[HN Gopher] As the California sea lion population got bigger, so...
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As the California sea lion population got bigger, so did male sea
lions
Author : Hooke
Score : 69 points
Date : 2023-05-10 20:36 UTC (1 days ago)
(HTM) web link (news.ucsc.edu)
(TXT) w3m dump (news.ucsc.edu)
| ghastmaster wrote:
| > 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]
| tokai wrote:
| 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
|
| [1] https://en.wikipedia.org/wiki/Ray_Bandar
| user3939382 wrote:
| 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.
| phendrenad2 wrote:
| Or is it the microplastics?
| jacquesm wrote:
| What's with all the middlebrow dismissals here?
| akiselev wrote:
| 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
|
| [2] https://psmag.com/environment/fish-stories-the-ones-that-
| got...
| pvaldes wrote:
| > 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 wrote:
| Yes they do. It's literally where the observation came from.
| mbrameld wrote:
| > 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.
| olddustytrail wrote:
| That's fine but the comment I was replying to said
| something very different.
| goosedragons wrote:
| There is also selectivity for smaller fish for those that are
| caught using gillnets since they target a specific size.
| Smaller fish can swim right through and thus are advantaged
| at avoiding being fished.
| rcme wrote:
| _These_ photos might not support the claim, but it is well
| known in fishing communities that many species of fish have
| gotten smaller. For instance, the size of lake trout in the
| great lakes has decline greatly. People used to catch 100+ lb
| lake trout. That 's unfathomable to me.
| lmpdev wrote:
| 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 wrote:
| 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.
| soperj wrote:
| 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 wrote:
| Sea lions mostly eat smaller fish, shellfish, and molluscs.
| They don't usually go after halibut and salmon.
| soperj wrote:
| I meant fish stocks, if fish stocks ever recover, will they
| get bigger again.
| jerrysievert wrote:
| 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.
| Alupis wrote:
| Is this because the fish are harvested/farmed and/or caught at
| younger ages, or is this because the adult size has decreased?
| jmartrican wrote:
| 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.
| darth_avocado wrote:
| 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 wrote:
| 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._
| natch wrote:
| So, well fed creatures grow bigger and have more offspring. Who
| would have thought.
| dudeinjapan wrote:
| This article de-sealionizes non-binary sealions.
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(page generated 2023-05-11 23:02 UTC)