A 6-year study of a New World spider reveals that although colonies composed of docile individuals fare better in the short term, their passive behavior ultimately does them in. A species may need a mean personality to keep from going extinct, the results suggest.

Colonies founded by aggressive spiders successfully fought the intruders off, but produced fewer offspring because of the continuous conflict. In contrast, the predominantly docile colonies ignored intruders and continued to reproduce. In 2009, the docile colonies were flourishing, and their offspring had begun three times as many new colonies on nearby trees and shrubs compared with offspring from aggressive communities. Yet by 2010, the docile spiders’ apparent advantage began to wane as invaders increasingly ate them and stole the insects snagged by the colonies’ webs. By 2012, not a thread remained from the webs established by docile pairs, and only a quarter of those started by mixed pairs were left. Meanwhile,three-quarters of the original 15 nests founded by aggressive pairs stood strong, the team reports today inEcology Letters.