Nature 455, 96-99 (4 September 2008) | doi:10.1038/nature07087
Multimodal warning signals for a multiple predator world
John M. Ratcliffe1,3 & Marie L. Nydam2,3
1. Center for Sound Communication, Institute of Biology, University of
Southern Denmark, DK-5230 Odense M, Denmark
2. Department of Ecology and Evolutionary Biology, Cornell University,
Ithaca, New York 14853, USA
3. These authors contributed equally to this work.
Correspondence and requests for materials should be addressed to M.L.N. (Email:
or J.M.R. (Email:
Aposematism is an anti-predator defence, dependent on a predator's ability to
associate unprofitable prey with a prey-borne signal1. Multimodal signals
should vary in efficacy according to the sensory systems of different
predators; however, until now, the impact of multiple predator classes on the
evolution of these signals had not been investigated2, 3. Here, using a
community-level molecular phylogeny to generate phylogenetically independent
contrasts, we show that warning signals of tiger moths vary according to the
seasonal and daily activity patterns of birds and bats—predators with divergent
sensory capacities. Many tiger moths advertise chemical defence4, 5 using
conspicuous colouration and/or ultrasonic clicks3, 6. During spring, when birds
are active and bats less so, we found that tiger moths did not produce
ultrasonic clicks. Throughout both spring and summer, tiger moths most active
during the day were visually conspicuous. Those species emerging later in the
ason produced ultrasonic clicks; those that were most nocturnal were visually
cryptic. Our results indicate that selective pressures from multiple predator
classes have distinct roles in the evolution of multimodal warning displays now
effective against a single predator class. We also suggest that the evolution
of acoustic warning signals may lack the theoretical difficulties associated
with the origination of conspicuous colouration.
XIAO, Jianqiang, Ph.D.
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