In September 2021, a video supposedly showing a "weird creature" that washed ashore on a beach in Panama racked up more than 25 million views on TikTok:
As this video circulated on social media, a number of people chimed in with attempts to identify this "weird creature." While some people guess that this video showed a mermaid, an alien, or some previously unknown deep sea creature, the majority of responses claimed that the video showed a partially decomposed howler monkey that had been floating in the waters off Panama.
We reached out to Dr. Jessica Mayhew, director of the primate behavior and ecology program at Central Washington University, for her opinion on the video, and she agreed that it was likely a howler monkey.
I agree with your initial assessment that this is a decomposing howler monkey. From the video you can readily see that it has grasping hands and feet (in particular those opposable toes), and it also has a head shape that matches living howler monkeys, namely high external ears and a broad mandibular ramus, which give it the appearance of having a thick neck. It has large canines, which may mean it was a male ...
I believe the white coloration to the body overall is adipocere, which is a fatty, waxy substance forming through the decomposition of adipose tissue. This happens when the decomp process is inhibited or slowed, e.g., a body submerged in water.
A picture of two living howler monkeys can be seen at the top of this story.
Without additional information or images, we can't definitively confirm that this is a howler monkey. Mayhew noted that a visible a prehensile tail or hyoid bone — a small bone found in most animals that evolved into a large resonating chamber in howler monkeys — would be of help to positively identify this "weird creature." As our current choices are mermaid, alien or monkey, we're going to put our money on a howler monkey.