Using native predators to deal with invasive species

Humans have been killing larger native predators and other species that they have competed with or feared throughout evolution. This process was especially successful in Ireland and the UK, where the lynxes and wolves with which people once shared their lives are no longer present.

Humans have also transported valuable species out of their natural ranges, inadvertently creating invasive species by introducing plants, animals, and microorganisms into ecosystems where they did not evolve. This caused the native species to become extinct by competing with them, eating them and exposing them to new diseases. Over the last century, studies have shown that invasive species have been the primary cause of vertebrate extinction.

Mounting evidence shows that once-scorned native predators are now critical for controlling invasive prey.

Love for native predators

According to new research, the eradication of native predators contributed to the current invasive species crisis. However, researchers in Ireland conducted a series of surveys between 2007 and 2019. It included public sightings of gray squirrels and pine martens to see how the return of a native predator can cause the rapid decline of a long-established invasive species. , the gray squirrel, across entire landscapes.

Joshua Twining, a Cornell University Population Ecology research scientist who is also a postdoctoral researcher at Queen’s University Belfast, collaborated on the study with Xavier Lambin and five other researchers.

Twining’s team analyzed the populations of both species to see what factors influence a native predator’s ability to control an invasive species after restoration. These factors include the invading prey’s failure to recognize or respond to the threat of a newly recovered predator, the predator’s ability to switch prey, and the availability of hiding places for the prey to flee.

predator-prey relationship

Native predators preferentially hunt invasive prey by a factor of two or even three, from wolves hunting non-native Corsican mouflons in the Mercantour mountains of southeastern France to red-banded snakes hunting invasive bullfrogs in China.

Understanding why this is the case can help determine when and where native predators can help control invasive species.

For example, Lynx have a proven ability to suppress deer populations by changing the species of deer they hunt. There are no areas accessible to deer that are restricted to the lynx. The combination of these factors suggests that restoring lynx populations will benefit ecosystems where sika deer are a problem. Where alternative prey such as roe deer are scarce or absent, such as in Ireland and Great Britain, the lynx is likely to have a greater impact on these invasive populations.

Also read: How invasive species thrive in the Mediterranean

Welcoming native predators

The natural recovery of some large predators in continental Europe, such as bears, lynxes and wolves, is well advanced. This challenges long held beliefs about the need for carnivores for pristine habitat. Despite urban sprawl and intensive agriculture, the only requirement was that people stop killing predator species to recolonize their former range. Extinct predators will not naturally recover in Britain because it is surrounded by sea. Any attempt to reintroduce them would require a social agreement, which currently does not exist.

The ecological rationale for restoring native predators is to help control and limit the spread of invasive species, according to our findings. However, living near large carnivores has its drawbacks, including the loss of livestock and sometimes even pets. This is unavoidable, but can be mitigated through proactive management.

Twining points out that if restoration of any native predator is to be accepted by people, the benefits, such as reduced damage from invasive species, must be balanced against plans to mitigate costs.

Related article: This is how non-human species drive others to extinction

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