1. "Hanging out" : In the above-mentioned context, it means both males and females are in the room together. But the males are not engaged in the activity studied by the scientists; therefore, not doing anything "important" or "specific." When people "hang out," it means they spend time together but don't do anything specific or important. For example, "I hang out with my friend Deborah on Saturdays." I spend time with Deborah but I don't say what we do together. ----------- 2. I had to research "duckitude." It's not a common word at all and I think even most scientists wouldn't know it. I found: https://en.wikipedia.org/wiki/Bio-duck. "Bio-duck" is a mysterious quacking-like sound recorded deep in the ocean. Maybe the word was poorly translated. I would write: "The minke whale is thus revealed to be the source of the mysterious so-called bio-duck sounds first recorded by submarines decades ago." ----------- 3. "Mellow": More relaxed, calmer, less prone to excitement and anger. ----------- Hope this helps! "Bio-duck" was a really interesting one. A new word for me!

1) 'hang out' in this context means that they are present somewhere. Usually though this phrasal verb means to spend time with your friends. Example: I don’t really know who she hangs out with. 2) Here's a Wikipedia page that explains what BIO-DUCK means : https://en.wikipedia.org/wiki/Bio-duck In this context it looks like the authors created a new noun to show that this was a long-term process. 3) 'mellow' means chilled, relaxed, not stressed. Hope this helps ))