http://www.sciencemag.org/news/2019/08/top-stories-manta-ray-friendships-preventing-suicide-and-hidden-hotbed-zika

These manta rays form ‘friendships’ that last longer than a summer fling

Although many sharks are solitary creatures, their manta ray relatives are surprisingly social: They copy one another’s movements, play together, and will even curiously approach nearby humans. Now, scientists have discovered they also form “friendships” with their fellow rays—loose associations that can last for weeks or months at a time.