Return of an apex predator to a suburban preserve triggers a rapid trophic cascade

Abstract

Absence of apex predators simplifies food chains, leading to trophic degradation of ecosystems and diminution of the services they provide1. However, most predators do not coexist well with humans, which has resulted in a decline of carnivores and functional ecosystems worldwide2. In some instances, cryptic carnivores manage to survive amidst human settlements, finding refuge in small biological islands surrounded by urban landscapes. In such a system, we used two non-invasive data collection methods (camera trapping and fecal sampling) to investigate the multiannual relationship between predators and prey, and between competitors, through analysis of: (1) relative abundance and detection probability of species over time, (2) causal interactions via empirical dynamic modeling, (3) diet, and (4) diel activity patterns. All approaches show concordance in the results: the natural return of an apex predator, the puma (Puma concolor), triggered a trophic cascade, affecting the abundance and behavior of its main prey, subordinate predators and other prey in the studied system. Our study demonstrates that trophic recovery can occur rapidly following the return of a top predator, even in small protected areas in increasingly urbanized landscapes.

A comparison of eDNA to camera trapping for assessment of terrestrial mammal diversity

“…Our study was conducted at the Jasper Ridge Biological Preserve (JRBP), California, USA, where we took advantage of a long-term camera-trapping effort initiated in 2009. As of October 2017, the date of soil sampling, 18 wireless camera traps were installed, mostly along trails, to monitor wildlife (see Leempoel et al [23]). Out of these, we selected six cameras in contrasting habitats (i.e.…”

Molecular Ecological Network Analyses: An Effective Conservation Tool for the Assessment of Biodiversity, Trophic Interactions, and Community Structure

“…A long-term camera-trapping effort (2009-2018) at JRBP elucidated dynamic shifts within the predator and herbivore populations, triggered when an apex predator, the puma, became resident after at least a decade of very low abundance (Leempoel et al, 2019). The (re)establishment of the puma coincides with a change in coyote behavior and abundance, which in turn, opened a niche for the smaller, omnivorous gray fox.…”

“…Sampling transects were non-random and predator scat was collected along 34 paths (trails 17 km; roads 7 km) throughout JRBP (Supplementary Figure S1). Camera trapping demonstrates that predators use these pathways at a high frequency (Kohn et al, 1999;Leempoel et al, 2019). During collection, onehalf of the scat sample was left in situ to ensure that the relevant inter-and intra-species scent cues were not disturbed.…”

“…(B) The colors in the scaled network represent the four different modular communities detected within the JRBP community and the icon represents the key species within each module. mephitis) (Figure 4; Leempoel et al, 2019Leempoel et al, , 2020. However, one misidentified skunk scat sample was sequenced, which we included in the biodiversity assessment.…”

“…We captured the same hierarchical patterns through network motifs as the long-term camera trap study, where the natural reoccurrence of puma to JRBP triggered a top-down effect on mesopredators and herbivores (Leempoel et al, 2019). Network motifs are the basic building blocks of communities and can be identified as overrepresented patterns throughout the network.…”