Numerical response of a mammalian specialist predator to multiple prey dynamics in Mediterranean farmlands

Abstract

The study of rodent population cycles has greatly contributed, both theoretically and empirically, to our understanding of the circumstances under which predator–prey interactions destabilize populations. According to the specialist predator hypothesis, reciprocal interactions between voles and small predators that specialize on voles, such as weasels, can cause multiannual cycles. A fundamental feature of classical weasel–vole models is a long time‐lag in the numerical response of the predator to variations in prey abundance: weasel abundance increases with that of voles and peaks approximately 1 yr later. We investigated the numerical response of the common weasel (Mustela nivalis) to fluctuating abundances of common voles (Microtus arvalis) in recently colonized agrosteppes of Castilla‐y‐Léon, northwestern Spain, at the southern limit of the species’ range. Populations of both weasels and voles exhibited multiannual cycles with a 3‐yr period. Weasels responded quickly and numerically to changes in common‐vole abundance, with a time lag between prey and weasel abundance that did not exceed 4 months and occurred during the breeding season, reflecting the quick conversion of prey into predator offspring and/or immigration to sites with high vole populations. We found no evidence of a sustained, high weasel abundance following vole abundance peaks. Weasel population growth rates showed spatial synchrony across study sites approximately 60 km apart. Weasel dynamics were more synchronized with that of common voles than with other prey species (mice or shrews). However, asynchrony within, as well as among sites, in the abundance of voles and alternative prey suggests that weasel mobility could allow them to avoid starvation during low‐vole phases, precluding the emergence of prolonged time lag in the numerical response to voles. Our observations are inconsistent with the specialist predator hypothesis as currently formulated, and suggest that weasels might follow rather than cause the vole cycles in northwestern Spain. The reliance of a specialized predator on a functional group of prey such as small rodents does not necessarily lead to a long delay in the numerical response by the predator, depending on the spatial and interspecific synchrony in prey dynamics.

Patterns of Flea Infestation in Rodents and Insectivores From Intensified Agro-ecosystems, Nw Spain

“…In the studied habitats, the bulk (> 95%) of the small mammal community includes three rodents and one insectivore: common voles (Microtus arvalis), wood mice (Apodemus sylvaticus), Algerian mice (Mus spretus) and white-toothed shrews (Crocidura russula) [16]. The common vole is a fossorial rodent [28] characterized by population outbreaks recorded every 3 years [13], whereas the two mouse species show seasonal uctuations [29,30]. Small mammals use burrows for resting, feeding, sheltering and breeding, spending large portions of time underground [31].…”

“…In NW Spain, common vole (Microtus arvalis) populations massively invaded lowland agricultural landscapes between 1970-1990s, putatively colonizing newly irrigated fodder crops from natural peripheral mountainous habitats [10][11][12]. In this recently colonized agro-ecosystem, common vole populations are cyclic [13], and periodically become a crop pest when overabundant (population outbreaks), causing serious public health impacts due to the ampli cation and spillover of zoonotic disease, mostly tularemia [10,14,15]. In these intensively farmed landscapes, common voles coexist with other sympatric rodents and insectivores (mainly, wood mouse Apodemus sylvaticus, Algerian mouse Mus spretus, and greater white-toothed shrew Crocidura russula).…”

Spatial capture-recapture models for the ecological study of common voles (Microtus arvalis) in NW Spain

“…Ecologists can use time series of animal abundance to explore predatorprey relationships (Gilg et al, 2003;Mougeot et al, 2019), examine the relationships between habitat and species (Hoek et al, 2015;Rodríguez-Pastor et al, 2016), or to evaluate the effects of experimental treatments in the study populations (Krebs, 2013;Paz et al, 2013). In a more applied context, wildlife managers often use abundance estimates to: (i) determine extraction quotas, making more precise decisions and evaluating the effectiveness of management actions (Delibes-Mateos et al, 2008), (ii) formulate conservation plans for rare or threatened species (Garrote et al, 2011) based on their distributions or population trends (Jiménez, 2017), (iii) understand the epidemiology of relevant pathogens (Acevedo et al, 2007;Gortázar et al, 2006) and (iv) establish management practices for wildlife control and pest management (Conn et al, 2006).…”

“…From a broad ecological perspective small burrowing rodents are a key component of the food web, generating ecosystem services such as the aeration of the inner parts of the ground, can act as plant seed dispersal, may be involved in soil fertilization and through creation of burrows provide shelter for many other species such other small mammals, reptiles or amphibians (Martin, 2003;Jacob et al, 2014;Zhang et al, 2003). Moreover, voles are important prey species for raptors (Baker & Brooks, 1981;Paz et al, 2013) and other generalist or specialized mammals like weasels (Graham & Lambin, 2002;Tapper, 1979;Mougeot et al, 2019). However, when over-abundant, voles cause damage to agriculture and forestry (O'Brien 1994;Pugh et al, 2003;Jacob & Tkadlec, 2010) or contribute to the transmission of diseases to humans (Pugh et al, 2003;Pikula et al, 2002) and are considered as pest species.…”

“…rodents) in order to estimate relative abundance (e.g. Rodríguez-Pastor et al, 2016;Quéré et al, 2000;Krebs, 2013;Mougeot et al, 2019), or to compare abundance estimates obtained by other alternative direct or indirect methods (e.g. Jareño et al, 2014;Fauteux et al, 2018).…”