I wanted to share one observation with the community and get to know whether this is common. Some years ago I was chilling with my friends in a cabin a couple of kilometers from a lake. The local ant hives started swarming. All hives released young queens and drones, and then hundreds of dragonflies started flying aroung and catching the ants. What is awesome, they only caught the flying ants and ate the big abdomens, then dropped the still living ants to the ground, which was in the end covered with thousands of ants without abdomens. There were many species of dragonflies there, ranging from medium to large but they were so busy with scooping ants that they were not aggressive to each other.
Woah!!! These dragonflies are interesting. Welcome to the forum!
It is not unusual that predators feed selectively when prey is overabundant. Brains for example are pretty energy dense. Years ago I watched a documentary of some orcas chasing a whale baby for hours until the mother had to give up on it. The pack of orcas ended up only eating the tongue (all muscle, jammy) and left the rest behind. Bears hunting salmon towards the end of the season often only feeding on the eggs and spare the rest. There is also multiple evidence from invertebrates showing this behaviour.
In your observation, the dragonflys focused on the protein rich abdomina in this situation, where prey was overabundant for this short time.
i’ve seen non-vegetarian humans refuse to eat chicken that was still attached to a bone. i’ve seen other humans refuse to eat anything on a broccoli plant but the early flower buds, leaving perfectly tasty stems, leaves, later buds, and flowers. or eat only a carrot root but not the greens, or a sweet potato tuber but not the leaves…
With big brain guys like mammals I would just think its logical but to think that even insects can process stuff like that. PS. I have a friend, who loves cartilage. She will clean chicken bones in minutes during lunch time at work, thats also some nice selective eating;)
In relation to what you said about bears eating salmon, I read an article years back about the impact the of salmon remains on the riparian environment. The leftover fish are vital for maintaining soil health close to the streams & rivers. Folks overhunted the bears in part because they thought this was “wasteful”. Less bears & less salmon remains meant a decline in the health of the riparian zones.
I used to have pea puffer fish (Carinotetraodon travancoricus). Snails are like candy to them. I used to take small snails from my larger tank and put them in the puffer tank. These small puffers are too small to crunch through the adult snails. Instead, they’d use their puffer skills to literally suck the snails out of their shells.
One time I thought it might be interesting to see what would happen if I put a puffer in to my other tank for a while becaus the tank was just crawling with snails. What the puffer did was basically go on a murderous rampage. Instead of bothering to suck the snail out of each shell, he just went around and bit their heads off and left the rest of the snails to rot. He even kept biting the heads off snails past the point where he could fit more snail meat in his belly. I had to take him out of there because he was out of control!
We have 2 orcas who visit False Bay i Cape Town annually. They catch seals, but only eat the liver.
I learnt my broccoli lesson at a Swiss farm stall.
Don’t you have any without those thick stalks?
She looked at me in wide eyed horror. But that’s the BEST part, it’s like asparagus!
Would love to see that!.. I mean, not so much the selective feeding, but Orcas (at all) hunting (even better!)
I don´t think that this is too much of a cognitive decision… more like when our body is telling us we need a certain resource when we for example grave for certain kinds of foods. It is more that our “big brain” hold us back in following these kinds of gravings all the time, even if we would be able to follow them.
For wild animals, it is probably a bit different, as they often can not be too picky due to restricted resources.
There is a study on spiders showing, that they can selectively extract different kinds of nutrients from their prey depending on what they need (e.g. nutrients for rapid growth vs. nutrients for egg development etc.). I find this extremely interesting!
The butterflies will avenge those ants, apparently:
Butterfly vs. Dragonfly
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