Data from: Foraging strategy predicts foraging economy in a facultative secondary nectar robber

In mutualistic interactions, the decision whether to cooperate or cheat
depends on the relative costs and benefits of each strategy. In
pollination mutualisms, secondary nectar robbing is a facultative behavior
employed by a diverse array of nectar-feeding organisms, and is thought to
be a form of cheating. Primary robbers create holes in floral tissue
through which they feed on nectar, whereas secondary robbers, which often
lack chewing mouthparts, feed on nectar through existing holes. Because
primary robbers make nectar more readily available to secondary robbers,
primary robbers facilitate the behaviors of secondary robbers. However,
the net effect of facilitation on secondary robber fitness has not been
empirically tested: it is unknown whether the benefit secondary robbers
receive is strong enough to overcome the cost of competing with primary
robbers for a shared resource. We conducted foraging experiments using the
bumble bee Bombus bifarius, which can alternatively forage ‘legitimately’
(from the floral opening) or secondary-rob. We measured the relative
foraging efficiencies (handling time per flower, flowers visited per
minute, proportion of foraging bout spent consuming nectar) of these
alternative behaviors, and tested whether the frequency of primary robbing
and nectar standing crop in primary-robbed flowers of Linaria vulgaris
(Plantaginaceae) affected foraging efficiency. Surprisingly, there was no
effect of primary robbing frequency on the foraging efficiency of
secondary-robbing B. bifarius. Instead, foraging strategy was a major
predictor of foraging efficiency, with legitimate foraging being
significantly more efficient than secondary robbing. Legitimate foraging
was the more common strategy used by B. bifarius in our study; however, it
is rarely used by B. bifarius foraging on L. vulgaris in nature, despite
indications that it is more efficient. Our results suggest the need for
deeper investigations into why bees adopt secondary robbing as a foraging
strategy, specifically, the environmental contexts that promote the
behavior.