Mesocarnivore Community Research Articles

Changes in Mediterranean mesocarnivore communities along urban and ex-urban gradients

Abstract Urbanization causes wildlife habitat loss, fragmentation, and the replacement of specialist species by generalists and/or exotic taxa. Because mesocarnivores are particularly vulnerable to habitat modifications, the rapid expansion of urban areas and the increasing trend for ex-urban development occurring in Mediterranean ecosystems may be major drivers of change in mesocarnivore communities. We combined camera trapping and sign surveys to quantify the richness and relative abundance of a set of wild and domestic mesocarnivores. We quantified these variables controlling for the gradient of urbanism, ex-urbanism, and other environmental variables in patches of natural vegetation in the region of Madrid (central Spain), and a non-urbanized control area ~220 km south of Madrid city. Using conditional autoregressive models (CAR) and model selection procedures, we found that urbanization influenced mesocarnivore community composition but this influence was not detrimental for all the species tested. Generalist carnivores such as the red fox Vulpes vulpes were more abundant in urban and ex-urban areas. Ex-urban development creates overlapping areas between wild and domestic species (such as the domestic cat Felis catus and the wildcat Felis silvestris) but contact between wild and domestic carnivores in natural areas is unlikely. Detection of species in the control area was very low. Therefore, the impact of urbanization in causing changes in mesocarnivore communities may be less than other factors such as illegal predator culling.

Modelling the dispersal of the two main hosts of the raccoon rabies variant in heterogeneous environments with landscape genetics.

Predicting the geographic spread of wildlife epidemics requires knowledge about the movement patterns of disease hosts or vectors. The field of landscape genetics provides valuable approaches to study dispersal indirectly, which in turn may be used to understand patterns of disease spread. Here, we applied landscape genetic analyses and spatially explicit models to identify the potential path of raccoon rabies spread in a mesocarnivore community. We used relatedness estimates derived from microsatellite genotypes of raccoons and striped skunks to investigate their dispersal patterns in a heterogeneous landscape composed predominantly of agricultural, forested and residential areas. Samples were collected in an area covering 22 000 km2 in southern Québec, where the raccoon rabies variant (RRV) was first detected in 2006. Multiple regressions on distance matrices revealed that genetic distance among male raccoons was strictly a function of geographic distance, while dispersal in female raccoons was significantly reduced by the presence of agricultural fields. In skunks, our results suggested that dispersal is increased in edge habitats between fields and forest fragments in both males and females. Resistance modelling allowed us to identify likely dispersal corridors used by these two rabies hosts, which may prove especially helpful for surveillance and control (e.g. oral vaccination) activities.

Tale of two metrics: density and biomass in a desert rodent community

Numerous studies have been made of rodent population and community dynamics, especially in arid ecosystems. Most have centered on understanding how total and species-specific densities of rodents change over time. The standing biomass each species contributes also is important to the energy available to the mesocarnivore community. Although density and standing biomass are related, how they might differ and if those differences are of importance to community structure and function have not received much attention. We analyzed 12 years of rodent density and body mass data from the Chihuahuan Desert in northern Mexico. Data were collected yearly in spring and fall from radial livetrapping webs. Total density and biomass changed significantly in a parallel manner from year to year, and both were related to precipitation and percent cover of grass and forbs. Based on density and biomass, the rodent community was dominated by 2 or 3 principal species. However, on a species-specific level, the numerically dominant species was a small-bodied granivore (Chaetodipus nelsoni), and a large-bodied folivore (Neotoma albigula) dominated in biomass. As total density increased, the proportion contributed by dominant species decreased. As total biomass increased, the proportion in the 2 dominant species increased and accounted for approximately 80% of total biomass. Over the 12 years of the study, species distributions based on density showed no directional change. In contrast, biomass of the rodent community gradually concentrated in a single, large-bodied folivore, N. albigula. Although total density and biomass responded similarly to precipitation and plant productivity, considerable differences between these 2 characteristics existed in their species-specific contributions to and changes within the community. The significance of these differences relative to foraging strategies and variable feeding opportunities within the community is discussed.