Endangered Bogong moths (Agrotis infusa) forage from local flowers after annual mass migration to alpine sites

Migration plays an important role in the life cycle of many insect species, allowing them to escape unfavourable seasonal conditions. The Bogong moth (Agrotis infusa) is a keystone species that undertakes a long-distance annual migration, with billions of individuals aestivating in summer in the Australian Alps. This species has undergone drastic population declines in the past five years, with steady long-term declines also recorded since the 1980s, and has recently been recognised as Endangered by the IUCN. Despite the role of Bogong moths as a keystone species in the Australian sub-alpine and alpine zones, their feeding habits during their time in the mountains remain understudied, although earlier research suggested that they do not feed during their summer aestivation. To examine whether Bogong moths visit flowers during the summer, we collected pollen from moths caught at a high elevation site in the Australia Alps over the 2021/22 summer period and then identified and counted pollen using light microscopy. We show for the first time that Bogong moths visit a broad range of plant species during their summer activity period and characterise the plant assemblage visited. Almost all the 129 moths sampled carried pollen in large quantities, with a mean of 521 grains per moth. Individual moths varied considerably in pollen load and species composition, suggesting generalist flower visitation. The pollen taxa present on moths indicates local flower feeding at high elevation sites, rather than pollen carried from the lowland origins of migrants. The presence of pollen throughout summer indicates continual flower feeding activity. These results provide important new insights into the ecology of Bogong moths and suggest they could play a previously unrecognised role in pollination in subalpine and alpine ecosystems.

Automated summary

Migration is crucial for many insect species, and the Bogong moth stands out as a keystone species undergoing a long-distance annual migration. Recent declines in the population of this species have raised concerns, leading to its recognition as an endangered species. In this study, we investigated for the first time the feeding habits of Bogong moths during their summer aestivation and found that they visit a variety of plant species, indicating their potential role in pollination in subalpine and alpine ecosystems.