Protected areas (PAs) networks are a pivotal tool to fight biodiversity loss, yet they often need to balance the mission of nature conservation with the socio-economic need of giving opportunity for outdoor recreation. Recreation in natural areas is important for human health in an urbanised society, but can prompt behavioural modifications in wild animals. Rarely, however, have these responses being studied across multiple PAs and using standardized methods. We deployed a systematic camera trapping protocol at over 200 sites to sample medium and large mammals in four PAs within the European Natura 2000 network to assess their spatio-temporal responses to human frequentation, proximity to towns, amount of open habitat, and topographical variables. By applying multi-species and single-species models on the number of diurnal, crepuscular, and nocturnal detections, and a multi-species model on nocturnality index, we estimated both species-specific and meta-community level effects, finding that increased nocturnality appeared the main strategy that the mammal meta-community used to cope with human disturbance. However, responses in the diurnal, crepuscular, and nocturnal site use were mediated by species’ body mass, with larger species exhibiting avoidance of humans and smaller species more opportunistic behaviours. Our results show the effectiveness of standardised sampling and provide insights for planning the expansion of PA networks as foreseen by the Kunming-Montreal biodiversity agreement.

In 2020 we surveyed one national park and three regional protected areas in northern and central Italy. The study areas (Figure 1) include: (1) Parco Naturale Adamello Brenta (Area 1; 46° 6' N, 10° 56' E), a regional protected area of 620 km² in the central Italian Alps, with highest elevation of 3558 m a. s. l., surveyed between the first day of June and the last of August. One third of Area 1 is covered by forest, dominated by broadleaved species at lower elevation, which are gradually replaced by conifers from 1000 to 2000 m a.s.l. Above the tree line the landscape is characterized by extensive grasslands and pastures, which precede steep slopes and cliffs of dolomite rocks. (2) Parco Naturale Paneveggio Pale di San Martino (Area 2; 46° 12' N, 11° 48' E), a regional protected area of 197 km² in the eastern Italian Alps, with the highest peak at 3192 m a.s.l, surveyed between early September and late November. This area is characterized by a vast coniferous forest, bordering a high and rocky dolomitic massif. (3) Parco Regionale Naturale delle Alpi Apuane (Area 3; 44° 4' N, 10° 15' E), located in the northern part of Apennines mountain range, central Italy, with the highest elevation of 1946 m a.s.l., and surveyed from June to November. This mountainous area of 206 km² is detached from the main Apennines ridge and neighbours the Ligurian Sea coast. Area 3 has a typical alpine-like environment, with widespread cliffs and peaks composed of limestone and white marble rocks, whose extraction involves many quarries intercluded and surrounding the protected area. Vegetation is mainly represented by broadleaved woods followed by grasslands above the tree line. (4) Parco Nazionale Foreste Casentinesi (Area 4; 44° 4' N, 10° 15' E), a National Park of 368 km² located in the centre-northern Apennines and established in 1993, with the highest peak reaching 1658 m a.s.l. The park was surveyed between early September and late November. The area is characterized by dense forests, in particular ancient fir forests, beech woods, and mixed forests, as well as a sub-montane vegetation area dominated by oak forests and chestnut groves, and pastures at higher elevations. All four areas are popular tourist destinations for outdoor recreation and have extensive networks of forestry roads, hiking and biking trails, and numerous touristic facilities. In areas 1 and 2 forestry roads are accessible by car only for residents, hunters and forestry personnel, and in area 3 access to forestry roads leading to quarry sites is forbidden . Finally, in area 4 their use by vehicles is restricted to forestry personnel and, upon authorization, to researchers for scientific purposes. In all areas mushroom collection is strictly regulated, and in areas 1 and 2 visitors are not allowed to leave the trails within the core areas of the park. In area 3 there are 11 integral protection zones established to protect particularly relevant ecological and geomorphological features, where all human activities, other than walking along official trails, are forbidden. Area 4 has inside 7 state natural reserves with increasing protection levels. Of these latter, the Integral Nature Reserve “Sasso Fratino”, which is a strictly protected biogenetic area and part of the UNESCO World Heritage, forms the core of the PA, where human access is limited to research and scientific activities only. 

Data collection

The sampling design applied in the four areas has been used in Area 1 since 2015 and is adapted from the Tropical Ecology Assessment and Monitoring Network, a pan-tropical biodiversity monitoring programme. Differences with the TEAM Network protocol include a larger spacing between camera locations to maximize the overall area monitored and to account for the larger home range size of the mammals of temperate forests compared to species in tropical rainforests. We designed a regular grid with side of cells of 2/3 km and placed one camera-trap site per cell, evenly spaced and positioned to cover the whole altitudinal gradient (Figure 1). In areas 1, 2, and 4 the number of sampling sites was 60, and 44 in Area 3, due to the smaller spatial extent of this study area. Camera traps were located in the field as close as possible to the centroid of the cells,  based on accessibility and on the presence of a trail or forestry road. Cameras were installed on trees at about 60 cm above the ground and at a distance of 3-5 meters from the target trail or road. For all areas, baits were not used, and cameras stayed active in the field for a minimum of 30 consecutive days. For this study, we used heat-in-motion triggered cameras of different brands: Reconyx (Holmen, WI, USA), Browning (Birmingham, AL, USA;), UWAY Outdoor Products (Norcross, GA, USA), Bushnell Outdoor Products (Overland Park, KA, USA), Boly Inc. (Santa Clara, CA, USA) and Apeman (Shenzhen, China). The pictures collected were classified at the species level by the authors through the software Wild.ID. The only exception refers to the sympatric species Martes foina and Martes martes, which were classified at the genus level only, due to the impossibility to distinguish them with certainty from camera trap detections. Since the sampling sites were positioned on trails and roads, our inference is generally related to wild mammals’ and humans’ use of these features only, and not of the whole study area (see Discussion). For the present study, trail-based sampling was necessary to monitor both wildlife and human site use, and thus to evaluate the potential consequences of human passage on wild mammals.

All data have been created through R programming environment.