A study by the Desertification Research Center (CIDE, CSIC-UV-GVA) shows that foxes eat less fruit and modify their feeding behavior within the territories of reintroduced lynxes in Andalusia
The study, published today in the Journal of Animal Ecology, involves the Doñana Biological Station (EDB-CSIC), the Rey Juan Carlos University and the Autonomous University of Madrid.
Research published today in the Journal of Animal Ecology shows that the reintroduction of a top predator, such as the Iberian lynx, into an ecosystem may lead other smaller carnivores to modify their feeding behavior as a consequence of the perceived risk of predation. This would have important repercussions on seed dispersal in these ecosystems. The study is led by the Universidad Rey Juan Carlos, with the participation of the Centro de Investigaciones sobre Desertificación (CIDE), the Consejo Superior de Investigaciones Científicas (CSIC), the Universitat de València and the Generalitat Valenciana, the Estación Biológica de Doñana (EDB-CSIC) and the Universidad Autónoma de Madrid.
Many carnivorous mammals play a key role in ecosystem functioning as seed dispersers, consuming a large number and variety of fleshy fruits due to their generalist and opportunistic diet. However, large carnivores have been extirpated from many ecosystems worldwide as a consequence of human persecution or loss of their habitats and food resources.
Rewilding processes allow these large carnivores such as the Iberian lynx to recover their historical ranges. Top predators are at the top of trophic chains and can produce so-called ‘cascading effects’, causing alterations in the abundance and behavior of species at lower trophic levels, critically influencing the functions and structure of ecosystems, known as a ‘trophic cascade’.
Tamara Burgos, researcher at the Universidad Rey Juan Carlos and lead author of the article, emphasizes that "although the area of this study does not have reintroduced populations of Iberian lynx, the heterogeneous distribution of this species throughout the Sierra de Andújar Natural Park offered us a unique opportunity to develop an experimental study in similar areas that practically differ only in the presence or absence of the lynx. We were thus able to evaluate more precisely the effects of reintroducing large predators on ecosystem services, such as seed dispersal".
Cameras equipped with motion detectors were used to monitor the environment from a fixed installation point. Thanks to these devices, it was possible to compare the feeding behavior on fruits of the pyrope tree, a tree with fleshy fruits whose seeds are dispersed mainly by carnivorous frugivores (foxes, badgers, martens...), between individuals coexisting with the Iberian lynx and those living outside the lynx's range in the Andalusian natural park. This protected area is home to one of the largest populations of Iberian lynx in the world, and was the last refuge along with Doñana for the species when it was on the verge of extinction.
Lynx reduces abundance of some carnivores
Although this feline has expanded its range in the last 20 years thanks to multiple conservation efforts of several LIFE projects, "the Iberian lynx is still threatened and we should not let our guard down. Urgent and useful conservation measures and captive breeding programs have borne fruit, but non-reintroduced populations still need our attention, mainly because of the lack of natural prey for this predator, the European rabbit" says Emilio Virgós, author of this study and leader of the research group at the Universidad Rey Juan Carlos.
The study shows that 70% and 100% of fox and marten visits, respectively, occurred in piruetanos located outside lynx territories. In addition, the researchers identified less than half as many different fox individuals visiting pygmy martens in areas with lynx presence compared to areas without lynx. Foxes and martens may be easily predated by a larger competitor, and the perceived risk of predation within lynx territories could lead them to use peripheral areas more intensively to avoid conflicting encounters with lynx.
Red foxes were the carnivore that consumed the most pyrope fruits, but ingested 38% fewer fruits within lynx territories compared to other foxes in non-lynx areas. Those that coexisted with lynx were less efficient frugivores, consuming fewer fruits and making shorter visits to pyrope trees, both behaviors typically linked to an anti-predatory response. Badgers, however, did not appear to show sensitivity to the presence of lynx, probably due to their greater size and corpulence.
“The badger could balance the loss of seeds dispersed by foxes within lynx territories in areas where badger populations have high densities, as occurs in some areas of Doñana, where the lynx is mainly dispersed by badgers” according to Jose Fedriani, another author of this study and researcher at the Desertification Research Center (CIDE, CSIC-UV-GVA).
Carnivores were not the only frugivores that consumed pyrope fruits. However, most of the other animals involved, such as deer, were very low quality seed dispersers breaking the ingested seeds during chewing. Therefore, the fox is the main seed disperser for the pyrethrum in the study area and the lack of this disperser could alter the demography and spatial structure of this scarce, fleshy-fruited tree. “Although we have evaluated these alterations on frugivory behavior at a local scale, we encourage reintroduction programs to consider trophic cascades as a powerful mechanism, which can alter key ecosystem functions in different ways” concludes Tamara Burgos.
Reference:
Tamara Burgos, Jose María Fedriani, Gema Escribano-Ávila, Javier Seoane, Javier Hernández-Hernández y Emilio Virgós. Predation risk can modify the foraging behaviour of frugivorous carnivores: implications of rewilding apex predators for plant-animal mutualisms. Journal of Animal Ecology. 2022. https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2656.13682
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