Weathering the storm for love? The mate-searching behaviour of wild male Sydney funnel-web spiders, Atrax robustus

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 a 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 mygalomorph spiders, females are highly sedentary and are thought to spend their entire 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 over several consecutive years 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 resightings. Males often spent several days in a female burrow and were recorded visiting multiple females; some female burrows were also visited by multiple males. When outside a female’s burrow, males constructed and occupied temporary shelters (‘temporacula’). Males were most likely to move when there was no rain and they (more tentatively) moved further on dry, warm nights after cool days. Our findings suggest that mate-searching A. robustus males prefer to search for females in less risky environmental conditions, revealing novel risk-minimizing strategies.