scholarly journals Predicting suitable coastal habitat for sei whales, southern right whales and dolphins around the Falkland Islands

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0244068
Author(s):  
Mick Baines ◽  
Caroline R. Weir
Keyword(s):  
Anthropogenic Activities ◽  
Generalized Additive Models ◽  
Habitat Preferences ◽  
Additive Models ◽  
Falkland Islands ◽  
Coastal Habitat ◽  
Distribution Models ◽  
Cetacean Species ◽  
Right Whales ◽  
Southern Right Whales

Species distribution models (SDMs) are valuable tools for describing the occurrence of species and predicting suitable habitats. This study used generalized additive models (GAMs) and MaxEnt models to predict the relative densities of four cetacean species (sei whale Balaeanoptera borealis, southern right whale Eubalaena australis, Peale’s dolphin Lagenorhynchus australis, and Commerson’s dolphin Cephalorhynchus commersonii) in neritic waters (≤100 m depth) around the Falkland Islands, using boat survey data collected over three seasons (2017–2019). The model predictor variables (PVs) included remotely sensed environmental variables (sea surface temperature, SST, and chlorophyll-a concentration) and static geographical variables (e.g. water depth, distance to shore, slope). The GAM results explained 35 to 41% of the total deviance for sei whale, combined sei whales and unidentified large baleen whales, and Commerson’s dolphins, but only 17% of the deviance for Peale’s dolphins. The MaxEnt models for all species had low to moderate discriminatory power. The relative density of sei whales increased with SST in both models, and their predicted distribution was widespread across the inner shelf which is consistent with the use of Falklands’ waters as a coastal summer feeding ground. Peale’s dolphins and Commerson’s dolphins were largely sympatric across the study area. However, the relative densities of Commerson’s dolphins were generally predicted to be higher in nearshore, semi-enclosed, waters compared with Peale’s dolphins, suggesting some habitat partitioning. The models for southern right whales performed poorly and the results were not considered meaningful, perhaps due to this species exhibiting fewer strong habitat preferences around the Falklands. The modelling results are applicable to marine spatial planning to identify where the occurrence of cetacean species and anthropogenic activities may most overlap. Additionally, the results can inform the process of delineating a potential Key Biodiversity Area for sei whales in the Falkland Islands.

scholarly journals Assessing the importance of High Nature Value farmlands for the conservation of Lesser Kestrels Falco naumanni

2017 ◽  
Vol 3 (2) ◽  
pp. 33-46
Author(s):  
Antonia Galanaki ◽  
Theodoros Kominos ◽  
Martin J. Jones
Keyword(s):  
Landscape Heterogeneity ◽  
Habitat Preferences ◽  
Farming Systems ◽  
Additive Models ◽  
Agricultural Policies ◽  
Distribution Models ◽  
Low Input ◽  
Falco Naumanni ◽  
The Mediterranean ◽  
Lesser Kestrel

AbstractAgricultural areas, such as cereal cultivations, that support species of European and/or national conservation concern are considered as ‘High Nature Value’ farmlands (HNVf) and are very important for the preservation of biodiversity in Europe. The lesser kestrel Falco naumanni is a migratory falcon breeding largely in the HNVf of the Mediterranean basin. The main cause of its decline in Europe has been habitat loss and degradation as a result of agricultural intensification driven largely by the EU Common Agricultural Policies (CAP). In Greece, its population dropped by about 50% since the 1970s and its preferred habitats have shrunk. The aim of this study was to assess habitat preferences of breeding Lesser Kestrels in agro-ecosystems of Greece and relate these habitats to HNVf for conservation purposes. The study area is located in the plain of Thessaly, Central Greece, holding the main lesser kestrel breeding populations in the country, where dry cereal crops have been significantly depleted over the past decades. Species distribution models were developed with generalised additive models for the analyses. Predicted probability of lesser kestrel occurrence was found to be positively associated with farmed landscapes of dry cereal cultivations. Other important predictors were cultivated irrigated farmland and landscape heterogeneity. Main results of the statistical models agree with the findings of other habitatbased studies that highlight the importance of low-input farming systems, that is, HNVf, for safeguarding vital Lesser Kestrels habitats in their breeding grounds in the Mediterranean. A key conservation priority for conserving species dependant on HNVf is the maintenance of those low-input farming systems and the implementation of a greener CAP that would promote environmental-friendly farming practices to preserve and enhance biodiversity in the agro-ecosystems of Europe.

scholarly journals Habitat preferences among three top predators inhabiting a degraded ecosystem, the Black Sea

2017 ◽  
Vol 81 (2) ◽  
pp. 217 ◽  
Author(s):  
Alicia Sánchez-Cabanes ◽  
Maja Nimak-Wood ◽  
Nicola Harris ◽  
Renaud De Stephanis
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Black Sea ◽  
Bottlenose Dolphins ◽  
Habitat Preferences ◽  
Additive Models ◽  
Sea Surface ◽  
The Black Sea ◽  
Cetacean Species ◽  
Common Dolphins

This study investigated whether there is evidence of widespread niche partitioning based on environmental factors in the Black Sea and tested the hypothesis that physiographic factors may be employed as predictors. It addresses poorly researched areas with good habitat potential for the only three cetacean subspecies living in this area: the Black Sea short-beaked common dolphin (Delphinus delphis spp. ponticus), the Black Sea bottlenose dolphin (Tursiops truncatus spp. ponticus) and the Black Sea harbour porpoise (Phocoena phocoena spp. relicta). Generalized additive models (GAMs) were used to analyse data collected from multiple sources. In total, 745 sightings of the three species between 1998 and 2010 throughout the Black Sea were included. The analysis found depth and sea surface temperature to be the most important variables for separating the occurrence of the three species. Common dolphins occurred mainly in deep waters and in areas where the sea surface temperature was low, bottlenose dolphins were distributed primarily in shallower and warmer waters than common dolphins, and harbour porpoises were distributed in shallower waters with lower sea surface temperature than bottlenose dolphins. This study suggests strong niche segregation among the three cetacean species. The study is also the first contribution to the basic information of cetacean species distribution and habitat preferences in the Black Sea as a whole. Knowledge of the distribution of the three dolphin species in the study area is essential to establish conservation measures for these populations.

scholarly journals Testing the ability of species distribution models to infer variable importance

2019 ◽  
Author(s):  
Adam B. Smith ◽  
Maria J. Santos
Keyword(s):  
Predictive Accuracy ◽  
Permutation Test ◽  
Generalized Additive Models ◽  
Simulated Data ◽  
Variable Importance ◽  
Additive Models ◽  
Environmental Data ◽  
Boosted Regression Trees ◽  
Distribution Models ◽  
Model Algorithm

AbstractModels of species’ distributions and niches are frequently used to infer the importance of range- and niche-defining variables. However, the degree to which these models can reliably identify important variables and quantify their influence remains unknown. Here we use a series of simulations to explore how well models can 1) discriminate between variables with different influence and 2) calibrate the magnitude of influence relative to an “omniscient” model. To quantify variable importance, we trained generalized additive models (GAMs), Maxent, and boosted regression trees (BRTs) on simulated data and tested their sensitivity to permutations in each predictor. Importance was inferred by calculating the correlation between permuted and unpermuted predictions, and by comparing predictive accuracy of permuted and unpermuted predictions using AUC and the Continuous Boyce Index. In scenarios with one influential and one uninfluential variable, models were unable to discriminate reliably between variables in conditions that are normally challenging for generating accurate predictions: training occurrences <8-64; prevalence >0.5; small spatial extent; environmental data with coarse resolution when spatial autocorrelation is low; and correlation between environmental variables where |r| >0.7. When two variables influenced the distribution equally, importance was underestimated when species had narrow or intermediate niche breadth. Interactions between variables in how they shaped the niche did not affect inferences about their importance. When variables acted unequally, the effect of the stronger variable was overestimated. GAMs and Maxent discriminated between variables more reliably than BRTs, but no algorithm was consistently well-calibrated vis-à-vis the omniscient model. Algorithm-specific measures of importance like Maxent’s change-in-gain metric were less robust than the permutation test. Overall, high predictive accuracy did not connote robust inferential capacity. As a result, requirements for reliably measuring variable importance are likely more stringent than for creating models with high predictive accuracy.

scholarly journals Species distribution modelling of Bryde’s whales, humpback whales, southern right whales, and sperm whales in the southern African region to inform their conservation in expanding economies

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9997 ◽  
Author(s):  
Jean Purdon ◽  
Fannie W. Shabangu ◽  
Dawit Yemane ◽  
Marc Pienaar ◽  
Michael J. Somers ◽  
...  
Keyword(s):  
Species Distribution ◽  
Environmental Variables ◽  
Sea Water ◽  
Habitat Preferences ◽  
Water Velocity ◽  
Humpback Whales ◽  
Environmental Drivers ◽  
Sperm Whales ◽  
Right Whales ◽  
Southern Right Whales

In southern African waters, information about species distribution and habitat preferences of many cetacean species is limited, despite the recent economic growth that may affect them. We determined the relative importance of eight environmental variables (bathymetry, distance to shore, slope, chlorophyll-a, salinity, eastwards sea water velocity, northwards sea water velocity and sea surface temperature) as drivers of seasonal habitat preferences of Bryde’s whales (Balaenoptera brydei), humpback whales (Megaptera novaeangliae), southern right whales (Eubalaena australis) and sperm whales (Physeter macrocephalus). Using presence only data from multiple sources, we constructed predictive species distribution models (SDMs) consisting of ensembles of seven algorithms for these species during both summer and winter. Predicted distribution for all cetaceans was high in southern Africa and, in particular, within the South African Exclusive Economic Zone (EEZ). Predictive models indicated a more pronounced seasonal variation for humpback, sperm and southern right whales than for Bryde’s whales. Southern right whales occurred closer to shore during winter, humpback whales were more likely to occur along the east coast in winter and the west coast in summer, and sperm whales were more concentrated off the shelf in winter. Our study shows that ensemble models using historical, incidental and scientific data, in conjunction with modern environmental variables, can provide baseline knowledge on important environmental drivers of cetacean distribution for conservation purposes. Results of this study can further be used to help develop marine spatial plans and identify important marine mammal areas.

The Falkland Islands (Malvinas) as sub-Antarctic foraging, migratory and wintering habitat for southern right whales

2019 ◽  
Vol 100 (1) ◽  
pp. 153-163
Author(s):  
Caroline R. Weir ◽  
Andrew Stanworth
Keyword(s):  
Current Knowledge ◽  
Austral Summer ◽  
Falkland Islands ◽  
North East ◽  
The North ◽  
South West ◽  
Right Whales ◽  
Southern Right Whales ◽  
Spatio Temporal ◽  
Feeding Grounds

AbstractThe historical and contemporary presence of southern right whales (SRWs; Eubalaena australis) around the Falkland Islands (Malvinas) has received little recognition. We assessed SRW occurrence in the Falklands via whaling records, a literature review, systematic surveys (boat, aerial and shore-based), and citizen science sightings. The combined data sources indicated a year-round (peaking in austral summer) presence of SRWs in pelagic areas around the Falklands. In contrast, most nearshore records originated in the austral late autumn and winter (May to August), including a marked increase in sightings along the north-east coast during 2017 compared with previous years. The data support spatio-temporal variation in the use of Falklands waters by SRWs. Pelagic waters appear to comprise summer foraging habitat, and may also be used by animals migrating between the Patagonian shelf and feeding grounds located further south and east. The peak numbers observed in nearshore waters occurred earlier in the winter (July) than those on the Argentinean or Brazilian calving grounds (Aug–Oct). Consequently, some whales may have continued migrating northwards to established breeding areas after departing Falklands waters. A component of the south-west Atlantic population could also be using the islands as a novel wintering destination, for mating and/or socializing (no calving has been confirmed to date). The importance of Falklands waters as a multi-use SRW habitat appears to be increasing. The region is important in the context of addressing current knowledge gaps regarding feeding grounds and migratory corridors highlighted in international SRW conservation and management plans for the wider South-west Atlantic.

scholarly journals Identifying key habitat and seasonal patterns of a critically endangered population of killer whales

2013 ◽  
Vol 94 (6) ◽  
pp. 1317-1325 ◽  
Author(s):  
Ruth Esteban ◽  
Philippe Verborgh ◽  
Pauline Gauffier ◽  
Joan Giménez ◽  
Isabel Afán ◽  
...  
Keyword(s):  
Generalized Additive Models ◽  
Bluefin Tuna ◽  
Additive Models ◽  
Killer Whales ◽  
Gulf Of Cadiz ◽  
Strait Of Gibraltar ◽  
Cetacean Species ◽  
Atlantic Bluefin Tuna ◽  
Presence Data ◽  
Gulf Of Cádiz

Killer whales have been described in the Gulf of Cadiz, southern Spain, in spring and in the Strait of Gibraltar in summer. A total of 11,276 cetaceans sightings coming from different sources (dedicated research surveys, whale watching companies and opportunistic observations) were used to create two presence–‘pseudo-absence’ predictive generalized additive models (GAM), where presence data were defined as sightings of killer whales and ‘pseudo-absence’ data as sightings of other cetacean species. One model was created using spring data when killer whales’ main prey, Atlantic bluefin tuna, enter the Mediterranean Sea, and the other model used summer data when Atlantic bluefin tuna return to the Atlantic Ocean. Both model predictions show that killer whales are highly associated with a probable distribution of bluefin tuna during their migration throughout the study area, constraining their distribution to the Gulf of Cadiz in spring and the Strait of Gibraltar in spring and summer. Knowledge of the distribution of killer whales in the study area is essential to establish conservation measures for this population.

Maternal body size and condition determine calf growth rates in southern right whales

2018 ◽  
Vol 592 ◽  
pp. 267-281 ◽  
Author(s):  
F Christiansen ◽  
F Vivier ◽  
C Charlton ◽  
R Ward ◽  
A Amerson ◽  
...  
Keyword(s):  
Body Size ◽  
Growth Rates ◽  
Maternal Body ◽  
Calf Growth ◽  
Right Whales ◽  
Southern Right Whales
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