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Survival instincts and not family ties bond spiders together

Spiders usually live alone – they are not so much group animals. However, in some rare cases they stay in groups, such as in the lowland tropical rainforest, where it is very wet and difficult to survive individually. Of course, people were thinking that family bonds formed these social groups, but scientists from the University of British Columbia now say that the reason behind this partnership is totally different.

Spiders in rainforest tend to stick together, which increases their chances of survival. Image credit: Judy Gallagher via Flickr, CC BY 2.0

Constant rain easily destroys light silk-like spider webs, which are essential for these animals to survive. And so spider choose to live in groups as living alone is just too difficult. There were some speculations that this behaviour stems from family ties and tendency to help their kin. Scientists now say that it is driven purely by their survival instinct. In other words, harsh environmental conditions are the reason, why some species live in cooperative social groups, while others do not. Staying with family, in this case, is just a mere coincidence.

One has to understand that scientists here are speaking about two different forms of sociality. On one had there are animals that stay together to help each other to raise their offspring. On the other – spider, who stay together only when environmental conditions dictate them to. By staying in groups they are able to occupy spaces that they could not one by one. Interestingly, scientists say that maybe that is how all animals become social – because environmental conditions teach them to stay together and they remain in groups even when conditions change.

Penguins stay in groups, because otherwise they could not survive in cold and windy climate. Even one-cell organisms group themselves, which also alters their evolutionary path. Scientists researched spiders in Ecuador, at higher elevations, where arachnids in question tend to live in small colonies containing a single family. Scientists took some families and transplanted them lower, where conditions where even harsher because of predators. They noticed that at these elevations spiders formed even larger colonies. Leticia Avilés, senior author of the study, noted: “When the webs get damaged by strong rains or colonies are attacked by predators, some spiders can protect their offspring while others go and make the repairs”.

Conditions form behaviours. Spiders stay in groups not because of family ties, but because of their survival instinct. However, maybe that is how they will evolve to be completely social, regardless of their environment.

Source: ubc.ca

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