Halloween day! a molossid bat trapped in a communal spider web in the Paraná flooded savanna of eastern Argentina

Bats are prey for several vertebrate and invertebrate predators including spiders. We report the first case of a subadult female mastiff bat (Molossus molossus, Molossidae) trapped in a communal spider web of Parawixia bistriata (Araneidae, Araneae) with photographs and videotapes. This event occurred in the garden of a house next to a wetland in the east of Santa Fe province, Argentina (Paraná flooded savanna ecoregion). The day after the event, the bat was found dead entangled in the spider web. However, it remained in the spider web for three days until falling due to the effects of a strong storm. During this time in the spider web, the bat was daily visited during twilight by one to four spiders at a time. Over three days, the spiders strengthened the web around the bat and bit it with their chelicerae, which could indicate that they engaged in cooperative feeding on the trapped mammal.