Comparing Responses of Four Ungulate Species to Playbacks of Baboon Alarm Calls

1. Comparing Responses of Four Ungulate Species to Playbacks of Baboon Alarm Calls Presented By Maeghyn Koehler

2. Background • Many animals have been shown to respond to interspecific alarm calls • This is both within and between taxonomic groups • Thought to occur due to convergence of acoustical similarities • Also shown in acoustically very different species, suggestive of learning • Vervet monkeys responding to superb starlings • No study to date has compared species exposure to strength of response to alarm calls

3. About Baboons- Papiohamadryasursinus • Both males and females produce alarm barks and contest calls • Females and juveniles calls are acoustically distinct • Males calls are acoustically very difficult to discriminate

4. Prediction • Impala will be the most accurate at discriminating between baboon alarm and contest calls • Predicted for two reasons: • Only the impala intermingle with the baboons regularly • Only the impala share the predator risk of leopards

5. Study Site and Subjects • The Okavango Delta located in northwester Botswana • A grassland region that floods annually from June to October • Due to flooding, the vehicles required for testing weren’t always able to fulfill testing • Species tested included: impala, zebra, wildebeest, and tsessebe • Association with baboons varied

6. Playback • Baboon calls recorded from known habituated individuals under long observation • Used software to construct 4 unique pairs of baboon calls • Pairs were matched for age and sex; each sequence included calls from several individuals • Controlled for proportion of calls made by each age/sex class, total number of calls, overall bout duration • Used Realistic sound level meter to insure amplitude was constant between pair and matched natural levels

7. Methods • Playback trials occurred from April-May 2001and February-May 2006 • To ensure no same group of animals was tested twice half of the trials were done on each side of the river • Trials conducted on the same day resulted in traveling down river 3 km between trials • Had two vehicles: one with speaker, one with video recorder • No playbacks were conducted if loud calls had been heard or predators spotted in the previous hour • Each trial involved playback of both call sequences In half of the paired trials alarm call was played first, in the other half contest calls were played first • Each species was presented with all four paired sequences at least once

8. Measurements • Filmed for 25s prior and 25s after call sequence • Measured 4 dependent responses • Latency to orient toward the speaker • Duration of looking toward the speaker • Latency to move at least 1m • Rate of moving (distance over time) • Latency measured from onset of vocalization • Main analysis of one randomly selected individual • Subsequent test used entire sample size

9. Results • Due to the fact that the measurements were highly correlated, it was combined into one fact PC1 • High PC1 scores reflect strong overall response • PC1 response scores were not affected by previously though potentially confounds • 30 of 40 playbacks subjects returned to relaxed state within one minute, other 10 took up to 10 minutes • Subjects were morel likely to travel toward speaker • Although body size and overall PC1 scores were inversely correlated, in the focal test they were not correlated

10. Effect of Species Identity

11. Effect of Sequence Type

12. Relative Effects of Sequence Type and Species Identity

13. Discussion • Consistent with previous studies of interspecific communication • All subjects excluding wildebeest showed stronger response to alarm call compared to contest calls • Impala showed the strongest response and largest difference in call types with Wildebeest with the opposite • No relationship between subject species body size and differences of scores of two call types • Subjects significantly more likely to move toward caller

14. What could be done? • Larger sample sizes • More trials • Test differences in distinguishing male and female calls • Test young ungulates with varying levels of baboon exposure • Test larger ungulate like Kudu with similar baboon association • Is it innate to respond to alarm and ignore contest calls? • Would be explained if they were acoustically similar