Episode 209 – Giant River Otter: Apex in the Amazon

“…And today we’re walking about a lanky tooth missile that isn’t scared of nobody. But more on that later.”

The Amazon is home to many of the western hemisphere’s most successful predators. But the most surprising apex predator isn’t the piranha, the anaconda, or even the legendary jaguar – it’s the giant otter! Alone, they can take on lots of different opponents. Together, there’s nothing that they can’t handle. You definitely don’t want to put your feet up on this otterman. But being on the top of the food chain definitely has its perks as the Giant Otter knows here in Life, Death, and Taxonomy.

Description of the Giant River Otter

  • The giant river otter is a mustelid and like other mustelids, it’s a long boy. 
  • Otters have long bodies compared to their short legs.
  • They have sleek, and very dense fur that makes them look smooth compared to their fuzzy sea otter kin. 
  • As far as mustelids go, they are pretty gnarly looking animals with large mouths and with long sharp canines. 
  • Their faces are similar to seals, with large nostrils high on the top of their rounded snout.
  • They have webbed feet and flat wing-like tails that act like a fin underwater.  

Measure Up

Welcome to the beloved Measure Up segment. The official listener’s favorite part of the show! The part of the show when we present the animal’s size and dimension in relatable terms through a quiz that’s fun for the whole family. It’s also the part of the show that’s introduced by you when you send in audio of yourself saying, singing, or chittering the words Measure Up into ldtaxonomy at gmail dot com. 

  1. Rabbit 
  2. Ruffed Grouse 
  3. Kangaroo
  4. Wood pecker


  • 1.5 and 1.7 m (4.9 and 5.6 ft)
  • How many giant otters go into the mean diameter of Halley’s Comet?
  • Hint: Halley’s Comet is the only comet that can be seen with the naked eye twice in a human lifetime. It’s elliptical orbital path brings it in close to the sun before launching it back out to the far reaches of the sun. Its aphelion, or the farthest orbital distance an object is from the sun, is about the same as Pluto’s orbit. Halley’s Comet’s aphelion is 35 AU (3,253,000,000 miles/ 5,236,900,000 kilometers). 
  • 6,470 otters. Halley’s Comet’s mean diameter is 6.8 miles (11 km).


  • 26 and 32 kg (57 and 71 lb)
  • How many yellow-crowned Amazon parrots could a giant otter eat if it ate its weight in parrots?
  • Hint: Amazon parrots are a genus of parrots native to South America, but they’re found all over the Americas and in the Caribbean. 
  • 76 parrots. The yellow-crowned Amazon parrot is 15 ounces (0.42 kilograms). 

Fast Facts about the Giant River Otter

  • They are very much the wolves of the Amazon. Otters live in large family groups and hunt in packs. 
    • They have been observed using more than 20 different vocalizations to communicate.
  • Their dense fur acts as a dry suit, not allowing water to reach their skin. This makes them more hydrodynamic, and it protects them from losing too much heat in the water. 
  • They can close their nostrils while under water and open them when they surface like other aquatic mammals. 
  • They mostly eat fish, and can eat up to 10% of their body weight in fish each day. 
  • Each dry season, the otters mark exposed muddy banks with their scent to mark their territory.
  • They are currently considered endangered, mostly due to habitat loss. 

Major Fact: Adorable Abominable Apex in the Amazon

  • The Amazon is well known for having a lot of deadly things in it, particularly in or near the river.
  • There are massive constrictor snakes like the anaconda, mini crocodiles called caimans, actual crocodiles, jaguars, and the river is full of piranhas: ravenous fish that strip the flesh from your bones in seconds.
  • While these things are formidable, you only get the title of apex predator if you eat without getting eaten. 
    • So the jaguar and the crocodile get to stay, but the piranha has to keep an eye out for crocodiles, birds, and dolphins.
    • The caiman and the anaconda would also make the list, but there is one cute little killer that looms over them like a furry shadow: the giant otter
  • The giant otter is uniquely suited for underwater combat.
    • It’s 5 feet long and weighs as much as a beefy dog
    • Its slender body and powerful muscles allow it to slice through the water quickly and change directions on a dime.
    • It has hyper-sensitive whiskers that can sense disturbances in the water at long distances
    • Its main food source is fish, which can be tricky to catch if you’ve ever tried to catch one by hand
    • But the otter is able to dart around and keep up with fish underwater. It rarely fails to catch what it goes for.
    • It even hunts piranhas
  • If fish aren’t available, they’ll eat crabs, birds, or even larger prey
    • If something is too big or too dangerous to take down alone, the otter will enlist some of its friends to join the hunt
    • Once they band together, they can take down juvenile anacondas or even black caimans, which can get up to 11 ft long!
    • As a group, they can fend off even a hungry jaguar!
    • Because of this, they have no serious natural predators – meaning no species regularly preys on giant otters. Though their young can still be gobbled up and if one is caught alone with a full-grown anaconda, caiman, or jaguar, things will go south quickly. But certainly not without a fight.

Ending: So take a swim, hone your hunting skills, and don’t take no guff from no one like the giant otter here in LDT