...Since these replies parallel each other I'm responding jointly.
What I'm getting at is that it seems to me that... Well, specialized predator/prey relationships do favor things like parasites or fungal infections. And don't favor large apex predators whose presence would be immediately obvious on a casual biological survey by a lone Starfleet explorer captain.
Parasites and disease germs (fungi, etc.) have short life-cycles and can rapidly evolve resistance to a new toxin. Apex predators, as a rule, don't, so they can't.
You can have a type of insect that "preys" solely on a specific species of herbivore and cannot survive on the blood of other herbivores. Or a type of hostile fungal infection that survives in that herbivore's gut and spreads itself through feces, and does not survive or thrive in other species. But something like a lion isn't going to do very well if it can only safely eat the flesh of one species, and may not even do well if it can only subsist on the flesh of a cluster of closely related species.
Likewise, if most or all large land animals are already toxic, and mutually toxic due to various species getting into toxicity arms races with different species of specialized parasites and infections... It presents a considerable barrier to any one species evolving to prey on other large land animals. Because you don't just have to evolve the ability to chew and digest larger amounts of meat, you have to evolve the corresponding poison resistance. The only time this would be viable is if a cluster of closely related species already had similar blends of toxins, and were thus mutually immune to each other's toxins, making it possible for a predatory species to evolve a sort of pseudo-cannibalistic behavior.
So you could have a species like bears, that can eat a mixed plant/animal diet... But the bears could only prey on other species closely related to bears (i.e. skunks and raccoons), not on unrelated species (i.e. deer, rabbits, and pigs). This would greatly limit the viability of being an apex predator, and you would not expect to see apex predator species flourish UNLESS they were well adapted to subsist on a mainly-vegetable diet.
Alternatively, you would see predation on other, more distantly classes of animal (e.g. mammals preying on fish or insects), because those other classes of animal would not have the toxicity adaptation and would therefore be edible.
Yes, but on the other hand, evolution tends to work incrementally. Some niches just don't get filled, if filling them would require multiple unrelated adaptations to evolve in the same species at the same time.
I'm not proposing an explanation that says GUARANTEED NO LARGE CARNIVORES EVER. I'm proposing an explanation that says "large, primarily carnivorous animals, occupying niches comparable to the apex predators of Earth, would be statistically less likely to emerge here."
I'm proposing a situation in which one specific class of animal on the Shanpurr homeworld, the one which through historical happenstance is the dominant species of land animal (analogous to mammals on Earth), has this adaptation. And different species would have different toxins or blends of same, precisely because they are in a constant evolutionary arms race with various kinds of parasites or pathogens. And this is a barrier, not an insurmountable barrier but nevertheless a barrier, for a hypothetical species in this class that evolves towards "carnivore" status of subsisting mainly on the flesh of other animals in that class.
So basically, if you are a [mammal-equivalent] on their planet, adapting to eat members of a new species presents some obstacles, and adapting to eat the flesh of large land animals in general presents considerable obstacles. This is in addition to any adaptations required in order to catch and kill members of those species in the first place, and to digest their meat.
Thus, evolution is slower to fill the "apex land predator" niches on this planet. Surviving in such a niche is more precarious*. And the species that do function in that niche are more likely to be "multirole" species that can also function reasonably well on a primarily plant-based diet.
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*(For instance, because climate change can introduce new prey species that you can't eat at all. Whereas if some new species of deer supplants the local pig population in an ecosystem on Earth, or if some kind of giant mutant rabbit replaces raccoons, wolves are going to be okay either way. To be sure, in real life on Earth, predator species can die out because of shifting populations of potential prey. But in this hypothetical planet that would happen even more often.)
This is true, but it's also a fully general objection that can be raised to any conceivable species or class of species evolving to have any conceivable adaptation.
Obviously, EVERYTHING involving biology and metabolism is a complicated multi-factor combination of different things. And every possible evolutionary adaptation is the result of SOME tradeoff point among all these multivariable factors- accepting more intelligence at the cost of more traumatic and risky births, accepting more resistance to some environmental factor at the cost of being maladapted to another environment, accepting toxins that kill noxious parasites dead dead dead at the cost of needing to eat more calories to survive, and so on.
What I'm getting at is that we can plausibly imagine alternate ecosystems, biochemistries, et cetera, such that these tradeoffs are made differently. Where different "price points" on the various sliding scales of tradeoffs are optimal. And that this can in principle have significant consequences. Consequences like "it's a lot harder to be an apex predator on this planet" or "it's a lot easier to be an apex predator on that planet."
And I'm proposing the 'toxicity' thing as one mechanism that might push a given planetary ecology, or at least the parts of it where intelligent life might notionally emerge, towards the "harder to be an apex predator here" end of the spectrum.
OK.
To start with, all alternate ecosystems must work with the same laws of physics. Energy is energy. Entropy is entropy. And every organism will try to get away with as much as possible.
And animals that are walking around are
really concentrated sources of nutrition. If an organism can eat them, that organism gets a big leg up. No need to sit there photosynthesizing, or chemosynthesizing, or filter feeding, or spending hours grazing... Against that, there are downsides to being a predator. Like risks of injury from fighting with prey. Like the risk that you'll starve from all your prey will run away. And there aren't room for too many creatures like you. (There may be billions of blades of grass, millions of insects living on that grass, hundreds of thousands of large herbivores but only thousands of predators in an area.) But generally, it's a pretty good strategy to eat meat.
So if you have a situation where the prey are deploying lots of toxins... Well, of course that makes things harder on the predators. But it is still a
great strategy. So less organisms might be predators, but there'd still be plenty of predators.
Especially since the prey are diverting energy from being fast, from being strong, from breeding faster, from being more social, from being able to eat themselves, and using it to make poison. So the prey are weaker in some other area to compensate for being better at poison.
The weakness of they prey and the necessity to adapt to eating very specific prey would, I would think, encourage the evolution of smaller and more social predators or of predators with very large ranges so they could get more out of the prey in their range.
I would think that flocks of predatory birds would be especially successful, since they could have very large ranges and their small size wouldn't be as much of a disadvantage as it is on Earth since predators would want to be small in any case, so that they could maintain useful breeding populations on the available population of prey.
Now, if you have a situation where rapid environmental change has disrupted the close relationships between evolved predators and prey, meaning the predators haven't been able to get enough food to maintain a viable population, well, that means there is a big fat opportunity for a new predator to evolve to fill that niche.
As an example, when we look back in the fossil record to see what happened after the great impact that killed the dinosaurs, ecosystems seem to have been heavily disrupted for a few hundred thousand years. But remarkably quickly, the ecological niches were filled up. After around 5 million years (an evolutionary blink of an eye) the diversity of land-based life had reached about the same level as before the impact.
If you have a situation where there are factors making things changing too fast for predators to emerge as a major part of the ecosystem, then selective pressure for prey species to maintain their toxin levels will fall, meaning that more fit but less toxic prey species will evolve and out-compete the slow, weak, less fertile, less sociable prey species and then provide opportunities for unspecialised predators.
Also, I would like to say that an ecosystem with rapid change and lots of toxic animals that required very specific strategies to detoxify and eat sounds like a
great environment to encourage the evolution of
intelligent predators.
The rapid change means there's not much competition from other predators but there is a big fat opportunity that makes a big expensive brain something that can pay off.
Sounds like a situation that should have encouraged predatory Shanpurr.
Also, what you are speaking about "apex predators", here's the actual quote from the omake by AKuz:
Shan is one of two known biospheres to produce intelligent life that posses a very limited degree of predation and aggression in flora and fauna. Most species, including the Shanpurr themselves, are Herbivorous.
Yes, it is easier to imagine an ecology that lacks apex predators like lions or tyrannosaurs. And maybe, as you say, the casual survey didn't notice the small predators, but the choice of words "very limited degree of predation and aggression" seems to imply more to me.
And it is less easy to imagine an ecology without foxes, jackals and falcons.
Nnnnot necessarily true. As my prof put it, the main reason you get more poisonous species in warm climates is that you get more species in warm climates, period.
Hm. I can't think of anything really toxic from outside the more fertile ecosystems on earth. The most toxic things I can think of all live in rainforests or coral reefs.
fasquardon