Historical ecology and current abundance of the translocated Chilla or Grey fox Lycalopex griseus on the large Tierra del Fuego Island shared by Argentina and Chile

Abstract

In 1951, a batch of 24 young animals of both sexes of Chilla or Grey fox Lycalopex griseus from continental Magallanes region, Chile -and perhaps also from adjacent continental Argentina -were released at Onaisin (65 km ESE Porvenir town, 53°18′S) on Tierra del Fuego Island in southernmost South America, to control a European rabbit (Oryctolagus cuniculus) irruption that was considered detrimental to sheep (Ovis aries) ranching. Up to now, no attention has been paid to the temporal course of that introduction. Here we provide a historical account of the presence of foxes on the Tierra del Fuego Archipelago, starting with Charles Darwin account of 1839 until present. We also review the regulatory framework concerning hunting of those foxes and tally their culling for export of pelts. Finally, we provide estimates of the abundance of Chilla foxes on Tierra del Fuego Island for the period 1999-2007 and for 2021, and highlight their current spread. These translocated foxes have become an abundant and functional part of both steppe and forest ecosystems on the Fuegian archipelago, even though they are killed by hunters, without spatial, temporal, or numerical limits. We conclude that interesting scientific opportunities are being missed regarding the population genetics of a species that may have left founding effects and genetic bottlenecks in Tierra del Fuego, and perhaps some peculiar continental markers among the island population. We also raise the question whether this introduced native species may be deemed invasive, calling for research to determine its impact in its new environment.

Temporal activity and detection rates of chilla (Lycalopex griseus) in Tierra del Fuego, Argentina

“…Chilla are considered of Least Concern by the International Union for Conservation of Nature (IUCN; Lucherini, 2016 ) and have received relatively little attention in the context of global carnivore research, as is typical of species endemic to the Southern Hemisphere (Allen et al., 2019 ; Nuñez et al., 2019 ). A total of 24 chillas were introduced to Tierra del Fuego Island (Isla Grande de Tierra del Fuego) in 1951 to control invasive European rabbits ( Oryctolagus cuniculus ) (Zurita et al., 2023 ). Tierra del Fuego Island is the largest island in South America at approximately 48,000 km 2 (Zurita et al., 2023 ) and is split between Chile and Argentina.…”

“…A total of 24 chillas were introduced to Tierra del Fuego Island (Isla Grande de Tierra del Fuego) in 1951 to control invasive European rabbits ( Oryctolagus cuniculus ) (Zurita et al., 2023 ). Tierra del Fuego Island is the largest island in South America at approximately 48,000 km 2 (Zurita et al., 2023 ) and is split between Chile and Argentina. Spreading at rate of at least 7.7 km per year across the island (Jaksić et al., 2002 ), the foxes thrived in this novel environment, with ~22,000 individuals estimated to be spread across the Chilean side of the island in 2021 (Zurita et al., 2023 ).…”

“…Tierra del Fuego Island is the largest island in South America at approximately 48,000 km 2 (Zurita et al., 2023 ) and is split between Chile and Argentina. Spreading at rate of at least 7.7 km per year across the island (Jaksić et al., 2002 ), the foxes thrived in this novel environment, with ~22,000 individuals estimated to be spread across the Chilean side of the island in 2021 (Zurita et al., 2023 ). Despite this estimate falling to around 13,000 in 2022, largely due to the increasing population of free‐living dogs and hunting pressure (Zurita et al., 2024 ), chillas have unquestionably become a major part of the natural ecosystems and anthropogenic landscapes; however, abundance data from the Argentinian side of the island have so far been lacking (Zurita et al., 2023 ).…”

“…Spreading at rate of at least 7.7 km per year across the island (Jaksić et al., 2002 ), the foxes thrived in this novel environment, with ~22,000 individuals estimated to be spread across the Chilean side of the island in 2021 (Zurita et al., 2023 ). Despite this estimate falling to around 13,000 in 2022, largely due to the increasing population of free‐living dogs and hunting pressure (Zurita et al., 2024 ), chillas have unquestionably become a major part of the natural ecosystems and anthropogenic landscapes; however, abundance data from the Argentinian side of the island have so far been lacking (Zurita et al., 2023 ). With no landforms dividing the island, chillas in Chile and Argentina are considered part of the same population; however, Chile has a hunting quota of 10 specimens per hunter per day (Zurita et al., 2024 ), whereas chillas in Argentina have zero protection (Zurita et al., 2023 ).…”

The ecological role of the European rabbit in the Magellanic/Fuegian ecosystem of southernmost Chile

“…They also compete with native mammals for food and habitat, but favor the population increase of predators and scavengers by being a subsidy of abundant prey (Lambertucci et al 2009, Barbar et al 2016). Among several other Magellanic/Fuegian predators, the puma (Puma concolor), Lycalopex foxes, Leopardus cats, and the Buzzard eagle (Geranoaetus melanoleucus) incorporate rabbits as staple prey to their diet , Zurita et al 2023. Also, facultative and carrion eaters such as the caracaras Caracara plancus and Milvago chimango, and the Andean condor (Vultur gryphus) benefit from their presence (Duclos et al 2020).…”