Data from: Context-dependent defences in turtle ants: resource defensibility and threat level induce dynamic shifts in soldier deployment

1. Induced defences involve the dynamic deployment of limited and
specialized defensive resources across multiple locations, to maximize
organismal defensive function and fitness. They have been studied
intensively in plants and solitary animals, but the induced defences of
complex animal societies are poorly understood by comparison, despite the
coordinated defensive actions of these taxa. 2. Here, we ask whether the
level of environmental danger induces shifts in the deployment of limited
and morphologically specialized soldiers across multiple nests in colonies
of the turtle ant Cephalotes rohweri. Specifically, we test whether less
defensible nests induce greater soldier deployment, and whether elevated
enemy threat induced further increases in deployment, or reduced
deployment consistent with a risk-limiting strategy. 3. We used
colony-collection data to provide natural ecological context to our
experiments, a field experiment to address how nest-entrance defensibility
and soldier number impact defensive performance, and laboratory
experiments to test whether differences in nest defensibility and threat
level induce dynamic shifts in soldier deployment to new nests. 4. Less
defensible nests were lost rapidly in our field experiment, irrespective
of soldier number, but soldier deployment significantly increased
survivorship of more defensible nests. Concordantly, less defensible nests
induced the deployment of more soldiers per nest under low threat in
laboratory experiments. Nevertheless, high-threat conditions revealed a
risk-limiting soldier deployment strategy: with more danger, the number of
soldiers per nest was significantly reduced in less defensible nests, as
was the overall number of new soldier-defended nests. Total deployment to
new nests was also consistently lower under high threat, dropping from 40%
to 30% across colonies. 5. Induced soldier-based defences in turtle ants
are therefore context-dependent, and dynamically scaled back at multiple
levels when the environment is more dangerous. This dynamic, risk-limiting
strategy is in strong contrast to stable patterns of soldier production in
ants, and to typical task-allocation dynamics in members of the worker
caste. Moreover, these findings establish that the evolution of
specialized defensive agents can be coupled with sophisticated and
inducible deployment strategies in complex social taxa, as we see for
organisms at other levels of biological complexity.