When an invasive species enters a new ecosystem, all native species must stay weary. Invasive species rapidly reproduce, which changes the dynamic of the entire ecosystem. The new species can directly threaten native species’ way of life by: predation, competing for the same food, preventing natives from reproducing and bringing diseases. In addition, the invasive species can also effect the natives indirectly by fighting for their acoustic space.
Animals have a limited amount of acoustic space that they have to share with other species within their ecosystem. When an invasive species enters the ecosystem they create overlapping sounds when they send mating signals and signals to defend their territory. These invasive sounds block natives from vocally communicating.
According to previous studies, native species have changed their vocals when outside noise, such as traffic or construction, increased. However, researchers question if this same vocal adjustment is made when an invasive species enters the ecosystem.
Jennifer Tennessen et al. from Vassar College tested this theory by conducting a study on an invasive Cuban tree frog, Ostenpilus septentrionalis. She studied the effect that the invasive tree frog’s vocal calls had on the native tree frog calls.
The researchers predicted that tree frogs with similar acoustic sounds, measured by structure and frequency, to the invasive tree frogs would modify their sounds but tree frogs with different calls would not adjust their sounds. To test this theory, they studied a native species that had similar calls, green tree frogs, Hyla cinerea, and a native species that had different calls, pine woods tree frogs, Hyla femoralis.
They concluded that the green tree frogs modified their sounds but the pine woods tree frogs did not. The green tree frogs would shorten their vocal calls and increase the loudness more often when the invasive Cuban tree frog was around.
This study helps prove that when an invasive species enters an ecosystem, some native species adjust their vocal calls to adhere to a new species’ vocal calls entering the limited acoustic space. Adjusting their calls lowers overlapping sounds in the acoustic space and strengthens their vocal signals.
These adjustments can have negative effects on mating success for native species due to their call duration. Future studies need to be conducted to examine the effects of modified calls from invasive species competition for acoustic space.
Credit: Earth.com author Hannah Parker