Exotic lagomorph may influence eagle abundances and breeding spatial aggregations: a field study and meta-analysis on the nearest neighbor distance

Abstract

The introduction of alien species could be changing food source composition, ultimately restructuring demography and spatial distribution of native communities. In Argentine Patagonia, the exotic European hare has one of the highest numbers recorded worldwide and is now a widely consumed prey for many predators. We examine the potential relationship between abundance of this relatively new prey and the abundance and breeding spacing of one of its main consumers, the Black-chested Buzzard-Eagle (Geranoaetus melanoleucus). First we analyze the abundance of individuals of a raptor guild in relation to hare abundance through a correspondence analysis. We then estimated the Nearest Neighbor Distance (NND) of the Black-chested Buzzard-eagle abundances in the two areas with high hare abundances. Finally, we performed a meta-regression between the NND and the body masses of Accipitridae raptors, to evaluate if Black-chested Buzzard-eagle NND deviates from the expected according to their mass. We found that eagle abundance was highly associated with hare abundance, more than with any other raptor species in the study area. Their NND deviates from the value expected, which was significantly lower than expected for a raptor species of this size in two areas with high hare abundance. Our results support the hypothesis that high local abundance of prey leads to a reduction of the breeding spacing of its main predator, which could potentially alter other interspecific interactions, and thus the entire community.

The roles of leporid species that have been translocated: a review of their ecosystem effects as native and exotic species

“…For instance, current Lepus europaeus densities in northern Patagonia, reaching up to 250 individuals per km 2 (Barbar et al. ), reduce the carrying capacity of agricultural land by one sheep every two hectares (Bonino , ). Other estimates are even worse, suggesting that, at this density, Lepus europaeus may consume nearly 15% of the palatable plants available for livestock in meadows (Amaya ).…”

Native forest and proximity to humans are stronger drivers of Brazilian cottontail habitat use than invasive European hare

“…Hare populations are currently widespread, but at relatively low densities (Pasqualotto et al. in press ) compared to other regions of Brazil and South America (Barbar et al., 2018; Kasper et al., 2012; Novaro et al., 2000). Even if the species' realized niches overlap substantially, low hare densities would naturally lead to a weak competitive interaction with the Brazilian cottontails, as supported by our findings.…”

Resource selection of apex raptors: implications for siting energy development in sagebrush and prairie ecosystems

“…An important caveat to this finding is that we investigated current patterns of nest‐site selection for a relatively short study period. The patterns of selection we observed were after the construction of energy infrastructure so we lacked the ability to understand potential changes before and after development of long‐term demographic responses of raptor or prey populations that could ultimately affect nearest‐neighbor distance and raptor nest density (Skalski et al 2005, Barbar et al 2018). However, we also demonstrated that more‐selected habitat (90% of use based on independent historical nests) for ferruginous hawks and golden eagles intersected the areas of greatest potential and current development of oil/gas reserves and wind energy.…”