Many juvenile crickets cannot survive the strain of human noise

As dusk falls at the end of a hot day, the air is typically filled with the melodious chirping of crickets – a sound as familiar as it is enchanting. Yet, this natural concert is increasingly being drowned out by the pervasive noise produced by human activity.

Researchers at the University of Denver have begun to unravel the extent to which noise pollution impacts the survival and reproduction of crickets.

The research team has dedicated three years to studying the effects of human-generated noise on field crickets, which make up a significant part of the terrestrial ecosystem. Despite invertebrates constituting over 95% of all animal species, they are seldom the focus of ecological noise research.

Noise pollution is a growing threat

“Noise pollution is a ubiquitous anthropogenic stressor that accompanies expanding urbanization. We tested whether the amplitude of traffic noise influences a suite of fitness-related traits (e.g. survival, life history, reproductive investment, immunity) and whether that depends on the life stage at which the noise is experienced (juvenile or adult),” wrote the researchers.

“Our treatments mimic the conditions experienced by animals living in urban roadside environments with variable vehicle types, but continuous movement of traffic. We used the Pacific field cricket, an acoustically communicating insect that was previously shown to experience some negative behavioral and life history responses to very loud, variable traffic noise, as a model system.”

Crickets exposed to noise

The team exposed the crickets to four levels of traffic noise that they might encounter in their natural habitats: complete silence, 50 decibels, 60 decibels, and 70 decibels. To put this into perspective, 55 decibels is akin to the sound of constant rainfall, while 70 decibels can be compared to a busy street or the hum of a vacuum cleaner.

The results were telling: crickets subjected to 70 decibels of noise had a 35% lower survival rate into adulthood compared to those raised in silence.

The subtle language of crickets

“Insects that communicate through sounds, like field crickets, are particularly vulnerable to noise pollution. These crickets use their airborne songs to communicate and are commonly found near urban areas, where noise is ever-present,” explained Professor Robin Tinghitella, the study’s principal investigator.

This backdrop of constant human noise, according to the study, acts as a stressor, significantly impacting their ability to survive and reproduce.

Cricket responses to noise

While the study found a definite impact on survival and reproductive rates, it’s interesting to note that 13 other measured traits in crickets remained unchanged despite the noise. This indicates a possible adaptation to the chronic presence of human noise.

“We found that juvenile traffic noise treatment impacted the percent of crickets that survived to eclosion, and the interaction between a female’s traffic noise experience during juvenile and adult life stages affected her reproductive success,” noted the researchers.

“However, the consistent traffic noise treatments (50dBA, 60dBA, 70dB) did not impact the other 13 fitness-related traits we investigated, irrespective of noise level and whether traffic noise was experienced by crickets during development only, at adulthood only, or during both life stages.”

Valuable study insights

Mark Mitchell, a professor of Zoological Medicine at Louisiana State University, praised the study for its comprehensive approach and its importance in understanding how traffic noise affects the physiological traits of invertebrates.

“This research provides valuable insights into the effects of anthropogenic activities on invertebrates, offering a foundation for future ecological planning and conservation efforts,” said Professor Michell.

A quieter coexistence is needed

This pioneering research underscores a critical need for awareness and action concerning the ecological impacts of human noise. As we continue to encroach upon natural habitats, understanding and mitigating our auditory footprint on wildlife becomes not just beneficial but essential for sustaining biodiversity.

“Our result that juvenile survival under noisy conditions is reduced is especially relevant for conservation and management decisions, and future work should clarify consequences in natural settings with varying noise characteristics and the generalizability across insects,” wrote the study authors.

The survival of crickets may seem like a minor concern in the grand scheme of environmental issues, but it is a poignant reminder of the pervasive impact of human activities on the planet.

The study is published in the journal BMC Ecology and Evolution.

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