Phantom oceans restructure bat communities

Area of Science:

• Ecology
• Bioacoustics
• Animal Behavior

Background:

• Coastal areas are dominated by intense natural ocean sounds, primarily breaking waves.
• The ecological impact of natural soundscapes on animal distribution, behavior, and community structure is understudied.
• Understanding how acoustic environments shape wildlife is crucial for conservation.

Purpose of the Study:

• To investigate the effects of ocean soundscapes on bat activity and distribution.
• To determine how different species of bats respond to varying levels and frequencies of ocean noise.
• To explore the role of natural sounds as a habitat feature influencing community composition.

Main Methods:

• Quantified bat activity across 19 sites with varying exposure to surf sounds over three seasons.
• Conducted large-scale playback experiments using realistic coastal soundscapes and spectrally shifted surf sounds.
• Analyzed species-specific responses in relation to their acoustic foraging strategies (passive listening vs. echolocation).

Main Results:

• Bat species exhibited divergent responses to acoustic environments, linked to their foraging niches.
• Passive listening bats showed reduced activity in high sound levels but increased activity in high-frequency soundscapes.
• Aerial hawking bats were more active in high sound levels and avoided high-frequency environments.
• Playback experiments revealed community turnover: passive listening species replaced hawking species with shifted sounds.
• Unaltered ocean sounds decreased species richness as passive listening bats avoided these sites.

Conclusions:

• Natural ocean sounds are a significant, yet overlooked, habitat feature shaping species distributions.
• Acoustic environments act as a non-random filter, influencing the structure and composition of ecological communities.
• Species-specific responses to soundscapes highlight the importance of acoustic niche partitioning in community assembly.