تاثیر وفور طعمه در اشغال زیستگاه توسط جگوارها
Abstract
1- Introduction
2- Materials and methods
3- Results
4- Discussion
References
Abstract
The jaguar (Panthera onca) is widely distributed across a broad range of habitat types, where its feeding habits and habitat use patterns vary significantly. The jaguar and its main arboreal prey – the brown-throated sloth (Bradypus variegatus) and the red howler monkey (Alouatta juara) – are widespread in the Amazonian floodplain forests of the Mamirauá Reserve. These forest-dwelling species are the most common mammal species both in the continuous forest and the forest patches surrounded by a river matrix – the fluvial islands – of the Solimões and Japurá rivers. We used sign surveys along line-transects to assess the pattern of habitat occupancy by jaguars in Amazonian floodplain forests. Specifically, we (i) tested whether habitat occupancy by jaguars differs between river islands and continuous forest; and (ii) evaluated whether and how the local abundance of sloths and howler monkeys influence the probability of site occupancy by jaguars. We built an occupancy model and used Bayesian inference to reach these goals. The proportion of sites estimated to be used by jaguars was ψ = 0.75 (HPD95: 0.36–1.00), and it did not differ between islands and continuous forest. The abundance of both prey species had a direct influence on jaguar's habitat use, whereas the aquatic matrix seems to have a negligible effect on the use of islands by jaguars. We conclude that the isolation of the river islands within the aquatic matrix does not hamper jaguars to use them. We also conclude that prey search modulates jaguars' habitat occupancy patterns with both prey species having a similar effect. This finding is compatible with the previously reported importance of sloths to the diet of jaguars in the study region despite its lower abundance than howlers. Finally, we suggest that sign surveys are an alternative method to assess the pattern of jaguar habitat occupancy in floodplain forests.
Introduction
Predation is a remarkable interspecific interaction that has long interested ecologists (Gause et al., 1936). Large carnivores are prominent top predators that prevent prey populations to overcrowd and deplete their food sources, and whose demise can initiate substantial cascading ecological effects in the food chain that compromise ecosystem structure and functioning (Ripple et al., 2014). Therefore, assessments of carnivore distribution and population size are essential for developing informed conservation actions for these species and their ecosystems. Jaguars (Panthera onca) are the largest American felids. They are widely distributed across a broad range of habitat types (Sanderson et al., 2002), where their feeding habits and habitat use patterns vary significantly (Astete et al., 2007; Morato et al., 2016). They are opportunistic predators that exploit most of their medium to large terrestrial prey species (González and Miller, 2002) according to their availability (Rabinowitz and Nottingham, 1986). The species is often range resident and move over long daily distances (2.3–16.4 km) in highly variable home ranges (8.8–718.6 km2 ; Morato et al., 2016). Jaguars’ predominant terrestriality does not preclude them from occurring in Amazonian seasonally flooded forests (herein várzea forests). This is the case at the Mamirauá Sustainable Development Reserve – a protected area of várzea forests in Central Amazon – where jaguars reach high densities probably because of high prey abundance (Ramalho, 2012).