5 ms·

As the California sea lion population got bigger, so did male sea lions

73 points by Hooke 3y ago

soperj 3y ago
Wonder if that'll be the case with fish if they ever recover. Halibut and Salmon have vastly decreased in size just over my lifetime.
- nradov 3y ago
  Sea lions mostly eat smaller fish, shellfish, and molluscs. They don't usually go after halibut and salmon.
  - jerrysievert 3y ago
    California sea lions have been swimming further and further up the Columbia River and destroying the salmon populations by eating them. They do indeed eat salmon and will go out of their way for the tasty treat.
  - soperj 3y ago
    I meant fish stocks, if fish stocks ever recover, will they get bigger again.
- Alupis 3y ago
  Is this because the fish are harvested/farmed and/or caught at younger ages, or is this because the adult size has decreased?
darth_avocado 3y ago
Another thing could be that as populations get bigger, so does genetic diversity, creating more sea lions that are bigger than usual. And since bigger male sea lions have an advantage in mating, those traits get passed on to more lions and over generations, become common.
- DoreenMichele 3y ago
  They actually covered that: By expanding the breadth of their diets, the sea lions have been able to get bigger even as their numbers increased. In theory, larger sea lions should be able to travel further, dive deeper, and handle larger prey. In addition, as their breeding sites became more crowded, increased competition between males during the breeding season may have favored larger males over time. “Body size is very important in competition with other males to control territory at breeding sites. Being bigger also means they can fast longer and stay on the beach to defend their territory,” Valenzuela-Toro said.
  - darth_avocado 3y ago
    Right, it talks about increased competition and size advantage. I was thinking more about the size itself. Increase in numbers means more genetic diversity, and more individuals with bigger size in a generation. Therefore, speeding up the generational size growth.
phendrenad2 3y ago
Or is it the microplastics?
- phendrenad2 3y ago
  The consensus seems to be that microplastics contribute to obesity[1], and if so, we might see it in many other mammals. [1] https://www.niehs.nih.gov/research/programs/geh/geh_newsletter/2022/6/spotlight/microplastics_may_increase_risk_for_obesity.cfm https://www.niehs.nih.gov/research/programs/geh/geh_newslett...
ghastmaster 3y ago
> Valenzuela-Toro looked at the size and morphology of sea lion skulls collected between 1962 and 2008 in central California and now held at the California Academy of Sciences "As the California sea lion population got bigger, so did the collected skulls", is what I read. I cannot find the method of collecting the skulls from the paper or the one paper I was able to read that this paper sourced. If humans were hunting, poaching, or collecting dead animal skulls, there could very well be some influence on the size of the skulls from their desire to hunt/poach bigger game and or collect a bigger specimen than they previously collected/hunted/poached. If I was out collecting for grins and giggles, and I had a sack full of skulls, I would likely throw out the small ones to fit a bigger one than is in my sack or larger than what I have at home. Another possibility is that they collected larger skulls because there is more pressure on the larger animals as time progressed in the study period, creating a larger supply of the larger skulls. On average, the animals may in fact be smaller.
- deleted 3y ago
  [deleted]
- tokai 3y ago
  Its a scientific collection. Not just some random poacher's loot. Building such collections of specimens to support is crucial to life sciences in particular.[0] This skull collection is the life work of Ray Bandar.[1] [0] https://en.wikipedia.org/wiki/Scientific_collection https://en.wikipedia.org/wiki/Scientific_collection [1] https://en.wikipedia.org/wiki/Ray_Bandar https://en.wikipedia.org/wiki/Ray_Bandar
akiselev 3y ago
My bet is that this is probably the first evidence of indeterminate growth [1] in the species. Increasing skeletal size is a pretty tell tale sign. With all the conservation programs working, they’ve started to get old enough that we can see enough of a difference to overcome individual variance in their growth cycle. Many fish used to be much bigger than today because they survived for much longer since they had no predators. Within years, the average fish size of those caught at any popular vacation destination fall precipitously as can be observed by vacation photos [2]. If a mammal were to acquire this adaptation, it makes sense that it would be a marine one - I think whales and dolphins exhibit it too [1] https://en.m.wikipedia.org/wiki/Indeterminate_growth https://en.m.wikipedia.org/wiki/Indeterminate_growth [2] https://psmag.com/environment/fish-stories-the-ones-that-got-away-3914 https://psmag.com/environment/fish-stories-the-ones-that-got...
- pvaldes 3y ago
  > Within years, the average fish size of those caught at any popular vacation destination fall precipitously as can be observed by vacation photos Must be taken in mind that the photos don't support that claim.
  - olddustytrail 3y ago
    Yes they do. It's literally where the observation came from.
    - mbrameld 3y ago
      > Many fish used to be much bigger than today because they survived for much longer since they had no predators. Within years, the average fish size of those caught at any popular vacation destination fall precipitously as can be observed by vacation photos My reading of the article is that the pictures don't show a particular species getting smaller over time, but that the species of fish that grow large aren't caught anymore. Yes the fish in the pictures got smaller over time, but they also changed species. From the article: > Yes. This really isn’t a story about shifts in size within a particular species. I didn’t find that. What I did find is that the big species just aren’t there anymore.
jmartrican 3y ago
Maybe the males are fighting for breading rights, and the bigger you are, the more likely you are to win. I think this is an example of sexual dimorphism.
natch 3y ago
So, well fed creatures grow bigger and have more offspring. Who would have thought.
jacquesm 3y ago
What's with all the middlebrow dismissals here?
user3939382 3y ago
I used to watch them playing by my great grandfather’s house in Carmel when I was little. Glad to know they’re still there and doing well.
dudeinjapan 3y ago
This article de-sealionizes non-binary sealions.
lmpdev 3y ago
I swam with a 32 year old male California Sea Lion I cannot understate their size. The males are terrifyingly large. I'm not surprised by these findings though, sexual dimorphism is pretty extreme in California Sea Lions, especially compared to the comparitively non-dimorphic earless (true) seals I'd be curious if this would replicate in Elephant Seals but I'm not sure how you could control the positive environment to grow their numbers in the same way
- teruakohatu 3y ago
  I am not sure how Californian sea lions compare in size with New Zealand sea lion but I wouldn't want to be swimming anywhere near one.
  - api_or_ipa 3y ago
    Members of the Dolphin Club & South End Rowing Club swim and co-exist happily with the seals and sea lions in the waters of the San Francisco Bay. Give them the space they deserve and they rarely are cause for much concern. Fairly frightening when you see one pop his head up close to where you're swimming, but it's not dangerous. The biggest danger to swimmers has been, is, and will likely always be boats, especially ones with propellers.

73 points by Hooke 3y ago

Wonder if that'll be the case with fish if they ever recover. Halibut and Salmon have vastly decreased in size just over my lifetime.

nradov 3y ago
Sea lions mostly eat smaller fish, shellfish, and molluscs. They don't usually go after halibut and salmon.
- jerrysievert 3y ago
  California sea lions have been swimming further and further up the Columbia River and destroying the salmon populations by eating them. They do indeed eat salmon and will go out of their way for the tasty treat.
- soperj 3y ago
  I meant fish stocks, if fish stocks ever recover, will they get bigger again.
Alupis 3y ago
Is this because the fish are harvested/farmed and/or caught at younger ages, or is this because the adult size has decreased?

darth_avocado 3y ago

Another thing could be that as populations get bigger, so does genetic diversity, creating more sea lions that are bigger than usual. And since bigger male sea lions have an advantage in mating, those traits get passed on to more lions and over generations, become common.

DoreenMichele 3y ago
They actually covered that: By expanding the breadth of their diets, the sea lions have been able to get bigger even as their numbers increased. In theory, larger sea lions should be able to travel further, dive deeper, and handle larger prey. In addition, as their breeding sites became more crowded, increased competition between males during the breeding season may have favored larger males over time. “Body size is very important in competition with other males to control territory at breeding sites. Being bigger also means they can fast longer and stay on the beach to defend their territory,” Valenzuela-Toro said.
- darth_avocado 3y ago
  Right, it talks about increased competition and size advantage. I was thinking more about the size itself. Increase in numbers means more genetic diversity, and more individuals with bigger size in a generation. Therefore, speeding up the generational size growth.

phendrenad2 3y ago

Or is it the microplastics?

phendrenad2 3y ago
The consensus seems to be that microplastics contribute to obesity[1], and if so, we might see it in many other mammals. [1] https://www.niehs.nih.gov/research/programs/geh/geh_newsletter/2022/6/spotlight/microplastics_may_increase_risk_for_obesity.cfm https://www.niehs.nih.gov/research/programs/geh/geh_newslett...

ghastmaster 3y ago

> Valenzuela-Toro looked at the size and morphology of sea lion skulls collected between 1962 and 2008 in central California and now held at the California Academy of Sciences "As the California sea lion population got bigger, so did the collected skulls", is what I read. I cannot find the method of collecting the skulls from the paper or the one paper I was able to read that this paper sourced. If humans were hunting, poaching, or collecting dead animal skulls, there could very well be some influence on the size of the skulls from their desire to hunt/poach bigger game and or collect a bigger specimen than they previously collected/hunted/poached. If I was out collecting for grins and giggles, and I had a sack full of skulls, I would likely throw out the small ones to fit a bigger one than is in my sack or larger than what I have at home. Another possibility is that they collected larger skulls because there is more pressure on the larger animals as time progressed in the study period, creating a larger supply of the larger skulls. On average, the animals may in fact be smaller.

deleted 3y ago
[deleted]
tokai 3y ago
Its a scientific collection. Not just some random poacher's loot. Building such collections of specimens to support is crucial to life sciences in particular.[0] This skull collection is the life work of Ray Bandar.[1] [0] https://en.wikipedia.org/wiki/Scientific_collection https://en.wikipedia.org/wiki/Scientific_collection [1] https://en.wikipedia.org/wiki/Ray_Bandar https://en.wikipedia.org/wiki/Ray_Bandar

akiselev 3y ago

My bet is that this is probably the first evidence of indeterminate growth [1] in the species. Increasing skeletal size is a pretty tell tale sign. With all the conservation programs working, they’ve started to get old enough that we can see enough of a difference to overcome individual variance in their growth cycle. Many fish used to be much bigger than today because they survived for much longer since they had no predators. Within years, the average fish size of those caught at any popular vacation destination fall precipitously as can be observed by vacation photos [2]. If a mammal were to acquire this adaptation, it makes sense that it would be a marine one - I think whales and dolphins exhibit it too [1] https://en.m.wikipedia.org/wiki/Indeterminate_growth https://en.m.wikipedia.org/wiki/Indeterminate_growth [2] https://psmag.com/environment/fish-stories-the-ones-that-got-away-3914 https://psmag.com/environment/fish-stories-the-ones-that-got...

pvaldes 3y ago
> Within years, the average fish size of those caught at any popular vacation destination fall precipitously as can be observed by vacation photos Must be taken in mind that the photos don't support that claim.
- olddustytrail 3y ago
  Yes they do. It's literally where the observation came from.
  - mbrameld 3y ago
    > Many fish used to be much bigger than today because they survived for much longer since they had no predators. Within years, the average fish size of those caught at any popular vacation destination fall precipitously as can be observed by vacation photos My reading of the article is that the pictures don't show a particular species getting smaller over time, but that the species of fish that grow large aren't caught anymore. Yes the fish in the pictures got smaller over time, but they also changed species. From the article: > Yes. This really isn’t a story about shifts in size within a particular species. I didn’t find that. What I did find is that the big species just aren’t there anymore.

jmartrican 3y ago

Maybe the males are fighting for breading rights, and the bigger you are, the more likely you are to win. I think this is an example of sexual dimorphism.

natch 3y ago

So, well fed creatures grow bigger and have more offspring. Who would have thought.

jacquesm 3y ago

What's with all the middlebrow dismissals here?

user3939382 3y ago

I used to watch them playing by my great grandfather’s house in Carmel when I was little. Glad to know they’re still there and doing well.

dudeinjapan 3y ago

This article de-sealionizes non-binary sealions.

lmpdev 3y ago

I swam with a 32 year old male California Sea Lion I cannot understate their size. The males are terrifyingly large. I'm not surprised by these findings though, sexual dimorphism is pretty extreme in California Sea Lions, especially compared to the comparitively non-dimorphic earless (true) seals I'd be curious if this would replicate in Elephant Seals but I'm not sure how you could control the positive environment to grow their numbers in the same way

teruakohatu 3y ago
I am not sure how Californian sea lions compare in size with New Zealand sea lion but I wouldn't want to be swimming anywhere near one.
- api_or_ipa 3y ago
  Members of the Dolphin Club & South End Rowing Club swim and co-exist happily with the seals and sea lions in the waters of the San Francisco Bay. Give them the space they deserve and they rarely are cause for much concern. Fairly frightening when you see one pop his head up close to where you're swimming, but it's not dangerous. The biggest danger to swimmers has been, is, and will likely always be boats, especially ones with propellers.