Methods and models to analyse the abundance and spatiotemporal relationships of mesocarnivore communities from camera-trapping data

Abstract

Over the past few decades, habitat destruction and anthropogenic factors have modified the structure of ecosystems. Among the species most affected are carnivores, which have faced constant threats from population declines due to the disappearance of their prey or habitat fragmentation. The disappearance of large carnivores has allowed smaller carnivores, or mesocarnivores, to occupy ecological niches abandoned by these large predators. However, this transition has exposed mesocarnivores to new threats, such as non-selective hunting and habitat loss due to human activity. This has generated the need to implement monitoring programs to understand their dynamics of abundance, functions, interactions with other species, and impact on ecosystems. The study of species abundance has been approached from numerous perspectives, such as through habitat suitability models derived from ecological niche models (ENM). While a positive relationship between habitat suitability and abundance is expected, this relationship can be more complex. The information provided by presence/absent data the involvement of biotic factors, dispersal limitations, and other coexistence interactions can affect this positive relationship. Technological and statistical advances have improved the precision in estimating species abundance. Among these, physical counts of individuals, as well as the use of relative abundance indices based on scat or camera trap captures, or individual identification through DNA extraction from scat, which are used to evaluate abundance. However, it is necessary to assess the differences and limitations of each method. The use of one method or another may be limited by the number of sampling sites, the number of captures of each individual, the possibility of individual identification of the species, or the detection probability, among others. Understanding the relationship between the different methods that estimate abundance can identify which method can be used under different scenarios. As a result, obtaining abundance data will be more efficient, and it‘s effect can be seen in various studies related to biotic interactions. Recent studies show the need to incorporate biotic variables, such as the abundance of prey and other coexisted species, to better understand species occupation in a habitat. The abundance of prey plays a crucial role in predator occupation, and competition for this resource can influence species coexistence. Resource partitioning and spatial and temporal segregation are mechanisms to minimize competition and facilitate coexistence. There is a complex interaction between habitat characteristics, prey abundance, interspecific competition, and patterns of activity and occupation in the coexistence of terrestrial carnivore species. These factors are fundamental to understanding the ecology of carnivore communities and can have important implications for biodiversity conservation. The red fox and the stone marten (Martes foina) are two of the most abundant intraguild mesocarnivores in the Community of Madrid. Both species have nocturnal behaviour, share habitats, and have a high trophic overlap, with their main prey being rodents (Apodemus sylvaticus, Mus spp.) and rabbits (Oryctolagus cuniculus). However, some studies have described predation of the stone marten by the red fox, indicating a certain dominance of the fox over the marten. Thus, the study of the coexistence between these two species and the factors driving it is of great interest in areas where large predators are absent.