Steller sea lions are absolutely huge. As the largest species of sea lion in the world, they can grow to be the size of a minivan! So how do animals this big simply disappear? What can wipe out 85% of their population? Scientists in Canada and the United States are investigating many theories as they try to figure out what’s going on. The Vancouver Aquarium plays a crucial role in helping test out some of those theories.
Steller sea lions are absolutely huge. As the largest species of sea lion in the world, they can grow to be the size of a minivan! So how do animals this big simply disappear? What can wipe out 85% of their population? Scientists in Canada and the United States are investigating many theories as they try to figure out what’s going on. The Vancouver Aquarium plays a crucial role in helping test out some of those theories.

© Vancouver Aquarium Marine Science Centre 2006. All rights reserved.

Steller sea lions are stellar, but they’re actually named after Georg Wilhelm Steller, a German naturalist who first classified them. Steller was shipwrecked on Bering Island, so he had a lot of time to write about the animals that he saw.

How big?

Steller sea lions can get pretty big. On average, full-grown male Steller sea lions (bulls) are about the size of a Volkswagen Beetle. Sometimes they can even get up to the size of a minivan! Females (cows) are smaller. They're about the size of a decked-out Harley.

Not that kind of sea lion

Steller sea lions are often confused with California sea lions, but the Stellers are bigger and have lighter fur. California sea lions make a distinctive barking noise, whereas Steller sea lions grunt and roar.

Food

Steller sea lions like to eat certain types of Read More
Steller sea lions are stellar, but they’re actually named after Georg Wilhelm Steller, a German naturalist who first classified them. Steller was shipwrecked on Bering Island, so he had a lot of time to write about the animals that he saw.

How big?

Steller sea lions can get pretty big. On average, full-grown male Steller sea lions (bulls) are about the size of a Volkswagen Beetle. Sometimes they can even get up to the size of a minivan! Females (cows) are smaller. They're about the size of a decked-out Harley.

Not that kind of sea lion

Steller sea lions are often confused with California sea lions, but the Stellers are bigger and have lighter fur. California sea lions make a distinctive barking noise, whereas Steller sea lions grunt and roar.

Food

Steller sea lions like to eat certain types of fish, like herring and salmon, as well as octopus and squid. In turn, the sea lions are eaten by sharks and killer whales.

Love, sea lion-style

Male Steller sea lions have it tough – compared to females, they are 3 times more likely to die when they are young and they usually don’t live as long. Those who survive still have to fight each other for territory and mates.

But to the long-suffering victor goes the spoils: a bevy of beauties for their very own harem...at least, until the girls wander off. Female sea lions show no loyalty to their mates, so males have to carefully watch over their harems to make sure the females don’t slip away until after they've mated. When bulls are guarding their mates and pups, they don’t even eat. Female sea lions only give birth to one pup every 2-3 years, so every pup is precious.

Vancouver Aquarium Marine Science Centre

Hang out with Steller sea lions at the Vancouver Aquarium and learn their personalities! Follow this link.

Vancouver Aquarium Marine Science Centre

© Vancouver Aquarium Marine Science Centre 2006. All rights reserved.


Closeup view of a male Steller sea lion's mug

Photo : A. Trites

© Vancouver Aquarium Marine Science Centre 2006. All rights reserved.


A crowded Steller sea lion haulout. Two Steller sea lions dive off the rocks into the ocean

Photo : A. Trites

© Vancouver Aquarium Marine Science Centre 2006. All rights reserved.


Steller sea lions have been recorded diving to depths of over 400 metres!
Steller sea lions have been recorded diving to depths of over 400 metres!

© Vancouver Aquarium Marine Science Centre 2006. All rights reserved.

If you suddenly had nothing to eat but popcorn and chips, you might enjoy your meals for a while, but sooner or later that junk food diet would take its toll on your body. Your immune system wouldn’t be as effective at fighting off diseases. You’d become tired more quickly. You wouldn’t have the energy to do much of anything.

The sea lion version

Steller sea lions in Alaska may have the same problem. As the amount of Steller “health food” in the North Pacific decreases, they have to turn more and more to their version of “junk food”. Instead of eating their usual diet of nutrient-rich salmon and herring, they are now eating the less nourishing pollock and cod. As a result, they may not be getting the nutrition they need to grow, keep healthy, have babies, or escape from danger. Scientists call this the “junk food hypothesis”.

The fish, they are a-changin’

Scientists a Read More
If you suddenly had nothing to eat but popcorn and chips, you might enjoy your meals for a while, but sooner or later that junk food diet would take its toll on your body. Your immune system wouldn’t be as effective at fighting off diseases. You’d become tired more quickly. You wouldn’t have the energy to do much of anything.

The sea lion version

Steller sea lions in Alaska may have the same problem. As the amount of Steller “health food” in the North Pacific decreases, they have to turn more and more to their version of “junk food”. Instead of eating their usual diet of nutrient-rich salmon and herring, they are now eating the less nourishing pollock and cod. As a result, they may not be getting the nutrition they need to grow, keep healthy, have babies, or escape from danger. Scientists call this the “junk food hypothesis”.

The fish, they are a-changin’

Scientists are not sure why the quantity of different types of fish living in the North Pacific has changed so much. This change might be due to global warming, overfishing, or other changes in the ecosystem. Whatever the reason, diet may be playing a great part in the mysterious decline of the Steller sea lion.

© Vancouver Aquarium Marine Science Centre 2006. All rights reserved.

Travel with sea lion researchers as they collect evidence to help determine what Steller sea lions are eating. Follow this link

Vancouver Aquarium Presents
in conjunction with The North Pacific Universities Marine Mammal Research Consortium

Introduction:

Over about the last 30 years, Steller sea lions have declined about 80% in Alaska, where most Steller sea lions are found, and the research here at the Vancouver Aquarium is part of a huge international effort to try to figure out what might be wrong with Steller sea lion populations.

Steller Sea Lion Research Project
B.C. Scat Cruise

Andrew Trites:

We’re collecting fecal samples to determine what the animals in this area are eating. This is part of the growing population and we’re trying to determine what’s different. Is it something that they’re eating that makes them a healthier population? And we want to compare it to regions of Alaska where Steller sea lions are declining.

Peter Olesiuk:

So this ah, here we are on North Danger. It’s one of the three breeding rookeries in British Columbia where pups are born. And ah, we’re about a month passed the peak pupping season so most of these pups are oh, one to two months old.

So, it’s particularly important to know what the animals at rookeries are feeding on. These females are tied to this site. The pups are too young to swim and so they have to forage locally and come back and nurse the pups.

The non-breeding animals at haulout sites are free to wander up and down the coast and take advantage of prey wherever they may be found.

But these animals, they come back, these females are returning to the rookeries from which they were born to reproduce and so what’s important here is that they have a dependable food supply that’s available every year.

Andrew Trites:

In British Columbia we’ve been finding that the animals here have an energy-rich diet. It’s quite diverse, but we’re finding a lot of species such as herring, sand lance, even sardines are showing up in their diet. They also eat some of the low energy fish: it’s part of a mixed diet. But overall they are getting higher energy per average meal.

Scat research helps us to identify which food sources are most abundant and important to Steller sea lion survival.

Vancouver Aquarium
Presents in conjunction with The North Pacific Universities Marine Mammal Research Consortium

© Vancouver Aquarium Marine Science Centre 2006. All rights reserved.


A school of herring

Photo : A. Trites

© Vancouver Aquarium Marine Science Centre 2006. All rights reserved.


The research at the Vancouver Aquarium concentrates on the theory that Steller sea lions aren’t getting enough healthy food, but there are many other theories for their mysterious disappearance. It’s likely that there’s no one reason for the decline of the Stellers. Here are some factors beyond food that may be causing the population drop.

Sea lion STDs?

Diseases can kill Stellers or make it difficult for them to have healthy babies. Some scientists have looked into whether there was a widespread sickness around the time that the Steller sea lions started dying off. They’ve even considered sexually transmitted diseases! So far, they haven’t found any evidence, and it’s likely that this is not a major cause of the problem.

Fighting for fish

Some scientists are looking into whether fisheries are taking too much of the fish that sea lions like to eat. It’s hard to tell, however, whether a large catch of fish means that we're taking too much from the ocean or just that there’s Read More
The research at the Vancouver Aquarium concentrates on the theory that Steller sea lions aren’t getting enough healthy food, but there are many other theories for their mysterious disappearance. It’s likely that there’s no one reason for the decline of the Stellers. Here are some factors beyond food that may be causing the population drop.

Sea lion STDs?

Diseases can kill Stellers or make it difficult for them to have healthy babies. Some scientists have looked into whether there was a widespread sickness around the time that the Steller sea lions started dying off. They’ve even considered sexually transmitted diseases! So far, they haven’t found any evidence, and it’s likely that this is not a major cause of the problem.

Fighting for fish

Some scientists are looking into whether fisheries are taking too much of the fish that sea lions like to eat. It’s hard to tell, however, whether a large catch of fish means that we're taking too much from the ocean or just that there’s a lot of fish in the water. To fully understand what’s going on, the scientists must figure out exactly what sea lions eat, how much they need and how large the fish populations are.

Scared to death

Steller sea lions are easily scared away from the places where they mate and raise their babies. Scientists are concerned that when people like fishers, scientists and whale watchers keep visiting, the Stellers will abandon these places before the pups are ready, making them more vulnerable to other threats.

© Vancouver Aquarium Marine Science Centre 2006. All rights reserved.

Ecosystem change

Another theory is that changes in the ocean ecosystem are throwing the food web out of whack. As a result, the populations of nutritious fish might be declining or moving further away, where the sea lions can't safely or easily get to them.

Shooting and entanglement

It is also possible that the harvesting, entanglement and shooting of baby sea lions in the 1960s and 70s led to really low populations in the 80s. The scientists considering this theory have reached the conclusion that not enough pups died to affect the population so drastically.

Killer whale kibbles

Transient killer whales eat marine mammals. After whaling took out the bigger whales that killer whales like to dine on, the orcas may have started to eat more sea lions. This theory is very controversial, and many top marine mammal scientists are arguing fiercely over it.
Ecosystem change

Another theory is that changes in the ocean ecosystem are throwing the food web out of whack. As a result, the populations of nutritious fish might be declining or moving further away, where the sea lions can't safely or easily get to them.

Shooting and entanglement

It is also possible that the harvesting, entanglement and shooting of baby sea lions in the 1960s and 70s led to really low populations in the 80s. The scientists considering this theory have reached the conclusion that not enough pups died to affect the population so drastically.

Killer whale kibbles

Transient killer whales eat marine mammals. After whaling took out the bigger whales that killer whales like to dine on, the orcas may have started to eat more sea lions. This theory is very controversial, and many top marine mammal scientists are arguing fiercely over it.

© Vancouver Aquarium Marine Science Centre 2006. All rights reserved.

A sea lion diving off a rock into the water

Photo : A. Trites

© Vancouver Aquarium Marine Science Centre 2006. All rights reserved.


Male Steller sea lions have a higher death rate then females. By the time they get to be 10 years old, females outnumber males three to one.
Male Steller sea lions have a higher death rate then females. By the time they get to be 10 years old, females outnumber males three to one.

© Vancouver Aquarium Marine Science Centre 2006. All rights reserved.

Learning Objectives

The learner will:
  • familiarize himself with the vocabulary used in biology;
  • assess human impacts on biodiversity, and identify ways of preserving biodiversity;
  • describe how personal actions help conserve natural resources and protect the environment in their region;
  • demonstrate an understanding of the dynamic nature of ecosystems.

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