Weathering the storm for love: Mate searching behaviour of wild males of the Sydney funnel-web spider (Atrax robustus)

Abstract

The risky business of mate-searching often leaves the actively searching sex facing threats and rapidly changing conditions. Yet, active mate-searching behaviour is rarely studied in invertebrates, and we have limited understanding of how mate-searching strategies have evolved to cope with risks posed by harsh weather. We investigated how mate-searching males move through their habitat and how their movement is affected by weather conditions in the Sydney funnel-web spider (Atrax robustus), one of the world's most venomous spiders. As is common in mygalomorphs spiders, females are functionally sessile, and are thought to spend their whole lives in a single burrow, whereas males must permanently abandon their burrows to mate during the breeding season. Nineteen male spiders were fitted with micro-radio transmitters and tracked during their mating seasons in 2020 (n = 2), 2021 (n = 8) and 2022 (n = 9) in Lane Cove National Park, in Sydney, Australia. Males moved at night, typically in a zig-zag pattern, and were found in new locations on approximately 50% of daily resighting's. Males often spent several days in a female's burrow, and some female burrows were visited by multiple males. When outside a female's burrow, males constructed and occupied temporary shelters ('temporacula'). Males were most likely to move and/or moved furthest when there was no rain, and on warm nights after cool days. Our findings suggest that mate-searching A. robustus males prefer to search for females in less risky conditions, revealing novel risk-minimizing strategies, especially in response to rainfall and temperature.