# All mammals die. What else dies? What lives? **URL:** \ **Category:** Factual Questions\ **Created:** [June 29, 2022, 3:26am UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084 "2022-06-29T03:26:35Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [June 29, 2022, 3:26am UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/1 "2022-06-29T03:26:35Z")
I was thinking of the scenario in _Y: the Last Man_ where every animal with a Y chromosome suddenly dies, leaving most mammal species to go extinct in the next few decades. I was wondering what other species would die. Many spieces of snake and owl would, for instance, but some species get some or most of their diets from lizards, birds, and eggs, but wouldn’t the majority die? How about alligators? Could they survive on fish alone? ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [June 29, 2022, 3:35am UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/2 "2022-06-29T03:35:34Z")
Some lizards have X and Y chromosomes. Are they included in this die-off? ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [June 29, 2022, 4:12am UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/3 "2022-06-29T04:12:18Z")
For the sake of the argument, I meant _only_ mammals, by whatever method, biological, technological, or magical. ---
**Author:** ![AHunter3](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ahunter3/32/368_2.png) [@AHunter3](https://boards.straightdope.com/u/AHunter3)\ **Post date:** [June 29, 2022, 4:33am UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/4 "2022-06-29T04:33:15Z")
I’m not sure it has any bearing on your hypothetical (although it might) but some species’ chromosomal configuration is other than XX and XY. The [XZ configuration](https://en.wikipedia.org/wiki/ZW_sex-determination_system) is one in which males have identical chromosomes (ZZ) and the females have dissimilar ones (XZ), which is opposite of the XY pattern in which it is the females who have identical ones and males with an asymmetric pair. Animals in this pattern don’t have any Y chromosomes; in your scenario either they’d be utterly unaffected. Other than sudden holes in their diet or the array of predators they need to worry about, I guess. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [June 29, 2022, 7:04am UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/5 "2022-06-29T07:04:39Z")
> [@AHunter3](#): > > I’m not sure it has any bearing on your hypothetical None whatsoever. The hypothetical is this: all mammals are dead. Period. Is it a mammal? It is dead. Is it not a mammal? It isn’t dead. The hypothetical is that simple. The question is which non-mammal species would survive in a world a world minus mammals and which would be screwed. (Almost all fish, for instance, I think would be fine.) ---
**Author:** ![Banksiaman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/banksiaman/32/3334_2.png) [@Banksiaman](https://boards.straightdope.com/u/Banksiaman)\ **Post date:** [June 29, 2022, 7:59am UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/6 "2022-06-29T07:59:04Z")
When scientists and conservationists do exclusionary fencing and culls to remove feral animals from parks, they are usually targeting particularly predatory and destructive beasties like feral dogs and cats, foxes and pigs. Usually there is a very quick upsurge in their former food species, which are often birds with vulnerable or easy to pilfer nests. Birds generally could be expected to flourish, not least because human habitat modification has a big impact on their breeding too. All that means other predatory birds would be having the time of their life as well. Since they all like a nice juicy lizard, the reptiles may not get the chance to boom. ---
**Author:** ![nightshadea](https://avatars.discourse-cdn.com/v4/letter/n/7ba0ec/32.png) [@nightshadea](https://boards.straightdope.com/u/nightshadea)\ **Post date:** [June 29, 2022, 8:09am UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/7 "2022-06-29T08:09:35Z")
isnt it strange that birds eat their cousins in the first place? ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [June 29, 2022, 11:08am UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/8 "2022-06-29T11:08:05Z")
In principle each ecological niche gets occupied by critters adapted to that niche. Given enough time every niche gets occupied by some critter or another. Mammals are better adapted to some of those niches, and tend to dominate them. Others, not so much. All things with the tag “mammal” vanish and two things happen, a lot of niches are freed up for critters that were less adapted and out competed by the now gone mammals, and a lot of niches vanish, as they were dependant upon mammals existing, probably as prey. So good for some remaining critters, not so good for others. Some critters that were prey for mammals would boom, but some might themselves have preyed upon other mammals, so the end result might not look good. A principle in ecology is that stable systems have a large number of paths up and down the various cycles, food chain, energy cycles, etc. Loss of a single path is usually not a problem as there is resilience in the ecosystem as others move slightly to cover the loss. Wiping out all mammals would be widespread loss of many pathways. Rich ecosystems with a wide diversity of critters filling niches would probably adapt. It is the sparse ecosystems, ones with a low diversity that may be wiped out. Too many links in the various pathways cut at one time, and the entire structure would unravel. Then, given enough time, something else will move in to occupy whatever food and energy sources there are to exploit. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [June 29, 2022, 11:11am UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/9 "2022-06-29T11:11:39Z")
> [@nightshadea](#): > > isnt it strange that birds eat their cousins in the first place? Why is this stranger than mammals eating other mammals? Here’s a phylogenetic overview of birds and mammals, with time shown. The time since common ancestor of the average bird predator & prey species is going to be a similar order of magnitude to the average mammalian predator & prey species. [Ornithologists Publish Most Comprehensive Avian Tree of Life | Sci.News](http://www.sci-news.com/biology/science-avian-tree-life-03326.html) [https://www.researchgate.net/figure/Phylogenetic-time-tree-of-mammalian-families-13-created-on-the-basis-of-an-analysis-of\_fig1\_51664364](https://www.researchgate.net/figure/Phylogenetic-time-tree-of-mammalian-families-13-created-on-the-basis-of-an-analysis-of_fig1_51664364) ---
**Author:** ![thorny\_locust](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thorny_locust/32/431_2.png) [@thorny\_locust](https://boards.straightdope.com/u/thorny_locust)\ **Post date:** [June 29, 2022, 2:41pm UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/10 "2022-06-29T14:41:00Z")
> [@nightshadea](#): > > isnt it strange that birds eat their cousins in the first place? Why would a human think so? Humans eat other mammals all the time. ---
**Author:** ![AHunter3](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ahunter3/32/368_2.png) [@AHunter3](https://boards.straightdope.com/u/AHunter3)\ **Post date:** [June 29, 2022, 3:00pm UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/11 "2022-06-29T15:00:10Z")
> [@Darren\_Garrison](#): > > The hypothetical is this: all mammals are dead Give me an F on reading comprehension. I thought you were extending the _Y: the Last Man_ scenario to ask the overall effect on all earthly life if all critters with Y chromosome were to die. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [June 29, 2022, 3:07pm UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/12 "2022-06-29T15:07:30Z")
No, that was just the inspiration for the idea. The “how” doesn’t matter, what I’m wondering about is the results. (Anyway, just because some non-mammals have something people _call_ a Y chromosome doesn’t mean it operates the same way, with [the sex-determining gene in placental mammals](https://en.wikipedia.org/wiki/Sex-determining_region_Y_protein) having evolved only after the monotreme/placental split.) ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [June 29, 2022, 3:15pm UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/13 "2022-06-29T15:15:40Z")
There would be a huge impact, but I’m struggling to come up with anything other than the snakes and owls mentioned in the OP that prey exclusively on mammals that would be direct and immediate casualties. You’d obviously be losing many pathogens (and commensals) that infect mammals. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [June 29, 2022, 3:19pm UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/14 "2022-06-29T15:19:51Z")
Some monitors would be in trouble, I think. Especially the Kimodo Dragon. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [June 29, 2022, 3:21pm UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/15 "2022-06-29T15:21:31Z")
I wondered about mosquitoes, but it looks like they all feed on birds too. There are probably parasites like lice that are adapted specifically to mammals. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [June 29, 2022, 3:25pm UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/16 "2022-06-29T15:25:22Z")
Dung beetles are another group that would face massive species loss. ---
**Author:** ![zimaane](https://avatars.discourse-cdn.com/v4/letter/z/a3d4f5/32.png) [@zimaane](https://boards.straightdope.com/u/zimaane)\ **Post date:** [June 29, 2022, 3:31pm UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/17 "2022-06-29T15:31:06Z")
Some birds, such as oxpeckers, are specialized in eating parasites off large mammals, so they’d be in trouble. It’s hard to see vultures surviving without mammal carrion. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [June 29, 2022, 3:40pm UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/18 "2022-06-29T15:40:07Z")
I don’t think it would change the basic scenario much if we gave monotremes a pass on the extinction event due to their weird chromosome arrangement. Platypuses and echidnas aren’t world-shaking in their ecological importance. In fact I wonder why the story even dragged in the whole mammalian extinction. As far as I can remember the storyline was entirely about the effect on humanity the death of nearly all males had. Did they even touch on how the death of nearly all mammals had on anything? ---
**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\ **Post date:** [June 29, 2022, 3:50pm UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/19 "2022-06-29T15:50:55Z")
Most species have their own parasite, some [several](https://www.ncbi.nlm.nih.gov/books/NBK214895/). The humpback’s barnacles are a different species from the finwhale’s barnacles, the wolf’s lice are different from the coyote’s lice, the lice on your armpit are different from the one’s on your head and those in turn are different from those on your genitals (this is a generic “you”, not implying you personally have those parasites). The mites on your face are highly species specific (those you personally have, like all of us). Parasites often go from one host to another in the course of their development. A tipical path could be: snail → bird → cat → snail (via feces). Missing the cat, the snail are free from this parasite after one generation, the birds too. So the parasites would suffer indeed. [Perhaps](https://www.agenciasinc.es/Alertas/Parasitos-helmintos-del-lince-iberico-Lynx-pardinus-en-peligro-de-extincion) the only species currently without it’s own parasite is the Iberian Lynx (the Pardelluchs in German whose name I adopted), because when about 15 years ago there were only about 30-40 left they were all collected and washed and desinfected. They still have parasites, of course, but they may not yet have adapted specifically to them. Today the Iberian Lynx has recovered a bit, there are a couple of hundred now. Not out of the woods yet, but better than I dared to hope. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 29, 2022, 6:17pm UTC](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084/20 "2022-06-29T18:17:54Z")
Just a note that a great deal of natural grassland is maintained in that state by grazing animals that are mammals. If mammals die, grassland starts turning into something else - usually forest; the effect is not instantaneous, but it’s not necessarily very slow either - years or decades. That alone has a significant impact on other organisms such as plants and invertebrates that are grassland specialists. [Next page](https://boards.straightdope.com/t/all-mammals-die-what-else-dies-what-lives/967084.md?page=2)