By Jennie Liu
Modern Beaver - BeaversFuture Beaver - Beaverine

Fig 1: Skeleton of Giant Beaver
The Giant Beaver (Castoroides Ohioensis) is an extinct beaver and was the largest rodent in North America. Giant Beavers were one of the Ice Age giants. It became extinct during the last Ice Age during the Pleistocene Era, which is around 10,000 years to 1.8 million years ago. It is estimated that the Giant Beaver was around 2.5 m long and weighed 60 to 100 kg. The Giant Beavers looked similar to today’s beavers but were a lot larger. Giant Beavers were around the same size as Grizzly Bears while current day beavers are only the size of domestic dogs. A few fossils of the Giant Beavers have been found in areas of North America. The exact reason as to why these Giant Beavers became extinct is still unsure.


Area of the World It Lived in:
Fig 2: Area of where the Giant Beavers lived in are shaded in red.
Specific locations or current countries of where the Giant Beavers lived are unsure however we do know that the Giant Beavers lived in the continent of North America. Two fossils were found, one in Florida and one in South Carolina. It is possible that these Giant Beavers’ original habitat is in North America and migrated to other areas of the world and this accounts for why beavers are now found in some areas of Asia, Britain etc.
Weather/Climate of Its Habitat:
The areas in which the fossils were found suggested that they lived in areas of hot and humid climates. The fossil found in Florida was in a location that is very humid and the fossil found in South Carolina was also in an area of very humid temperatures, lots of rain and many hurricanes. However, since Giant Beavers existed around 2 million years ago, it is unsure whether the climate and weather of the time in one location are the same as the climate and weather now in that location. So it is only possible that the Giant Beaver lived in such climates and weathers.
Vegetation of Its Habitat:
Like today’s beavers, the Giant Beavers also had a semi-aquatic lifestyle since its big body did not allow them to move freely and sleekly on land. The Giant Beavers are similar to today’s Beavers and were good swimmers. This suggests that they lived in wet swamps, marshes and open water with many trees and bushes. It is possible that the Giant Beavers also lived in rivers and lakes or along the banks. So the Giant Beaver had a habitat quite similar to the current beavers.
Preys & Predators:
Even though the Giant Beavers were the same size as bears they were still preys themselves. The Giant Beavers ate plants, wood, trees and aquatic plants such as pond-weeds. However some say that the Giant Beavers may have been carnivores but there is no evidence for this. Predators of the Giant Beaver were Smilodon or Sabre-toothed cat, which is also an extinct animal and it is possible that the ancestors of crocodiles, leopards, tigers and coyotes were also predators of the Giant Beaver.


Fig 3: Diagram of beaver's adaptations

Structural - Enormous Body:
The Giant Beaver was the biggest beaver ever with a length of around 2.5 meters. This is around the same size as the modern Grizzly Bear. Having such a large body allowed them to protect themselves from the predators stated earlier in the ‘Habitat’ section. The most likely reason as to why the Giant Beaver evolved to be so large in size is that their predators of that time were much larger and stronger than they were so in order to survive they evolved to have bigger bodies to defend themselves from predators.

Structural - Thick Fur Coat

The Giant Beaver also had a thick and furry coat like nowadays beavers. However it is unsure whether the Giant Beavers’ also produced oil to keep the coats waterproof. The thick coat protected them form the cold and chilly winters and kept them war and dry. This feature is believed to have evolved around the time of the Ice Age. Since Giant Beavers lived in hot and humid environments, it is believed that the Giant Beaver did not have very thick coats before the Ice Age but during the period of the Ice Age, the Giant Beavers developed thicker coats to shield off the cold weather and help them adapt to the new cold environment.

Structural - Sharp Teeth

Giant Beavers had teeth up to fifteen centimeters long with very uneven and ridged surfaces, which is different to the smooth incisors of modern beavers. These sharp teeth helped them cut wood and gougers. Some say that Giant Beavers were once carnivores and these sharp teeth helped them fight off predators by biting them and tear through the meat of their food. This is not proven but both reasons for their sharp teeth may be true. There are two possible environmental pressures that could have given rise to this adaptation. Firstly, the predators of the Giant Beaver may have been much stronger than them and thus they evolved to have sharper teeth in which they relied on to fight off predators. Secondly, some scientists suggest that beavers were once fully aquatic and when they became semi-aquatic animals they had to find food on land and it could be true that the only source of food available during the time were trees and in order to cut down these trees, they developed sharp and ridged teeth.

Behavioral - Active at Night

A behavioral adaptation of the Giant Beaver is that it is more active at night when it needed movement on land. This protected the Giant Beaver from their predators when they were moving around in the habitat. The environment pressure that led to this is that almost all of the Giant Beaver’s predators are land and diurnal animals so in order to keep themselves away from their predators and not be in danger, they evolved to conduct activities on land at night and not during the daytime.

Physiological – Warm Blooded

Giant Beavers were also warm blooded like modern beavers. Its internal system could constantly produce heat as long as they have energy. This feature allowed them to stay warm underwater and helped them adapt to cold weathers. It also allowed some Giant Beavers to survive the extreme cold during the Ice Age. Beavers have been warm blooded for millions of years already so the exact environment pressure that led to this is unknown. However, if there had been an environmental pressure that resulted to this adaptation it would have been that the beavers moved from a warm climate to a much colder climate in order to adjust to the cold.


The Ancient Giant Beavers became extinct during the Ice Age of the Pleistocene Era, which started around 1.8 million years ago and ended around 10,000 years ago. Scientists still do not know exactly why the Giant Beavers became extinct however there are a few factors in which scientists believe might have caused the extinction of beavers. The first assumption is that the Giant Beavers could not adapt to extremely cold environments during the Ice Age so many died. Another is that the change of the environment might have caused elimination in food sources, which may have caused many Giant Beavers to starve to death. Also, it is possible that the lost of one type of species during the Ice Age affected the others animals due to the disproportion between predators and preys which may have resulted in the extinction of the Giant Beavers. Scientists believe that a small amount of subspecies survived the Ice Age and eventually evolved to today’s North American Beavers and Eurasian Beavers.

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Fig 1: Skeleton of Giant Beaver -

Fig 2: Area of where the Giant Beavers lived in -