Special reading - communication 1 - deception by flexible alarm mimicry in an African bird

Question 1

what are the hypotheses?

Answer 1

wild drongos use vocal mimicry to flexibly vary their false alarm calls to 1) increases the likelihood of target deception 2) maintain target deception during repeated interactions

Question 2

what are the methods for the importance of target specific calls?

Answer 2

1st part: observation of 688 food theft attempts by drongos - indicated that they used target specific mimicry when known

experimentally tested wether target specific alarms increased the intensity of target response. Did this by playing four different call types at 20 min intervals

1) non alarm territory call (control)
2) A drongo specific alarm call
3) A mimicked Cape glossy starling alarm call (common in research site and freq mimicked by drongos)
4) mimicked pied babbler alarm call (target species)

then measured babbler response time, i.e. how long it was disturbed fro before resuming foraging

Question 3

Methods for variance of false alarm calls to increase effectiveness

Answer 3

testing alarm call variance hypothesis

Played four treatments of 3 alarm calls to individual babblerss (n=22) provisioned with a food item and measured their response Time. (3 days between treatments and 20 mins between calls)

of the four treatments 2 contained 3 alarm calls of the same type (drone or mimicked starling) whereas in the other two treatments the 3rd call was changed to opposite type.

Question 4

Results of mimicked call test

Answer 4

Babblers were slower to resume foraging in response to mimicked alarm calls when compared to drone specific alarm calls. However there was no difference when compared to the mimicked starling call. This is because starlings are common and emit honest signals so good to listen to.

Question 5

Results of call variance test

Answer 5

Babblers decreased their response when the same alarm call type was played 3 times in succession but maintained their response when 3rd alarm call was changed

Furthermore , the duration of their response to the 3rd alarm was greater wen it was changed relative to when it was kept the same

Question 6

Overall conclusion

Answer 6

Results suggest that, by flexibly varying their deceptive signal, drongos benefit in two ways. First , they produce signals more likely to deceive their targets . Second, they avoid target habituation to repeated use of the same deceptive signal and thereby evade the frequency-dependant constraints that typically limit payoffs from deceptive communication.