Edge effects on small mammals: Differences between arboreal and ground‐dwelling species living near roads in Brazilian fragmented landscapes

Abstract

Habitat fragmentation often induces edge effects that can increase, decrease or have minimal effect upon the population density of a species, depending upon environmental conditions and the requirements of the species. Using a trapping study and generalized linear mixed models, we evaluated edge effects on small tropical mammals living near roads, including two ground-dwelling (Akodon sp. and Cerradomys subflavus) and two arboreal (Marmosops incanus and Rhipidomys sp.) species. We examined the relationship of these edge effects to environmental factors at both plot and patch scales. Generalist ground-dwelling species were attracted to edges, with higher population densities recorded in habitats close to road or matrix edges where vegetation density was lower. In contrast, populations of the generalist arboreal species avoided edge habitats, their populations were found in greater density in habitats far from roads/matrix edges. Thus, our results show that patterns of edge habitat utilization were related to the ecological requirements of each species. These findings are especially important in the tropics, where demand for economic growth in many countries has accelerated the fragmentation process and has recently culminated in increased road construction and expansion. Fragmented habitats promote an increase in edge environments, and consequently will reduce the abundance of arboreal small mammal species, such as those used as models in this study.

Effects of habitat edges on vegetation structure and the vulnerable golden-brown mouse lemur (Microcebus ravelobensis) in northwestern Madagascar

“…For example, interior trees had a greater dbh (defined as diameter at breast height) than edge trees in a fragmented rainforest in Costa Rica [5]. Similar results were reported in Brazilian fragmented landscapes, with the basal area of trees being lower in proximity to the edge [6]. In contrast, the density of some woody species was higher near the edge in Morogoro Region, Tanzania [7].…”

“…No spatial variations in edge-related abundance were observed in some Neotropical primate species [5,11]. However, edge responses of mammals are not always stable across landscapes [6], an insight which resulted from a long-term fragmentation study in the Amazon region and was incorporated in the "landscape-divergence-hypothesis" [14]. This hypothesis states that as a consequence of high local landscape and weather dynamics, sites from different landscapes will diverge more over time (in species composition and possibly ecosystem functioning) than sites from the same landscape.…”

“…For example, some mammals species, such as primates and some rodents, had higher abundance metrics in habitat edges compared to interior forest habitats [6,11]. In contrast, some marsupial, bird or other rodent species showed higher population densities far away from edges [6,12,13]. No spatial variations in edge-related abundance were observed in some Neotropical primate species [5,11].…”

“…Positive, neutral, and negative edge responses have also been reported for various vertebrate taxa. For example, some mammals species, such as primates and some rodents, had higher abundance metrics in habitat edges compared to interior forest habitats [6,11]. In contrast, some marsupial, bird or other rodent species showed higher population densities far away from edges [6,12,13].…”

Short recce transects or camera trap surveys—Short recce surveys highlighted as a useful supplement for rapid biodiversity assessments in the Republic of the Congo

“…Mining areas are often located near protected areas (PAs) (Durán et al, 2013) or within intact landscapes (Kobayashi et al, 2014; Plumptre et al, 2019), which can concentrate effects in or near areas of high conservation value and may detract from their goals (World Bank, 2019a, 2019b). Where such development occurs, landscapes are subject to fragmentation (da Rosa et al, 2018; Rabanal et al, 2010) and degradation (Munguia‐Rosas et al, 2014; World Bank, 2019b). Fragmentation due to development is perhaps the greatest threat to natural systems (da Rosa et al, 2018; Guo et al, 2018; Plumptre et al, 2019) in Africa (Attua et al, 2018; Laurance et al, 2006), a situation made worse by weak governance (Salum et al, 2018).…”