共查询到20条相似文献,搜索用时 390 毫秒
1.
Sex- and age-class-specific survival probabilities of a southern Great Barrier Reef green sea turtle population were estimated using a capture–mark–recapture (CMR) study and a Cormack–Jolly–Seber (CJS) modelling approach. The CMR history profiles for 954 individual turtles tagged over a 9-year period (1984–1992) were classified into three age classes (adult, subadult, juvenile) based on somatic growth and reproductive traits. Reduced-parameter CJS models, accounting for constant survival and time-specific recapture, fitted best for all age classes. There were no significant sex-specific differences in either survival or recapture probabilities for any age class. Mean annual adult survival was estimated at 0.9482 (95% CI: 0.92–0.98) and was significantly higher than survival for either subadults or juveniles. Mean annual subadult survival was 0.8474 (95% CI: 0.79–0.91), which was not significantly different from mean annual juvenile survival estimated at 0.8804 (95% CI: 0.84–0.93). The time-specific adult recapture probabilities were a function of sampling effort but this was not the case for either juveniles or subadults. The sampling effort effect was accounted for explicitly in the estimation of adult survival and recapture probabilities. These are the first comprehensive sex- and age-class-specific survival and recapture probability estimates for a green sea turtle population derived from a long-term CMR program.Communicated by M.S. Johnson, Crawley 相似文献
2.
Katrina F. Phillips Katherine L. Mansfield David J. Die David S. Addison 《Marine Biology》2014,161(4):863-870
Few long-term mark-recapture tagging datasets exist to estimate population parameters for loggerhead sea turtle (Caretta caretta) recovery units. Using a two-state open robust design model, we analyzed a 20-year (1990–2009) mark-recapture dataset from the Keewaydin Island loggerhead nesting assemblage off the southwest coast of Florida (USA) in the eastern Gulf of Mexico. For this analysis, 2,292 turtle encounters were evaluated, representing 841 individual nesting turtles. Survival was estimated at 0.73 (95 % CI 0.69–0.76). This estimate is comparable with survival estimates elsewhere in the Peninsular Florida subpopulation and is among the lowest estimates for the Northwest Atlantic loggerhead population. We documented no changes in remigration rates or clutch frequency over time. These are the first survival and remigration probabilities estimated for a loggerhead nesting assemblage in the eastern Gulf of Mexico. 相似文献
3.
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. 相似文献
4.
The green turtle (Chelonia mydas) nesting population at Tortuguero, Costa Rica, is the largest nesting aggregation in the Atlantic, by at least an order of
magnitude. Previous mitochondrial DNA (mtDNA) surveys based on limited sampling (n = 41) indicated low genetic diversity and low gene flow with other Caribbean nesting colonies. Furthermore, a survey of nuclear
DNA diversity invoked the possibility of substructure within the Tortuguero rookery. To evaluate these characteristics, mtDNA
control region sequences were determined for green turtles nesting at Tortuguero in 2001 (n = 157) and 2002 (n = 235). The increased sample revealed three additional haplotypes; five haplotypes are now known for Tortuguero female green
turtles. Analyses of molecular variance indicated that there was no significant spatial population structure along the 30-km
nesting beach. In addition, no temporal population structure was detected either between the two nesting seasons or within
the nesting season. As a result of the larger sample size and additional haplotypes, estimates of genetic separation among
Caribbean nesting colonies have changed and the concordance of phylogenetic and phylogeographic patterns reported in the past
for green turtles in the Greater Caribbean has weakened. The five haplotypes from Tortuguero represent 36% of the haplotypes
identified in green turtle nesting aggregations in the Greater Caribbean and 17% of the haplotypes known to occur in nesting
or foraging aggregations in the Greater Caribbean. Haplotype diversity (0.16) and nucleotide diversity (0.0034) for the Tortuguero
population are substantially lower than those for the combined rookeries in the Greater Caribbean (0.44 and 0.0078, respectively).
Although comprehensive evaluation of regional genetic diversity requires nuclear DNA data, our study indicates that conserving
genetic diversity in Caribbean green turtles will require careful management of the smaller rookeries in addition to the Tortuguero
rookery. 相似文献
5.
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. 相似文献
6.
Tomoharu Eguchi Jeffrey A. Seminoff Robin A. LeRoux Peter H. Dutton Donna L. Dutton 《Marine Biology》2010,157(8):1869-1877
Longitudinal capture-mark-recapture data were used to estimate abundance and survival rates for green turtles (Chelonia mydas) in San Diego Bay, California, USA. These turtles were closely associated with warm effluent from a power plant during winter
months. The life stage distribution of green turtles in the bay ranged from post-pelagic juveniles to adults (44.0–110.4 cm
straight carapace length). During 99 capture sessions between December 2, 1990, and March 25, 2009, 96 individual green turtles
were caught. To estimate abundance and survival rates, robust-design mark-recapture models were fitted to capture-recapture
histories using software MARK. The estimated annual survival rate was 0.861 (SE = 0.147, 95% CI = 0.356–0.986), whereas annual
abundance ranged from 16 (SE = 6.3, 95% CI = 4–29) to 61 (SE = 13.2, 95% CI = 36–88). This study provides the first survival
rate and abundance estimates for a green turtle foraging population in the highly industrialized San Diego Bay. 相似文献
7.
Sex- and age-class-specific survival of a loggerhead turtle population resident in southern Great Barrier Reef waters was estimated using a long-term capture-mark-recapture (CMR) study and the Cormack-Jolly-Seber modelling approach. The CMR history profiles for 271 loggerheads tagged over 9 years (1984-1992) were classified into two age classes (adult, immature) based on somatic growth and reproductive traits. The sex and maturity status of each turtle was determined from visual examination of reproductive organs using laparoscopy. A reduced-parameter model accounting for constant survival with sex- and time-specific recapture was adequate for estimating age-class-specific survival probabilities, but inclusion of time-specific transient behaviour was informative for the immature age class. The annual fluctuations in the estimated proportion of transient immatures was not a function of sampling effort, but could be due to anomalous oceanographic conditions affecting dispersal of the immature class. There was no sex-specific difference in survival probabilities for either age class, but females were more likely to be recaptured than males, which might be related to behavioural differences such as sex-biased dispersal. The expected annual survival probability for adults was 0.875 (95% CI: 0.84-0.91). The expected annual survival probability for immatures was 0.859 (95% CI: 0.83-0.89), but when the transients were accounted for, the expected annual survival for the resident immature loggerheads was 0.918 (95% CI: 0.88-0.96). These are the first substantive estimates of annual survival probabilities for any loggerhead sea-turtle stock and provide a basis for developing a better understanding of loggerhead population dynamics. 相似文献
8.
Milani Chaloupka Thierry M. Work George H. Balazs Shawn K. K. Murakawa Robert Morris 《Marine Biology》2008,154(5):887-898
We investigated cause-specific temporal and spatial trends in sea turtle strandings in the Hawaiian Archipelago. Five species
of sea turtle were recorded in 3,861 strandings over a 22-year period (1982–2003). Green turtles comprised 97% of these strandings
with size and gender composition reflecting the demographic structure of the resident green turtle population and relative
green turtle abundance in Hawaiian waters. The cause of strandings was determined by necropsy based on a complete gross external
and internal examination. Totally 75% of the 3,732 green turtle strandings were from Oahu where strandings occur year-round.
The most common known cause of the green turtle strandings was the tumour-forming disease, fibropapillomatosis (28%) followed
by hook-and-line fishing gear-induced trauma (7%), gillnet fishing gear-induced trauma (5%), boat strike (2.5%), and shark
attack (2.7%). Miscellaneous causes comprised 5.4% of strandings whereas 49% of green turtle strandings could not be attributed
to any known cause. Green turtle strandings attributable to boat strike were more likely from Kauai and Oahu while fibropapilloma
strandings were more likely from Oahu and Maui. Hook-and-line gear strandings were more likely from Oahu due to higher per
capita inshore fishing effort. The specific mortality rate (conditional probability) for fibropapillomatosis was 88%, 69%
for gillnet gear and 52% for hook-and-line gear. The probability of a dead green turtle stranding increased from 1982 but
levelled off by the mid-1990s. The declining mortality risk was because the prevalence and severity of fibropapillomatosis
has decreased recently and so has the mortality risk attributable to gillnet gear. Despite exposure to disease and inshore
fishing gears, the Hawaiian green turtle stock continues to recover following protection since the late 1970s. Nevertheless,
measures to reduce incidental capture of sea turtles in coastal Hawaiian fisheries would be prudent, especially since strandings
attributable to hook-and-line fishing gear have increased steadily since 1982. 相似文献
9.
PILAR SANTIDRIÁN TOMILLO VINCENT S. SABA ROTNEY PIEDRA FRANK V. PALADINO JAMES R. SPOTILA 《Conservation biology》2008,22(5):1216-1224
Abstract: Within 19 years the nesting population of leatherback turtles (Dermochelys coriacea) at Parque Nacional Marino Las Baulas declined from 1500 turtles nesting per year to about 100. We analyzed the effects of fishery bycatch and illegal harvesting (poaching) of eggs on this population. We modeled the population response to different levels of egg harvest (90, 75, 50, and 25%) and the effect of eradicating poaching at different times during the population decline. We compared effects of 90% poaching with those of 20% adult mortality because both of these processes were present in the population at Las Baulas. There was a stepwise decline in number of nesting turtles at all levels of egg harvest. Extirpation times for different levels of poaching ranged from 45 to 282 years. The nesting population declined more slowly and survived longer with 20% adult mortality (146 years) than it did with 90% poaching (45 years). Time that elapsed until poaching stopped determined the average population size at which the population stabilized, ranging from 90 to 420 nesting turtles. Our model predicted that saving clutches lost naturally would restore the population when adult mortality rates were low and would contribute more to population recovery when there were short remigration intervals between nesting seasons and a large proportion of natural loss of clutches. Because the model indicated that poaching was the most important cause of the leatherback decline at Las Baulas, protecting nests on the beach and protecting the beach from development are critical for survival of this population. Nevertheless, the model predicted that current high mortality rates of adults will prevent population recovery. Therefore, protection of the beach habitat and nests must be continued and fishery bycatch must be reduced to save this population. 相似文献
10.
Twenty-Six Years of Green Turtle Nesting at Tortuguero, Costa Rica: An Encouraging Trend 总被引:4,自引:0,他引:4
Karen A. Bjorndal Jerry A. Wetherall Alan B. Bolten & Jeanne A. Mortimer 《Conservation biology》1999,13(1):126-134
The green turtle ( Chelonia mydas ) population that nests at Tortuguero, Costa Rica, is the largest in the Atlantic by at least an order of magnitude. Surveys to monitor the nesting activity on the northern 18 km of the 36-km beach were initiated in 1971 and extended to the entire beach in 1986. From the survey data, we estimated the total number of nesting emergences on the northern 18 km for each year from 1971 through 1996. Evaluation of the trend in nesting emergences indicated a relatively consistent increase from 1971 to the mid-1980s, constant or perhaps decreasing nesting during the late 1980s, and then resumption of an upward trend in the 1990s. Evaluation of trends in sea turtle nesting populations requires many years of data because of the large degree of annual variation in nesting numbers. The trends reported in this study must be evaluated with caution for several reasons. First, if the mean number of nests deposited by each female each year (clutch frequency) varies significantly among years, changes in the number of nesting emergences among years could reflect changes in the number of nesting females, clutch frequency, or both. Second, we only assessed the trend in one segment of the population (mature females), which may or may not represent the trend of the entire green turtle population and which, because of late maturity, may not reflect changes in juvenile mortality for many years. Third, survey frequency, and thus confidence in annual estimates, varied among years. The upward population trend must be assessed from the perspective of the catastrophic decline that the Caribbean green turtle populations have experienced since the arrival of Europeans. If careful management is continued in Costa Rica and adopted throughout the region, the collapse of the Caribbean green turtle populations—which seemed imminent in the 1950s—can be avoided. 相似文献
11.
Seasonal aerial surveys were conducted in the waters of the central Spanish Mediterranean from 2001 to 2003 using the line transect sampling methodology to estimate cetacean abundance. The density of the three most abundant species, striped dolphin (Stenella coeruleoalba), bottlenose dolphin (Tursiops truncatus) and Risso’s dolphins (Grampus griseus), was estimated. In the case of the first two species, the density was estimated accounting for the proportion of submerged animals, while for Risso’s dolphin only the surface density could be estimated. The striped dolphin was the most abundant species in the study area with a mean density of 0.489 dolphins km−2 (95% CI = 0.339–0.705) and a mean abundance of 15,778 dolphins (95% CI = 10,940–22,756). This density is comparable to that obtained in the International Ligurian Sea Cetacean Sanctuary. Striped dolphins were observed throughout the whole year and no seasonal changes in the density were detected. The mean density of bottlenose dolphins was an order of magnitude lower than that of striped dolphins (0.041 dolphins km−2; 95% CI = 0.023–0.075) with a mean abundance of 1,333 dolphins (95% CI = 739–2,407). The Risso’s dolphin had a surface estimated density of 0.015 dolphins km−2 (95% CI = 0.005–0.046) and a mean abundance of 493 dolphins (95% CI = 162–1,498). These results provide valuable biological information useful to develop conservation plans and establish a baseline for future population trend studies. 相似文献
12.
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 相似文献
13.
The mangrove channels of Bahía Magdalena, Mexico, are important developmental areas for juvenile green, or black turtles (Chelonia mydas), but incidental bycatch and illegal hunting threaten population persistence. We studied size distribution, condition index
(CI), growth rates, and mortality of black turtles in Estero Banderitas, the largest mangrove channel in Bahía Magdalena,
to supply information for the development of effective conservation strategies. A total of 213 black turtles (including 88
recaptures) were caught in entanglement nets between July 2000 and July 2003. Average yearly catch per unit of effort (CPUE,
1 unit: 100 m of net fishing for 12 h) dropped during the study from 2.19 to 0.76. About 97% of all turtles were considered
juveniles, average size was 54.6 ± 9.5 cm. Turtles were significantly smaller at the head of Estero Banderitas than in the
central part of the Estero and in the open bay, indicating size-based habitat segregation. Average growth rate was 1.62 cm/year
and declined with increasing size. Growth was seasonal and three times higher in summer (0.28 cm/month) than in winter (0.09 cm/month),
body CI was also significantly higher during the summer months. A seasonalized von Bertalanffy growth function (VBGF) was
used to model growth for the size range studied (43–73 cm SCL), with the parameters: L
∞ = 101 cm SCL; K = 0.04 year−1; t
0 = 0; C = 0.4 and t
s = 0.75. Growth data indicate that black turtles may spend up to 20 years in Bahía Magdalena before they reach maturity at
about 77 cm SCL. The total mortality estimate (Z) from the length converted catch curve was 0.16, corresponding to a yearly survival probability of 0.85. 相似文献
14.
Young green turtles (Chelonia mydas) spend their early lives as oceanic omnivores with a prevalence of animal prey. Once they settle into neritic habitats (recruitment),
they are thought to shift rapidly to an herbivorous diet, as revealed by studies in the Greater Caribbean. However, the precise
timing of the ontogenic dietary shift and the actual relevance of animal prey in the diet of neritic green turtles are poorly
known elsewhere. Stable isotopes of carbon, sulfur and nitrogen in the carapace scutes of 19 green turtles from Mauritania
(NW Africa), ranging from 26 to 102 cm in curved carapace length (CCLmin), were analyzed to test the hypothesis of a rapid
dietary shift after recruitment. Although the length of residence time in neritic habitats increased with turtle length, as
revealed by a significant correlation between turtle length and the δ13C and the δ34S of the scutes, comparison of the δ15N of the innermost and outermost layers of carapace scutes demonstrated that consumption of macrophytes did not always start
immediately after recruitment, and turtles often resumed an animal-based diet after starting to graze on seagrasses. As a
consequence, seagrass consumption did not increase gradually with turtle size and animal prey largely contributed to the diet
of turtles within the range 29–59 cm CCLmin (76–99% of assimilated nutrients). Seagrass consumption by turtles larger than
59 cm CCLmin was higher, but they still relied largely on animal prey (53–76% of assimilated nutrients). Thus, throughout
most of their neritic juvenile life, green turtles from NW Africa would be better classified as omnivores rather than herbivores.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
15.
The effect of the tumour-forming disease, fibropapillomatosis, on the somatic growth dynamics of green turtles resident in
the Pala’au foraging grounds (Moloka’i, Hawai’i) was evaluated using a Bayesian generalised additive mixed modelling approach.
This regression model enabled us to account for fixed effects (fibropapilloma tumour severity), nonlinear covariate functional
form (carapace size, sampling year) as well as random effects due to individual heterogeneity and correlation between repeated
growth measurements on some turtles. Somatic growth rates were found to be nonlinear functions of carapace size and sampling
year but were not a function of low-to-moderate tumour severity. On the other hand, growth rates were significantly lower
for turtles with advanced fibropapillomatosis, which suggests a limited or threshold-specific disease effect. However, tumour
severity was an increasing function of carapace size—larger turtles tended to have higher tumour severity scores, presumably
due to longer exposure of larger (older) turtles to the factors that cause the disease. Hence turtles with advanced fibropapillomatosis
tended to be the larger turtles, which confounds size and tumour severity in this study. But somatic growth rates for the
Pala’au population have also declined since the mid-1980s (sampling year effect) while disease prevalence and severity increased
from the mid-1980s before levelling off by the mid-1990s. It is unlikely that this decline was related to the increasing tumour
severity because growth rates have also declined over the last 10–20 years for other green turtle populations resident in
Hawaiian waters that have low or no disease prevalence. The declining somatic growth rate trends evident in the Hawaiian stock
are more likely a density-dependent effect caused by a dramatic increase in abundance by this once-seriously-depleted stock
since the mid-1980s. So despite increasing fibropapillomatosis risk over the last 20 years, only a limited effect on somatic
growth dynamics was apparent and the Hawaiian green turtle stock continues to increase in abundance. 相似文献
16.
J. Durban D. Ellifrit M. Dahlheim J. Waite C. Matkin L. Barrett-Lennard G. Ellis R. Pitman R. LeDuc P. Wade 《Marine Biology》2010,157(7):1591-1604
We used photographic mark-recapture methods to estimate the number of mammal-eating “transient” killer whales using the coastal
waters from the central Gulf of Alaska to the central Aleutian Islands, around breeding rookeries of endangered Steller sea
lions. We identified 154 individual killer whales from 6,489 photographs collected between July 2001 and August 2003. A Bayesian
mixture model estimated seven distinct clusters (95% probability interval = 7–10) of individuals that were differentially
covered by 14 boat-based surveys exhibiting varying degrees of association in space and time. Markov Chain Monte Carlo methods
were used to sample identification probabilities across the distribution of clusters to estimate a total of 345 identified
and undetected whales (95% probability interval = 255–487). Estimates of covariance between surveys, in terms of their coverage
of these clusters, indicated spatial population structure and seasonal movements from these near-shore waters, suggesting
spatial and temporal variation in the predation pressure on coastal marine mammals. 相似文献
17.
Lisa R. Goshe Larisa Avens Frederick S. Scharf Amanda L. Southwood 《Marine Biology》2010,157(8):1725-1740
Despite the vast amount of research on threatened and endangered green turtle populations, some uncertainty regarding stage
durations, growth rates, and age at maturation remains. We used skeletochronology to address this gap in knowledge for green
turtle populations in the North Atlantic Ocean that use coastal waters along the southeastern U.S. as developmental habitat.
Oceanic stage duration was estimated at 1–7 years (
[`(\textX)] \overline{\text{X}} = 3 years). Several growth models, including von Bertalanffy, logistic, Gompertz, and power functions were evaluated for
describing sex-specific length-at-age data. Ages at maturation estimated using mean size at nesting for females from each
genetic sub-population contributing juveniles to this neritic foraging area were 44 years (Florida), 42.5 years (Costa Rica),
and 42 years (Mexico), which were higher than previously reported ages. This implies that nesting populations comprising primarily
individuals utilizing foraging grounds in the southeastern U.S. may take longer to recover than previously estimated. 相似文献
18.
《Rev Environmental Economics and Policy》2007,1(2):319-320
19.
Michael D. Arendt Albert L. Segars Julia I. Byrd Jessica Boynton Jeffrey A. Schwenter J. David Whitaker Lindsey Parker 《Marine Biology》2012,159(1):113-125
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. 相似文献
20.
Stefan Van Dongen 《Environmental and Ecological Statistics》2006,13(2):213-228
Plant–herbivore interactions are complex and affect herbivore fitness components and life history traits in many different
ways. In this paper, we present results from an experiment studying the effects of leaf quality on pupal survival and duration
of pupation (as measured by time-to-emergence) in the winter moth. Because only surviving pupae are at risk of emerging, analysis
of time-to-emergence should exclude the dead pupae. However, due to right censoring, the survival status could not be determined
for each individual. This failure to determine the group of moths at risk of emerging a priori motivated the development of
a joint model of both survival probability and time-to-emergence. We formulate the model in a Bayesian framework and apply
Monte Carlo Markov Chain (MCMC) to obtain posterior distributions. Time-to-emergence is modeled by a Cox Proportional Hazards
(CPH) model where only the surviving pupae are at risk of emergence. Probability of pupal survival was modeled by a Generalized
Linear Mixed Model (GLMM). The censored individuals were included in the analysis as a missing value in the GLMM. The GLMM
then generated prior distributions of survival probabilties—and thus of the probability of being at risk of emergence—for
these 19 individuals, conditional on the model parameters. The CPH model was formulated as a count process and the binary
frailty was incorporated as a zero-inflated Poisson model. Zeros in this model represent the non-survivors. Leaf quality did
not appear to influence time-to-emergence. Pupal survival was affected in a complex and unexpected way showing opposite effects
in males and females. We also explored the robustness of our model against increased levels of censoring. While the degree
of censoring was low in our study (< 1%), we artificially increased it to 67%. Although further study is required to study
the generality of these results in a theoretical framework, our explorations suggest that the newly proposed technique may
be widely applicable in a variety of situations where the identification of the at risk population cannot be done in a straightforward
way.
Received: January 2005 / Revised: June 2005 相似文献