Human-modified landscapes alter mammal resource and habitat use and trophic structure

Abstract

The broad negative consequences of habitat degradation on biodiversity have been studied, but the complex effects of natural–agricultural landscape matrices remain poorly understood. Here we used stable carbon and nitrogen isotopes to detect changes in mammal resource and habitat use and trophic structure between preserved areas and human-modified landscapes (HMLs) in a biodiversity hot spot in South America. We classified mammals into trophic guilds and compared resource use (in terms of C3- and C4-derived carbon), isotopic niches, and trophic structure across the 2 systems. In HMLs, approximately one-third of individuals fed exclusively on items from the agricultural matrix (C4), while in preserved areas, ∼68% depended on forest remnant resources (C3). Herbivores, omnivores, and carnivores were the guilds that most incorporated C4carbon in HMLs. Frugivores maintained the same resource use between systems (C3resources), while insectivores showed no significant difference. All guilds in HMLs except insectivores presented larger isotopic niches than those in preserved areas. We observed a complex trophic structure in preserved areas, with increasing δ15N values from herbivores to insectivores and carnivores, differing from that in HMLs. This difference is partially explained by species loss and turnover and mainly by the behavioral plasticity of resilient species that use nitrogen-enriched food items. We concluded that the landscape cannot be seen as a habitat/nonhabitat dichotomy because the agricultural landscape matrix in HMLs provides mammal habitat and opportunities for food acquisition. Thus, favorable management of the agricultural matrix and slowing the conversion of forests to agriculture are important for conservation in this region.

Prey choice of the common vampire bat on introduced species in an Atlantic forest land-bridge island

“…To understand if the common vampire bat uses the mainland nearby Anchieta Island to feed on wild animals, we used isotopic values obtained by Magioli et al (2019) on five large-bodied mammals [white-lipped peccary ( Tayassu pecari ), collared peccary ( Pecari tajacu ), deer ( Mazama sp. ), lowland tapir ( Tapirus terrestris ) and capybara] from a protected area of the mainland (Núcleo Santa Virgínia, an administrative division of the Serra do Mar State Park).…”

“…To obtain information on resource use of common vampire bats, we adapted the analytical approach used by Magioli et al (2014, 2019). The analysis consists of using a simple mixed model that interpolates the stable carbon isotopic values of samples, accounting for specific fractionation factors, with the mean values of the different vegetation types (C 3 and C 4 plant photosynthetic cycles), while also considering the minimum and maximum values obtained for all animal samples analyzed.…”

A methodological roadmap to quantify animal-vectored spatial ecosystem subsidies

“…population density, infrastructure and agricultural areas) that vary in permeability. Human modification of landscapes, such as urban development of roads or C4 plant monocultures for agriculture, can alter diet and nutrient transfer by animals (Magioli et al 2019). For example, Roe deer (Capreolus capreolus) in central France routinely act as vectors for large quantities of artificially-introduced nitrogen, which they obtain by foraging in agricultural areas, which are deposited near resting sites in forested areas (Abbas et al 2012).…”

Opportunities for prioritizing and expanding conservation enterprise in India using a guild of carnivores as flagships

“…Brito et al 2013). Even cultivated agricultural lands support many large mammalian species that persist in transformed food webs and systems (Magioli et al 2019). Such multi-use areas rarely figure in global priority locations for conservation (Jenkins et al 2013), whilst being lost at an alarming rate or rapidly transitioning into unsustainable use (Dobrovolski et al 2013).…”