New study investigates beetle communication and its affect on brood care

Researchers at the University of Bayreuth have discovered that burying beetle larvae tend to have lower weights and higher mortality rates when their parents are unable to communicate acoustically during brood care. This study marks a first step in deciphering animal communication.

Communication is essential for the development of cooperative behavior, such as parental care. Animal family life involves a variety of interactions among family members, with species differing in the complexity of their social structures.

To understand the role communication plays in the evolution of family life—and how communication itself evolves with increasingly complex social interactions—a simpler system, such as that of the burying beetles, with only a few family members, must first be examined.

This new research, published in Animal Behaviour, offers insights into the evolution of social behaviors more broadly, aiding the decryption of animal communication.

Animals need to recognize and interact with potential mates, as well as care for their offspring during rearing. Although the central role of communication has long been acknowledged, the functions of individual signals often remain unexplored.

Some studies have already examined communication within insect family life, focusing mainly on chemical signals. Researchers at the University of Bayreuth, led by Dr. Taina Conrad at Professor Sandra Steiger’s Chair of Evolutionary Animal Ecology, have now published the first study examining the role of acoustic signals in burying beetles (Nicrophorus) before and during brood care.

Burying beetles display an unusually intense form of brood care for insects, with both parents tending to their young. They bury the carcass of a small mammal as a food source for the larvae before egg-laying. After the larvae hatch, both parents feed them, continuously emitting acoustic signals in the form of stridulation: The beetles create a chirping sound by rubbing the edges of their hardened wing cases against ridges on their abdomens.

“It’s surprising that we still know so little about the function of these stridulatory signals in burying beetles, given that Darwin himself suggested that stridulation likely plays a role in brood care,” says Conrad.

To investigate the role of acoustic communication before and during brood care, the Bayreuth researchers silenced the stridulatory apparatus of parent beetles from three Nicrophorus species by taping over them. The three species vary in their larvae’s dependency on parental care: while the larvae of one species cannot survive without parental care, those of a second species are largely independent. The third species falls somewhere in between.

The researchers found that the three species responded differently to the “silencing” of the parents, but all showed measurable negative effects. The lack of acoustic communication affected the weight of the larvae across all species, impacting their survival chances.

At first glance, the effect seems related to the dependency of the larvae, as the dependent larvae were the most affected, while the least dependent showed fewer effects. However, the timing during brood care when communication is essential also differs across species.

“Our study is an important first step in showing that stridulation during brood care in burying beetles is indeed crucial. We aim to uncover what exactly is being communicated and how brood care is coordinated in the future,” says Conrad.