Spatio-temporal niche specialization and coexistence mechanisms between Patagonian terrestrial mesopredators

Abstract

Potential competitors ensure their coexistence adjusting the ecological niche by guaranteeing energy gain and avoiding competitive exclusion. We evaluated the spatio-temporal specialization and competition between Leopardus geoffroyi (Geoffroy´s Cat: GC) and Lycalopex gymnocercus (Gray Fox: GF) in Cabo dos Bahías, Argentine Patagonian cost. The area hosts a colony of Spheniscus magellanicus (Magellanic Penguin), which maintains resource availability throughout the year. We used 23 camera-traps (within the colony: eight; surroundings: 15) between August/22 and January/24. The level of spatio-temporal specialization was defined, and these niche dimensions were compared between environments and seasons (warm: October-March; cold: April-September) using inter/intraspecific overlap (NOlnter/NOlntra) of the spatial/temporal dimensions (S/T). We obtained 230 records of each species (colony-warm season-GC: 45, GF: 11, always in this order; colony-cold: 109, 50; surrounding-warm: 39, 83; surrounding-cold: 37, 86), being GC alwaysdominant in the colony and GF in the surroundings. There was no difference in spatial nichespecialization (0.405; 0.419), but GC had less similarity regarding space use between seasons(NOlntraS: 0.715, 0.845). Both species were more generalist during cold seasons (warm: <0.243, cold: >0.431), with higher NOlInterS (general: 0.366; warm: 0.305; cold: 0.428). Within the colony, both carnivores were specialized in warm (<0.264) and generalists in cold periods (>0.732). The niche was moderately adjusted between periods (NOlntraS: 0.716, 0.664), maintaining similar levels of NOlnterS that tend to decrease during cold periods (warm: 0.760, cold: 0.701). In the surroundings (higher habitat diversity), GC showed high specialization and GF showed greater variation in the specialization level (warm: 0.190, 0.295; cold: 0.275, 0.455), although both expanded the niche during cold periods. GC showed a greater alternation of habitats used between seasons (NOlntraS: 0.376, 0.490). In the colony, there was a reduction in NOlnterS during cold periods (warm: 0.335; cold: 0.249). The temporal niche was more specialized for GC in warm (warm: 0.523, 0.681; cold: 0.629, 0.676) and NOlInterT was high, but with a tendency to decrease in cold periods (warm: 0.750; cold: 0.704). In the colony, GC was more generalist (0.521, 0.469) and NOlnterT was intermediate during cold periods (0.557). The warm period was only evaluated for GC and showed high temporal similarity between seasons (NOlntraT: 0.713). In the surroundings, GC niche was more specialized, and both species expanded their niche during cold periods (warm: 0.540, 0.641; cold: 0.711, 0.743). The temporal niche of GC was relatively more variable between seasons (NOlntraT: 0.677, 0.798). NOlnterT was high between seasons, with a slightly increasing in cold seasons (warm: 0.771; cold: 0.797). In general, NOlnter was inverse with specialization level and the space-time niche complemented itself between seasons. This mechanism can maintain niche partition, with specialization in different components responsible for reducing direct competition. Niche adjustments can also be attributed to variations in resource availability, what may have induced greater variation in foraging areas in the cold period (fewer resources) and greater specialization in the warm period, when more resources are available. Greater competitive potential is suggested for GC by dominating the colony, although GF may increase its use when resources are scarce.