Listen to marine iguan calls of mockingbirds, flee them and escape enemy buzzards. Image: Marc Figueras,
Reading iguanas do not communicate about sounds or sounds, but they respond to warning calls from mockingbirds with escape reflexes. The lizards can distinguish the alarm cries from other bird calls. This has been shown by American scientists in experiments on the Galapagos Islands. Previously, escape responses to warning calls from other species were known only from species that communicate with each other via sounds. The Galapagos mockingbirds (Nesomimus parvulus) and the marine iguanas (Amblyrhynchus cristatus) live in close proximity to each other and are hunted by the same predator, the Galapagos buzzard (Buteo galapagoensis). Due to the rocky and rugged coastline, the iguanas often only discover the birds of prey when they have come very close. The mockingbirds, however, can usually make out the buzzards from a greater distance and warn each other by special alarm signals. Thus, the iguanas have the ability to detect warning calls from the mockingbirds to respond earlier and better to the birds of prey. The marine iguanas communicate with each other via visual signals and fragrances, which are less suitable for transmitting information over longer distances than sounds or sounds.

The scientists made their experiments on the island of Santa Fe. There they recorded warning calls and songs from individual mockingbirds and played them close to individual groups of iguanas. Responses from 10 to 15 animals each were documented and assigned to one of three categories: no answer, head lift or flight.

About half of the marine iguanas studied responded to the warnings being played, while less than a third noticed the songs of the mockingbirds, which were not warning calls. The iguanas could thus at least partially distinguish the sound sequences of the birds and thus connect the acoustic signals of another species with a threat of a predator. So far, researchers are not yet sure if this behavior is a learned response to the alarm signals or an innate ability of the marine iguanas. The researchers want to clarify this in further investigations. Experiments will also show whether marine iguanas that do not live on Santa Fe respond to warning calls from mockingbirds.

Maren Vitousek (University of Princeton) et al .: Biology Letters of the Royal Society, online pre-publication, DOI: 10.1098 / rsbl.2007.0443 ddp / Tobias Becker advertisement


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