Identifying key denning habitat to conserve brown bear (Ursus arctos) in Croatia

CONTEXT: The preservation of denning habitat is paramount to the recovery of threatened bear populations because of the effect that den site disturbance can have on cub mortality. Understanding habitat suitability for denning can allow management efforts to be directed towards the regions where conservation interventions would be most effective. AIM: We sought to identify the environmental and anthropogenic habitat variables associated with the presence of Eurasian brown bear (Ursus arctos) den sites in Croatia. Based on these associations, in order to inform future conservation decisions, we also sought to identify regions of high suitability for denning across Croatia. METHODS: Using the locations of 91 dens inhabited by bears between 1982 and 2011, we opted for the presence-only modelling option in software Maxent to determine the most important predictors of den presence, and thus predict the distribution of high-value denning habitat across Croatia. KEY RESULTS: We found that structural elements were the most important predictors, with ruggedness and elevation both relating positively to den presence. However, distance to nearest settlement was also positively associated with den presence. CONCLUSION: We determine that there is considerable denning habitat value in areas with high and rugged terrain as well as areas with limited human activity. We suspect that high and rugged terrain contains a greater concentration of the karstic formations used for denning than lower-lying regions. IMPLICATIONS: Our study presents the first habitat suitability model for brown bears in Croatia, and identifies core areas suitable for denning both within and outside the species’ current range. As such, it provides useful evidence for conservation decision making and the development of scientifically-based management plans. Our results also support the need for finer spatial scale studies that can reveal specific denning preferences of subpopulations

Land snails Brephulopsis cylindrica and Xeropicta derbentina (Gastropoda: Stylommatophora): case study of invasive species distribution modelling

The terrestrial snails Brephulopsis cylindrica and Xeropicta derbentina are native to steppes of the Northern Black Sea region; X. derbentina has also initially inhabited Eastern Mediterranean, the Caucasus, and Anatolia. However, in last decades the species are increasingly reported outside of their natural range which renders them as likely invasiv

Longitudinal Trends of Bird Community Richness and Abundance over Fifteen Years in the Northern Reaches of the Sonoran Desert

abstract: Although many studies have identified environmental factors as primary drivers of bird richness and abundance, there is still uncertainty about the extent to which climate, topography and vegetation influence richness and abundance patterns seen in local extents of the northern Sonoran Desert. I investigated how bird richness and abundance differed between years and seasons and which environmental variables most influenced the patterns of richness and abundance in the Greater Phoenix Metropolitan Area. I compiled a geodatabase of climate, bioclimatic (interactions between precipitation and temperature), vegetation, soil, and topographical variables that are known to influence both richness and abundance and used 15 years of bird point count survey data from urban and non-urban sites established by Central Arizona–Phoenix Long-Term Ecological Research project to test that relationship. I built generalized linear models (GLM) to elucidate the influence of each environmental variable on richness and abundance values taken from 47 sites. I used principal component analysis (PCA) to reduce 43 environmental variables to 9 synthetic factors influenced by measures of vegetation, climate, topography, and energy. I also used the PCA to identify uncorrelated raw variables and modeled bird richness and abundance with these uncorrelated environmental variables (EV) with GLM. I found that bird richness and abundance were significantly different between seasons, but that richness and winter abundance were not significantly different across years. Bird richness was most influenced by soil characteristics and vegetation while abundance was most influenced by vegetation and climate. Models using EV as independent variables consistently outperformed those models using synthetically produced components from PCA. The results suggest that richness and abundance are both driven by climate and aspects of vegetation that may also be influenced by climate such as total annual precipitation and average temperature of the warmest quarter. Annual oscillations of bird richness and abundance throughout the urban Phoenix area seem to be strongly associated with climate and vegetation.Dissertation/ThesisMasters Thesis Applied Biological Sciences 201

Modeling Species Distribution Using Niche-Based Proxies Derived from Composite Bioclimatic Variables and MODIS NDVI

Abstract: Vegetation mapping based on niche theory has proven useful in understanding the rules governing species assembly at various spatial scales. Remote-sensing derived distribution maps depicting occurrences of target species are frequently based on biophysical and biochemical properties of species. However, environmental conditions, such as climatic variables, also affect spectral signals simultaneously. Further, climatic variables are the major drivers of species distribution at macroscales. Therefore, the objective of this study is to determine if species distribution can be modeled using an indirect link to climate and remote sensing data (MODIS NDVI time series). We used plant occurrence data in the US states of North Carolina and South Carolina and 19 climatic variables to generate floristic and climatic gradients using principal component analysis, then we further modeled the correlations between floristic gradients and NDVI using Partial Least Square regression. We found strong statistical relationship between species distribution and NDVI time series in a region where clear floristic and climatic gradients exist. If this precondition is given, the use of niche-based proxies may be suitable for predictive modeling of species distributions at regional scales. This indirect estimatio

Modeling species distribution using niche-based proxies derived from composite bioclimatic variables and MODIS NDVI

Vegetation mapping based on niche theory has proven useful in understanding the rules governing species assembly at various spatial scales. Remote-sensing derived distribution maps depicting occurrences of target species are frequently based on biophysical and biochemical properties of species. However, environmental conditions, such as climatic variables, also affect spectral signals simultaneously. Further, climatic variables are the major drivers of species distribution at macroscales. Therefore, the objective of this study is to determine if species distribution can be modeled using an indirect link to climate and remote sensing data (MODIS NDVI time series). We used plant occurrence data in the US states of North Carolina and South Carolina and 19 climatic variables to generate floristic and climatic gradients using principal component analysis, then we further modeled the correlations between floristic gradients and NDVI using Partial Least Square regression. We found strong statistical relationship between species distribution and NDVI time series in a region where clear floristic and climatic gradients exist. If this precondition is given, the use of niche-based proxies may be suitable for predictive modeling of species distributions at regional scales. This indirect estimation of vegetation patterns may be a viable alternative to mapping approaches using biochemistry-driven spectral signature of species

The potential overlap in habitat space of caracal (Caracal caracal) and blue duiker (Philantomba monticola) in KwaZulu-Natal, South Africa : an environmental niche modelling approach.

Master of Science in Ecology. University of KwaZulu-Natal, Westville 2016.According to the mesopredator release hypothesis, when apex predators disappear from an ecosystem, the number of mesopredators increase and thus predation of prey species increases. Since the extermination of large predators in KwaZulu-Natal (KZN), South Africa, the caracal (Caracal caracal), a feline mesopredator, is presumed to have spread throughout the province. At the same time, populations of the rare blue duiker (Philantomba monticola), a small forest antelope, have markedly declined; probably due to habitat loss and degradation, yet possibly also by increasing numbers of mesopredators. As forest patches become smaller and more isolated, the blue duiker’s ability to disperse and find refuges becomes limited. Any additional predation threats due to increased probability of encounters between blue duiker and caracal could drive local populations to extinction. However, quantitative data on current broad-scale distribution ranges and habitat requirements of both species are scant. The aim of this study was to use an environmental niche modelling approach to test the hypotheses that the caracal has expanded its distribution range; that its suitable habitat space (i.e. Grinnellian niche) overlaps considerably with that of the blue duiker; and that human impact affects suitable habitat space. I compiled a comprehensive occurrence database for caracal and blue duiker using historical data, recent sightings and survey responses from conservancies and protected areas throughout KZN. I then used niche-based environmental models (Maxent) to map the potential suitable habitat space of caracal and blue duiker, based on the occurrence data and different combinations of environmental and human impact variables. I calculated two niche overlap indices to quantify habitat niche overlap and compared these to 1000 expected overlap indices in a null model to test for niche equivalence. After spatial filtering, my database comprised 94 caracal and 90 blue duiker occurrence points for 1994 to 2013. For both species, vegetation biome, specifically forests, was the most important variable, with rainfall second most important. Approximately two-thirds of KZN was moderate to highly suitable habitat for caracal and one third was moderate to highly suitable habitat for blue duiker. The potential suitable habitat maps matched mostly with published distribution ranges for both species. Nonetheless, occurrence data within comparably lower habitat suitability, suggest caracal may have expanded their range further towards the north east of the province. The niche overlap scores were considerably high (D = 0.683 and I = 0.924), yet the caracal and blue duiker niche models were not identical, which can be expected of a generalist carnivore with a broad niche compared to the narrow niche of a specialist herbivore. At the highest threshold of habitat suitability the overlap between caracal and blue duiker covered 7% of KZN with 20% of the overlap occurring in 70% of the forest biome. The overlap consisted primarily of a large region in the midlands, smaller regions in the south and forest patches throughout KZN. Human impact variables contributed much less to the models than environmental variables and although the negative impact was mostly < 10%, the effect was widespread over ~60% of KZN for both species. My results confirm that the caracal distribution range has expanded historically from the western highlands to the south coast of KZN and thus overlaps considerably with the blue duiker distribution range in the midlands and southern coastal forests. Although the proportion of blue duiker in caracal diet reported in studies elsewhere is low (5% or less), any new threat to a blue duiker population already under pressure from a variety of other threats, could lead to an irrecoverable decline. Thus further studies investigating the effects of the expanding caracal population on the diminishing blue duiker population and other vulnerable prey species are warranted.Consult page 52, Appendix B for the Duiker Identification Chart