Interaction of food resources and landscape structure in determining the probability of patch use by carnivores in fragmented landscapes

Abstract

Studies on the distribution of mammalian carnivores in fragmented landscapes have focused mainly on structural aspects such as patch and landscape features; similarly, habitat connectivity is usually associated with landscape structure. The influence of food resources on carnivore patch use and the important effect on habitat connectivity have been overlooked. The aim of this study is to evaluate the relative importance of food resources on patch use patterns and to test if food availability can overcome structural constraints on patch use. We carried out a patch-use survey of two carnivores: the beech marten (Martes foina) and the badger (Meles meles) in a sample of 39 woodland patches in a fragmented landscape in central Italy. We used the logistic model to investigate the relative effects on carnivore distribution of patch, patch neighbourhood and landscape scale variables as well as the relative abundance of food resources. Our results show how carnivore movements in fragmented landscapes are determined not only by patch/landscape structure but also by the relative abundance of food resources. The important take-home message of our research is that, within certain structural limits (e.g. within certain limits of patch isolation), by modifying the relative amount of resources and their distribution, it is possible to increase suitability in smaller/relatively isolated patches. Conversely, however, there are certain thresholds above which an increase in resources will not achieve high probability of presence. Our findings have important and generalizable consequences for highly fragmented landscapes in areas where it may not be possible to increase patch sizes and/or reduce isolation so, for instance, forest regimes that will increase resource availability could be implemented

Do well-connected landscapes promote road-related mortality?

“…Their avoidance of open areas is well documented (Rondinini and Boitani 2002;Virgós and García 2002;Goszczyński et al 2007;Mortelliti and Boitani 2008), but how far they will move across open areas is not well understood. Additionally, riparian areas within open areas appear to be of little importance as potential corridors in promoting connectivity among the montado patches.…”

“…Nevertheless, despite the well-documented cumulative effects of landscape change and road mortality on biodiversity conservation, their effects often are evaluated independently. Landscape connectivity assessments generally take into account the amount and spatial arrangement of suitable habitat patches, but often exclude anthropogenic features (Mortelliti and Boitani 2008). Similarly, the effects of roads may be evaluated using mortality risk or road permeability, but often lack a landscape context (Ramp et al 2005).…”

“…Sunquist and Sunquist (2001), Crooks (2002), andMcRae et al (2005) have shown that some endangered mammalian carnivores are particularly vulnerable to habitat fragmentation and road network expansion and are facing threats of local extinction in some regions (Ferreras 2001;Naves et al 2003). Although the stone marten is currently a widespread and common carnivore, recent research documented that they are particularly sensitive to forest fragmentation in cork oak woodlands, hereafter called montado (Virgós and García 2002;Santos-Reis et al 2004;Mortelliti and Boitani 2008), and are vulnerable to traffic (Grilo et al 2009). They are the second most frequently killed carnivore on roads in Portugal during the period when females are provisioning young (Grilo et al 2009).…”

Differential response of a carnivore community to predator control: a spatio-temporal observational study

“…Despite these clear differences, recovery rates are not solely dependent upon species biology. In addition to intrinsic growth rates and immigration, the composition and physiognomy of the various components of the landscape explain the differential response of carnivores to the use of vacated plots (Bender et al 2003;Mortelliti & Boitani 2008) and recovery time (Fleishman et al 2002). Most landscapes are complex mosaics of many kinds of habitat, some of which meet the ecological requirements to ensure the fitness of the species, whilst the most inhospitable take longer to be occupied (Hanski 2009).…”

The role of habitat quality in fragmented landscapes: a conceptual overview and prospectus for future research

“…An important role of ''patch quality'' as determinant of occupancy patterns has been shown for plants (Adriaens et al 2009), butterflies (Thomas et al 2001;Fleishman et al 2002), moths (Summerville and Crist 2004), other insects (Wettstein and Schmid 1999;Heisswolf et al 2009), amphibians (Marsh and Trenham 2001) birds (Verboom et al 1991;Lloyd 2008), small mammals (Holland and Bennett 2007), primates (Arroyo-Rodriguez and Mandujano 2006), and carnivores (Virgos 2001;Mortelliti and Boitani 2008). Several authors have made a plea for the incorporation of habitat quality in metapopulation models (Thomas et al 2001;Armstrong 2005), and the importance of habitat quality has been recognized by theoretical studies that have investigated the usefulness of including patch quality in metapopulation models (Moilanen and Hanski 1998;DeWoody et al 2005) and in connectivity metrics (Visconti and Elkin 2009).…”