Nursery-web spiders have their own version of fifty shades of grey: the males tie the females with silk during mating to avoid sexual cannibalism. The ‘practice’ is documented in a paper published in the journal Biology Letters.
While bondage in the animal kingdom (apart from humans, that is) might sound pretty exciting at first, it is so much more for the male nursery-web spider (Pisaurina mira): it is actually a matter of life or death for poor him. Obviously, he won’t be able to live a sexless life, but, he also has to deal with the female’s ‘uncontrollable’ appetite.
As is the practice among various species of spiders (and, other insects), the females tend to literally consume their mates after copulation. Thus, to avoid being murdered after sex, the nursery-web male will restrain its partner by entangling her in silk.
This behaviour of the male spider has been mentioned in previous studies. Other researchers have found how it would wrap silk around the legs of the female (which are shorter than the male’s even though its body is larger) before and during mating. The authors of the new paper then wondered whether the longer legs allowed the males to restrain the hungry females. In their quest to finding out the details, they came up with other interesting findings.
The silk spinning otherwise is used as getaway in cases of threat by both the male and female, like if they are about to fall, they will use it to hang themselves. Also, the female will use the “nursery webs” of silk to hold their newly-hatched babies. Additionally, the male nursery-web spider will put the silk to an apparently kinky use: physically limiting the female (it is the only species doing so). This was confirmed by the researchers when they paired male and female spiders into different groups: some were inhibited from spinning their silk while others could. The results show that the males that could not limit the females could mate almost as much as the other males. However, the difference was whether they would still be alive after copulation: the males who were inhibited were actually much more likely to get eaten.
Another observation was that longer-legged males with larger bodies were better able to wrap silk around their partners, thereby supporting the hypothesis of the authors.
The silk spinning has another advantage: the males can do “more insertions”, which is linked with greater chances of successful fertilisation as has been documented in other species of spiders.
The findings further indicate that the mating process of spiders is so much more than just fertilisation. So much is at stake. For the female, she will often consider the male as potential food because this will benefit her offspring. Co-author Alissa Anderson explains this intricate web of roles, desires, and needs, describing the male spider as a “Happy Meal with legs” for its partner. Consumption of the male will potentially increase the number of offspring, and the latter’s weight. Furthermore, the baby spiders have more chances of survival when their mother preys on the father. So, as the female weighs her options, the male has to deal with this conflict she faces, with the dooming possibility that she chooses death for him. Therefore, these unusual sexual-survival strategies find their way into nature to help strike the balance between the female’s need to cater for the lives of her offspring and the male’s self-protection, explains Anderson.
The male nursery-web spider will, therefore, practise safe sex by tying his female mate — it is about safety first for him, and not about some kinky predilection.