Czech researchers recently observed strange behavior in males of a species of spider native to Israel. In order to avoid being devoured, these attack the females and use their silk to tie them up before mating.
Escape from a doom
While male specimens of many spider species court females to convince them to mate, in some of them the ritual turns out to be quite different. As part of this study published in the journal Animal Behavior, researchers fromMasaryk University collected males and females of the species Thanatus fabricii and studied their behavior in the laboratory during mating. This enabled them to see that the latter immobilized the females in order to avoid being eaten.
Extremely rare in spiders due to the physical superiority of females, this behavior is essential for the males of the species T. fabricii mate. Czech scientists found that males first bite females on the legs to paralyze them, then quickly tied up their bodies and limbs using their silk. Once the mating was finished, the females remained motionless for some time before tearing the self-strings they were covered with, allowing their partners to leave the area quietly.
The team also found that females were less active and found it more difficult to catch their prey. This suggests that males use this coercive strategy not only to avoid being devoured by the latter, more massive, but also to overcome their resistance to mating.
“Sexual cannibalism is common in spiders and other invertebrates”
” Restraining females, which is typical of forced copulation, may be of particular benefit to males at risk of being attacked and devoured by their mates during courtship. ”, Note the authors of the study. ” Sexual cannibalism is common in spiders and other invertebrates when females are larger and control sexual interactions. Although their size does not usually allow them to coerce females to mate by physical force, male spiders possess weapons such as silk to immobilize them.. “
The strategy of the males of T. fabricii was not always sufficient to protect them, however: in 11% of mating cases, the females actually attacked and devoured the male before copulation. Despite the seemingly aggressive nature of this mating behavior, researchers are currently uncertain whether females are actually immobilized by males or whether this inactivity simply symbolizes that they are receptive to approaching males.
” Restrained females may allow the male to mate, while unresponsive females will continue to struggle and reject him. “, The researchers conclude.