Why is there a higher pilot whale population than orcas?
Posted by Concern-Excellent@reddit | whales | View on Reddit | 12 comments
Posted by Concern-Excellent@reddit | whales | View on Reddit | 12 comments
brydeswhale@reddit
You’re going to hear a lot of high faluting science talk, but here’s some salt of the earth truth:
Pilot whales eat orcas.
Concern-Excellent@reddit (OP)
Really? My Google search said that there had been no documented cases of pilot whale eating or even killing an orca even once but there are verified cases of an Orca hunting down a pilot whale. I am also aware of the fact that Orcas flee away from pilot whales. Can you tell me about your source please.
brydeswhale@reddit
I gotta remember to add the joke indicator.
Concern-Excellent@reddit (OP)
oh so that was a sarcasm
5seat@reddit
They're smaller. Population size and body size have an inverse relationship. It's really more about available resources but there will almost always be more smaller things than bigger things because of that. Let's say an orca needs 200 pounds of food a day and pilot whales need 100 and there's 500,00lbs of fish in an imaginary part of the ocean. (Made up numbers) This imagined ecosystem could support twice as many pilot whales for the same amount of time as the orcas. They require less resources and exhaust them slower. This allows them to expend less energy over all which plays a huge role in any animals' ability to grow/maintain populations. All of this is a gross oversimplification but that's basically it and it's pretty consistent across all biomes.
Concern-Excellent@reddit (OP)
Exactly what I thought could be the case but I feel like we are missing something big. The population of Orcas if far less than pilot whale, about 1 to 20 ratio. They are less than even sperm whale, humpback whale, false killer whale (from my searches). Sperm whale is larger than orca and was even targeted in one of the deadliest hunt by humans and still has more population than Orcas. Although Orcas don't rely on squids which both pilot whale and sperm whale consume and they replenish quickly. So Orcas population can be explained from their feeding style and pickiness particularly.
5seat@reddit
Yeah, with orcas specifically their diet plays a huge role. As someone else said below, they either eat one type of fish (for pescavourous orcas in the northern Pacific it's Chinook salmon) or large marine mammals. Following the logic of my original comment, there's less food available to them because they only eat big things and there's always less big things than small things. Pilot whales, on the other hand, are fairly indiscriminate. If it swims and they can catch it, they'll probably take a shot at it. Same with the smaller dolphin species that also exist in huge numbers. I hate that it's this simple but it really is: the harder it is for an animal to meet it's energy needs, the less of them there will be. I looked it up after my first comment and pilot whales need between 60 and 90kg of food a day. An orca needs 330 to 550kg. Even the most favorable comparison of those numbers means that an orca needs almost FOUR TIMES as much food. Disparity of that degree isn't inconsequential, it will have a massive impact on population. Animals won't reproduce if there isn't enough food to support it. They don't know this in like, a conscious way. They just don't go into estrus and won't until they're well fed enough. To close it out: there's really no way around it, there will always, And I mean always, be more of a smaller thing than a bigger thing. It's just how nature works.
wiz28ultra@reddit
Humpback Whales eat Krill, Antarctic Krill alone have a biomass comparable to that of all the human beings in the world.
wiz28ultra@reddit
Piscivorous Orcas are highly specialized for salmon and other near shore fish while Offshore & Mammal-Eating Orcas eat higher-trophic level animals that are rarer.
They have bigger populations for the same reason Sperm Whales do, their prey are cephalopods and pelagic fish with much larger populations
Concern-Excellent@reddit (OP)
Seems counter intuitive. We humans could survive because we eat almost anything at the time of necessity and we can digest and make use of literally anything. If they can eat a diverse set of things then their survival chance increases. I don't understand the pickiness as it's less effective and specialists in eating do not fare well, example pandas.
wiz28ultra@reddit
Pandas are a poor analogy because Bamboo has far less energy. Cetaceans are the opposite; fish, cephalopods, and mammals are very energy-dense prey.
I think you under-estimate how picky piscivorous Orcas are, they literally will starve if just one or two species of Salmon or another respective species have a population decline. Furthermore, the more generalist Orcas like Transients and Offshore Orcas are predators of other large predators, we're talking animals like Marine Mammals & Cartilaginous Fish that are far more K-selected and inevitably have lower populations due to that and being higher on the trophic level. That's also complicated by the fact that Transients, Offshore, and Resident Orcas don't interbreed.
You're also over-estimating how "picky" Pilot & Sperm Whales are, Cephalopods are immensely diverse, and Sperm Whales have been documented eating everything from Octopi, to Giant Squid, to even Basking Sharks on occasion, whereas Pilot Whales have been noted to not just hunt animals ranging from short-finned to humboldt squid, but also mackerel, cod, herring, etc. All of which are very R-Selected mesopredators with massive populations.
VixxSynn@reddit
Clearly…orcas aren’t having enough sexy time! 😀