Temporal Partitioning: An Experiment With Two Species of Spiny Mice

Abstract

We studied temporal partitioning between two spiny mouse species that coexist in hot rocky deserts in the Middle East: nocturnal common spiny mice (Acomys cahirinus) and diurnally active golden spiny mice (A. russatus). Although A. russatus is diurnally active, it retains the physical activity and body temperature rhythms of nocturnal mammals. We studied the two species in four 1000‐m2 enclosures at Ein Gedi, Israel: two experimental enclosures with A. russatus kept alone, and two controls with individuals of both species kept together. We monitored activity with Sherman traps and by studying foraging microhabitat use and efficiency using giving‐up densities (GUDs) in food trays. The trays contained broken sunflower seeds mixed in local soil and placed in three microhabitats: under boulders, between boulders, and in the open. Trapping revealed that, in the absence of A. cahirinus, the usually diurnal A. russatus was active both day and night. However, during the day A. russatus still foraged in significantly more patches and to significantly lower GUDs than during the night. Both species, but in particular A. russatus, preferred to forage in the boulder habitat. Spiny mice foraged in the same number of trays in the under‐ and between‐boulder microhabitats, but to lower GUDs in the under‐boulder microhabitat, both during the day (A. russatus) and during the night (both species). The nocturnal A. cahirinus exploited more patches with greater efficiency than did A. russatus either during the day or during the night. This result suggests that foraging trade‐offs that give each species a competitive advantage along some portion of the resource axis cannot be a mechanism of nocturnal coexistence between the two species. Perhaps this is why A. russatus resorts to diurnal activity in this hot rocky desert and why the otherwise rare mechanism of temporal partitioning occurs for these species.

Effect of artificial night lighting on temporally partitioned spiny mice

“…Spiny mice were marked individually with passive integrated transponder tags (details below), and each enclosure was populated with 8 individuals, 4 of each species, with a sex ratio of 1:1. A constant amount of food was added once a week (200 g of mouse pellets and mixed seeds), and water was available ad libitum (Gutman and Dayan 2005).…”

“…Three AMF patches were placed in each enclosure, each at a different microhabitat-under-boulder (UB) microhabitat (on the rocky terrace with overhead shelter), between-boulders (BB) microhabitat (on the terrace surrounded by large stones but no direct overhead cover), and open (O) microhabitat (at a distance of 1 m from the rocky terrace- Gutman and Dayan 2005). These microhabitats constitute a gradient in the degree of shelter, with UB the safest from avian predators and O the least protective.…”

“…A. russatus will extend its activity into the night in response to light pollution and reduction of activity of its nocturnal congener. Previous studies show that when kept alone, individuals of A. russatus also become nocturnally active (Gutman and Dayan 2005;Shkolnik 1971). Finally, because the light cycle plays a major role in this system (Kronfeld-Schor and Dayan 2003), light pollution will disrupt this natural cycle and induce temporal overlap and interspecific competition.…”

“…Our research focused on 2 omnivorous congeners, the nocturnal common spiny mouse (Acomys cahirinus) and the diurnally active golden spiny mouse (Acomys russatus- Shargal et al 2000). Such extreme temporal segregation between congeners is unusual (Roll et al 2006) and appears to be a response of A. russatus to the presence of A. cahirinus (Gutman and Dayan 2005;Shkolnik 1971). We have been studying this system for almost 2 decades to gain insight into the physiological mechanisms controlling activity patterns (Elvert et al 1999;Kronfeld-Schor et al 2001;Levy et al 2007), the roles of biotic interactions at 3 trophic levels, and abiotic pressures in the evolution and maintenance of temporal partitioning along the diel axis (Gutman and Dayan 2005;Jones and Dayan 2000;Jones et al 2001;Kronfeld-Schor and Dayan 2003;Mandelik et al 2003).…”

Biogeography of time partitioning in mammals

“…Furthermore, energetic constraints may force some species to be active throughout hours of both light and darkness (8). Where energetic and thermal costs are not prohibitive, temporal niche partitioning may occur as species specialize and avoid competition by concentrating their activity within a particular section along the light gradient (9,10). Behavioral traits are associated with a range of specialized adaptations, particularly in visual systems and eye morphology (11) and energetics and resource use (6,12).…”