Hurry up and sing: early onset of diel calling behaviour and ecological drivers of calling behaviour of Acanthoplus discoidalis

ABSTRACT

Animals adopt circadian rhythms and diel calling patterns to ensure successful breeding, avoid predators, and reduce intra- and inter-species competition. We determine the diel calling behaviour of the bush cricket, Acanthoplus discoidalis, across different vegetation types in the southern Kalahari, and whether any variation in calling behaviour exists across the different regions of the landscape. We identify potential environmental drivers impacting its calling behaviour, as well as any impact temperature and wind may have on the species’ calling behaviour. Acanthoplus discoidalis was recorded singing in all vegetation types, calling starts around 10h00 and ceases at 00h00, with a peak from 15h00 to 23h00, a longer peak than expected based on previous studies. This pattern was consistent across all vegetation types, although calling intensity was less in mountainous, rocky, and windy areas. A likely explanation for the expanded diel pattern is that sampling occurred during a mass emergence of the species, and so a wider temporal niche could be a response to reduce intraspecies competition for females. Furthermore, this diel calling pattern may reduce encounters with predators, which are typically either strictly nocturnal or diurnal, yet it is likely this species relies on physical defences over acoustic adaptations to avoid predation.

KEYWORDS:

• Orthoptera
• Tettigoniidae
• calling times
• acoustic behaviour

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author’s contributions

ACvdM and DC conceptualised the study. ACvdM, CL, and RvdM conducted the fieldwork. ACvdM conducted the acoustic analyses, as well as the statistical analyses with input from DC. The initial manuscript was written by ACvdM, with all authors contributing to its revision.

Ethical statement

Collection permit (FAUNA 0244/2021) and transport permit (FAUNA 0245/2021) were issued by the Northern Cape Department of Environment and Nature Conservation. Ethical approval for the sampling protocol and handling of the insects was approved by the University of the Free State (UFS-AED2021/000701).

Additional information

Funding

Funding for the project was provided by the National Research Foundation [UID 129172] and the University of the Free State. Access to Tswalu Kalahari Reserve was facilitated by the Tswalu Foundation and Dylan Smith. iButtons were provided by Mr Hennie Butler.