Masculinisation of leatherback turtle Dermochelys coriacea hatchlings from eggs incubated in styrofoam boxes

A masculinising bias was found in the sex ratio of hatchling leatherback sea turtles Dermochelys coriacea from eggs incubated artificially in styrofoam boxes, when compared with the natural sex ratio in Suriname. This bias is much larger than that reported for green turtles. Boxes failed to produce any females at all during two thermally different times of the season, while natural sex ratios varied seasonally with averages of 30% female for clutches laid in May and 100% female for clutches laid in June. These findings are consistent with the boxes being 1·4–2·4°C cooler than the sand. Clutches reburied in the sand produced the same sex ratio as natural nests. Some options for the use of styrofoam boxes in sea turtle conservation programmes are discussed.     

Reproductive biology of the Hawksbill Eretmochelys imbricata at Tortuguero,Costa Rica,with notes on the ecology of the species in the caribbean

From 1955 through 1983, 246 hawksbills Eretmochelys imbricata have been tagged as they came ashore to nest at Tortuguero, Costa Rica, a beach they share with a large colony of green turtles Chelonia mydas. Nesting hawksbills average 82 cm in straight carapace length and grow at a mean rate of 0·3 cm year⁻¹. Mean clutch size is 158 eggs; clutch size is poorly correlated with female body size. Average time from egg deposition to hatching emergence is 58·5 days. Mean emergence success ff hatchling is 58·3% in all clutches and 91·6% in clutches that produced hatchlings. The internesting interval averaged between 16 and 17 days. Site-fixity of females both within and between seasons was examined; a greater degree of site-fixity was exhibited between seasons than within. The distribution of hawksbill nesting activity at Tortuguero is spatially similar to, but temporally different from, that of the green turtle. There is increasing evidence from tag returns that the Tortuguero hawksbill may also share the feeding grounds of the Tortuguero green turtle in the Miskito Cays, Nicaragua. Notes on the movements and feeding habits of juveniles on their feeding grounds are included.Following a decline from 1956, there has been no consistent trend in the number of hawksbills nesting at Tortuguero since 1972. However, the mean carapace length of hawksbills has shown a steady decline, suggesting that the population is not demographically stable. The stability of an entire population cannot be determined from monitoring the number of nesting turtles each year.     

High levels of hatching failure in an insular population of the South Island robin: a consequence of food limitation?

Endangered birds in insular environments like New Zealand are often translocated to predator-free offshore islands for conservation purposes. Some translocated populations however exhibit reduced fecundity, and it has been suggested that either inbreeding (due to small number of founders) or resource shortages (due to high population density) may limit reproductive success. For example, the South Island robin (Petroica a. australis) population on Motuara Island (59 ha) was founded by only five birds but has increased to ∼600 individuals, or a density >10 times that of the mainland. Despite this apparent success, the rate of hatching failure in this population is three times higher than in mainland populations, with more than a third of eggs failing to hatch. To test if elevated hatching failure is the result of food limitation, we carried out a food supplementation experiment by providing females with mealworms equivalent to ∼50% of their daily energy requirements. Food supplementation had no effect on hatching success, clutch size, incubation attentiveness or nest size. Egg volume increased with food supplementation in one of the two years of this study, but both egg volume and incubation attentiveness were unrelated to rate of hatching failure. As previous genetic analyses confirmed that the bottlenecked population of robins on Motuara Island have significantly less genetic variation than their source population, we conclude that inbreeding depression, and not food limitation, is the most likely explanation for their high rate of hatching failure. We suggest that the experimental translocation of genetically dissimilar individuals be considered as a possible remedy for low productivity in island populations that were initiated with few founders.     

Infertility,embryonic mortality and nest-site selection in leatherback and green sea turtles in Suriname

Nest-site selection and causes of non-viability in eggs of leatherbacks Dermochelys coriacea and green turtles Chelonia mydas were investigated for two consecutive seasons on a beach used for nesting by both species in Suriname. Examination of nests and artificially incubated clutches after hatching showed that the main cause of an interspecies difference in hatching success was higher embryonic mortality in leatherbacks. Rupturing of eggs, used as an index of predation, was also greater in leatherback nests. Although infertility was slightly higher in leatherbacks, it was relatively low in both species.An interspecies difference in nest-site selection was found, with leatherbacks laying predominantly in open sand and green turtles in vegetated areas. Hatching success in the different areas was similar for green turtles, but only 12% of green turtle nests were occasionally washed over by sea swell compared to 40% of leatherback nests. Washover caused embryonic mortality in both species and is one of the causes of the increased embryonic mortality in leatherbacks. However, embryonic mortality was also higher in leatherback than in green turtle nests that were not washed over. Approximately half of the embryonic mortality occurred before days 22–24 of incubation in both species.Artificial incubation produced hatching successes similar to those in nests laid above spring high tide level. Predation was eliminated in styrofoam boxes and reduced in reburied clutches. Increased embryonic mortality during late development was found in the boxes. The implications for conservation of sea turtles are discussed.     

Survival and reproductive performance of Hawksbill turtles Eretmochelys imbricata L. on Cousin Island,seychelles

Hawksbill turtles have been tagged on Cousin Island from 1973 to the present day. Recently therefore the breeding females in a season have included turtles not previously tagged and remigrants, turtles known from their tags to have nested on Cousin in at least one past season. This paper details some differences in the two groups. Remigrants produced larger clutches (176 v. 153), laid more clutches on Cousin in a season (3·68 v. 2·50) and were about five times more likely to be recaptured there in a subsequent season. Overall 25–30% of the hawksbills tagged were recaptured in a later season. The mean interval between the successive breeding seasons of individual females was 2·67 years.     

An analysis of the role of local fishermen in the conservation of the loggerhead turtle (Caretta caretta) in Pontal do Ipiranga, Linhares, ES, Brazil

The role of researchers and fishermen in the clutch management of loggerhead sea turtles was evaluated for 10 nesting seasons at Pontal do Ipiranga TAMAR station, Linhares, ES. The comparison of nests transferred by researchers and locals (carebeiros) showed that clutches transferred by researchers presented higher clutch size. Clutch size between nests transferred by carebeiros and left in situ did not show significant differences. Hatching success was significantly higher for clutches left in situ than for those transferred to other places in the beach or to hatcheries. The clutches transferred exclusively by researchers achieved a higher hatching success than those transferred partially or totally by carebeiros. The relocation time of clutches collected by carebeiros and handed to researchers affected hatching success. It is recommended that clutches be left in situ, provided they have adequate conditions for monitoring, but careful clutch translocation, independent of the interval elapsed after laying, may also constitute a viable technique for the conservation of sea turtles in the region.     

Rodent control and food supplementation increase productivity of endangered San Clemente Loggerhead Shrikes (Lanius ludovicianus mearnsi)

Habitat loss and predation by exotic predators have contributed to the decline of many island populations of birds, including San Clemente Loggerhead Shrikes (Lanius ludovicianus mearnsi). This critically endangered subspecies has been the recipient of an extensive and expensive recovery effort, including a captive breeding and release program. We examined the effects of life-history characteristics, rainfall, and management, particularly food supplementation and rat (Rattus rattus) control, on the breeding productivity of 172 San Clemente Loggerhead Shrike pairs from 2000 to 2006. Annual fecundity and the number of fledglings reaching independence per pair varied with year and were closely correlated with prebreeding (November-March) precipitation levels. Annual fecundity increased as a result of management implemented between April and July each year. Shrike pairs receiving no management during this period produced a mean of 1.9 fledglings. Pairs receiving both food and rat control produced an average of 2.5 more fledglings than pairs receiving no management, while pairs receiving rat control alone produced an average of 1.1 more fledglings than pairs receiving no management during this period. Wild-origin females produced an average of 0.8 more fledglings per pair than captive-origin females, while older males produced an average of 0.9 more fledglings and independent young relative to inexperienced males. The effects of food supplementation and rat control on San Clemente Loggerhead Shrikes were most pronounced during dry years, suggesting such management should be emphasized when prebreeding precipitation levels are below historical averages. These techniques offer an effective means to increase breeding productivity of avian species in immediate threat of extinction.     

Population ecology of the Chinese grouse, Bonasa sewerzowi, in a fragmented landscape

We report the first population ecology study of the endangered Chinese grouse (Bonasa sewerzowi). The study population was stable during 1995-2000. Annual rates of survival were 0.64 for adults and only 0.17 for chicks to 13 weeks of age. Reproductive parameters were 6.1 eggs/clutch, 63% nest success, and overall 3.6 chicks hatched/female/year. The spring sex ratio was 64% males, with 44% of the males unmated in spring. Local people found an estimated 10-29% of the nests and took the eggs for food. Only about 9% of the reserve containing the study area is mature mixed forest, the preferred habitat. Inadequate brood habitat may have influenced chick survival and the skewed adult sex ratio may be a result of habitat fragmentation. We recommend protecting the remaining mixed forest, creating more brood habitat, and stopping the taking of eggs.     

Effects of landscape change on clutches of Phyllomedusa tarsius, a neotropical treefrog

Phyllomedusa tarsius is an arboreal frog species that suspends its eggs on leaves above water in order to achieve the high relative humidity necessary for embryo development. I compared the hatching success of P. tarsius in ponds located in pasture, Vismia spp. regrowth, Cecropia spp. regrowth, forest fragments and continuous forest at a site in central Amazônia. Reproductive success of P. tarsius is measured as percentage of clutches producing at least one tadpole and number of tadpoles produced per clutch. Reproductive success was higher in Cecropia regrowth, forest fragments and continuous forest, compared to pasture and Vismia regrowth. Desiccation and flooding were the main causes of clutch loss in pasture and Vismia regrowth, while predation was more frequent in forest and Cecropia regrowth. The levels of successful of P. tarsius clutches observed across all habitat types suggests that a landscape mosaic including pasture, secondary growth and forest fragments may allow for recolonization and genetic exchange to occur in isolated forest patches.     

Impact of grassland farming intensification on the breeding ecology of an indicator insectivorous passerine, the Whinchat Saxicola rubetra: Lessons for overall Alpine meadowland management

The decline of insectivorous farmland passerines has been attributed mostly to global decrease in arthropod availability, as a result of intensification of agricultural practices. The diminution of the Alpine Whinchat, once a widespread insectivorous passerine, has been ascribed to nest losses due to earlier and more frequent mowings. However, potential conjugated effects of deteriorated arthropod food availability had yet to be investigated. We compared food supply and nestling diet in intensively vs. traditionally managed grassland. Abundance and diversity of arthropods were much lower in intensive areas, where small-sized invertebrates, which do not enter nestling diet, were also predominant. Parents breeding in intensive habitats fed less biomass to nestlings than adults from traditional habitats. Nestling diet was less diverse and dominated by less profitable prey items in intensive than in traditional habitats. Feeding rate did not differ between the two habitats, but foraging distances from nest tended to be greater in intensive farmland. There were no significant differences in clutch sizes and hatching success with respect to management intensity, but fledging success was higher in traditional habitats. The recent intensification of farming practices has led to a decrease in the availability of grassland invertebrates, and of important Whinchat nestling food in particular, affecting parents’ foraging efficiency and reproductive success. Conservation actions must not only reduce nest losses by postponing mowing, but should also promote grassland farming that is less detrimental to invertebrates. Dominant at the study site, organic grassland farming does seemingly not provide sufficient conditions for Alpine Whinchats.     

Breeding performance of the Indian sarus crane in the agricultural landscape of western India

The breeding performance of the Indian sarus crane Grus antigone antigone Linn. was studied in the agricultural landscape of western India during 1996-1998. Detailed records of 70 nests were maintained from egg laying till fledging. At least one chick hatched from 50 clutches (71.43%). Nineteen clutches (27.14%) were destroyed due to various factors, but at least 7 pairs re-nested. Egg mortality was mainly due to flooding (7.35%), predation (11.03%) and conflict with farmers (8.09%). Chick mortality due to predation was 8.24% and to unknown factors was 30%. Number of chicks hatched and number fledged did not differ significantly in different microhabitats. Average breeding success was 25.74%. Breeding success was comparatively lower in paddy crop fields than in other microhabitats due to human disturbance and higher predation risk. The juveniles formed only 10.14% of the total sarus sighted during the post-breeding period. An increasing conflict of sarus crane with the farmers in the agricultural landscape is a matter of concern for sarus crane conservation. The economic loss due to nesting in the crop field, if compensated, will help in sarus crane conservation.     

Effects of supplementary feeding on the offspring sex ratio of kakapo: a dilemma for the conservation of a polygynous parrot

The kakapo (Strigops habroptilus) is a large, flightless, nocturnal parrot, endemic to New Zealand. It is critically endangered, with a world population of ca. 62 individuals and a male-biased adult sex ratio. The species has a polygynous “lek” mating system and adult males typically weigh 30-40% more than females. The kakapo is subject to intensive conservation efforts, including the provision of supplementary food to wild birds to encourage successful nesting. There is mounting evidence that, in polygynous species with large variance of male reproductive success, females in better condition may maximise their fitness by producing more offspring of the larger, more costly sex to be reared. We used data on the sex ratio of progeny of female kakapo that had or had not received supplementary food, to test the hypothesis that supplementary feeding might cause a male-biased offspring sex ratio. There was a significant excess of males in the clutches of females provided with supplementary food, suggesting that changes need to be made to the feeding regime to increase recruitment of females. This is an example of applying evolutionary theory to a practical conservation problem.     

A comparative study of clutch size, range size, and the conservation status of island vs. mainland lacertid lizards

Whereas the range size of endangered species is undoubtfuly useful to predict risk of extinction, the role of their life-history characteristics is much less clear, and their effects may depend on the nature of the threatening factors. Such factors, for instance, are known to be different on islands and on the mainland. We used phylogenetically based statistical analyses to study the relationships among conservation status, insularity, range size, and life-history traits in a clade of Western Palaearctic lacertids including insular and continental species. These lizards are ecologically similar, but they show wide variation in life-history traits and vulnerability to extinction. Insular species of a given size had smaller clutches than mainland ones. Degree of threat was best predicted by a logistic regression including range size, insularity, clutch size, and the insularity × clutch size interaction. On the mainland, but not on islands, threatened species had smaller clutches than non-threatened ones. On islands, small clutch size is probably an adaptive trait, and it might predispose certain species to extinction, but the intrinsic characteristics of such species remain unclear. However, small clutch size was a good predictor of extinction risk on the mainland, having evolved most frequently in late maturing species from montane habitats in which climatic conditions limit their reproductive output and increase their vulnerability to stochastic hazards or habitat fragmentation.     

Molecular degradation rate of rice and corn starches during acid-methanol treatment and its relation to the molecular structure of starch

The degradation rates of rice and corn starches with different contents of amylose treated in methanol containing 0.36% HCl at 25 degrees C for 1-15 days were evaluated by monitoring the weight average degree of polymerization of starch. A two-stage degradation pattern during acid-methanol treatment was found for the starches studied, which were the slow (first) and the rapid (second) degradation stages. Waxy starches showed a shorter time period of the first stage than that of nonwaxy starch. Rice starch showed a shorter time period of the first stage and a higher degradation rate of the second stage than the counterpart corn starch with similar amylose content. Despite the botanic source and amylose content of starch, the degradation rate of starch in the second stage significantly (p < 0.05) correlated to the S/L ratio (r = -0.886) and polydispersity (r = 0.859) of amylopectin branch chains of native starch.     

Low reproductive success of leatherback turtles, Dermochelys coriacea, is due to high embryonic mortality

We examined the mechanism responsible for low reproductive success in leatherback turtles (Dermochelys coriacea) at Playa Grande, Costa Rica: low egg fertilization versus high rates of embryonic death. Leatherbacks at this beach had a high rate of fertility (=93.3%±2.5%, n=819). We incubated 10 eggs from every clutch encountered of 19 females during 3 months of the 1998-1999 nesting season. Fertility rate of some females decreased during the nesting season, but overall was high. Detection of fertility was difficult using standard methods because fertility rates cannot be determined accurately from nests excavated after hatching because of egg decomposition. Removal and incubation of eggs from nests provided a better estimate. Embryonic death, particularly in the beginning of incubation before embryos are visible to the unaided eye, was the cause of low hatching success in this population. Hatching success increased with increasing fertility and differed between females, with some mothers having 71-81% success and others 23-32%. Embryonic death and not low egg fertility drives poor recruitment at Playa Grande. Improved conservation of this species at Playa Grande will require a better understanding of the mechanism behind embryonic death.     

Breeding success of hawksbill turtles Eretmochelys imbricata at Cousin island,seychelles and the implications for their conservation

The Cousin Island population of hawksbill turtles Eretmochelys imbricata has been studied for ten years. Each season new (untagged) and return (tagged) turtles are seen on the beaches; having once nested successfully these females are apparently faithful to the island.Most of the females breeding in the 1981–1982 and 1982–1983 seasons were intercepted and 144 nests were followed through to the emergence of young. Egg losses were mainly attributable to crab predation.Individual females laid up to six times (mean 3·1 times) in a season; clutch size and hatchling weight declined significantly in their later nests. Hatching and emergence success were high, especially in early nests; late in the season proportionally more developed embryos died.It is suggested that the completion of early, more successful and more productive nests could be safeguarded by delaying the start of the turtle hunting season.     

拖拉机液压机械无级变速箱换段控制优化与试验

为了提高无级变速拖拉机的换段质量,该文对所开发的一种新型液压机械无级变速箱的换段过程进行了试验研究。离合器充油特性试验中,通过改变离合器控制油路参数,获得主油路压力与充油流量对换段时间的影响规律;单因素加载试验中,通过单独改变发动机转速、主油路压力、充油流量、负载转矩,获得各因素单独作用时对换段质量的影响规律;多因素组合加载试验中,设计了3水平4因素组合试验方案,对多个因素综合作用时的变速箱换段质量问题进行了研究;时序优化试验中,通过控制器改变离合器动作时机,获得最佳的换段时序。试验结果表明：离合器主油路压力、充油流量可通过影响换段时间而间接影响到换段质量;重叠时序换段会引起油压陷阱,证明了重叠换段的安全性和可行性;单因素作用时,换段质量与离合器压力、流量正相关,与负载转矩负相关,与发动机转速无关;多因素共同作用时,换段质量的主次影响因素依次为充油流量、负载转矩、主油路压力、发动机转速;此外,采用重叠时序换段可显著改善换段质量。根据试验结果得出,为使该变速箱获得最佳的换段质量,其离合器主油路压力应取值4MPa,充油流量取值5L/min,重叠时序取值120ms。该结论为换段控制策略的制定提供了重要参考。     

Nature-based tourism impacts on yellow-eyed penguins Megadyptes antipodes: does unregulated visitor access affect fledging weight and juvenile survival?

The Otago Peninsula, South Island, New Zealand offers tourists opportunities for unregulated access to breeding sites of the yellow-eyed penguin (Megadyptes antipodes). The presence of people on beaches delays post-foraging landing by penguins, which in turn may affect the amount of food delivered by parents to their chicks, with consequences for chick growth and fledging mass. This study explored the relationship between human disturbance and yellow-eyed penguin chick fledging weight and survival by comparing five yellow-eyed penguin breeding areas with different levels of visitor frequency. We investigated whether chick fledging weights vary between breeding areas, and whether fledging weight is a predictor of juvenile survival. In 2002, chicks at Sandfly Bay, an area with high numbers of tourists, had significantly lower fledging weights than chicks at Highcliff, an area with no tourist visitors. An analysis of sightings of 2125 yellow-eyed penguin chicks banded between 1981 and 2000 indicated probability of survival was positively associated with mass at fledging. Thus lower fledging weights may have long-term population consequences. Fledging weight is influenced by many factors, however the results suggest the possibility of an effect of tourist numbers on chick fledging weight. This is noteworthy, especially in light of the rapid rate at which wildlife tourism is increasing in coastal areas of southern New Zealand.     

Relative fitness of wild and captive-reared piping plovers: Does egg salvage contribute to recovery of the endangered Great Lakes population?

Since 1992, efforts to recover the US federally endangered Great Lakes piping plover (Charadrius melodus) have included population supplementation with captive-reared young raised from abandoned eggs. Using banding data collected 1993-2008 and Cormack-Jolly-Seber models in program MARK we estimated resighting rates (ρ) and apparent survival (Φ) of first-year (1) and after-first-year (2+) plovers. Reproductive success was measured by estimating mean number of eggs laid, chicks hatched and chicks fledged per wild-reared or captive-reared parent, and these values were compared with a permutation test. The best-supported mark-resighting model indicated wild-reared plovers had higher Φ₁ and Φ₂₊ than captive-reared plovers. Breeding propensity influenced detection of wild plovers, whereas unique band combinations facilitated detection of yearling captive-reared plovers. Captive-reared (n = 10) and wild-reared (n = 57) plovers laid similar numbers of eggs, but wild-reared plovers hatched 36% more chicks and fledged 56% more young. Reproductive values derived from matrix models suggest captive-reared piping plovers are less fit than similarly aged wild-reared birds upon release and demonstrate reduced fitness in subsequent years. The Great Lakes captive-rearing effort has successfully produced a minimum of 10 breeding adults from 192 eggs that otherwise would have had no reproductive value; these captive-reared individuals now constitute up to 3% of the total population. Small scale salvage and captive-rearing of abandoned eggs should be considered as a technique to supplement existing recovery efforts in highly imperiled populations.     

Factors affecting egg-laying and clutch size of Archispirostreptus tumuliporus judaicus (attems) (myriapoda), diplopoda in Israel

The number of oocytes in the ovaries of Archispirostreplus tumuliporus judaicus, and the clutch size were determined in two populations of millipedes: one from a mesic habitat and one from a xeric habitat. The presence of males was found to be essential for egg-laying by the females. Daylength did not affect the onset of egg-laying or the clutch size, whereas soil moisture conditions affected egg-laying. Dry soil did not stimulate egg-laying in the xeric-inhabiting females, and caused a decline in clutch size in the mesic ones. Females from the xeric habitat when kept in the laboratory “preferred” laying eggs in the moist soil when given a choice, regardless of the depth at which the soil was moist.