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609 results for “Critically endangered”

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dryad36/100

Dietary plasticity linked to divergent growth trajectories in a critically endangered sea turtle

Foraging habitat selection and diet quality are key factors that influence individual fitness and metapopulation dynamics through effects on demographic rates. There is growing evidence that sea turtles exhibit regional differences in somatic growth linked to alternative dispersal patterns during the oceanic life stage. Yet, the role of habitat quality and diet in shaping somatic growth rates is poorly understood. Here, we evaluate whether diet variation is linked to regional growth variation in hawksbill sea turtles (Eretmochelys imbricata), which grow significantly slower in Texas versus Florida (USA), through novel integrations of skeletal growth, gastrointestinal content (GI), and bulk tissue and amino acid (AA)-specific stable nitrogen (δ15N) and carbon (δ13C) isotope analyses. We also used AA δ15N ΣV values (heterotrophic bacterial re-synthesis index) and δ13C essential AA (δ13CEAA) fingerprinting to test assumptions about the energy sources fueling hawksbill food webs regionally. GI content analyses, framed within a global synthesis of hawksbill dietary plasticity, revealed that relatively fast-growing hawksbills stranded in Florida conformed with assumptions of extensive spongivory for this species. In contrast, relatively slow-growing hawksbills stranded in Texas consumed considerable amounts of non-sponge invertebrate prey and appear to forage higher in the food web as indicated by isotopic niche metrics and higher AA δ15N-based trophic position estimates internally indexed to baseline N variation. However, regional differences in estimated trophic position may also be driven by unique isotope dynamics of sponge food webs. AA δ15N ΣV values and δ13CEAA fingerprinting indicated minimal bacterial resynthesis of organic matter (ΣV < 2) and that eukaryotic microalgae were the primary energy source supporting hawksbill food webs. These findings run contrary to assumptions that hawksbill diets predominantly comprise high microbial abundance sponges expected to primarily derive energy from bacterial symbionts. Our findings suggest alternative foraging patterns could underlie regional variation in hawksbill growth rates, as divergence from conventional sponge prey might correspond with increased energy expenditure and reduced foraging success or diet quality. As a result, differential dispersal patterns may infer substantial individual and population fitness costs and represent a previously unrecognized challenge to the persistence and recovery of this critically endangered species.

opencc-zeroDec 2022View details →

dryad36/100

Drawing on local knowledge and attitudes for the conservation of critically endangered rhino rays in Goa, India

In the context of marine species declines in data-limited regions, local ecological knowledge (LEK) is a valuable source of information on species ecology and historical trends. LEK can also help understand how threatened species exist within a local culture, in terms of their uses and values, and reveal attitudes toward their conservation. Rhino rays (guitarfish and wedgefish) are highly threatened by overfishing with most species Critically Endangered, yet poorly studied in countries like India that fish them the most. We drew on LEK to understand the socio-ecological status of rhino rays in Goa, on the west coast of India. We investigated their habitat use and seasonality, interaction with fisheries, socio-economic uses, and relational values. We also explored attitudes of fishers towards rhino rays and their conservation. A combination of semi-structured interviews and key informant interviews (88 in total) were conducted with fishers at multiple sites. Local knowledge suggests that nearshore habitats around river mouths form important nursery grounds for some rhino rays, and provided insights into their seasonality and breeding. Rhino rays appeared to be targeted historically but are entirely bycaught at present, with the highest catches in gillnets and in the South Goa district, during September and October. LEK indicated that taxa like sawfish (Pristis spp.) and wedgefish (Rhynchobatus spp.) have severely declined or disappeared from this region. We coded different relational values, from recreation (rhino rays are consumed and enjoyed with alcohol) to symbolic values (rhino rays are considered lucky). All key informants expressed positive attitudes towards rhino ray conservation and stated that a ban on landing these species would have little to no impact on fisher earnings. The usefulness of LEK suggests it should be brought into the scientific mainstream to support development of more equitable and socially-appropriate management plans. Fostering relational values can reinforce fishers' positive attitudes, thereby enhancing rhino ray conservation. Their low commercial value and potentially high post-capture survival suggest that using norm-based approaches to promote live release may be successful. Further research on rhino ray ecology and human dimensions can support the development of appropriate conservation interventions.

opencc-zeroDec 2022View details →

dryad36/100

Navigating agricultural landscapes: Responses of critically endangered giant tortoises to farmland vegetation and infrastructure

Context: Interactions between wildlife and anthropogenic infrastructure, such as roads, fences, and dams, can influence wildlife movement, and potentially cause human-wildlife conflict. In the Galapagos archipelago, two species of critically endangered giant tortoise encounter infrastructure and human-modified vegetation in farms, which could influence movement choices. Objectives: We investigated factors influencing tortoise movement and habitat selection in the agricultural landscape of Santa Cruz Island, Galapagos. Methods: We examined the movement of 27 tortoises collected using GPS tracking between 2014 and 2020, in relation to the location of vegetation, ponds, fences, and roads. Results: We found that tortoises preferred pasture over native vegetation, but there was little difference among their preferences for native vegetation, crops, or invasive vegetation. Tortoises also travelled slower in pasture, and faster in invasive vegetation, compared to crops and native vegetation. Tortoises were more likely to be found closer to ponds than predicted by chance. Our results indicated that most fences were porous to tortoises, with limited impact on their movement. Tortoises were more likely to use areas near roads with low-traffic. Conclusions: Pastures and ponds are important habitats for tortoises in farms and are likely to be used preferentially by tortoises. Overall, fences and roads did not strongly obstruct tortoise movements, however, this may lead to potential injury to tortoises on roads and property damage for farmers. To best identify priority areas for managing wildlife on farms, we recommend evaluating the combined effects of multiple anthropogenic landscape features on wildlife movements.

opencc-zeroFeb 2023View details →

dryad36/100

Data on range-wide breeding habitat use of the critically endangered Yellow-breasted Bunting Emberiza aureola after population collapse

The population of the Yellow-breasted Bunting Emberiza aureola, a formerly widely distributed and abundant songbird of northern Eurasia, suffered a catastrophic decline and a strong range contraction between 1980 and 2013. There is evidence that the decline was driven by illegal trapping during migration, but potential contributions of other factors to the decline, such as land-use change, have not yet been evaluated. Before effects of land-use change can be evaluated, a basic understanding of the ecological requirements of the species is needed. We therefore compared habitat use in ten remaining breeding regions across the range, from European Russia to Japan and the Russian Far East. We also assessed large-scale variation in habitat parameters across the breeding range. We found large variation in habitat use, within and between populations. Differences were related to the cover and height of trees and shrubs at Yellow-breasted Bunting territories. In many regions, Yellow-breasted Buntings occupied early successional stages, including anthropogenic habitats characterized by mowing, grazing or fire regimes. We found that the probability of presence can be best predicted with the cover of shrubs, herbs and grasses. Highest probabilities were found at shrub cover values of 40 to 70 %. Differences in habitat use along a longitudinal gradient were small, but we found strong differences across latitudes, possibly related to habitat availability. We conclude that the remaining Yellow-breasted Bunting populations are not limited to specific habitat types. Our results provide important baseline information to model the range-wide distribution of this critically endangered species and to guide targeted conservation measures.

opencc-zeroFeb 2022View details →

zenodo36/100

Fig. 1 in Ex-situ conservation of the critically endangered swamp forest crab Parathelphusa reticulata Ng, 1990 (Decapoda: Brachyura: Gecarcinucidae): observations on its reproduction and biology in captivity

Fig. 1. Captive breeding facility in the Singapore Botanic Gardens. Photograph: Daniel J. J. Ng.

opencc-by-4.0May 2023View details →

dryad36/100