Manatees have it hard. They might be the world's most adorable aquatic mammals, but they're soft targets in the wild. They're basically deaf to boat engines (their chief nemeisis), they can't tolerate cold, and they're not really great swimmers as much as they're just aggressive floaters.

Still, it was surprising to see them die off in such drastic numbers in 2013. There were 829 recorded manatee deaths last year, the highest known total since scientists began tracking the species. Up to 450 of Florida's manatees will die every year from natural causes, but some unusual conditions in 2013 led to a drastic spike in deaths.

Two hundred seventy-six manatees were killed by a high concentration of the toxic marine algae known as red tide. During especially voluminous blooms, underwater plant life, the manatees' primary food source, became contaminated, poisoning the creatures. More than 100 manatees also died of unknown causes in the Indian River area of east-central Florida. Necropsies have yet to turn up any evidence.

"It started out pretty baffling, and to this point they still have no clue," research biologist Bob Bonde told National Geographic.

Increasingly frigid winters have also been a problem for the highly temperature-sensitive mammals. Cold waters were a big factor in 2010, when manatee deaths hit their previous high of 766. Nonetheless, the U.S. Fish and Wildlife Service is still considering downlisting the manatees' status from "endangered" to "threatened."

Now, stem your tears with these videos of manatees being insufferably adorable.