Seismic noise influences brood size dynamics in a subterranean insect with biparental care

Abstract

Anthropogenic noise pollution is known to alter the behaviour of acoustically sensitive animals. Many animals also sense vibrations through solid substrates and use substrate-borne vibrations in conspecific communication. The effects of substrate-borne noise pollution, however, remain largely unknown. Here, we investigate the potential for seismic (soil-borne) noise to alter the reproductive behaviour of the burying beetle Nicrophorus marginatus, a species that breeds below the soil surface on vertebrate carcasses and provides biparental care to offspring. Nicrophorus marginatus beetles produce sound using stridulatory structures on the elytra and abdomen, but no ears have been identified in these beetles, suggesting that stridulation might function to produce substrate-borne signals. We examined the timing of stridulation during reproduction, measured neural responses of beetles to substrate-borne vibrations, and measured beetle reproduction in the presence and absence of seismic noise. We found that parental beetles stridulate throughout carcass preparation and the burial process and confirmed that adult beetles are sensitive to low-frequency seismic vibrations. Variables related to brood size were affected in treatments with seismic noise, with burying beetles producing smaller broods with lower total mass than those in control treatments, providing support for the hypothesis that substrate-borne noise may impose fitness costs for soil-dwelling animals. The precise mechanisms leading to reduced brood size remain unknown but may relate to disruption of seismic communication or inaccurate assessment of resource size. Additional investigations are required to understand the degree to which human-generated seismic noise in natural settings influences other edaphic species, and whether these behavioural impacts lead to shifts in edaphic community structure or function.