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Tipping points in social animals
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| A hysteresis window between an environmental condition (heat) and group behavior (degree of infighting) in social spiders as they respond to heat stress. Groups that have been in an agitated state (red) tend to remain agitated, whereas calm groups (blue) tend to remain calm over a common temperature range. Credit: Mesa Schumacher |
Complex adaptive systems
We know that there are tipping points in many different complex systems. Although they may be hard to study and exactly define. For example in large systems such as the global economy or climate system. A recent study shows beautifully, in simpler ways, how social animals that lives in communities also have tipping points, before the function of the system changes fundamentally.
In this case the research focused on the communal spider which lay their eggs, spin webs and share their prey in cooperatives colonies, from Massachusetts to Argentina, in relatively cool temperatures. However, only until 31 degrees C, after which they start to attack each other. Suggesting a tipping point where some small perturbation can cause an abrupt and dramatic shift in the behavior of the system.
Reversal is difficult
As ecologists familiar with complex systems all know, once the system crosses the tipping point it will be difficult or perhaps even impossible to return to its previous state even if environmental conditions are reversed. This phenomenon, called hysteresis, implies that a system can have two very different stable states and which state the system is in depends on environmental conditions and its historical dynamics.
Its common that conservation efforts claim that returning to previous environmental conditions in a ecosystem will lead to a recover. However, this is not necessarily true if the system has already crossed a tipping point, in which case you may have to rewind the system to a much earlier set of environmental conditions to drive its recovery. As demonstrated in the studied heat-stressed spiders, turning temperatures down just below 30 degrees C did not alter the behavior of fighting. Not until temperatures dropped down to 28 C degrees did the communal spiders stop fighting again.
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