… because we can only hear some of the sounds they communicate. Hippopotamuses have a special anatomical structure and they can receive sounds in the water … with a jaw.

Using the system of specialist microphones, acoustics specialists from the Academy of Mining and Metallurgy in Krakow (AGH) stated that animals communicate in low and very low frequencies.

– It is highly probable that they are infrasounds – said Marcin Zastawnik from AGH – whose human ear is unable to capture. Scientific certainty will be obtained after acoustic processing of recordings obtained during the research.

Audible sounds issued by hippopotamuses are similar to a croak interrupted by hiccups. (Kp)