Tangle web spiders don’t do half measures, according to a new study that claims these eight-legged creepy-crawlies have only two types of personalities – docile or highly aggressive. Yet rather than dividing the spiders, their differences are in fact the source of their strength, as just as human societies benefit from the diversity of their members, so too do spider colonies prosper when they contain a good mix of personalities, particularly when it comes to protecting themselves from increasing temperatures.
Explaining their findings in the journal Behavioral Ecology, the researchers describe how they closely monitored the survival and reproduction rates of both individual spiders and entire colonies at six different lab-controlled temperatures, ranging from 24 to 34°C (75 to 93°F). As the temperature increased, aggressive spiders began to suffer from decreased survival rates and reproductive failure, while docile ones experienced the exact opposite effect, struggling at low temperatures yet thriving in the heat.
The same occurred at the colony-wide level, with societies consisting exclusively of aggressive spiders dying out at the highest temperature, as none of its members were able to produce eggs. Conversely, docile colonies perished at the lowest temperature, for the same reason.
Attempting to explain this phenomenon, the study authors suggest it may have something to do with the overactive metabolism of highly jumped-up, angsty spiders, whose cells may go into overdrive in order to produce all that aggressive energy. This, in turn, releases molecules called reactive oxygen species (ROS) that cause damage to tissues via a process called oxidative stress. Increases in temperature may therefore exacerbate this effect, causing spiders to burn even more energy and produce yet more ROS.
However, all is not lost for these multi-limbed bullies, as the study authors found that colonies consisting of an even split of docile and aggressive spiders tended to thrive at both extremes of temperature, with individual spiders surviving and reproducing with much greater success.
Though the study authors can’t currently explain this strange finding, they suggest it may have something to with the fact that spiders of different personality types are able to cooperate and perform different tasks, allowing both types to moderate their behavior slightly. For instance, the presence of docile spiders may enable some of the aggressive ones to become a little calmer, as they aren’t constantly surrounded by competitors trying to pick a fight with them.
While this discovery raises some interesting questions about how human societies may benefit from diversity, it also provides some fascinating new insights into how man-made climate change may impact on populations of other species.