Landscape fragmentation influences winter body mass of roe deer

Abstract

Body size of large herbivores is a crucial life history variable influencing individual fitness‐related traits. While the importance of this parameter in determining temporal trends in population dynamics is well established, much less information is available on spatial variation in body size at a local infra‐population scale. The relatively recent increase in landscape fragmentation over the last century has lead to substantial spatial heterogeneity in habitat quality across much of the modern agricultural landscape. In this paper, we analyse variation in body mass and size of roe deer inhabiting a heterogeneous agricultural landscape characterised by a variable degree of woodland fragmentation. We predicted that body mass should vary in relation to the degree of access to cultivated meadows and crops providing high quality diet supplements. In support of our prediction, roe deer body mass increased along a gradient of habitat fragmentation, with the heaviest deer occurring in the most open sectors and the lightest in the strict forest environment. These spatial differences were particularly pronounced for juveniles, reaching >3 kg (ca 20% of total body mass) between the two extremes of this gradient, and likely have a marked impact on individual fates. We also found that levels of both nitrogen and phosphorous were higher in deer faecal samples in the more open sectors compared to the forest environment, suggesting that the spatial patterns in body mass could be linked to the availability of high quality feeding habitat provided by the cultivated agricultural plain. Finally, we found that adults in the forest sector were ca 1 kg lighter for a given body size than their counterparts in the more open sectors, suggesting that access to nutrient rich foods allowed deer to accumulate substantial fat reserves, which is unusual for roe deer, with likely knock‐on effects for demographic traits and, hence, population dynamics.

Landscape fragmentation generates spatial variation of diet composition and quality in a generalist herbivore

“…This flexibility may confer nutritional advantages to individuals living in fragmented landscapes when their native food resources become scarce or decrease in quality, such as in non-mast winters and in summer drought. This may constitute a mechanistic explanation for the recent observation that roe deer body mass increases along a gradient of habitat fragmentation in our study site, with the heaviest deer occurring in the most open sectors and the lightest in the strict forest environment (Hewison et al 2009). However, the nutritional benefits of foraging in open habitats may be counterbalanced by higher predation risk when cover is scarce (Benhaiem et al 2008).…”

“…Within populations, individuals may show plastic behaviours in response to landscape heterogeneity in terms of space use (Tufto et al 1996;Lovari and San José 1997;Lamberti et al 2006;Said et al 2009), group size Jepsen and Topping 2004), activity rhythms and diet composition (Barancekova 2004). Furthermore, in agricultural landscapes, both roe deer body mass and faecal indicators of diet quality have been shown to increase along a gradient of forest fragmentation, suggesting that individuals with access to cultivated food resources obtain diets of better nutritional quality than those living in remnant forest (Hewison et al 2009). …”

“…McLoughlin et al 2007;Hewison et al 2009) in response to better access to valuable food resources, but, equally, fragmentation may induce marked local variations in individual performance, with potentially important consequences for the spatiotemporal dynamics of the population. For example, in the Boso peninsula (Japan), where the native forest has been fragmented by agricultural intensification, the reproductive rate of sika deer (Cervus nippon) increased in relation to the length of forest edge available to a given individual (Miyashita et al 2008).…”

Diet quality and immunocompetence influence parasite load of roe deer in a fragmented landscape

“…The human population occurs in small villages and farms connected by an extensive road network. Within this study site, at the scale of a deer's home range, the local landscape structure is spatially variable in terms of the degree of forestation and the type of agricultural activity (see Hewison et al 2001Hewison et al , 2009 for a more detailed description).…”

“…This host species, originally considered forest dwelling, relatively recently expanded its range into modern agricultural landscapes (Hewison et al 2001), thus gaining access to highly nutritious cultivated meadows and crops (Hewison et al 2009). However, previous work has indicated that human disturbance and restriction in home range has resulted in increased parasite load of this Cervidae (Lutz and Kierdorf 1997).…”