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1.
Introduced Rattus norvegicus (Norway rats) caused the decline of Synthliboramphus antiquus (ancient murrelets) and other seabirds breeding on Langara Island (approximately 3,100 ha), British Columbia. Using funds from the litigation settlement following the Nestucca oil spill, Environment Canada eradicated Norway rats using a technique developed in New Zealand which involved dispensing wax baits containing the anticoagulant brodifacoum at 50 ppm from fixed bait stations. Bait stations were placed every 75 to 100 m on a grid over the entire island (1 station/ha). Rats removed bait for 26 days, after which crews placed baits in protective plastic bags in each bait station. Stations loaded with baits were left on the island and rechecked four times over 2 years, after which bait stations and remaining bait were removed. The eradication succeeded. No signs of rats have been detected on Langara Island and its associated islands since January 1996. No rats were trapped during 1,700 trap‐nights following the poison campaign. Incisor marks of rats were not found on apples or oil‐dipped chew‐sticks. Corvus corax (common ravens) likely suffered greater than 50% mortality from the eradication after apparently gaining access to the poison directly from bait stations and from scavenging rat carcasses. A monitoring and response system is being developed in conjunction with current users of the islands. The success on Langara Island demonstrates how the technique proven on small New Zealand islands of less than 300 ha can be effectively extrapolated to much larger islands.  相似文献   

2.
We radiomarked 153 Xantus' Murrelets Synthliboramphus hypoleucus captured at sea near Santa Barbara Island (SBI), the largest murrelet colony in the California Channel Islands, USA. We tracked these radiomarked murrelets in the Southern California Bight (SCB) off coastal southern California during the 1995-97 breeding seasons. In 1995 during mild El Niño conditions, the murrelets were distributed in non-upwelling areas. In 1996-97, they were distributed in dense patches, aggregating in cool upwelled waters near the northern Channel Islands or south of San Nicolas Island. Murrelets flew longer distances from SBI to foraging areas in 1997 (̄= 111 ± 44 km) than in 1996 (̄= 62 ± 25 km), but the distances they travelled did not differ between months (Apr and May) within years. Mean foraging distances from SBI were similar for 'incubating' murrelets (determined on the basis of repeated visits to SBI) and 'non-incubating' murrelets during the colony attendance period. We attributed the low return rate of radiomarked murrelets to SBI to the capture and marking of a large proportion of birds that were not actively incubating rather than to any adverse effects of radio attachment. We believe changes in murrelet foraging patterns between the 1970s and 1990s are associated with changes in prey resources in the SCB. Flexibility in the foraging strategies of these murrelets may be related to the highly variable marine environment at the southern end of the California Current Up welling System.  相似文献   

3.
Abstract: The marbled murrelet (Brachyramphus marmoratus) is a small Pacific seabird with a breeding range that extends from the Aleutian Islands to central California. Throughout most of its breeding range, it uses mature and old-growth coniferous forests as nesting habitat. Although most murrelets seem to nest within 60 km of the coast, occupied nesting habitat has been identified as far as 84 km from the ocean in Washington state. Due to the extensive inland distances within which birds are known to breed, the area requiring surveys to identify breeding sites can be enormous. Therefore, the standard 2-year survey protocol can be expensive and time-consuming for forest management agencies and companies to administer. We developed a logistic regression model to determine whether a suite of forest structural characteristics could be used to reliably predict occupancy of a forest patch by marbled murrelets. We tested the performance of the final model using cross-validation procedures and a sample of independent sites. We used 50 sites surveyed for marbled murrelets to estimate the model, and 48 independent sites were available to test model performance. All 50 sites were on private forestland owned by Rayonier located in the western lowlands of Olympic Peninsula within the Sitka spruce and western hemlock transition zones. We sampled forest habitat at each site, and we collected information on 15 explanatory variables. The best-fitting logistic regression model contained variables that measured number of canopy layers (P<0.001, approx. F test) and mistletoe (Arceuthobium sp.) abundance (P = 0.031, approx. F test). The model misclassified 2 of 33 (94% correct) unoccupied sites as occupied using a classification cut-off (c) of c=0.25. In the other direction, under cross-validation the final model misclassified 2 of 17 (88% correct) occupied sites as unoccupied. On a test of the model against an independent sample, using a classification cut-off value of c = 0.25, the final model correctly classified 36 of 48 sites (75% correct). The final model misclassified 3 of 31 occupied sites as unoccupied (90% correct). Use of predictive models could greatly reduce the amount of forest that requires surveys by screening out those sites with little probability of use and by focusing remaining effort on higher probability sites, resulting in a higher likelihood of identifying occupied sites and thereby more efficiently conserving marbled murrelet nesting habitat.  相似文献   

4.
ABSTRACT Many land-trust organizations attempt to preserve habitat that will benefit specific wildlife species or suites of species. With limited resources available, these organizations need tools to prioritize preservation efforts. One such organization, the Kiawah Island Natural Habitat Conservancy (KINHC), is attempting to preserve wildlife habitat in the face of ever-increasing property values and development pressure on Kiawah Island, South Carolina, USA. We modified an existing bobcat (Lynx rufus) habitat suitability index model, which focuses on suitability of habitats for food, by including components for concealment cover and den habitat. We developed a windows-based computer program that calculates modified habitat suitability index (MHSI) values that can easily be imported into a Geographic Information System for display in map form, allowing for frequent reevaluation of site-specific habitat suitability as land-cover patterns change. We used locations collected from radiocollared bobcats to assess validity of the food and cover components of the MHSI. Bobcats used areas identified as highly suitable for food more than expected during nocturnal time periods (G52 = 640.9, P < 0.001) and areas identified as highly suitable for cover more than expected during diurnal time periods (G37 = 1,194.0, P < 0.001). Our approach for evaluating bobcat habitat suitability will allow KINHC to identify parcels that likely provide the greatest ecological benefit to bobcats and their associated wildlife community. Our approach could be altered to consider habitat requirements of other species, or multiple species, at virtually any location for which fine-scale land-cover data are available.  相似文献   

5.

Aim

The impact of climate change on forest biodiversity and ecosystem services will be partly determined by the relative fortunes of invasive and native forest trees under future conditions. Aotearoa New Zealand has high conservation value native forests and one of the world's worst invasive tree problems. We assess the relative effects of habitat redistribution on native Nothofagus and invasive conifer (Pinaceae) species in New Zealand as a case study on the compounding impacts of climate change and tree invasions.

Location

Aotearoa New Zealand.

Methods

We use species distribution models (SDMs) to predict the current and future distribution of habitat for five native Nothofagus species and 13 invasive conifer species under two 2070 climate scenarios. We calculate habitat loss/gain for all species and examine overlap between the invasive and native species now and in future.

Results

Most species will lose habitat overall. The native species saw large changes in the distribution of habitat with extensive losses in North Island and gains mostly in South Island. Concerningly, we found that most new habitat for Nothofagus was also suitable for at least one invasive species. However, there were refugia for the native species in the wetter parts of the climate space.

Main Conclusion

If the predicted changes in habitat distribution translate to shifts in forest distribution, it would cause widespread ecological disruption. We discuss how acclimation, adaptation and biotic interactions may prevent/delay some changes. But we also highlight that the poor establishment capacity of Nothofagus, and the contrasting ability of the conifers to invade, will present persistent conservation challenges in areas of both new habitat and forest retreat. Pinaceae are problematic invaders globally, and our results highlight that control of invasions and active native forest restoration will likely be key to managing forest biodiversity under future climates.  相似文献   

6.

Background

Long-lived seabirds face a conflict between current and lifelong reproductive success. During incubation shifts, egg neglect is sometimes necessary to avoid starvation, but may compromise the current reproductive attempt. However, factors underlying this decision process are poorly understood. We focus on the ancient murrelet, Synthliboramphus antiquus, an alcid with exceptionally long incubation shift lengths, and test the impact of environmental factors on incubation shift length in relation to reproductive success.

Methodology/Principal Findings

Using an information theoretic approach, we show that incubation shift length was a strong predictor of reproductive success for ancient murrelets at Reef Island, Haida Gwaii, British Columbia, Canada during the 2007 and 2008 breeding seasons. The most important factors explaining an individual''s shift length were egg size, wind speed and the length of the mate''s previous shift. Wind speed and tide height were the two most important factors for determining foraging behavior, as measured by dive frequency and depth.

Conclusions/Significance

Our study demonstrates that (i) species-specific reproductive strategies interact with environmental conditions such as wind speed to form multiple incubation patterns and (ii) maintaining regular incubation shifts is an essential component of reproductive success.  相似文献   

7.
In most studies about ant communities, species are grouped into competitive hierarchies where top dominants drive the majority of other species away from resources. Nevertheless, in some ecosystems high ground temperatures may disrupt this hierarchical organization. Other changes in community structure are caused by the arrival of invasive ant species, which rapidly disassemble local communities. We studied the effects of competition and temperature on ant community organization on Surprise Island (New Caledonia). Four different habitats were distinguished: a central plain, a sea shore Argusia shrubland, a dense Scaveola shrub, and an arboreal Pisonia strata. Eight ant species were identified from pitfall traps (seven introduced and only one native species, Pheidole oceanica). Ant assemblages in each habitat had a different ecologically dominant species, and a dominant species in one habitat could be non-dominant and less abundant in another. From interactions at baits, we built a competitive hierarchy where the top dominant species was the native Ph. oceanica. Daily foraging activity rhythms of the different species mostly overlapped. The relationship between bait occupation and ground temperature followed a negative linear pattern at all sites and for most species, except for the relatively thermophilous Monomorium floricola. Indices of co-occurrence in pitfall traps indicated that species co-occurred randomly with respect to one another. Conversely, species appeared to be segregated when we examined co-occurrence at baits at the sites where Ph. oceanica was abundant. Oceanic islands are very susceptible to alien species, but on Surprise Island it seems that the sole native species dominates in some habitats when confronted by invasive species.  相似文献   

8.
Abstract.— Mechanisms of population differentiation in highly vagile species such as seabirds are poorly understood. Previous studies of marbled murrelets ( Brachyramphus marmoratus ; Charadriiformes: Alcidae) found significant population genetic structure, but could not determine whether this structure is due to historical vicariance (e.g., due to Pleistocene glaciers), isolation by distance, drift or selection in peripheral populations, or nesting habitat selection. To discriminate among these possibilities, we analyzed sequence variation in nine nuclear introns from 120 marbled murrelets sampled from British Columbia to the western Aleutian Islands. Mismatch distributions indicated that murrelets underwent at least one population expansion during the Pleistocene and probably are not in genetic equilibrium. Maximum-likelihood analysis of allele frequencies suggested that murrelets from "mainland" sites (from the Alaskan Peninsula east) are genetically different from those in the Aleutians and that these two lineages diverged prior to the last glaciation. Analyses of molecular variance, as well as estimates of gene flow derived using coalescent theory, indicate that population genetic structure is best explained by peripheral isolation of murrelets in the Aleutian Islands, rather than by selection associated with different nesting habitats. No isolation-by-distance effects could be detected. Our results are consistent with a rapid expansion of murrelets from a single refugium during the early–mid Pleistocene, subsequent isolation and divergence in two or more refugia during the final Pleistocene glacial advance, and secondary contact following retreat of the ice sheets. Population genetic structure now appears to be maintained by distance effects combined with small populations and a highly fragmented habitat in the Aleutian Islands.  相似文献   

9.
ABSTRACT We estimated carrying capacity for sea otters (Enhydra lutris) in the coastal waters of British Columbia, Canada, by characterizing habitat according to the complexity of nearshore intertidal and sub-tidal contours. We modeled the total area of complex habitat on the west coast of Vancouver Island by first calculating the complexity of the Checleset Bay-Kyuquot Sound (CB-KS) region, where sea otters have been at equilibrium since the mid-1990s. We then identified similarly complex areas on the west coast of Vancouver Island (WCVI model), and adapted the model to identify areas of similar complexity along the entire British Columbia coast (BC model). Using survey data from the CB-KS region, we calculated otter densities for the habitat predicted by the 2 models. The density estimates for CB-KS were 3.93 otters/km2 and 2.53 otters/km2 for the WCVI and BC models, respectively, and the resulting 2 estimates of west coast of Vancouver Island complex habitat carrying capacity were not significantly different (WCVI model: 5,123, 95% CI = 3,337–7,104; BC model: 4,883, 95% CI = 3,223–6,832). The BC model identified the region presently occupied by otters on the central British Columbia coast, but the amount of coast-wide habitat it predicted (5,862 km2) was relatively small, and the associated carrying capacity estimate (14,831, 95% CI = 9,790–20,751) was low compared to historical accounts. We suggest that our model captured a type of high-quality or optimum habitat prevalent on the west coast of Vancouver Island, typified by the CB-KS region, and that suitable sea otter habitat elsewhere on the coast must include other habitat characteristics. We therefore calculated a linear, coast-wide carrying capacity of 52,459 sea otters (95% CI = 34,264–73,489)—a more realistic upper limit to sea otters in British Columbia. Our carrying capacity estimates are helping set population recovery targets for sea otters in Canada, and our habitat predictions represent a first step in Critical Habitat identification. This habitat-based approach to estimating carrying capacity is likely suitable for other nonmigratory, density-dependent species.  相似文献   

10.
Marbled murrelets (Brachyramphus marmoratus) are coastal seabirds that nest from California to the Aleutian Islands. They are declining and considered threatened in several regions. We compared variation in the mitochondrial control region, four nuclear introns and three microsatellite loci among194 murrelets from throughout their range except Washington and Oregon. Significant population genetic structure was found: nine private control region haplotypes and three private intron alleles occurred at high frequency in the Aleutians and California; global estimates of F ST or ΦST and most pairwise estimates involving the Aleutians and/or California were significant; and marked isolation-by-distance was found. Given the available samples, murrelets appear to comprise five genetic management units: (1) western Aleutian Islands, (2) central Aleutian Islands, (3) mainland Alaska and British Columbia, (4) northern California, and (5) central California.  相似文献   

11.
刘超  丁志锋  丁平 《生态学报》2015,35(20):6759-6768
为探究千岛湖陆桥岛屿不同鸟类集团对栖息地片段化敏感性的差异和季节变化,于2009年4月—2012年1月鸟类繁殖季(4、5、6月)和冬季(11、12、1月)对千岛湖41个陆桥岛屿鸟类集团进行了研究。结果表明,冬季杂食鸟对片段化敏感性高于食虫鸟,繁殖季时二者无显著差异,繁殖季和冬季时下层鸟对片段化敏感性均高于林冠鸟,冬季留鸟对片段化敏感性高于候鸟,繁殖季则无显著差异。杂食鸟和留鸟对片段化敏感性存在季节差异,而食虫鸟、林冠鸟、下层鸟和候鸟对片段化敏感性均无季节差异。不同鸟类集团对栖息地片段化敏感性的差异和季节变化规律,有助于人们在栖息地管理和保护区设计时采取更有针对性的鸟类保护措施。  相似文献   

12.

Island populations are at higher risk of extinction than mainland populations. Therefore, understanding the factors that facilitate connectivity is particularly pressing for the conservation of island taxa. Sceloporus occidentalis becki, the Island Fence Lizard, is an endemic taxon restricted to the Northern Channel Islands, part of a nearshore archipelago in Southern California, USA. Since the Last Glacial Maximum, fence lizard habitat on the Northern Channel Islands has decreased with rising sea levels and increasing temperatures that have reduced the availability of woody vegetation. More recently, the introduction (and subsequent removal) of invasive ungulates over the last 170 years and recovery of vegetation has resulted in further dramatic habitat modification. Given the potential for genetic bottlenecks, the history of habitat alteration, and topographic and landscape complexity, we used landscape and population genetic approaches to characterize patterns of genetic diversity and structure of Island Fence Lizards on Santa Cruz Island, the largest of the Northern Channel Islands. Our analyses revealed shallow population structure across the island, low effective population size (Ne?=??~?200), and evidence for a recent genetic bottleneck. Landscape genetic analyses showed that connectivity is facilitated by tree canopy cover and shrubland, as well as by intermediate temperatures, emphasizing the importance of woody vegetation and habitats with variable thermal regimes as the climate warms. Combined, these population and landscape genetic analyses suggest that the Island Fence Lizard is of greater conservation concern than currently appreciated, and increased conservation management focus is warranted for this island endemic.

  相似文献   

13.
This study focussed on the demography and ecology of Scolopsis bilineatus at three locations on the Great Barrier Reef: the Lizard Island Group, Orpheus Island and One Tree Island. Scolopsis bilineatus lived for up to 16 years and had four distinct life‐history stages, which varied in their distribution patterns, habitat use and reproductive behaviour. Pre‐maturational sex change occurred whereby all males were derived from immature females, and males grew faster and larger than females. Small females and larger males generally formed pairs, which influenced their spatial distributions at small scales. Distributions of S. bilineatus were influenced by depth and exposure within reefs, particularly for juveniles, and most fish were found in shallow, sheltered habitats. Abundance was influenced by benthic cover, and was higher in areas of high coral cover and low where algae were abundant. Habitat associations were stronger at the microhabitat scale, and shelter sites were important for adults. Ontogenetic changes in microhabitat associations were found: juveniles occupied sand and rubble, and adults occupied shelters such as caves and overhangs. Adults showed site fidelity for shelter sites over a period of 4 days and returned to specific shelter sites repeatedly. These findings illustrate the importance of understanding the spatial ecology and habitat use of coral reef fishes, particularly with reference to size‐based changes within species.  相似文献   

14.
选取2008年寒害后和恢复重建5年后红树林群落水土生要素进行纵向对比,选取水域pH、化学需氧量(COD)、溶解氧(DO)、总悬浮物(TSS)、总无机氮(TIN)、正磷酸盐(PO_4-P)等水环境指标和(S)pH、氧化还原电位(Eh)、有机质(OM)等沉积物指标进行不同类型红树林群落间的横向对比。自变量指标中水环境指标所占比例较大,约为2—3,弥补了红树林湿地植被、沉积物和水文等3个自然因素中水文条件研究较为缺乏的现状。结合各类红树林群落水、土、生三要素进行典范对应分析(CCA)的结果表明:1)典范对应分析方法用于分析淇澳岛大围湾各类红树林典型群落寒害后及寒害5年后的群落生物过程特征与各种生境因子间的相关关系,效果良好,前4组自变量的典型变量可以解释标准变量中绝大部分(约80%以上)的信息。2)恢复重建5年后,淇澳岛大围湾各类红树林群落中中潮位的无瓣海桑(Sonneratia apetala)群落和高潮位的桐花树(Aegiceras comiculatum)群落拓展最快,面积分别增加26.58hm~2和23.1 hm~2,而互花米草(Spartina alterniflora)群落因无瓣海桑群落的扩张而受到抑制,面积下降31.51hm~2。3)水域pH、沉积物(S)pH、OM、DO、COD等水土指标与冠幅、胸径、基径、盖度和高度等生物过程指标依次正相关,而PO_4-P、TSS和TIN等水域指标与生物过程指标依次负相关。4)珠海淇澳岛大围湾红树林湿地生态系统对水域悬浮物和营养元素的固定效果明显,但其植被生物过程受水土因素,尤其是水文因素,影响较大,其中影响最大的生境因素是pH值(包括水域pH值和沉积物(S)pH值)。低中潮位、中性至弱碱性的表层沉积物生境条件较为适合无瓣海桑和老鼠簕(Acanthus ilicifolius)等红树植物群落的初期恢复。  相似文献   

15.
Translocation to areas free of exotic predators, habitat degradation, or disease may be the most viable restoration option for many endangered species. We report on a successful translocation of the critically endangered St. Croix ground lizard, Ameiva polops, extirpated from St. Croix, U.S. Virgin Islands, Caribbean, by predation from introduced mongooses (Herpestes auropunctatus). We translocated 57 adult A. polops from Green Cay to Buck Island in May 2008. We placed 4 females and 3 males each in eight, 100 m2, enclosures on Buck Island for 71 days, then the enclosures were opened. During the enclosure period, 20 individuals were identified and 32 others were seen. The average number sighted per survey was only 5.28 (range = 2–10). One hatchling was sighted in an enclosure, indicating a translocated female successfully nested. Body condition of the translocated individuals increased significantly by the end of the enclosure period. Population monitoring surveys at 61 sites across Buck Island showed that 5 years after the initial translocation in June 2013, the new population had grown to an estimated 1,473 individuals and occupied 58.9% of the island. We attribute eradication of mongoose, life history of the species, large propagule size, condition of habitat, soft‐release, use of adults, interagency collaboration, and systematic assessment as primary factors that facilitated this successful translocation. Our findings provide meaningful insights on factors that enhance the potential for successful translocations, and point to new strategies aimed at restoring populations of endangered reptiles in their native ranges.  相似文献   

16.
Abstract Large predators play important ecological roles, but often are sensitive to habitat changes and thus are early casualties of habitat perturbation. Pythons are among the largest predators in many Australian environments, and hence warrant conservation‐orientated research. Carpet pythons (Morelia spilota imbricata) have declined across much of south‐western Australia presumably because of habitat clearance and degradation. Information on habitat use, home range sizes and movements is needed to plan for the conservation of this important predator. We studied pythons at two study sites (Garden Island and Dryandra Woodland) with markedly different climates, habitat types and disturbance histories. We surgically implanted radio‐transmitters in 91 pythons and tracked them for periods of 1 month to 4 years. Dryandra pythons remained inactive inside tree hollows during cooler months (May–September), whereas some (especially small) pythons on Garden Island continued to move and feed. Overall weekly displacements (mean = 100–150 m) were similar at the two study sites and among sex/age classes, except that reproductive females were sedentary during summer while they were incubating eggs. Home ranges averaged 15–20 ha. Adult male pythons had larger home ranges than adult females at Dryandra, but not at Garden Island. Radio‐tracked snakes at Dryandra exhibited high site fidelity, returning to previously occupied logs after long absences and reusing tree hollows for winter shelter. Many of the logs used by snakes had been felled during plantation establishment >70 years ago, with little subsequent regeneration of source trees. In contrast, Garden Island snakes usually sheltered under dense shrubs. Habitat usage was similar among different sex/age classes of snakes at each site, except that juvenile pythons were more arboreal than adults. Although carpet pythons demonstrate great flexibility in habitat use, certain habitat elements appear critical for the persistence of viable populations. Fire plays a central role in this process, albeit in complex ways. For example, low‐intensity fires reduce the availability of hollow logs on the ground at Dryandra and fail to regenerate shrub thickets required by prey species. Paradoxically, high‐intensity fires stimulate shrub thickets and fell trees creating new logs – but might also threaten overwinter trees. Thus, the impact of disturbances (such as wildfires) on the viability of python populations will be mediated in complex ways by alteration to important microhabitats such as vegetation cover or log availability. At Dryandra, landscape management should include occasional fire events to generate new logs as well as shrub thickets used by prey. Strategic burning may also be required at Garden Island to regenerate some vegetation communities.  相似文献   

17.
Uncertain taxonomy hinders the effective prioritization of taxa for conservation. This problem is acute for understudied island populations in the southwest Pacific Ocean, which are increasingly threatened by habitat loss, predation and climate change. Here, we offer the first test of taxonomic limits and phylogenetic affinities of the iconic Pacific Robin radiation (Petroica multicolor) in order to prioritize the conservation of its nominotypical subspecies, the endangered Norfolk Island Robin (P. m. multicolor). We integrate phylogenetic analyses of ancient DNA and quantitative measures of plumage and morphometric variation to show that the Norfolk Island Robin should be recognized as a distinct species. Phenotypic and genetic datasets contradict the longstanding treatment of Pacific Robins (including Norfolk Island Robins) and Scarlet Robins (P. boodang) as a single species. Instead, we show that Norfolk Island Robins are deeply divergent from Scarlet Robins and have more genetic similarity to Red-capped Robins (P. goodenovii) than to other Pacific Robins. This finding is unrepresentative of the current taxonomic and conservation status of the Norfolk Island Robin, which we propose should be recognised as an endemic endangered species. Our study clearly shows that in the absence of contemporary tissues, ancient DNA approaches using historical museum specimens can address taxonomic questions that morphological traits are unable to resolve. Further, it highlights the need for similar studies of other threatened Norfolk fauna with uncertain taxonomic status in order to ensure appropriate conservation prioritization.  相似文献   

18.
Aquatic turtles worldwide are plagued with habitat loss due to development and shoreline alteration that destroys the terrestrial–aquatic linkage which they must cross to reproduce successfully. Furthermore, nesting habitat loss can concentrate nesting, increasing nest predator efficiency. We describe how the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island created nesting habitat for Malaclemys terrapin (Diamondback Terrapin), and document nesting success in response to construction progress and the absence of raccoons and foxes, the primary nest predators. We monitored terrapin nests throughout the nesting seasons from 2002 to 2011 to determine overall and within‐nest survivorship. Female terrapins began nesting on the restoration project within 1 year but planned construction during the study eliminated some nesting areas and opened previously inaccessible areas. Overall, nest survivorship was considerably higher than mainland nesting areas due to the absence of raccoons and foxes on the island and within‐nest survivorship was similar. Egg size, hatchling size, and the frequency of shell scute anomalies were similar to other terrapin populations, suggesting normal developmental conditions on the island. We documented annual variation in hatchling size that correlated negatively with mean air temperature during the incubation season. Our results indicate that restored or created isolated island habitat can be located rapidly by terrapins and can become an important source of recruitment in regions where nesting habitat is limited and predation is high. Poplar Island illustrates how habitat loss and restoration can affect turtle populations by revealing the changes in nesting patterns and success in newly created, predator‐free habitat.  相似文献   

19.
New Zealand's native frogs (genus Leiopelma) display a very high degree of endemism and belong to a distinctive and ancient evolutionary lineage. All four extant species are considered to be threatened or endangered, but the mechanisms behind their decline are poorly understood. Many of the potential factors causing population declines are confounded for the two species living on the mainland; in particular, habitat degradation and the presence of introduced mammalian pests have been difficult to disentangle in the past. Here we present data on a population of Hochstetter's Frog (Leiopelma hochstetteri) living in a pest‐free mainland sanctuary, the 3363‐ha Maungatautari Ecological Island. Survey data from this population shows a fourfold increase in numbers between 2009 and 2012 from a very low initial density. Our results suggest that for Hochstetter's Frog at least, and possibly the other mainland species of Leiopelma, introduced mammals are a major driving factor in population declines. Given that the frog population at Maungatautari was discovered by serendipity when planning for the pest‐free sanctuary was already well underway, this also highlights the conservation value of large pest‐free areas and ecosystem‐level management.  相似文献   

20.
Suitability of small (< 1km2) marine reserves for protecting a commercially important endemic Hawaiian goatfish, Parupeneus porphyreus, was examined by quantifying goatfish habitat use, home range size and site fidelity in an existing marine reserve (Coconut Island in Kaneohe Bay, Hawaii). Five goatfish equipped with acoustic transmitters were tracked for up to 93h each over 3–14 days. Daytime habitat use patterns of two of these fish were continuously monitored for one month using a fixed hydrophone hardwired to an onshore computer. Acoustically tagged fish showed consistent diel patterns of behavior, refuging in holes in the reef by day and moving over extensive areas of sand and coral rubble habitat at night. Remote monitoring of daytime habitat use by two goatfish revealed that the same daytime refuge was used by both fish for at least one month (the battery life of the transmitters). Home ranges of all fish were within the boundaries of the Coconut Island reserve suggesting that even small areas containing suitable habitat can make effective reserves for this species. A relatively low abundance of reproductive size P. porphyreus at Coconut Island in comparison with deeper areas may indicate an ontogenetic shift to deeper habitat in this species.  相似文献   

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