Information regarding the status and distribution of species is crucial for an effective management and conservation of biodiversity, from local to global scales. Despite being included in the Mediterranean biodiversity hotspot, Portugal lacks a detailed assessment of the distribution patterns of mammalian carnivores, which are important both ecologically and economically. Moreover, the available information is scattered, often unreliable and biased towards some species or regions.
The goals of this study were: i) to compile historical and current distribution data and evaluate the research trends on all species of mammalian carnivores in Portugal; ii) to determine the potential distribution of each species, using species distribution models based on the currently available records, and identify variables associated with their presence; and iii) to produce a detailed account of each carnivore species occurring since historical times in Portugal, as a baseline for a future distribution atlas.
On a first approach, a comprehensive review of 755 scientific studies was conducted to analyse several publication metrics (e.g. year of publication, publication type and research topic). 20,189 presence records of all mammalian terrestrial carnivores occurring in Portugal since historical times were also compiled, to evaluate their distribution patterns, including Extent of Occurrence, Area of Occupancy and range trends.
Carnivore research in Portugal began in the 18th century, with a boost in the mid-1990s, and has been biased towards regionally threatened species and mainly focused on the topics of General Ecology and Conservation. There are fifteen extant species in Portugal, with nine occurring across the country (>85% of the mainland area) and six showing a relatively limited range (<40%), while an additional species is currently extinct (Ursus arctos). During the last decades, the distribution ranges of seven species seem to have remained stable, two expanded, two contracted, and three showed unclear trends. The historical presence of the Eurasian Lynx (Lynx lynx) in the north of Portugal was hypothesised, based on historical records, and the confirmed presence of a new invasive carnivore in Portugal, the raccoon (Procyon lotor), is documented here for the first time.
On a second chapter, the compiled presence data were used to produce predictive ensemble models of the distribution of all extant carnivore species in Portugal (except for the racoon, due to low sample size), and several criteria of variable selection were used to determine which predictor variables were most strongly related to species occurrences. As expected, the best-surveyed carnivore species produced the best performing models. For all species, at least one environmental variable was selected, and for nine species, also human-related variables emerged, mostly showing a negative relationship between species and human presence or activity. For several species known to occur throughout the country, a higher potential for occurrence was found in the north, suggesting better general conditions in this region. Furthermore, a possible connection was found between reduced consensus between model predictions and the latest range limits of expanding species.
Finally, all the information collected was gathered and presented in a detailed account for each carnivore species with a summary of the general distributional context, bibliometric analysis, presence records and distribution patterns. The species of some conservation concern, either by being threatened, nationally or internationally or by currently undergoing an expansion process, are the ones for which there was generally more data and a better knowledge. Other common and widespread species with no pressing conservation concerns, along with Data Deficient and Extinct species, had the least available data. Concerning the records compiled, non-genetically validated presence signs constituted the majority of records, and most records were collected inside protected areas, stressing the need for collecting more reliable records (either by validating them genetically or using other methodologies) and for reducing survey bias.
This study demonstrates the relevance of non-systematic data to assess the historical and current status of mammalian terrestrial carnivores in Portugal, allowing the identification of knowledge gaps and research priorities. It is the first study on Species Distribution Modelling addressing all carnivore species in Portugal, by using a large number of occurrence data for modelling purposes. Furthermore, it allows a preliminary assessment of the factors associated with each carnivore species, particularly those for which there were no previous studies on ecological modelling. The results of this work will serve as a baseline to produce a future Atlas of Portuguese Carnivores. This information will contribute to updating assessments of species presence and distribution at the level of Iberian Peninsula, Europe and the Mediterranean biodiversity hotspot, with important conservation and management implications.