florida
hatchlings respond most strongly to orbital movements closely resembling those of waves that occur near their natal beach.
Received: 28 May 1996 / Accepted: 17 September 1996 相似文献
5.
Pilar Santidrián Tomillo Jack S. Suss Bryan P. Wallace Kimberly D. Magrini Gabriela Blanco Frank V. Paladino James R. Spotila 《Marine Biology》2009,156(10):2021-2031
Reproductive output of leatherback turtles (Dermochelys coriacea) is affected by the stochastic nature of emergence success. Average emergence success of nests at Playa Grande, Costa Rica
was 0.38 ± 0.27. Incubation temperature affected development of leatherback turtle eggs and emergence of hatchlings from the
nest. We found that high temperatures reduced hatching success and emergence rate and increased embryonic mortality both early
and late during incubation at Playa Grande. There was a temporal effect on emergence success that resulted in more hatchlings
being produced at the beginning of the season, because of higher emergence success, than toward the end. Likewise, production
of hatchlings varied from year to year. The average annual reproductive output was 252 ± 141 hatchlings per female. The 2005–2006
nesting season had the highest emergence success and produced the greatest number of hatchlings per female compared to the
2004–2005 (+120%) and 2006–2007 (+41%) seasons. However, average clutch size (62 ± 10) and clutch frequency (9.45 ± 1.63),
were not different among years. Turtles that had nested a high number of years exhibited greater clutch frequency and arrived
earlier to nest than turtles that had nested in fewer numbers of years. Nesting when environmental conditions favor high developmental
success and emergence rate may constitute an advantageous reproductive strategy. 相似文献
6.
E. J. Buskey 《Marine Biology》1998,130(3):425-431
The cyclopoid copepod Dioithona oculata forms dense swarms within shafts of sunlight that penetrate the mangrove prop-root habitat of islands off the coast of Belize.
Previous studies, based on in situ video recordings and laboratory studies, have shown that D. oculata is capable of maintaining fixed-position swarms in spite of currents of up to 2 cm s−1. The purpose of this study was to examine the energetic costs of maintaining these swarms, in terms of increased metabolic
costs of maintaining position in currents and in terms of reduced feeding rates in densely packed swarms during the day. Using
a sealed, variable-speed flow-through chamber, the respiration rates of D. oculata were measured while swarms maintained position in different current speeds. The results indicate that active metabolism (swimming
at maximum speed to maintain the swarm in a current) is approximately three times greater than routine metabolism (normal
swimming speeds in the absence of currents), indicating a significant metabolic cost of maintaining swarms in the presence
of currents. In addition, gut-pigment analysis indicated that feeding rates of these copepods were often reduced in swarms
during the day compared to when the copepods were dispersed at night. Given the high “cost” of swarming, the adaptive value
of swarming in terms of reduced predation, increased opportunities for mating, and reduced dispersal, must be substantial.
Received: 4 June 1997 / Accepted: 18 September 1997 相似文献
7.
Skeletochronological analysis of Kemp’s ridley (Lepidochelys kempii) and loggerhead (Caretta caretta) sea turtle humeri and scleral ossicles was conducted to (1) describe the characteristics of scleral ossicles in these species,
(2) determine whether the scleral ossicles contain annually deposited skeletal growth marks and (3) evaluate the potential
for skeletochronological analysis of ossicles to obtain age data for size classes and species of sea turtles whose humeri
exhibit prohibitive amounts of growth mark resorption. Humeri, entire eyes, and/or individual scleral ossicles were collected
from stranded, dead sea turtles that were found along the coasts of Florida, North Carolina, Virginia, and Texas, USA. Samples
were taken from a total of 77 neritic, juvenile Kemp’s ridleys ranging from 21.1 to 56.8 cm straightline carapace length (SCL),
as well as two Kemp’s ridley hatchlings. For loggerheads, samples were obtained from 65 neritic juvenile and adult turtles
ranging from 44.7 to 103.6 cm SCL and ten hatchlings. Examination of the ossicles revealed the presence of marks similar in
appearance to those found in humeri. The number of marks in the ossicles and humeri of individual juvenile Kemp’s ridleys
for which both structures were collected (n = 55) was equivalent, strongly indicating that the marks are annual. However, in large juvenile and adult loggerhead turtles
(n = 65), some significant resorption of early growth marks was observed, suggesting that although ossicles might be useful
for skeletochronological analysis of small juveniles, they may not provide a reasonable alternative to humeri for obtaining
age estimates for older loggerhead sea turtles. 相似文献
8.
Junichi Okuyama Takashi Kitagawa Kei Zenimoto Shingo Kimura Nobuaki Arai Yoshikazu Sasai Hideharu Sasaki 《Marine Biology》2011,158(9):2055-2063
We used Lagrangian numerical simulations to examine the trans-Pacific dispersal processes of loggerhead turtle hatchlings.
Ten thousand simulated particles were released from each of the three nesting regions in Japan and tracked for 5 years. Results
showed many particles moving eastward, drifting in the Kuroshio Current followed by the Kuroshio Extension Current. However,
no particles reached Baja California, a known feeding area, through passive processes, indicating that trans-Pacific transportation
requires active swimming by turtles. The duration of the trans-Pacific dispersal was estimated to be at least 1.6–3.4 years,
with some turtles drifting in the Kuroshio Countercurrent and remaining in the western Pacific even after 5 years. This indicates
that as revealed by previous genetic studies, not all loggerheads always disperse along a trans-Pacific route. The findings
showed that survival and expected growth rates varied widely according to ambient temperatures during drifting, which in turn
depended on nesting location. 相似文献
9.
Low level aerial observations were used to obtain synoptic records of the distribution of sea turtle nesting activity along both coasts of Costa Rica. Pertinent environmental information was simultaneously recorded including beach characteristics, river effluents, and evidence of coastal currents. Other correlative information was obtained from detailed maps, current charts, and climatological data. On the Caribbean coast, as expected, green turtle (Chelonia mydas) nesting was concentrated on the beaches between the Tortuguero and Parismina Rivers. On the Pacific coast, two major nesting beaches for the Pacific ridley Lepidochelys olivacea were found, each having over 100 thousand turtles aggregated offshore during the peak period between September and November. Aggregations were present at least from July through December. Massed nesting occurs each year on these same beaches and the event is known as the salida de flota by the natives of Guanacaste Province. Numerous less important nesting beaches were also found. Nesting density did not correlate well with beach quality but, instead, appeared to be related to the proximity of the beach to offshore currents. Oceanic current systems apparently facilitate the transport of sea turtles to the general vicinity of the important nesting beaches on both coasts of Coata Rica.Contribution No. 1557 from the Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA. 相似文献
10.
Whilst a range of animals have been shown to respond behaviourally to components of the Earth’s magnetic field, evidence of
the value of this sensory perception for small animals advected by strong flows (wind/ocean currents) is equivocal. We added
geomagnetic directional swimming behaviour for North Atlantic loggerhead turtle hatchlings (Caretta
caretta) into a high-resolution (1/4°) global general circulation ocean model to simulate 2,925-year-long hatchling trajectories
comprising 355,875 locations. A little directional swimming (1–3 h per day) had a major impact on trajectories; simulated
hatchlings travelled further south into warmer water. As a result, thermal elevation of hatchling metabolic rates was estimated
to be between 63.3 and 114.5% after 220 days. We show that even small animals in strong flows can benefit from geomagnetic
orientation and thus the potential implications of directional swimming for other taxa may be broad. 相似文献
11.
Modelling the fate of marine turtle hatchlings 总被引:1,自引:0,他引:1
Mark Hamann Alana Grech Eric WolanskiJonathan Lambrechts 《Ecological modelling》2011,222(8):1515-1521
The SLIM oceanographic model was used to examine the fate of hatchling flatback turtles (Natator depressus) in the first two weeks of their dispersal starting at Wild Duck Island, a major turtle-nesting site in the central Great Barrier Reef region of Australia. We ran simulations to investigate the effects of spring versus neap tides, hatchling's swimming behaviour during their first three days at sea, and the location of nesting beaches. The model predicted that up to 50% of the turtle hatchlings entering the sea from the windward, southern beach remained after 14 days in shallow, nearshore waters, irrespective of tides and swimming. These waters are turbid and may be inhospitable to hatchlings. In contrast >80% of hatchlings dispersing from the leeward, northern beach were dispersed to deeper water (10-40 m) in a quasi-stationary dispersion core centred around 10 km north of the nesting beach after 14 days and the offshore spread of the turtle plume was enhanced by the hatchling's seaward swimming during the first three days. This was due to the presence of a coastal boundary layer and a stagnation zone around the northern side of island, but not the southern side. The model confirmed that dispersal from eastern Queensland flatback turtle rookeries is restricted to the lagoons and coastal waters, and that water circulation and hatchling's swimming control dispersion. The model explains why more turtles nest on the northern than the southern side. This study highlights the usefulness of oceanographic models to increase knowledge about a cryptic life stage of marine turtles. 相似文献
12.
This study is the first report of post-nesting migrations of loggerhead sea turtles (Caretta caretta) nesting in Sarasota County (Florida, USA), their most important rookery in the Gulf of Mexico (GOM). In total, 28 females
(curved carapace length CCL between 82.2 and 112.0 cm) were satellite-tracked between May 2005 and December 2007. Post-nesting
migrations were completed in 3–68 days (mean ± SD = 23 ± 16 days). Five different migration patterns were observed: six turtles
remained in the vicinity of their nesting site while the other individuals moved either to the south-western part of the Florida
Shelf (n = 9 turtles), the Northeast GOM (n = 2 turtles), the South GOM (Yucatán Shelf and Campeche Bay, Mexico, and Cuba; n = 5 turtles) or the Bahamas (n = 6 turtles). In average, turtles moved along rather straight routes over the continental shelf but showed more indirect
paths in oceanic waters. Path analyses coupled with remote sensing oceanographic data suggest that most of long-distance migrants
reached their intended foraging destinations but did not compensate for the deflecting action of ocean currents. While six
out of seven small individuals (CCL < 90 cm) remained on the Florida Shelf, larger individuals showed various migration strategies,
staying on the Florida Shelf or moving to long-distance foraging grounds. This study highlights the primary importance the
Western Florida Shelf in the management of the Florida Nesting Subpopulation, as well as the need of multi-national effort
to promote the conservation of the loggerhead turtle in the Western Atlantic.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
13.
Satellite tracking reveals a dichotomy in migration strategies among juvenile loggerhead turtles in the Northwest Atlantic 总被引:2,自引:2,他引:0
Katherine L. Mansfield Vincent S. Saba John A. Keinath John A. Musick 《Marine Biology》2009,156(12):2555-2570
Few data are available on the movements and behavior of immature Atlantic loggerhead sea turtles (Caretta caretta) from their seasonal neritic foraging grounds within the western north Atlantic. These waters provide developmental habitat
for loggerheads originating from several western Atlantic nesting stocks. We examined the long-term movements of 23 immature
loggerheads (16 wild-caught and seven headstart turtles) characterizing their seasonal distribution, habitat use, site fidelity,
and the oceanographic conditions encountered during their migrations. We identified two movement strategies: (1) a seasonal
shelf-constrained north–south migratory pattern; and (2) a year-round oceanic dispersal strategy where turtles travel in the
Gulf Stream to the North Atlantic and their northern dispersal is limited by the 10–15°C isotherm. When sea surface temperatures
dropped below 20°C, neritic turtles began a migration south of Cape Hatteras, North Carolina (USA) where they established
fidelity to the waters between North Carolina’s Outer Banks and the western edge of the Gulf Stream along outer continental
shelf. Two turtles traveled as far south as Florida. Several turtles returned to their seasonal foraging grounds during subsequent
summers. Northern movements were associated with both increased sea surface temperature (>21°C) and increased primary productivity.
Our results indicate strong seasonal and interannual philopatry to the waters of Virginia (summer foraging habitat) and North
Carolina (winter habitat). We suggest that the waters of Virginia and North Carolina provide important seasonal habitat and
serve as a seasonal migratory pathway for immature loggerhead sea turtles. North Carolina’s Cape Hatteras acts as a seasonal
“migratory bottleneck” for this species; special management consideration should be given to this region. Six turtles spent
time farther from the continental shelf. Three entered the Gulf Stream near Cape Hatteras, traveling in the current to the
northwest Atlantic. Two of these turtles remained within an oceanic habitat from 1 to 3 years and were associated with mesoscale
features and frontal systems. The ability of large benthic subadults to resume an oceanic lifestyle for extended periods indicates
plasticity in habitat use and migratory strategies. Therefore, traditional life history models for loggerhead sea turtles
should be reevaluated. 相似文献
14.
M. Thiel 《Marine Biology》2000,137(4):661-674
The population dynamics and reproductive biology of an ascidian- and a sponge-dwelling amphipod were examined. The two undescribed
amphipod species, Leucothoe“ascidicola” and L.“spongicola”, are closely related to each other, and occur in ascidians and sponges, respectively, along the Florida Atlantic coast.
L. “ascidicola” was abundant in solitary ascidians during fall 1997, disappeared during spring/early summer, and became abundant again in
September 1998. During the time when L. “ascidicola” were absent from their hosts, a copepod became a frequent inhabitant of the ascidians but disappeared again when L.“ascidicola” returned to the ascidians in September 1998. The numbers of L.“spongicola” in sponges increased substantially during spring, when high reproductive activity was observed. Following this reproductive
peak, both adult and juvenile amphipods apparently left the sponges, and during the summer amphipod numbers in the sponges
were very low. Another small amphipod species, which often co-occurred with L.“spongicola”, showed less seasonal variation and was found in sponges throughout the whole study period. The percentage of ovigerous
females per host unit was usually lower in the ascidian-dwelling than in the sponge-dwelling amphipods. In solitary ascidians,
L.“ascidicola” amphipods usually occurred in groups of several adults, yet there never was more than one ovigerous female per ascidian.
In contrast, several ovigerous L.“spongicola” females were found to cohabit in the same spongocoel. This suggests that intrasexual aggression may be stronger among reproductive
amphipod females in the ascidians than in sponges. The size distributions of juvenile cohorts indicate that juvenile L.“ascidicola” remain for relatively long time periods in the parental ascidian, where they may reach sexual maturity. In contrast, in
L.“spongicola”, only cohorts of very small juveniles could be identified, indicating that juveniles disperse shortly after emerging from
the female's brood pouch. It is concluded that extended parental care is of very short duration or does not occur in the sponge-dwelling
amphipod L. “spongicola”, possibly because fast-growing sponges with a highly branched spongocoel system do not allow long-lasting coexistence of
parent-offspring groups. In contrast, the discrete character of the solitary ascidians may enhance the potential for exclusion
of other species, resource monopolization by reproductive females, and furthermore for long-lasting extended parental care
in the ascidian-dwelling amphipod. Groups of single parents together with cohorts of large juveniles are reported in the literature
for amphipods and isopods from brachiopods, bivalves and ascidians, suggesting that these discrete biotic microhabitats may
favor the evolution of extended parental care in peracarid crustaceans.
Received: 30 July 1999 / Accepted: 8 May 2000 相似文献
15.
Parental care may be costly to parents because it decreases resources allocated to self-maintenance and may thus reduce survival
and future reproductive success. An inter-sexual conflict may exist in animals with obligatory bi-parental care, such as birds
of prey, in which females incubate and brood, whereas males provision food for their families. We analysed 29 years of data
(1981–2009) from a study population of Tengmalm’s owls Aegolius funereus in western Finland to examine the occurrence and timing of brood desertion and sequential polyandry, and recorded a total
of 1,123 monogamous and 12 polyandrous females. These data were supplemented with the 29-year nationwide Finnish ringing data,
which included 11,590 monogamous and 20 polyandrous females. The 12 polyandrous females started egg-laying in their two nests
at intervals of 54–68 days (mean 60 days), thus deserting their first broods when the age of oldest young averaged 21 days.
Thirty-two polyandrous females re-mated and raised a second brood at a median distance of 4.5 km (range 1–196 km). These females
produced 79% more eggs, 93% more hatchlings and 73% more fledglings than did females that laid simultaneously but remained
monogamous. Our results show that not only males, but also females of altricial species with bi-parental care can increase
their fitness by deserting their first brood when it will be cared for by the males. Earlier studies have shown that male
owls can increase their lifetime reproductive success by simultaneous polygyny, and we suggest that an inter-sexual “tug-of-war”
over bi-parental care exists in Tengmalm’s owls. 相似文献
16.
The extent to which behaviour affects the dispersal of pelagic larvae in reef fishes has been a topic of major discussion
among marine ecologists. Here, we experimentally quantified the extent to which the displacement of late-stage larvae of Abudefduf saxatilis is due to active movement (i.e. swimming) and drifting. We consider drifting as the component of larval displacement accounted
for by the current. Drifting was quantified by comparing larval displacement to the displacement of passive particles in an
extended flow chamber that gave larvae the free choice of swimming (i.e. swim with or against the current or not swim at all).
We also determine whether drifting results from currents exceeding larval swimming capabilities or from the behavioural choice
of larvae of not to swim against adverse currents. To do this, we compare the speeds of larval swimming in the extended flow
chamber to those obtained in a smaller chamber in which larvae are behaviourally forced to swim due to space constraints and
a retaining fence (most available data on larval swimming is based on this sort of chamber). Within the extended chamber,
larvae tended to face the current and swim slower than it. This resulted in a net displacement increasingly determined by
drifting. We also found that in the extended chamber, larvae swam at speeds between one and six times slower than the speeds
they achieved in the “behaviourally modifying” smaller chamber. This suggests that the net displacement in the extended chamber
was in part due to the behavioural choice of the larvae of not to swim. The importance of this “behavioural drifting” is discussed
in terms of energy savings required for successful completion of the larval period and post-settlement survival. The idea
that larvae may modulate their swimming behaviour raises caution for the use of published data regarding swimming capabilities
of reef fish larvae when assessing the extent to which these fish actively affect their dispersal. 相似文献
17.
L. A. Ferry-Graham 《Marine Biology》1998,131(4):703-718
Capture, manipulation, and transport of prey were quantified from high-speed video of hatchling swellsharks, Cephaloscyllium ventriosum. Kinematic variables were contrasted with those of 1 yr-old swellsharks. Hatchling prey-captures were ram-dominated, while
1 yr-old prey-capture events had a detectable suction component. Timing differences between kinematic patterns of the age
groups were not detected. Significant differences in displacement maxima of kinematic variables between the two age groups
during feeding were detected, but were consistent with the expectations of isometry; they doubled in accordance with a doubling
in shark length. A scaling analysis confirmed that swellsharks grow isometrically. A simple model of the head during prey
capture confirmed that buccal expansion scaled isometrically between age groups. Thus, this study suggests that hatchlings
generally perform the suite of movements necessary for suction generation within the buccal cavity during feeding. A suction
component to the strike, however, was generally not detected by the “ram:suction index”. It appears that although it is probably
generated within the buccal cavity, suction has little effect on the prey item and makes a minimal contribution to prey capture.
Suction may be ineffective due to the highly active nature of the hatchlings. During a strike, a hatchling's forward locomotion
may be sufficient to overwhelm any suction produced by the expanding buccal cavity; thus, the swimming shark effectively “scoops”
the prey up in its open mouth (i.e. ram feeding) before the prey can be entrained in the flow of water entering the mouth
(i.e. suction feeding). It is also likely that the hatchling sharks are sufficiently small to render any suction generated
ineffective. Even though the sharks scale isometrically, the sheer size of the 1 yr-old sharks allows a greater amount of
force to be generated, that will ultimately draw the prey to the open mouth. Thus, there are absolute consequences of size
for feeding behaviors.
Received: 17 June 1997 / Accepted: 6 March 1998 相似文献
18.
Often in colonial seabirds, all colony members are believed to defend against nest predators and experience equal nest predation
risk. However, the variation of defense behavior among members and its reproductive consequences are largely unknown. We investigated
(1) individual variation in the nest defense of breeding Black-tailed Gulls Larus crassirostris against a natural egg predator, the Jungle Crow Corvus macrorhynchos and (2) how this behavioral variation affects an individual’s own nest predation risk and that of their neighbors. Results
were compared between 2 years where crow attack levels were manipulated to average 5 and 22 times normal rates (“low” and
“high” predation risk years, respectively) by the placement of varying numbers of artificial nests containing unguarded eggs
at the perimeter of the gull colony. In both years, 23–38% of parents, mostly males, showed “aggressive” defense behavior
(strikes or chases) against crows and decoys. Other “non-aggressive” gulls showed no defense. In the year of low predation
risk, intrusion rates by crows (landing within 0.5 m of an individual gull’s nest) were similar for aggressive and non-aggressive
gulls. In the year of high predation risk, however, the rates of intrusion for aggressive gulls (4%) and for non-aggressive
gulls with an aggressive neighbor (37%) were significantly lower than for non-aggressive gulls without an aggressive neighbor
(76%). These results indicate that aggressive individuals reduce nest predation risk for themselves and conspecific neighbors
in a colonially breeding species. 相似文献
19.
The extent to which male birds in polygynous species with biparental care assist in nestling feeding often varies considerably
between nests of different mating status. Both how much polygynous males assist and how they divide their effort between nests
may have a profound effect on the evolution of mating systems. In this study we investigated how males in the facultatively
polygynous European starling Sturnus vulgaris invested in their different nests. The amount of male assistance affected the quality of the offspring. Polygynous males
invested as much as monogamous males, but divided their effort asymmetrically between nests, predominantly feeding nestlings
of first-mated (primary) females. Although females partly compensated for loss of male assistance, total feeding frequency
was lower at primary females’ nests than at monogamous females nests. Secondary females received even less assistance with
nestling rearing, and the extent to which males assisted decreased with the length of the interval between the hatching of
the primary and secondary clutches. These results are contrasted with those from a Belgian populations of starlings with a
much more protracted breeding season and thus greater opportunities for males to attract additional mates during the nestling
rearing period. The results show that both the “defence of male parental investment model” and the “asynchronous settlement
model” have explanatory power, but that their validity depends on the potential length of the breeding season.
Received: 21 July 1995/Accepted after revision: 13 July 1996 相似文献
20.
The emergence patterns of both green (Chelonia mydas) and loggerhead (Caretta caretta) turtle hatchlings were observed in great detail over three seasons at Alagadi beach, northern Cyprus. In total, 38 green turtle and 50 loggerhead turtle nests were monitored, accounting for the emergence of 2,807 and 2,259 hatchlings, respectively. We quantified these emergences into 397 green turtle and 302 loggerhead turtle emergence groups. Overall, 85.0% of green turtle and 79.5% of loggerhead turtle groups emerged at night; these accounted for 85.5 and 90.8% of hatchlings, respectively. The remaining emergences were dispersed throughout the day for green turtle nests but confined to the morning in loggerhead turtle nests. Hatchling emergence from individual nests occurred over periods of between 1 and 7 nights, with most hatchlings typically emerging on the first night. Group sizes of green turtles emerging during the day were significantly smaller than those emerging at night. Hatchlings of both species that emerged from nests during the day had longer emergence durations than those that emerged from nests at night only.Communicated by R.J. Thompson, St. Johns 相似文献