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- Biotic interactions as structuring factors of mesocarnivore communities in human-altered landscapesPublication . Barros, Ana Luisa; Reis, Margarida Santos; MacKenzie, DarrylThe conversion of natural landscapes for agricultural purposes is a main driver of biodiversity loss worldwide, but in Europe many of these agroecosystems still maintain a high species richness. Low-intensity farming systems are mostly preserved in the Mediterranean region creating a mosaic of natural and cultural landscapes. Mammalian carnivores assume complex regulatory roles on ecosystems as top predators. In Europe, mostly mesocarnivores persist as many species thrive in humanized landscapes and in the absence of large carnivores. The taxonomic and ecological diversity of this group leads to species-specific responses to human disturbance and sub-lethal interactions between similar-sized species are thought to shape mesocarnivore community structure. In this thesis, I investigated the species and community ecology of a mesocarnivore guild in human-altered landscapes. The reliance on extensive camera-trapping datasets led me to first examine recent technological and methodological developments for camera traps, providing evidence on their performance and cost-benefit for carnivore research. I then assessed the species-specific response to agroforestry practices and demonstrated the conservation value of sustainable and dynamic management in these systems. To determine the potential for interspecific interactions, I explored the mechanisms of coexistence through niche segregation at multiple dimensions and different scales. Empirical evidence of spatial association seems to support similar habitat preferences between species and could also be a consequence of the largely generalist requirements of this carnivore guild. Nonetheless, fine adjustments in trophic resource use and temporal activity somewhat explained mesocarnivore coexistence. Lastly, I assessed the geographical variation in mesocarnivore community structure by addressing assumptions of conservation-surrogacy and ecological regulation from large carnivores. Across Europe’s humanized landscapes, the environmental and anthropogenic context structures the mesocarnivore communities, as the occurrence of low-density wolf populations weakens spatial signatures of top-down effects. The research from this thesis contributes to mesocarnivore community ecology in human-altered landscapes and supports the capacity of predator species to coexist with human presence and potential competitors.
- Comparing the performance of two camera trap-based methods to survey small mustelidsPublication . Barros, Ana Luisa; Marques, Margarida; Alcobia, Sandra; MacKenzie, Darryl I.; Santos-Reis, MargaridaSmall mustelids are an understudied group partly due to the challenges in detecting and monitoring their populations. Despite the classification as Least Concern for several small mustelid species, some studies indicate a population decline in parts of their range. Therefore, efficient and group-specific methods are essential to support monitoring efforts. Camera traps are widely used, particularly to monitor cryptic and nocturnal species such as most carnivores. However, they tend to miss small-sized and fast-moving species due to the sensitivity of the passive infrared sensor. The Mostela is a device which consists of a camera trap and a tracking tunnel inside a wooden box, designed specifically to detect small mustelids. Here, we propose testing the performance of this device and comparing it to a tree-mounted camera trap, using the least weasel (M. nivalis) as a case study. We used multi-scale occupancy models to estimate differences in the detection probability between devices. Although both methods detected the least weasel, the detection probability was higher with the Mostela (0.8, BCI: 0.52–0.97 vs 0.2, BCI: 0.03–0.48). Furthermore, we obtained a higher trapping rate when using a shorter distance between sampling stations (∼350 m). Although the Mostela performed better at detecting the weasel, the number of independent events was low (N = 11). Therefore, we present recommendations in terms of deployment and future research since the development and testing of new methods are essential for the conservation efforts of small mustelids.
- Do Mesocarnivores Respond to the Seasonality in Management Practices in an Agroforestry Landscape?Publication . Barros, Ana Luisa; Raposo, Diogo; Almeida, João David; Alcobia, Sandra; Oliveira, Maria Alexandra; MacKenzie, Darryl I.; Santos-Reis, MargaridaIn the Mediterranean, we find a mosaic of natural and cultural landscapes, where a variety of forest management practices created intermediate disturbance regimes that potentially increased biodiversity values. Nonetheless, it is essential to understand the species’ long-term response to the dynamic management in agroecosystems, since the species tolerance to disturbance can change throughout the life cycle. Mammalian carnivores can be sensitive to human disturbance and are an essential part of ecosystems due to their regulatory and community structuring effects. We investigated the spatial response of five mesocarnivores species to spatially- and temporally- varying management practices in an agroforestry landscape. More specifically, we assessed the mesocarnivores’ temporal changes in space use by implementing multi-season occupancy models in a Bayesian framework, using seasonal camera-trapping surveys for a 2-year period. All species had a weak response of local extinction to forestry management and livestock grazing pressure. For forest-dwelling species, occupancy was higher where productivity of perennial vegetation was high, while colonization between seasons was positively associated with vegetation cover. For habitat generalist species, we found that occupancy in the wet season increased with the distance to cattle exclusion plots. Most of these plots are pine stands which are subject to forestry interventions during winter. During the 2-year period we found seasonal fluctuations in occupancy for all species, with an overall slight decrease for three mesocarnivore species, while for the two forest-dwelling species there was an increase in occupancy between years. The weak species response to management practices supports the importance of traditional management for upholding a diverse mesocarnivore community in agroforestry systems but could also reflect these species’ ecological plasticity and resilience to disturbance.
- Assessment of technological developments for camera‐traps: a wireless transmission system and solar panelsPublication . Barros, Ana Luisa; Alcobia, Sandra; Gonçalves, Paula Isabel; MacKenzie, Darryl I.; Santos-Reis, MargaridaCamera-trapping is considered a cost-efficient method to monitor wildlife, but relevant performance constraints remain. We assessed performance and cost-benefit for 2 recent technological innovations: (i) a wireless transmission system where cameras communicate in a network, and (ii) using solar panels as a camera's sole power supply. The maximum distance between cameras that ensured wireless connection varied between 2 km in open habitats and 335 m in forest habitats with dense tree cover. The cost of using the wireless transmission system was lower for surveys run for >45 days and for >15 sampling units (i.e., camera-trap sites). For surveys longer than 15 days, using the wireless transmission system required, on average, 8 fewer days of fieldwork. We measured the performance of the solar panels in terms of capture probability, and the solar-powered cameras (β = −0.015 ± 0.01 in the log scale) outperformed battery-powered cameras (β = −0.103 ± 0.005) as capture rate decreased more slowly, particularly for nighttime events (difference in capture probability of the solar-powered relative to the battery-powered cameras at night, β = 0.09 ± 0.01). We consider that, although camera-traps with wireless transmission can provide a return on investment for a wide range of survey designs, the constraints on maximum distance for transmission are a limitation. Despite the higher cost, we recommend solar-powered camera-traps as they had improved performance with a higher proportion of species events captured than by battery-powered cameras.
- An integrated assessment of niche partitioning reveals mechanisms of coexistence between mesocarnivoresPublication . Barros, Ana Luisa; Raposo, Diogo; Almeida, João David; Jesus, Hugo; Oliveira, Maria Alexandra; FERNANDES, CARLOS; MacKenzie, Darryl I.; Santos-Reis, MargaridaSpecies diversity depends on the capacity of species to coexist, and when these share similar ecological requirements some degree of partitioning of the ecological niche is expected. Within the order Carnivora, direct and indirect interspecific interactions shape community structure and composition. Although strong negative interactions (e.g., interspecific killing) are expected between large carnivores and subordinate species, mesocarnivores that dominate most human disturbed landscapes can still strongly compete for resources given their similar body size and energy requirements. To identify the mechanisms of coexistence between mesocarnivore species in a Mediterranean landscape we assessed the ecological niche overlap between five species (Vulpes vulpes, Meles meles, Martes foina, Herpestes ichneumon, Genetta genetta), by simultaneously measuring the space, time, and trophic resource use. The multi-species occupancy model fit to camera-trapping data revealed spatial co-occurrence between most species’ pairs and an avoidance pattern between only stone marten and Eurasian badger (78 % probability of a negative effect). Using genetically identified scats, we assessed trophic niche breadth and overlap. Niche breadth was narrow for red fox, Eurasian badger, and stone marten, given these species consumed almost exclusively fruits and arthropods, and so trophic niche overlap was high. For the genet and the mongoose, the consumption of different food resources (e.g., mammals, birds, and reptiles) increased niche breadth and decreased the niche overlap with the other sympatric species. Finally, niche segregation was more significant along the temporal axis, since the mongoose has a diurnal activity pattern and the remaining carnivore species, although mostly nocturnal, had small asynchronies in the activity peaks which could decrease the chance of direct encounters. Therefore, our results suggest that similar habitat preferences and ecological requirements rather than interspecific competition shape the mesocarnivores’ resource use in this landscape. Nonetheless, fine-scale temporal segregation seems the main mechanism to facilitate coexistence, together with small differences in trophic resource use, especially for species with high spatial and temporal overlap.