Prey animals are capable of assessing their surrounding environment for any potential threats to their safety. Many can form associations between an environmental event and their own response to the event. Other members of the same species have “the capacity to glean information from other individuals in order to identify and locate potential predator threats” (Dawson and Chittka, 2014). They achieve this through communicating directly that there is a threat, detecting any cues left by previous attacks, or even eavesdropping on anti-predator cues. These cues can be visual, chemical, or auditory. By using social information, animals can detect where danger lurks and where it is absent. This exchange of information allows many animal species to “aggregate with other individuals in response to predation pressures” (Dawson and Chittka, 2014).
Dawson and Chittka (2014) demonstrated, for the first time, that past experiences with predation causes bumblebees (Bombus terrestris) to gather together with members of the same species, or better known as conspecifics. They behave in this manner because bees face “significant predation from ambush predators that sit and wait for their prey, often on flowers themselves” (Dawson and Chittka, 2014). Crab spiders have been the best studied predators of bumblebees. Since bumblebees use their visual sensory systems to locate flowers or learn from watching others, the spiders exploit this high reliability on vision by changing color to camouflage themselves against a floral background.
Figure 1. Goldenrod crab spider with captured bumblebee.
Luckily, most of the attacks are unsuccessful, giving bees the opportunity to learn and avoid the location of dangerous floral patches. Dawson and Chittka (2014) state that although personal sampling of an environment may impose severe fitness costs, there is more benefit in using information from other individuals as a means to bypass these costs. Previous evidence has found that pollinating bees use social information to avoid predation by relaying the threat to nest-mates or identifying the sites where other individuals were attacked. Unfortunately, a problem arises with these social strategies because bees can only account for the interactions with predators that occurred recently.
So, this led Dawson and Chittka (2014) to propose a “scenario where bumblebees identify safe food sources by joining feeding conspecifics.” In a prior study, these researchers found that bees learned to avoid both camouflaged and highly visible spiders equally well—and very quickly.
You can see a video of this in an artificial meadow here: http://news.bbc.co.uk/1/hi/sci/tech/7596808.stm
In this current study, they found that bees are highly successful in learning to associate flower colors with safety and danger (Fig. 2). It turns out that the environment had a significant effect on whether bees would join other bees or not. Hesitation would be seen in front of flowers that were unoccupied by nestmates, but if the flower was safe then many bees would be observed, leading to the notion that bees acquire social foraging experience. The researchers also attempted to provide sucrose as a reward on both dangerous and safe flowers, and still found significant preference to join the flower occupied by other conspecifics.
Figure 2. Proportion of bees, in the various treatment groups, that landed on the occupied flower.
Based on individual previous experiences, bees choose to feed with other individuals so as to avoid the risk of predation. Social information can be ignored when no threat is detected. This suggests that bumblebees “actively decide when to use social information according to the environmental context” (Dawson and Chittka, 2014). We must continue to actively study such behaviors to enhance our understanding of social learning. Interpretation of social information in anti-predator situations reveals “unknown social predator avoidance tactic in pollinators” (Dawson and Chittka, 2014).
As for the larger impact, we are currently witnessing the presence of environmental concerns in daily media and bumblebees have become the subject of widespread study. They play a critical role as agricultural pollinators. They seem to be built to pollinate, for the following reasons; can fly at low temperatures; many species have longer tongues than honey bees, so they can pollinate flowers with long, narrow corollas; and they are very hairy, allowing them to pick up and transfer pollen. Thanks to bees we have the current variety flower species, fruits, and vegetables. We must continue to investigate the mechanisms involved in such a tiny, yet important organism.
References:
Dawson, E.H. and Chittka, L. (2014). Bumblebees (Bombus terrestris) use social information as an indicator of safety in dangerous environments. Proc. R. Soc. B, 281: 20133174
