Animals use a variety of signals to communicate. These are often honest and convey important messages, however, (subject to constraints) some species use deception to exploit honest communications.
It has been shown that species that use a single inflexible deception signal are only successful in the presence of abundant honest counterparts.
Scientists investigated if there would be such limitations with a more flexible deception by using the fork-tailed drongo, which is known to mimic alarm calls of other species to steal food.
Researchers tested 2 hypotheses:
- Drongos use vocal mimicry to vary their false alarm calls to steal more food and repeatedly do so without losing effectiveness
- They specifically mimic the calls of the species they are trying to steal from to increase response
Research was conducted in the Kalahari Desert on native drongos. The birds were found to spend 25% of their time following targeted foraging species and stolen food made up 23% of their diet. Alarm calls were produced when a valuable food item was found.
Their success appears to be the result of producing a combination of honest and false alarm calls, with many foraging species relaxing vigilance in the presences of drongo sentries.
Recordings indicated that drongos can mimic 51 different alarm call types, using false calls 69% of the time. They often mimic the specific alarm call of the target species to cause fleeing behaviour (presenting a theft opportunity) and change the alarm call type 74 % of the time when a previous attempt was not successful.
The work shows that flexible deception does present a greater advantage than inflexible deception.
Summarised paper -Deception by Flexible Alarm Mimicry in an African Bird by Flower et al.