Ungulate presence and predation risks reduce acorn predation by mice in dehesas

Abstract

Foraging decisions by rodents are key for the long-term maintenance of oak populations in which avian seed dispersers are absent or inefficient. Decisions are determined by the environmental setting in which acorn-rodent encounters occur. In particular, seed value, competition and predation risks have been found to modify rodent foraging decisions in forest and human-modified habitats. Nonetheless, there is little information about their joint effects on rodent behavior, and hence, local acorn dispersal (or predation). In this work, we manipulate and model the mouse-oak interaction in a Spanish dehesa, an anthropogenic savanna system in which nearby areas can show contrasting levels of ungulate densities and antipredatory cover. First, we conducted a large-scale cafeteria field experiment, where we modified ungulate presence and predation risk, and followed mouse foraging decisions under contrasting levels of moonlight and acorn availability. Then, we estimated the net effects of competition and risk by means of a transition probability model that simulated mouse foraging decisions. Our results show that mice are able to adapt their foraging decisions to the environmental context, affecting initial fates of handled acorns. Under high predation risks mice foraged opportunistically carrying away large and small seeds, whereas under safe conditions large acorns tended to be predated in situ. In addition, in the presence of ungulates lack of antipredatory cover around trees reduced mice activity outside tree canopies, and hence, large acorns had a higher probability of survival. Overall, our results point out that inter-specific interactions preventing efficient foraging by scatter-hoarders can reduce acorn predation. This suggests that the maintenance of the full set of seed consumers as well as top predators in dehesas may be key for promoting local dispersal.

Indirect Human Influences in Fear Landscapes: Varying Effects of Moonlight on Small Mammal Activity along Man-Made Gradients of Vegetation Structure

“…Rather surprisingly, the Algerian mouse showed a positive effect of moonlight on its abundance/activity. This species reduced or shifted its foraging activity under predation risk [ 12 , 46 ], but in our case, the indirect cues of perceived predation risk increased abundance/activity. The cover of tall vegetation decreased the effects of moonlight for this species: Algerian mice respond less to indirect cues of risk in open habitats, where small mammal predators are more scarce [ 11 , 47 ].…”

“…Most of the literature and theoretical framework on predation risk and small mammals has been developed in unusually risky environments, where predation risk is likely highest (e.g., deserts, [ 8 ]), but these models have been generalized and applied worldwide, from the tropics to the poles [ 9 , 10 ]. In the Mediterranean basin, predators’ presence (or direct cues of it) alters small mammal behavior in response to the auditory, visual, and chemosensory cues of predators [ 11 , 12 ]. Behavioral effects of predation include altered movement and activity patterns (shifting activity to less risky microhabitats or to less risky time periods [ 4 ]), grouping behavior, and ultimately changes in fecundity and stress levels, causing decreasing population growth rates and altering community interactions [ 2 ].…”

An Experimental Study in Wild Wood Mice Testing Elemental and Isotope Analysis in Faeces to Determine Variations in Food Intake Amount

“…Hence, the degree of exploitation may also depend on each individual’s needs, but also on their efforts and experience to overcome any limiting barriers [ 4 , 5 , 6 ]. Furthermore, environmental factors (e.g., competition, predation risk and weather conditions) and individual traits can also strongly impact body condition and energetic demands of individuals, as well as feeding behaviour [ 7 , 8 , 9 , 10 , 11 , 12 ]. Thus, studies on feeding ecology are paramount for assessing the status of wild animal populations as well as to understand the wildlife relationship with the habitat and environmental changes [ 3 ].…”

Mice population dynamics and structure over time and space after wildfires

“…Rodent populations respond quickly to changes in habitat structure and composition caused by ecological disturbances, such as wildfires (Horncastle et al., 2019; Puig‐Gironès et al., 2018). Rodents constitute a fundamental food source for vertebrate predators (Long & Smith, 2000) and influence vegetation structure and regeneration through seed predation and dispersal (Gordon & Letnic, 2019; Morán‐López et al., 2022). Understanding the population dynamics of rodents in burnt areas, including surviving and immigrating animals after fire, is a key question for understanding the recovery of trophic networks after disturbances.…”