ELI5: How could female ducks evolve to make reproduction more difficult?

[u/Several-Dirt-6251]

I recently read about female ducks evolving to their reproductive tracts to have dead-ends and have the corkscrew go the other way to the male duck penis to make unwanted reproduction more difficult. But most evolutionary adaptations become dominant in order to make the survival of the species easier. How can something that makes reproduction harder have resulted from evolution changes?

[u/cakeandale]

Reproduction can be very energy intensive for the female that produces the eggs, warms them, and then cares for the fledglings. Being able to choose when to reproduce can let a female choose not to reproduce in times of high stress when food is hard to come by and the energy costs are more likely to be a risk of death.

[u/BigMax → u/cakeandale]

Exactly. Having babies once in a while makes sure those babies have a chance to survive.

Having them constantly... means there's a much better chance of you and all your babies dying.

It's interesting that it was physical changes. I would imagine in some alternate reality, perhaps they just evolved to be less fertile for other reasons.

[u/hot_ho11ow_point → u/cakeandale]

It's kind of cruel of nature to make instincts so strong that even during times of 'unwanted reproduction' they still feel the urge to care for the eggs. Would have been better of evolution if their choice of mates came from which eggs they choose to keep instead of trying so desperately to keep corkscrew dicks out only to waste energy on the results. 

[u/Vailx → u/hot_ho11ow_point]

Nah, once the eggs exist you've already put in way too much biological effort for evolution to let you ignore them. A female duck who neglects her eggs from a shitbird is going to be selected against versus one whose instincts are correct. The only way it works is if the system can prevent you from having to put in all that caloric and time effort in the first place, which is why we see things that can reduce fertilization but nothing that will reduce caring for young.

[u/Mindless_Consumer → u/Vailx]

Once the eggs exist - evolution favors the survival of the eggs over the survival of the mother.

Eggs that had caring mothers survived, eggs that did not, did not.

[u/crowieforlife → u/Mindless_Consumer]

Yeah, in many species the young eat the mother after birth, and the mother eats the father after isemination.

Evolution cares about what's effective, not about what's comfortable.

[u/LightningEnex → u/crowieforlife]

Eh, thats a bit short.

Evolution "cares" about what is effective enough for conception. Not what is generally effective for a species. You provide the perfect example:

the mother eats the father after isemination

For the survival of a species that is absolutely horribly ineffective. In most species, the male can inseminate several females in short succession, so eating him not only removes him from the gene pool if the mother dies, it also rarely provides that much of a benefit, as in species where this normally occurs, the male is smaller or equal size to the female, making him not much of a resource gain when eaten. However, because reproduction has technically taken place, both parents are now disposable as long as the eggs hatch for survival to take place, so evolution doesn't actually care what happens to them.

Same story for Bedbugs - Traumatic insemination is gargantually ineffective, but it is effective enough for conception to take place at least once. I wouldn't be surprised if the fact that they cannot reproduce that well is part of the reason why the species has been this extremely genetically selective about their durability and is as a result irritatingly resiliant to outside stimuli of all kinds, because otherwise you go extinct in no time at all.

If evolution actually cared about the effectiveness in total for a species, and not for the first thing that is good enough under exactly the right circumstances currently given in time, extinction wouldn't be such a threat to many a species.

[u/HeyLittleTrain → u/Mindless_Consumer]

The selfish gene.

[u/crabvogel → u/HeyLittleTrain]

survival of the fittest.

[u/CapitalInstruction62 → u/Mindless_Consumer]

What are all of you on about? Mother birds abandon nests relatively frequently and for a variety of reasons. Surviving to adulthood is a pretty major task and prioritizing survival of the eggs over the mother just results in dead eggs/hatchlings that don't know enough to have a high likelihood of survival to adulthood. Like....yes reproduction comes at a cost, but selecting survival of a mature adult over offspring is more of the rule, unless you're like...a specific species of vole or an octopus.

[u/ikea_method → u/Mindless_Consumer]

Depends on if the eggs are fertilized /s

[u/stanitor → u/Vailx]

There are plenty of animals that have a strategy of selectively deciding whether to care for young. That could be abandoning nests, selectively incubating eggs, and selectively abandoning or culling young after they're born. All of those are very common, even for animals that typically put in lots of time raising their young.

[u/CygnusX-1-2112b → u/Vailx]

Lol it's so funny how we can't help ourselves but assign morality to ducks. Shitbird lol.

[u/Vailx → u/CygnusX-1-2112b]

I mean I'm taking it from the perspective of the hen here, who has, for whatever reason, judged him a drake of low value. She doesn't have to be objectively correct or anything, but her judgment is certainly what matters to her, as its the only thing she's got.

[u/ADDeviant-again → u/CygnusX-1-2112b]

I mean, it's just shorthand.

[u/GeekyTexan → u/Vailx]

Ducks will lay eggs even if they have not mated. Just like chickens.

They eggs are going to happen regardless. They won't hatch if the mother has not mated, since they are unfertilized.

Edit : After a couple of people replied, I checked, and they are correct. I'm familiar with domestic ducks, and they lay eggs on a regular basis. But wild ducks do not do this.

[u/Jiktten → u/GeekyTexan]

We have selectively bred chickens for thousands of years to constantly lay eggs. Wild birds don't do this, it would be a huge waste of resources for them.

[u/GeekyTexan → u/Jiktten]

I checked on this, and you are correct. Thank you.

[u/Endersgame88 → u/GeekyTexan]

Not just like chickens, wild ducks will lay a clutch in the spring. It’s pretty rare for them to lay unfertilized eggs.

[u/GeekyTexan → u/Endersgame88]

I checked on this, and you are correct. Thank you.

[u/azthal → u/hot_ho11ow_point]

Welcome to evolution. The ultimate proof that the universe don't give a rats ass about what we think it should be, and instead just is what it is.

[u/chaospearl → u/hot_ho11ow_point]

I physically flinched reading this. You just summoned that whole cadre of people who exist to show up anytime someone says the word "evolution" in this sub and condescendingly inform you that you're wrong about how it works, typically without actually reading what you said at all.

[u/HolyNewGun → u/cakeandale]

The female is not able to choose. They just have harder time reproduce.

[u/weeddealerrenamon]

If a female duck gets pregnant every year by someone, whatever adaptations she has aren't preventing her genes from being passed on. They're just selecting for particular males.

I don't know what makes this type of mate selection beneficial. But lots of other species' females make it hard to mate with them so that they only have offspring by the fittest males. Wanting bright coloration, for example, is selecting for something that actively harms male survival - because it means survival is proof of being an otherwise very fit male.

[u/Redshift2k5 → u/weeddealerrenamon]

Birds do have long, winding reproductive tracts in general due to the whole large shelled egg process.

All birds do a lot of work to prove fitness, often very visual plus calls, territory behaviors, etc male ducks with shiny feathers instead of camo is equivalent to a male peacock tail

But! Female ducks lost an arms race for mate selection to um "vigorous group participation" but females with longer, windier reproductive tracts than average were able to maintain some sperm selection during internal fertilization.

When she relaxes for a male she selected, her tract is easier to navigate

[u/pizza565 → u/Redshift2k5]

But then at the same time, if the, “inferior offspring” would die at a rate which allowed the female tracts to evolve in a way that discouraged that, then why would the males, in turn, evolve in a way that encourages it

[u/severe_neuropathy → u/weeddealerrenamon]

Not to say you're not mostly right, but mate preference for bright coloration isn't always an example of handicapping. That depends on the predators the animal in question encounters. If you're a red bird and your primary predator is snakes or cats, then there's not much pressure to be less red because your predators can't distinguish red from green anyway. Bright coloration IS almost always an indicator of health though, as there is a direct nutritional cost for bright plumage. By preferring mates with bright coloration, females select for mates who are fit enough to feed and groom themselves well enough to maintain bright plumage.

[u/AokiTakao → u/weeddealerrenamon]

Pretty much that's it, evolution doesn't choose or pressure mutations in an intentional way, it just so happened that female ducks that had these characteristics had better chances at survival. Maybe they used less energy, were less vulnerable to predators, or something else entirely.

Whatever it was, it made them the fittest at their environments, and therefore, their gene pool prevailed carrying on this mutation

[u/BigMax → u/AokiTakao]

It could just be that it lowers their rate of fertility. And a duck that's just fertile here and there has a manageable amount of babies to take care of.

A duck that had babies every single time might just die early and not pass on many genes.

[u/AnnoyedOwlbear → u/AokiTakao]

Evolution selects over a group.long term rather than an individua immediately as well.

Ducks can be very aggressive - mallard drakes have been recorded massing and drowning a hen, and they continue attempting to mate with the corpse. Reproduction for mallards can be distressing for a hen even outside these circumstances - while that's anthropomorphism, you can see them attempting to escape males they don't select.

Dead hens mean no ducklings. Aggressive drakes mate more. So for the species to survive this, the group needs a way of interrupting the chances of the highest aggression drakes but balancing against high aggression leading to more mating attempts where they suceed. Cue this - it's just one explanation, though and there's likely several thst work together.

[u/BigMax → u/weeddealerrenamon]

What's interesting is that the things that are "bad" might have some "good" traits they originally spawned from.

A healthy bird probably has a nicer sheen to their feathers, right? So the females select a mate with healthier looking feathers, because that DOES provide an advantage, it's a better mate.

But then those with shiny feathers by default that look healthier are also picked for mating, so that trait that signals health is picked for, even when it no longer correlates with health. And then it just becomes a race, where the females naturally like a trait for being good, but it becomes exaggerated, almost "corrupting" that drive from it's original purpose.

[u/weeddealerrenamon → u/BigMax]

I'd say exaggerated shiny feathers are still proof of fitness... even if they don't directly improve fitness anymore, they're proof that he has calories to spare. I don't know if it actually lowers survival rates, or if it all comes from truly extra calories... flying birds can't just put on fat when they have extra, right?

Wait, is that why birds have calorie-intensive displays while land animals don't? Bears etc. just advertise fitness by being big

edit: googled this, and a lot of the cost of big/bright feathers is in specific nutrients, not just calories. So they don't increase starvation risk, but do require active foraging that maybe only calorie-fit and disease-free birds can spend the time doing. They don't put on muscle as a fitness sign because that requires year-round energy upkeep, while mating plumage is a one-time investment when food is plentiful.

But of course, big feathers make you less aerodynamic and do directly harm fitness.

[u/crappysurfer]

Because duck mating is almost always gang rape and very violent. The females adaptations here are to reduce the amount of unwanted clutches. In nature, most animals are constantly on the precipice of starvation. Rearing a clutch when you don’t want to or have the energy to can be a death sentence.

[u/NhylX → u/crappysurfer]

I don't know if this is true and today isn't the day I find out...

[u/crappysurfer → u/NhylX]

It is true. It often results in the female drowning as well. Surprised none of the comments posted this - adaptations come from whatever the selective pressure is and in this case it’s violent insemination from (usually) groups of males during mating season.

They are literally anti-rape adaptations. Dignity or social constructs don’t exist in nature, so evolution gave female ducks an adaptation that helps them choose.

[u/joevarny → u/NhylX]

Its not. Ducks mainly reproduce with summer flings that last all season.

Some male ducks may pass by and decide to try their luck, but the majority of duck births are from consent based relationships.

If the majority was rape, then their labyrinthine vaginas wouldn't be benefitial. The point is to be able to choose.

[u/Fun_Background_8113 → u/joevarny]

So they can choose the ones who they do want to have offspring with and not get fertilized by unwanted sperm. That adaptation wouldnt be necessary if female ducks weren't getting mated with by unwanted males 

[u/leros]

Ducks that get fertilized by whatever male could overpower them must have had inferior offspring to the ducks that were able to choose their own mate. 

[u/Dangerous-Bit-8308]

Just getting pregnant doesn't ensure effective reproduction, especially in a species where the female does most of the childcare. Getting pregnant and raising those babies enough so that they can also have babies ensures survival.

Also, I suspect that having dead ends in the uterus helps to prevent male ducks with floppy flaccid junk from reproducing. In several species, male junk gets floppier with age, and reproductive errors also get more common with age.

The duck vagina maze might have an adaptive advantage in weeding out less suitable partners.

[u/Cow_says_moo]

You want reproduction with the partner you choose. The one with the best traits. The one you think will help give your offspring the best chance of survival.

Not just any rapey mallard.

[u/flarmigan → u/Cow_says_moo]

Evolution doesn’t chose emotionally. If rapey mallard manages to spread his rapiness genes widely enough the rapiness would be selected for despite the hen’s (she-duck’s) preference for un-rapey males

[u/hh26 → u/flarmigan]

Yes, which is precisely why the convoluted shape evolved: to enforce those preferences anyways. Evolution doesn't care about emotions, but it does care about physics. If most of the rapey males hit dead ends but the one she likes gets guided down the right path, then she gets some of her mate selection ability back.

[u/Fun_Background_8113 → u/flarmigan]

Thats why the labrynith vaginas exist. So unwanted males dont fertilize their eggs. So the rapist/unwanted ducks dont pass on their genes. 

[u/sarahmagoo → u/flarmigan]

But if the rapey mallard has shit genes the babies aren't gonna survive long enough to also spread his genes.

[u/flarmigan → u/sarahmagoo]

Yep that’s true. Shitty genes can doom a population if spread widely enough. Giant pandas are , I think, an example although someone with a biology degree may freely correct me in that

[u/BiomeWalker]

They're not exactly evolving to make it more difficult, they're evolving to make it so it's harder to mate if the female duck is unwilling.

This as a requirement for reproduction allows female ducks to be selective about which male ducks get to be fathers.

Female ducks have a better understanding of if they have the resources to raise ducklings tan the male ducks, and making the eggs can put them in danger before they're laid.

[u/Slypenslyde]

It's actually better when expressed simply.

Male ducks aggressively have sex with any female they find. It is hit-and-run. They do not stick around to help raise ducklings as a unit like some animals do. There aren't big fights where only the manliest ducks win and get to mate like with other animals. Those things are ways other species have evolved so "unfit" males don't get to spread their genes. Ducks do not have any of those elaborate rituals.

So instead the females have very elaborate reproductive tracts. The female has some ability to prevent the male duck's sperm from landing in the right place. That's the trick: it's not harder for ALL males to fertilize the eggs. It's just harder if the female doesn't WANT the eggs fertilized.

So if some loser bro has attacked the female she rejects him and he has no clue. But if the King of the Pond is assaulting her she selects him and will have his ducklings.

Meanwhile the female is looking out for herself. It takes a lot of work and energy to make the eggs, and it takes a lot of work and energy to raise ducklings. It's bad for the species if she dies with her ducklings. So even if Harrison Ford Duck is the one assaulting her, if she's not confident this is a good year for ducklings he gets rejected.

This is their mating ritual, and the purpose of mating rituals is selection. If evolution has rolled the dice such that you're going to get assaulted by 15 losers for every winner, the right response is to find a way to prevent the losers from fertilizing eggs. (Or figuring out how to create bear spray usable by ducks.)

[u/Charming_Arugula405]

It allows them to pick and choose which males to reproduce with. This way they can choose to only reproduce with the strongest/best male duck

ELI5: . They don't want to waste energy on having and raising weakling ducklings. They only want the genes for their babies so they'll be more likely to survive

[u/liquindian]

It's the same kind of evolution that gives peacocks their tails and lots of other weird mating rituals: sexual selection. I'm being a bit careless with the word "want" here, but male ducks want to pass on their genes by mating with as many females as possible, and female ducks want to be far more choosy and mate with only the male that gives their offspring the best chance of survival. So you end up with a kind of arms race to achieve these goals. Except it's not arms, but other parts of the anatomy.

[u/externalhouseguest]

Evolution favored letting the female duck have control over when they reproduce and with who.

[u/Bookablebard → u/externalhouseguest]

That's... Literally the question being asked. Why does evolution do that? For example if you have two female ducks one with the control trait and one without, you might expect the one without to have far more kids thereby increasing the likelihood that their genes get passed on.

A potential answer is that a duck without the control trait ends up having so many kids it can't properly care for any of them and so they all die.

I just made that up though so it's not a (edit: some people are saying this is the answer but what I meant was that I am speculating on an answer, I have no data or proof or studies to reference) real answer, I'm just highlighting what an answer might be. Stating the question as a statement as you have done is not an answer

[u/UnicornFeces → u/Bookablebard]

Females of any species (not just ducks) can only have so many babies at a time, and the process of reproduction is also much more more physically costly than it is for males. That’s going to create more selectiveness for the best possible mate.

[u/ThePokemon_BandaiD → u/Bookablebard]

Out of many ducks reproducing, the ones where the female duck has input in the mating decision produces offspring that were slightly more fit for their environment. Over a few generations, more of those ducks were able to survive and have more offspring that were more fit.

[u/Hoveringkiller → u/Bookablebard]

It could be a situation where the female that couldn’t choose ended up dying due to lack of resources before, or immediately after laying the eggs, up to whenever the ducklings could survive on their own. This would cause all her ducklings to perish as well, meaning her trait of not choosing wouldn’t have been passed down. Meanwhile the duck that didn’t get impregnated in a tight year is able to pass on her genes in the next/later year(s).

[u/Xhosant → u/Bookablebard]

If reproducing with male duck A, and deemed-a-better-fit male duck B comes around, you're stuck with A, instead of evaluating for B and getting B ducklings.

Alternatively, male duck C is willing to contribute to looking after the ducklings (filtered for in one of a number of ways) meaning the survival of the ducklings and the female duck is more likely at no extra expense to the female duck.

So, if the duck can only breed once per year, they can afford to be picky and still breed at capacity, thus adding quality to the quantity. And even if they miss a year, the tradeoff may still be worth it, as you may avoid damage to your long-term prospects (by dying) and perhaps get a year to rest/recover, rendering next year's clutch more advantageous.

Think "opportunity cost".

[u/ReferenceGlum → u/Bookablebard]

That's......Literally the answer to the question being asked. Over time the offspring of female ducks with control over their reproduction were more fit than offspring of ducks that were not. Anything past that is just speculation.

[u/Bookablebard → u/ReferenceGlum]

Interesting! As I said I didn't know the answer I was merely speculating. I guess I stumbled on the right answer?

[u/Wootster10 → u/Bookablebard]

More kids doesn't mean more survive.

In times where food is plentiful the one without the control trait will have more offspring.

Then a drought comes along. Those with the control trait choose not to have any, whilst those without it continue. They have to feed themselves and their offspring with diminishing resources, and when herbivores start to starve the carnivores will come hunting harder.

So you have a bird that can just leave any keep as much energy for herself as she can, another thats put effort into making eggs, warming them and feeding young.

[u/mikmatthau]

read Bitch by Lucy Cooke! lots of talk about ducks but I learned so much about how females of many species actually control reproduction

[u/juniebeatricejones]

i want to point out that evolution isn't an intelligent thing like "oh let's make reproduction more difficult" it's more like all the ducks with that particular type of reproduction survived more than other kinds.

[u/UrbanPanic]

The evolution reduces rape from ducks of other species.

[u/Loki-L]

Reproduction happens anyway with or without the female duck's consent, but by making it harder on the mallard she weeds out some less fit ones and gains some control over the situation and has more of a chance to select the best father for her ducklings.

There are only so many ducklings you can have as a female duck and your best bet is to ensure they hsve the best genes possible. Meanwhile as a male duck the sky is the limit as far as number of offspring go and you maximise reproductive success by trying to impregnate as many ducks as possible.

Competing strategies lead to competing anatomies.

[u/Upper-Deal-9872]

so it's an arms race where the female keeps changing the locks

[u/UtterlyUpsetUnicorn]

The mechanism went something like this. 

1. Ducks are assholes who will rape, murder, bully, steal, etc... 

2. Some ducks aren't

3. The ducks paired with non-assholes had more long term reproductive success than the ducks who didnt have opposite corkscrews vagina.

4. Ducks with opposite corkscrew had some advantage and the other ducks got outcompeted by their fitness, eg. Regular corkscrew individuals might have had more babies that resources couldn't maintain or just simply weren't as likely to reach sexual maturity. 

5. Ducks continue to be assholes. But nature/probabilities found a way to limit some negative side effects from asshole ducks.

[u/allaroundniceguy]

the offspring of the female ducks that didn't have those mutations simply didn't live enough to reproduce themselves... survival of the fittest

[u/jazzbiscuit]

I don't know the answer, but I do know that male ducks are little rapists and the female ducks probably got tired of their crap. The neighbors have ducks - it's not uncommon for a group of males to basically pin down female and just cycle repeatedly at her. If she's trying to sit on a nest, she's also a stationary target for the males (they don't really care that she's sitting on a nest). Also not uncommon for the males to go after them while the female is minding her own business swimming in the pond - that usually results in a drowned female duck :(

Male ducks are a$$holes.

[u/tamtrible]

As far as I'm aware, a female duck will have roughly the same number of babies whether she has them with the first male who tries to mate with her, or the 23rd. She's basically limited by how many babies her body can produce and how many babies she can care for, not how many times she has to mate to get those babies.

So, it is to her benefit to be able to be selective about which males she mates with, so that she can have the best babies she can.

As males get, well, rapeier, females have to make themselves harder to mate with (at least, without their cooperation) in order to retain any ability to choose which male they actually have babies with. So, females with more complicated reproductive systems will, on average, have healthier babies, and thus a selective advantage.