current and past projects
Communication in crocodilians
In this ongoing project, I study the vocalizations of crocodilians to understand the evolution of communication in mammals and birds
Spontaneous sensitivity to structure
During my PhD, I studied the pattern perception capacities of songbirds and primates
Social cognition in meerkats
Please, get in touch with me if you have questions or collaboration ideas.
Most of my publications are open access, everybody can download them for free. If you have problems to find any of my written work, just ask me directly
Mathias, Ivo Jacobs, Helena Osvath, and I are reconstructing the cognition of extinct dinosaurs (e.g. T-Rex) by studying their closest living relatives: crocodilians and palaeognaths (less derived birds, e.g. emu). These lineages share a common ancestor with all dinosaurs, and whatever they have in common was most probably already present in these fascinating long-gone creatures.
We developed an extensive test battery to study basic cognition in junglefowls (earliest derived neognath bird), emus, nandus, elegant-crested tinamous, Tataupa tinamous, and American alligators.
We built our own alligator research station and have infinite ideas for future projects.
Formant frequencies in alligators
The members of the Crocodylia are promising intermediate model organisms for comparative communication research. Their brain is very similar to that of birds (their closest relatives) but they produce their calls with the larynx, just like mammals.
Mammals and birds can advertise their body size with the resonances in their vocalizations. It was unknown whether reptiles (besides birds) could do the same.
We could show that the calls of a Chinese alligator contained resonances by letting her inhales heliox (helium/oxygen mixture). Acoustic parameters, which shift to higher frequencies in helium are caused by the vibration of air (resonances) in the vocal tract. Because the alligator’s calls sounded different in ambient air and heliox, we knew that she produced resonances.
Here are two calls of the Chinese alligator in ambient air and two in heliox. You can hear that they differ.
We were subsequently found that these resonances are reliable indicators of body size in American alligators. We measured the total length/head length of 43 captive alligators in Florida, USA and recorded their calls.
Here are two calls of a small (252 cm long) and a large (380 cm long) American alligator male, both are sexually mature.
Ravens are sensitive to acoustic structure
Songbirds are typical model species for studying the evolution of language. In language, the sequence (syntax) of elements (e.g. words) creates meaning. It was unknown whether songbirds were able to perceive acoustic structure without previous training.
We used recorded calls of male and female common ravens to create sequences with different patterns. These artificial duets we then played to captive raven pairs in Austria, Germany, and Sweden. The ravens discriminated between the different patterns, providing the first evidence that songbirds are indeed spontaneously sensitive to structure.
Here are two of our artificial raven duets. The calls are from the same ravens but you will hear that the pattern is different.
Discrimination of close calls is related to conflict situations in female meerkats
Meerkats are small carnivores which live in social groups. Only the dominant pair is allowed to reproduce; all the other group members help in raising their offspring. During some periods of the year, the dominant female evicts subordinate females from the group.
I spent 7 months in the Kalahari in South Africa and together with colleagues managed to show that wild meerkat females monitor the position of the dominant female during these periods of conflict. They do this by listening to the individually distinct close calls.
Here are two close calls of two meerkat females. They are sisters from the same litter. Listen to them, you will hear that you can also discriminate between them.