Dolphins use stereotyped, individually distinctive, frequency modulated whistles, referred to as signature whistles, in order to broadcast their identity. In this study, we trained six dolphins at Kolmården Zoo, Sweden, to be called over, either upon hearing their own signature whistle (SW) or upon hearing a biologically irrelevant ”trivial” sound (TS), with the aim to prove the Whistle caller concept. The Whistle caller concept is based on the fact that dolphins occasionally use other dolphins’ signature whistles in order to address specific group members and convene.  Our hypotheses were that (1) dolphins call-over trained using their SW would learn the behaviour faster than dolphins trained using TSs, and (2) dolphins trained with their SW would be able to discriminate between different SWs better than dolphins trained with a TS would be at discriminating between different TSs.  Three out of three dolphins were successfully call-over trained using their SW, and two out of three dolphins using their assigned TS. When discriminating between different sounds, two of the dolphins trained using their SW performed significantly better than one of the dolphins trained using a TS. However, there were large intra-group differences in the results, indicating that we cannot eliminate the possibility that these results stem from individual differences in these dolphins’ ability to learn new behaviours overall, rather than an understanding of the sounds they heard. We suggest that future studies focus on (1) male-female differences in discrimination success when applying the Whistle caller concept, (2) how the characteristics of the trivial sounds affect discrimination success, and (3) the option of calling more than one animal at a time by sending out several SWs in succession.

Background: Histone modifications play an important role in gene regulation. Their genomic locations are of great interest. Usually, the location is measured by ChIP-seq and analyzed with a peak-caller. Replicated ChIP-seq experiments become more and more available. However, their analysis is based on single-experiment peak-calling or on tools like PePr which allows peak-calling of replicates but whose underlying model might not be suitable for the conditions under which the experiments are performed. Results: We propose a new peak-caller called \"Sierra Platinum\" that allows peak-calling of replicated ChIP-seq experiments. Moreover, it provides a variety of quality measures together with integrated visualizations supporting the assessment of the replicates and the resulting peaks, as well as steering the peak-calling process. Conclusion: We show that Sierra Platinum outperforms currently available methods using a newly generated benchmark data set and using real data from the NIH Roadmap Epigenomics Project. It is robust against noisy replicates.