Brown bears live in a hierarchy, where dominance allows greater access to food and the most productive fishing areas. One recent interaction between bears 32 Chunk and 480 Otis represents a shift in this social order. This is a story of maturation for two bears going in opposite hierarchical directions.

The hierarchy at Brooks River allows bears to quickly assess their competitors, avoiding most physical fights and saving valuable energy. Within the hierarchy large, mature males rank highest followed by other adult males, females with cubs, single females, and finally subadult bears. While this pattern holds as a general rule, bears shift their position in the hierarchy depending on their size, strength, and overall health.

As an adult male in his early teens, 32 Chunk is well positioned to rank near the top of the hierarchy. Chunk was first identified in 2007 as a chunky subadult bear. We don’t know his exact age, but bear monitoring staff noted he appeared to be a young subadult, perhaps 3.5 or 4.5 years old at the time. Since then, he’s grown considerably and is among the largest bears at Brooks River.

In contrast, 480 Otis was a mature adult in his early teens in 2007. He was a big, walrus-shaped bear who, like today, was skilled at fishing in the jacuzzi and far pool. He was not often displaced from his preferred fishing spots.

In 2007 and 2008, a young subadult bear like Chunk wouldn’t even consider challenging a larger adult like Otis. Since then both bears have matured, but their life histories since then lead in different directions within the hierarchy. Recently, 32 Chunk demonstrated his dominance over the older 480 Otis.

When the video begins, 480 Otis is standing upstream of the falls in the middle of the river. 32 Chunk is the darker colored bear in the jacuzzi below the falls.

After Chunk notices Otis above the falls, he leaves the jacuzzi and begins to approach Otis.

480 Otis starts to move away, possibly to avoid 32 Chunk’s approach. This is one sign Otis could be subordinate to 32. The rest of the interaction leaves no doubt who is dominant, however.

Chunk moves through the river faster than Otis. When Chunk nears the older bear, Otis turns to face the younger competitor. They stand mostly still, yawning and assessing each other’s size.

32 Chunk then swats at 480 Otis.

In the video, the bears’ ear positions aren’t easy to see, but 480’s ears seem to be held back against his head, indicating he’s somewhat defensive. Chunk’s ears, in contrast, are mostly upright and oriented forward, a sign of assertiveness and dominance in this context.

The interaction ends when 32 Chunk walks away with 480 Otis watching.

Several behavioral cues demonstrate 32 Chunk’s dominance and 480 Otis’ subordinate status in this interaction.

• 32 directly approached 480.
• 480 attempted to avoid 32.
• 32 lunged at 480 and 480 did not attempt to engage.
• 32’s ears were upright and forward, while 480’s ears were held slightly back against his head.
• 32 ended the encounter, turning his back on 480 and walking away. (Dominant bears decide when an interaction ends unless they have good reason to usurp a resource such as food, a fishing spot, or access to a potential mate.)

Chunk is now entering the prime of his life where he’ll attain his greatest size and rank, and while Otis remains a large bear he’s no longer able to compete with the largest male bears for fishing spots. It seems that Chunk recognizes his size and strength and Otis recognizes the great risks of challenging a younger, larger bear. For the rest of the summer, 32 may displace 480 from fishing spots at Brooks Falls.

Chunk appears to be moving up the hierarchy while Otis continues to slide down it. With these bears, there are two tales of maturation.