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1.
Although snakes traditionally have been regarded as asocial animals, recent studies have revealed complex interactions among neonatal snakes and their mothers. We noticed frequent aggregation by captive neonatal Australian elapids (tiger snakes, Notechis scutatus), and conducted simple experiments to clarify the proximate causation of, and potential consequences of, aggregative behaviour. Litters of neonates exhibited statistically significant aggregation (clustering) in empty containers, especially if the test area was subjected to rapid cooling. Aggregation was most pronounced inside shelter‐sites, and familiar shelters (i.e. containing scent cues from the litter) attracted snakes more than did novel (unscented) shelters. Snakes in larger aggregations cooled more slowly (reflecting their higher combined mass and thus, thermal inertia) and higher body temperatures facilitated neonatal locomotor performance, retreat‐site location and anti‐predator tactics. Plausibly, aggregation in neonatal tiger snakes (and other reptiles) functions to retard cooling rates, with the result that the young snakes are better able to evade or repel attacks by predators. 相似文献
2.
TSILAVO RAFELIARISOA GARY SHORE SHANNON ENGBERG EDWARD LOUIS RICK BRENNEMAN 《Molecular ecology resources》2006,6(4):1228-1230
The Malagasy big‐headed turtle (Erymnochelys madagascariensis) is the only Erymnochelys species living in lakes, rivers and watersheds of western Madagascar. This species is endangered due to over harvesting of natural populations for human consumption. Eleven nuclear microsatellite loci were isolated from a genomic DNA library derived from a free‐ranging Malagasy big‐headed turtle from the Beroboka Classified Forest, Madagascar. Population genetic parameters were estimated on 10 individuals sampled from Ampijoroa and Andranohobaka River, Madagascar, to determine marker utility and as preliminary baseline values to study future populations in these locations. 相似文献
3.
David A. Steen Lora L. Smith Gail Morris L. Mike Conner Andrea R. Litt Scott Pokswinski Craig Guyer 《Restoration Ecology》2013,21(4):457-463
Six‐lined racerunner (Aspidoscelis sexlineata) is an indicator species of frequently burned Longleaf pine (Pinus palustris) forests. To evaluate how the species responded to forest restoration, we conducted a mark‐recapture study in formerly fire‐suppressed Longleaf pine forests exposed to prescribed fire or fire surrogates (i.e. mechanical or herbicide‐facilitated hardwood removal) as well as in fire‐suppressed control sites and reference sites, which represented the historic condition. After initial treatment, all sites were exposed to over a decade of prescribed burning with an average return interval of approximately 2 years. We used population‐level response of A. sexlineata as an indicator of the effectiveness of the different treatments in restoring habitat. Specifically, we compared mean numbers of marked adults and juveniles at treatment sites to that of reference sites. After 4 years, restoration objectives were met at sites treated with burning alone and at sites treated with mechanical removal of hardwoods followed by fire. After over 10 years of prescribed burning, restoration objectives were met at all treatments. We conclude that prescribed burning alone was sufficient to restore fire‐suppressed Longleaf pine sandhills for A. sexlineata populations. 相似文献
4.
Kim Urian Antoinette Gorgone Andrew Read Brian Balmer Randall S. Wells Per Berggren John Durban Tomoharu Eguchi William Rayment Philip S. Hammond 《Marine Mammal Science》2015,31(1):298-321
Capture‐recapture methods are frequently employed to estimate abundance of cetaceans using photographic techniques and a variety of statistical models. However, there are many unresolved issues regarding the selection and manipulation of images that can potentially impose bias on resulting estimates. To examine the potential impact of these issues we circulated a test data set of dorsal fin images from bottlenose dolphins to several independent research groups. Photo‐identification methods were generally similar, but the selection, scoring, and matching of images varied greatly amongst groups. Based on these results we make the following recommendations. Researchers should: (1) determine the degree of marking, or level of distinctiveness, and use images of sufficient quality to recognize animals of that level of distinctiveness; (2) ensure that markings are sufficiently distinct to eliminate the potential for “twins” to occur; (3) stratify data sets by distinctiveness and generate a series of abundance estimates to investigate the influence of including animals of varying degrees of markings; and (4) strive to examine and incorporate variability among analysts into capture‐recapture estimation. In this paper we summarize these potential sources of bias and provide recommendations for best practices for using natural markings in a capture‐recapture framework. 相似文献
5.
Virginia striatula is a viviparous snake with a complex pattern of embryonic nutrition. Nutrients for embryonic development are provided by large, yolked eggs, supplemented by placental transfer. Placentation in this species is surprisingly elaborate for a predominantly lecithotrophic squamate reptile. The embryonic-maternal interface consists of three structurally distinct areas, an omphalallantoic placenta and a regionally diversified chorioallantoic placenta. The chorioallantoic placenta over the embryonic hemisphere (paramesometrial region) of the egg, features close apposition of embryonic and uterine blood vessels because of the attenuate form of the interceding epithelial cells. The periphery of the chorioallantoic placenta, which is adjacent to the omphalallantoic placenta, is characterized by a simple cuboidal uterine epithelium apposed to a stratified cuboidal chorionic epithelium. There are no sites with attenuate epithelial cells and close vascular apposition. The morphology of the omphalallantoic placenta is similar to that of the peripheral chorioallantoic placenta, except that the height of uterine epithelial cells is greater and allantoic blood vessels are not associated with the embryonic epithelium. The functional capabilities of the three placental regions are not known, but structural characteristics suggest that the omphalallantoic placenta and peripheral zone of the chorioallantoic placenta are sites of nutritional provision via histotrophy. The paramesometrial region of the chorioallantoic placenta is also nutritive, in addition to functioning as the primary embryonic respiratory system. The structure of the chorioallantoic placenta of V. striatula is a new placental morphotype for squamate reptiles that is not represented by a classic model for the evolution of reptilian placentation. 相似文献
6.
alia Islam Bengt Persson Zafar H. Zaidi Hans J?rnvall 《Journal of Protein Chemistry》1990,9(5):533-541
The hemoglobin of the sea snakeMicrocephalophis gracilis was purified and the primary structure of the and chains determined. This is the first sea snake hemoglobin structure characterized, and apparently also the first complete structure of any snake hemoglobin (an chain of a viper was known), allowing judgments of reptilian variants. Variations between the sea snake form and other reptilian forms are large (52–65 differences for the chains), of similar order as those between the sea snake and avian (56–65 differences) or human (58 differences) forms. Functionally, 19 residues at / contact areas and 7 at heme contacts are exchanged in relation to the human and chains. Four positions of the sea snake hemoglobin contain residues thus far unique to this form. However, all replacements appear compatible with conserved overall functional properties. 相似文献
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8.
ABSTRACT The validity of treating counts as indices to abundance is based on the assumption that the expected detection probability, E(p), is constant over time or comparison groups or, more realistically, that variation in p is small relative to variation in population size that investigators seek to detect. Unfortunately, reliable estimates of E(p) and var(p) are lacking for most index methods. As a case study, we applied the time‐of‐detection method to temporally replicated (within season) aural counts of crowing male Ring‐necked Pheasants (Phasianus colchicus) at 18 sites in southern Minnesota in 2007 to evaluate the detectability assumptions. More specifically, we used the time‐of‐detection method to estimate E(p) and var(p), and then used these estimates in a Monte Carlo simulation to evaluate bias‐variance tradeoffs associated with adjusting count indices for imperfect detection. The estimated mean detection probability in our case study was 0.533 (SE = 0.030) and estimated spatial variation in E(p) was 0.081 (95% CI: 0.057–0.126). On average, both adjusted (for) and unadjusted counts of crowing males qualitatively described the simulated relationship between pheasant abundance and grassland abundance, but the bias‐variance tradeoff was smaller for adjusted counts (MSE = 0.003 vs. 0.045, respectively). Our case study supports the general recommendation to use, whenever feasible, formal population‐estimation procedures (e.g., mark‐recapture, distance sampling, double sampling) to account for imperfect detection. However, we caution that interpreting estimates of absolute abundance can be complicated, even if formal estimation methods are used. For example, the time‐of‐detection method was useful for evaluating detectability assumptions in our case study and the method could be used to adjust aural count indices for imperfect detection. Conversely, using the time‐of‐detection method to estimate absolute abundances in our case study was problematic because the biological populations and sampling coverage could not be clearly delineated. These estimation and inference challenges may also be important in other avian surveys that involve mobile species (whose home ranges may overlap several sampling sites), temporally replicated counts, and inexact sampling coverage. 相似文献
9.
Anthony D. Arthur Terry Dennis Mel Berris Simon D. Goldsworthy Peter D. Shaughnessy Carlos E. P. Teixeira 《Marine Mammal Science》2013,29(1):84-108
The Australian sea lion (Neophoca cinerea) population at Seal Bay Conservation Park, South Australia, is estimated to be declining at a rate of 1.14% per breeding season. To better understand the potential causes of this decline, survival rates were examined to 14 yr of age for eight cohorts marked as pups (aged 0.17 yr) between 1991 and 2002. Apparent yearly survival rates (Φ) varied by cohort for pups from marking to weaning at 1.5 yr (Φ= 0.30–0.67). Postweaning juvenile survival (1.5–3 yr) was 0.89 and survival from 3 to 14 yr was constant (Φ female:male = 0.96:0.89). Φ of pup cohorts was negatively correlated to local sea surface temperature where the sea lions forage (SST) and was especially low for cohort 7 in 2000 (0.30). It is possible that periods of unusually warm oceanographic conditions may be limiting primary production and inhibiting maternal provisioning to pups. Pup survival to weaning is relatively low compared to other otariid species, is likely to limit recruitment, and may be contributing to the decline in pup abundance observed in the colony. 相似文献
10.
Fuller's rose weevil (FRW; Asynonychus cervinus (Boheman)) is a pest of quarantine concern in many Asian markets for Australian citrus. We investigated vertical (tree climbing) and horizontal movements (inter‐tree movements) of FRW adults in a citrus orchard during 2009–2011 with mark‐recapture experiments. Trunk traps were used to intercept tree‐climbing adults. The results showed that the majority of the adults released on the foliage stayed in the canopy, however considerable numbers did drop and some dropped multiple times. The rate of drops appeared to be fixed, independent of how many times the weevils had dropped before. Inter‐tree movements of adults in the canopy occurred mainly within rows, probably because of touching foliage between within‐row neighboring trees. Movement directions on the ground were more random, when reliance on touching foliage was not necessary. According to fitted dispersal equations, the average dispersal distance was 38 m for weevils released on foliage and 127 m for those released on the ground. Trunk banding with chemicals is an important control tactic for FRW, and based on our results, chemicals should be applied at a high enough rate (or in a wide enough band) to ensure the weevils are killed by a single crossing. For maximum reductions of FRW populations in citrus, control actions should be applied not only to infested blocks but also to neighboring blocks in the orchard. 相似文献
11.
2007年12月至2008年12月,对小磨新路、小磨老路的云路制胶厂至曼粉段和附近的一条乡村公路对蛇类的影响进行了研究。通过Logistic回归模型探讨蛇类出现在公路上的地点与各种环境因子的关系;通过多元逐步线性回归模型探讨蛇类出现在公路上的时间与气候因子的关系。研究期间巡路52d,共记录到蛇类20只10种。结果显示:天然林边蛇上公路的概率显著低于农田和人工林;2d前的最高温越低,最大湿度越大,蛇上公路的概率越大。此外,在公路及附近区域总共记录到的14种蛇中,包括一些中国最稀有的种类,比如绿林蛇(Boiga cyanea)和金花蛇(Chrysopelea ornate)。 相似文献
12.
Yoshiyuki Matsubara Atsushi Kuroiwa Takayuki Suzuki 《Development, growth & differentiation》2016,58(3):241-249
Reptile development is an intriguing research target for understating the unique morphogenesis of reptiles as well as the evolution of vertebrates. However, there are numerous difficulties associated with studying development in reptiles. The number of available reptile eggs is usually quite limited. In addition, the reptile embryo is tightly adhered to the eggshell, making it a challenge to isolate reptile embryos intact. Furthermore, there have been few reports describing efficient procedures for isolating intact embryos especially prior to pharyngula stage. Thus, the aim of this review is to present efficient procedures for obtaining early‐stage reptilian embryos intact. We first describe the method for isolating early‐stage embryos of the Japanese striped snake. This is the first detailed method for obtaining embryos prior to oviposition in oviparous snake species. Second, we describe an efficient strategy for isolating early‐stage embryos of the soft‐shelled turtle. 相似文献
13.
Ray T. Alisauskas Todd W. Arnold James O. Leafloor David L. Otis James S. Sedinger 《Ecology and evolution》2014,4(2):132-143
Estimates of range‐wide abundance, harvest, and harvest rate are fundamental for sound inferences about the role of exploitation in the dynamics of free‐ranging wildlife populations, but reliability of existing survey methods for abundance estimation is rarely assessed using alternative approaches. North American mallard populations have been surveyed each spring since 1955 using internationally coordinated aerial surveys, but population size can also be estimated with Lincoln's method using banding and harvest data. We estimated late summer population size of adult and juvenile male and female mallards in western, midcontinent, and eastern North America using Lincoln's method of dividing (i) total estimated harvest, , by estimated harvest rate, , calculated as (ii) direct band recovery rate, , divided by the (iii) band reporting rate, . Our goal was to compare estimates based on Lincoln's method with traditional estimates based on aerial surveys. Lincoln estimates of adult males and females alive in the period June–September were 4.0 (range: 2.5–5.9), 1.8 (range: 0.6–3.0), and 1.8 (range: 1.3–2.7) times larger than respective aerial survey estimates for the western, midcontinent, and eastern mallard populations, and the two population estimates were only modestly correlated with each other (western: r = 0.70, 1993–2011; midcontinent: r = 0.54, 1961–2011; eastern: r = 0.50, 1993–2011). Higher Lincoln estimates are predictable given that the geographic scope of inference from Lincoln estimates is the entire population range, whereas sampling frames for aerial surveys are incomplete. Although each estimation method has a number of important potential biases, our review suggests that underestimation of total population size by aerial surveys is the most likely explanation. In addition to providing measures of total abundance, Lincoln's method provides estimates of fecundity and population sex ratio and could be used in integrated population models to provide greater insights about population dynamics and management of North American mallards and most other harvested species. 相似文献
14.
Abstract Ecological specialization, such as major dependence upon a single‐prey species, can render a predator taxon vulnerable to extinction. In such cases, understanding the population dynamics of that prey type is important for conserving the predator that relies upon it. In eastern Australia, the endangered broad‐headed snake Hoplocephalus bungaroides feeds largely on velvet geckos (Oedura lesueurii). We studied growth, longevity and reproduction in a population of velvet geckos in Morton National Park in south‐eastern Australia. We marked 458 individual geckos over a 3‐year period (1992–1995) and made yearly visits to field sites from 1995–2006 to recapture marked individuals. Female geckos grew larger than males, and produced their first clutch at age 4 years. Males can mature at 2 years, but male–male combat for females probably forces males to delay reproduction until age 3 years. Females lay a single clutch of two eggs in communal nests in November, and up to 22 females deposited eggs in a single nest. Egg hatching success was high (100%), and juveniles had high survival (76%) during their first 6 months of life. Velvet geckos are long‐lived, and the mean age of marked animals recaptured after 1995 was 6.1 years (males) and 8.4 years (females). Older females (7.5–9.5 years) were all gravid when last recaptured. Like other temperate‐climate gekkonids, O. lesueurii has a ‘slow’ life history, and population viability could be threatened by any factors that increase egg or adult mortality. Two such factors – the removal of ‘bush rocks’ for urban gardens, and the overgrowth of rock outcrops by vegetation – could render small gecko populations vulnerable to extinction. In turn, the reliance of predatory broad‐headed snakes on this slow‐growing lizard species may increase its vulnerability to extinction. 相似文献
15.
《Animal cells and systems.》2012,16(2):177-181
Blood samples collected from green (Chelonia mydas), loggerhead (Caretta caretta), and Kemp's ridley (Lepidochelys kempii) sea turtles were analyzed by radioimmunoassay to detect seasonal variations in thyroid hormones and compare levels in wild and captive individuals. Sexual dimorphism in the annual cycle of thyroxine was observed in adult Kemp's ridley. No differences were observed between immature male and female green and loggerhead sea turtles. The level of triiodothyronine was consistently low relative to thyroxine in all species investigated, and captive sea turtles exhibit higher plasma thyroid levels than do wild ones 相似文献
16.
Population‐level data are urgently needed for amphibians in light of the ongoing amphibian extinction crisis. Studies focused on population dynamics are not only important for rare species but also for common species which shape ecosystems to a greater degree than those that are rare. Some of the greatest global amphibian species diversity is found in Madagascar, yet there are few studies on the ecology of frog species on the island. We carried out a mark‐recapture study on the widespread frog Mantidactylus betsileanus (Mantellidae: Mantellinae: Mantidactylus) at two adjacent rainforest sites in east‐central Madagascar to assess its population size and structure. To do so, we validated and implemented an individual identification protocol using photographs of the ventral patterns of frogs and identified individuals with photographic‐matching software. Using this rapid, non‐invasive survey method, we were able to estimate a density of 26 and 28 frogs per 100 m2 at each of the two sites sampled. Our results show the rainforests near the village of Andasibe, Madagascar support remarkably high amphibian abundance, helping illustrate the significant ecological role of frogs in this ecosystem. Further, individual frog markings allowed us to develop more precise estimates than traditional survey methods. This study provides a blueprint to augment existing population studies or develop new monitoring programs in Madagascar and beyond. 相似文献
17.
Line S. Cordes Helen E. Hedworth David Cabot Maurice Cassidy Paul M. Thompson 《Ibis》2015,157(3):631-636
Assessing broad‐scale changes in seabird populations across the North Atlantic requires an integration of available datasets to understand the spatial extent of potential drivers and demographic change. Here, we compared survival of Northern Fulmars Fulmarus glacialis from a Scottish and an Irish colony from 1974 to 2009. Despite lower recapture probabilities of monel‐ringed Irish birds compared with colour‐ringed Scottish birds, survival probability decreased at both colonies. The extent to which the decline in survival is related to density‐dependent processes or other external drivers remains uncertain, but our results suggest that these changes in survival are possibly indicative of larger‐scale processes and are not confined to local colony dynamics. 相似文献
18.
Danielle A. Schmidt Purnima Govindarajulu Karl W. Larsen Michael A. Russello 《Ecology and evolution》2020,10(14):7157-7172
Delineation of units below the species level is critical for prioritizing conservation actions for species at‐risk. Genetic studies play an important role in characterizing patterns of population connectivity and diversity to inform the designation of conservation units, especially for populations that are geographically isolated. The northernmost range margin of Western Rattlesnakes (Crotalus oreganus) occurs in British Columbia, Canada, where it is federally classified as threatened and restricted to five geographic regions. In these areas, Western Rattlesnakes hibernate (den) communally, raising questions about connectivity within and between den complexes. At present, Western Rattlesnake conservation efforts are hindered by a complete lack of information on genetic structure and degree of isolation at multiple scales, from the den to the regional level. To fill this knowledge gap, we used Genotyping‐in‐Thousands by sequencing (GT‐seq) to genotype an optimized panel of 362 single nucleotide polymorphisms (SNPs) from individual samples (n = 461) collected across the snake's distribution in western Canada and neighboring Washington (USA). Hierarchical STRUCTURE analyses found evidence for population structure within and among the five geographic regions in BC, as well as in Washington. Within these regions, 11 genetically distinct complexes of dens were identified, with some regions having multiple complexes. No significant pattern of isolation‐by‐distance and generally low levels of migration were detected among den complexes across regions. Additionally, snakes within dens generally were more related than those among den complexes within a region, indicating limited movement. Overall, our results suggest that the single, recognized designatable unit for Western Rattlesnakes in Canada should be re‐assessed to proactively focus conservation efforts on preserving total genetic variation detected range‐wide. More broadly, our study demonstrates a novel application of GT‐seq for investigating patterns of diversity in wild populations at multiple scales to better inform conservation management. 相似文献
19.
XIU‐SHAN LI YA‐LIN ZHANG JOSEF SETTELE MARKUS FRANZN OLIVER SCHWEIGER 《Insect Conservation and Diversity》2013,6(2):170-178
Abstract. 1. Central and Southeast Asia currently faces rapid loss and degradation of tropical and subtropical forests with potentially severe effects on its biodiversity. 2. We analysed population characteristics and dispersal of the butterfly Byasa impediens in eleven patches of a fragmented subtropical forest in Western China. 3. In an area covering 30 km2, we found an unexpected high dispersal capacity of more than 5 km, and estimated a mean dispersal distance of 1 km according to the negative exponential function. However, the inverse power function gave a better fit and predicted a reasonably large fraction of long‐distance displacements: 4% of all movements were estimated to exceed 5 km. 4. In spite of the high level of fragmentation and small sizes of some patches, we did not observe extinction or (re)colonisation events. Matching dispersal ability with the spatial grain of the resource patches in the landscape is seen as a major cause. In addition, persistence, emigration and immigration of individuals were exclusively affected by the amount of larval host plants, nectar plants and forest cover. 5. Our study indicates the importance of long‐distance dispersal and shows that species with large dispersal abilities and a somewhat broader dietary niche, such as B. impediens, can sustain in fragmented areas if patch quality is sufficient. 6. We suggest that conservation action may not only focus on particularly endangered species but also on relatively common, but often endemic, insect species. This is of particular concern given the global dominance of insects and their importance for ecosystem services, especially in an area of constantly increasing demands of agricultural products. 相似文献
20.
Lacking the capacity for thermogenesis, most ectotherms inhabiting thermally heterogeneous environments rely instead upon exploiting that ambient heterogeneity. In many cases they maintain body temperatures within a narrow range despite massive spatial and temporal variation in ambient conditions. Reliance on diverse thermal opportunities is reflected in specific terms for organisms that bask in sunlight to regulate their temperature (heliotherms), or that press their bodies against warm substrates to facilitate heat flow (thigmotherms), or that rely on large body mass to maintain thermal constancy (gigantothermy). We propose an additional category of thermoregulators: kleptotherms, which regulate their own temperature by ‘stealing’ heat from other organisms. This concept involves two major conditions: the thermal heterogeneity created by the presence of a warm organism in a cool environment and the selective use of that heterogeneity by another animal to maintain body temperatures at higher (and more stable) levels than would be possible elsewhere in the local area. Kleptothermy occurs in endotherms also, but is usually reciprocal (rather than unilateral as in ectotherms). Thermal monitoring on a small tropical island documents a possible example of kleptothermy, based on high stable temperatures of a sea snake (Laticauda laticaudata) inside a burrow occupied by seabirds. 相似文献