How to Create an Alien Ecosystem
Part 4: Firming Up Your Ecosystem
Welcome back! In part 3 we added details to our Orders and then meshed them into a cohesive ecosystem. Now we're going to update our Order blurbs. As before, I'm only going to focus on the Orders that are strictly from warm environments for now, because we've generated quite a lot of data to work with. In this part I'm going to figure out what survival challenges these Classes face based on the bottom level of Maslow's Hierarchy of Needs (ie., their need for air, water, food, shelter, and to reproduce).
By the time we're done we'll have a rough idea of what the Orders look like and how they behave.
This is where knowing what your planet is like gets really helpful. Does the sun provide more light or less (assuming there is one)? What's the surface of the planet like? What kind of temperatures and climate do they have to cope with? I'll focus on that in another post, but for now, we're assuming an Earth-like world.
If you're following along with me, don't forget to refer to your spot-charts from part 3 to remind yourself of the relationships between your different Orders! This part of your ecosystem's development will not be linear: I moved up and down the following list to add details as I thought of them - and you probably will too. If this proves to be a job you want support with, I offer consultations specifically for this kind of work, plus asynchronous ('Asynch') species development support (check my price list for further details about what you get for this and how it's done).
I've added my descriptions from part 1 of this series of each Class, for easy reference.
Wabl'o poba
Wabl'o poba are primarily land-dwelling animals that stand on six limbs and lay hard-shelled eggs. Their skin comes in a range of thicknesses with patterns, callouses, and natural thickening. They are relatively limited in their colour palette.
Insectivores
Appearance: Small-bodied and quick-footed, these little creatures are in the middle of the food chain. They are voracious creatures that eat insects, taking advantage of their extreme flexibility and light weight to hang from plants or rough overhangs of rock to grab insects, sometimes in mid-flight.
Predators: Smaller sharks and rays tend to hunt them, and as a result the insectivores have evolved a naturally thick skin. This is not always sufficient by itself, and many insectivore species have developed habits that actively serve to toughen their skin. They make their burrows in cracks between rocks rather than digging their own burrows, and this is thought to improve the roughness of their skins (EDIT: Yes! I thought of this while writing and am definitely keeping it in!).
Beneficial Relationships: Toughening themselves up isn't the only thing they do to protect themselves. They also tend to hide, and have developed a cooperative relationship with pheasants, to live with them in their nests. The two species have a mutually-compatible arrangement where the pheasants dig the nests, and the insectivores come and live with them. (EDIT: I'm not sure at this point how each benefits, especially since this sounds more beneficial to the insectivores than the pheasants, but I'll think of something while writing up the pheasants' profile.)
(EDIT 2: I have just finished writing the pheasants' section and can add that the insectivores are highly sensitive to danger and will cry to warn any nearby creatures of predators before running back to the pheasants' warren. This arrangement has been happening for so long that pheasants have become less adept at spotting danger and rely on their insectivore companions to call out danger for them. The pheasants' tendency to attract predators due to their bright colours and ostentatious displays means that predators are attracted more often, which in turn has honed the insectivores' acuity.)
As an extension to the above cooperative arrangement, insectivores tend to feel dissatisfied with pheasant burrows and will continue digging when the pheasants consider their burrow complete, until there are extra exits. This allows for additional escape routes when needed.
Such is the insectivores' vigilance that they have developed an ability to read the behaviour of gliding tree mammals. Gliding tree mammals spend most of their time above eye-level in the trees, but insectivores have a good upwards range of vision and will notice when one of these tree-creatures leaps. Younger insectivores, or ones that don't see gliding tree mammals very often, will warn their pheasant hosts unnecessarily when they see a gliding tree mammal leap, but more experienced ones learn to tell the difference between a gliding tree mammal leaping when it is trying to escape danger, and when it is not.
While the gliding tree mammals don't tend to actively benefit from insectivores' vigilance, the two species do seem to appreciate one anothers' presence. It is unknown why this is, but the best guess is that gliding tree mammals take a cue from burrows of insectivores that this territory is a safe one to settle in.
EDIT: The part with the burrows in cracks in the rock doesn't fit any more since I riffed on the insectivore-pheasant relationship, which turned out to have more potential. For now I'll keep all my notes here in place so you can see how I started working on these animals, but will tidy them up in future parts of this series.
Pheasants
Appearance: The animals of this Class are known for their dazzling patches, flaps, and calluses of red flesh, which they use to display to one another. (EDIT: I was still keen to give these guys some colour, but since this whole Class is heavily influenced by mammals, there weren't many colours to choose from. Mandrills have colourful faces though, and when I think about it, rooster combs are red skin too, so I figured that red should be permissible.)
Reproduction: They use this to attract a mate or warn off rivals, and can demonstrate their suitability with graceful movements of their long bodies, that further draw attention.
Beneficial Relationships: The insectivores that invariably come to live in pheasants' burrows are highly sensitive to danger, and the pheasants benefit from this. Over the millennia that this partnership has been happening, pheasants have become less adept at noticing danger as the insectivores tend to be vigilant for them. As a side effect of this early-warning system, pheasants have developed striking patterns and colouration, hence their displays of red, and developed their elaborate courtship rituals.
Predators: Unfortunately their bright colour can make them conspicuous if they don't keep their red parts hidden underneath the extra, dull-coloured skin-flaps they've evolved for the purpose, and put them firmly on the menus of many predators including eels and morays, smaller sharks and rays, lizards and snakes, and anglerfish.
Small sharks are particularly good at bypassing the insectivores' and pheasants' cooperative strategy. It is the insectivores that combat this the most effectively: they continue digging after the pheasants have completed their burrows, to ensure that there are multiple exits. The pheasants will use these exits when necessary.
Toadfish
Appearance: Toadfish are squat creatures with very flat bodies and sensitive skin on their bellies. They use this sensitivity to lay on the ground and feel for vibrations. These vibrations warn them of approaching danger. They grow particularly rough callouses on their backs which mimic rocky, stony, or gritty ground.
Reproduction: Their biggest survival challenge comes in the form of their eggs. Toadfish do not climb well and are more or less forced to nest on the ground. However, they have a strategy to prevent their eggs from being eaten by predators: an egg-laden female finds a tree and lays her eggs against the lowest portion of its trunk and roots. She deposits a liquid protein along with these which binds the eggs to the bark, and simulates the rough texture of the bark so as to camouflage the eggs. (EDIT: That's pretty nasty, but hey, I can see it working.)
Predators: Toadfish are not readily eaten by many species due to being poisonous (EDIT: it turns out that eating toadfish isn't a good idea!) and their tendency to listen to their environments. Due to these two levels of protection, only snakes and lizards have the talent for silence and patience, along with the poison immunity, to eat them.
It's starting to come together, isn't it?
Cob'li po-fea
A cold-blooded family, the majority of cob'li po-fea are both feathered and finned. For the ones that live in warmer environments however, their feathers are unnecessary for warmth. Instead they use them to streamline themselves when running, display, or to create protective 'spines'.
Most cob'li po-fea are made for swift movement and are therefore streamlined. The majority have two legs which are used to generate movement, plus an extra two sets of limbs which are usually closer in appearance to fins, to help steer the animal.
Hares and rabbits
Appearance: Smooth, silvery feathers and stiff 'wing' and tail primaries allow these creatures to run swiftly with minimal wind-resistance and stall at a moment's notice if required. They are a prey animal that runs on two legs with excellent backwards-forwards reach, and two sets of fins that they use to steer while running, which allow them to dodge predators.
They live in colonies and feed together. When alarmed, their silvery colour and tendency to 'weave' during their first few steps makes them catch the light and alerts other members of the colony. While these creatures tend to live on land, beach colonies are not unusual, and these creatures have been known to run through rock pools to generate extra confusion to slow down their predators - they can be hard to see in amongst sprays of sea-water.
Reproduction: They breed in huge numbers, and hundreds can be seen basking in areas where these creatures live.
Predators: They have several predators to outrun: anglerfish, sharks and rays, eels and morays, and snakes and lizards all pick off slow, unaware, or sick animals. Given the need for hares and rabbits to bask, they are particularly vulnerable to being picked off during the early mornings or late at night on cooler nights or at higher altitudes (EDIT: I'm not sure if these animals would live at high enough altitudes to have this problem, but the biggest air-breather alive today lives in the sea, so anything is possible).
Beneficial relationships: They do tend to follow turtles around and eat any vegetable scraps left behind.
(EDIT: I'm going to include an extra detail here to match the gill-like structures that an artist, Gij, drew onto this species: rabbits can and sometimes do burrow, and use this as a means of protection. They retain vestigial gills which allows them to stay underwater for up to two hours if necessary. While they don't usually live in their burrows, they will dig them where they are liable to flood, and use them as bolt-holes when predators such as sharks come by.)
Turtles
Appearance: Turtles are all feather and fin, and spend a relatively large amount of time at sea. They favour small islands and shallow coastal areas, where they can remain close to the surface to soak up the sun's warmth. Stiff, short, rounded feathers behind their necks help to cut through the water as they swim, and blade-like fore-and hind-fins provide forward momentum.
These creatures are usually coloured black and have shiny backs (EDIT: I'll admit I'm cheating here slightly. I already researched colours in animals by the time I wrote this, which you'll see in one of the posts to come. Melanin improves the strength of feathers, and the shapes that produce iridescence on feathers can have a further strengthening effect. Add that to the fact that these guys spend a lot of time underwater and they're going to shine like black mirrors!). This is more to improve the strength of their dorsal feathers for the purpose of cutting through the water than for display, but the end result is that when one looks down into the sea and sees turtles, they appear as jet-black ovals with a purple-green gloss. The effect is quite stunning.
Feeding: They are physically stocky and powerful, and use this to pull down entire branches of trees to eat the smaller twigs and bark. It's not unusual to look up at a tree by a beach and see one of these creatures bearing the weight of two of its stout limbs on a branch to make it fall. (EDIT: That means that I would need to make sure any artist would give the turtles dexterity in their limbs as well as feathers and fins.) An undisturbed turtle will then climb back down and enjoy its meal.
They rarely show an interest in leaves, and this attracts coastal hares and rabbits, which happily eat the leaves left behind by the turtles.
Predators: Large sharks can and do ambush turtles in trees, to corner them.
Beneficial relationships: The hares and rabbits aren't the only ones who benefit from the turtles' tank-like constitution. Lizards and snakes have been known to hitch a ride on these creatures' backs. The turtles' black backs make them excellent absorbers of heat, which radiates enough heat back out that the lizards and snakes will bask on their backs. Turtles are a poor choice of prey for many species, so the lizards and snakes benefit from this when riding on a turtle's back.
Sharks and rays
Appearance: These creatures are graceful, which is surprising given the sheer size of some species in this Class. Their general body shape varies from sleek to much broader than they are flat. Feathers and fins tend to be relatively minimal, and their limbs tend to make them better-adapted for land. However, a level of variation applies from one species to the next.
Their legs and feet are powerful, and their fins are often hook-or-barb-like to help them get purchase on trees when climbing after their prey.
Feeding: Smaller ones are able to run faster and invade burrows, and can put on a burst of speed to catch faster prey such as rabbits or insectivores. As such, small sharks are able to bypass the insectivores and pheasants' mutual system of alerting predators. (EDIT: note to self - we'll need a way to keep small shark numbers low to make sure they don't predate the insectivores and pheasants to extinction. Making sure the pheasant nests have several entrances and exits should help)
Larger sharks and rays are able to catch and kill seals and turtles, although with seals being poisonous, only a few species are immune and able to eat them. Some species can climb trees, and the sight of a turtle trying to fend off a large shark can be a harrowing sight.
While smaller sharks enjoy insectivores as part of their diet, larger sharks ignore them due to their small size and manoeuvrability. As a result of this, insectivores don't avoid them. Large sharks will tend to kill large prey and eat from them over an extended period of time, which attracts insects. These attract the insectivores. This in turn tends to attract smaller sharks, but the large sharks recognise them as a threat (indeed, smaller sharks will also scavenge from larger sharks' kills) and will ward them off.
Predators: Sharks currently have no predators. (EDIT: I just did a Google search for Does anything eat sharks? It turns out some do - large whales, including Sperm Whales, which tend to have a rather... combative diet anyway (Google it yourself and see what I mean. It takes courage to eat something that could just as easily kill you!). There are also large sharks and small sharks, so I want to revisit this section at some point.)
Beneficial relationships: Sharks do have some relationships with non-sharks, so I'll revisit this, but at the current state of this ecosystem's development: none.
Hornbills
Appearance: Generally bland in appearance except for their colourful and often oversized fins. Fin-struts are bulky and can function as weights to help them sink with lungfuls of air, or to signal strength and health.
Feeding: Hornbills eat fruit and insects, which they eat on land. They can climb trees and, once among the branches, will hop from one to another. Their legs and feet are strong, but this is one time where they use their heavy fin-struts to help them balance while in the trees.
Breeding: Hornbills have developed an intriguing strategy to protect their young: they seek out rocky overhangs underwater and, when they find one with a concave shape, fill it with air by taking lungfuls of air at the surface, diving down, and releasing it inside the cave. Mated pairs of hornbills can be seen repeatedly breaking the ocean surface, then diving in turn.
When the overhang has trapped enough air beneath the surface, the female lays her soft-shelled eggs, which float in their underwater cave. The young remain close to this air bubble, using it for their oxygen supply. When they have grown enough they leave.
Predators: Eels and morays are large and fierce enough to try to catch and eat them, but mated pairs can be equally fierce in their protection of their nests and eggs. Fights between predator and prey can be vicious. Larger lizards and snakes will try to eat hornbills, and the story is similar for them: catching dinner (or avoiding being caught for dinner) can be a fight to the death. However, as lizards and snakes prefer to spend more time on land, they are less likely to find a hornbill nest, so the pressure tends to be lower for them. They are most likely to come into contact when hornbills seek out food: they eat seeds and nuts, and lizards and snakes tend to hide where these foods can be found.
Beneficial relationships: With the intense rivalry between hornbills and eels, it is perhaps surprising that hornbills will seek out deserted eel nests as breeding spots.
Hornbills enjoy an interesting relationship with turtles. Turtles are capable of tearing branches from trees, bringing the insects and lizards that live on them, with them. The hornbills are quick to check over the branches for insects. The turtles' activities in the trees often also leads insects to drop off the leaves in the hope of escape, and the hornbills take advantage of this also.
Lizards and snakes
(The majority of cob'li po-fea are 6-limbed, however snakes and some species of lizard have evolved away their limbs. I'd like to take advantage of that here.)
Appearance: Snake feathers vary widely in appearance, from dull or tawny browns with a similar texture to dead plants or bark, to bright colours similar to those of leaves and flowers: greens, purples, and every other colour imaginable.
Feeding: Larger insects and small animals. They wrap themselves around plant stems and wait in ambush.
Predators: (I need to get a clearer idea of what eats these guys.)
Beneficial relationships: Snakes are commonly found wherever there are large enough plants for them to wrap around. Indeed, they have evolved a mutually cooperative relationship with some plants: the plant produces nuts or seeds, which attract small animals. The snakes like to eat the animals that visit, but had difficulty reaching the ones that ate from the plants, so the plants developed a system to attract snakes.
They developed rough stems that the snakes could climb up. A thermogenic (heat-generating) segment of the plant right below the seed-head prompted the cold-blooded snakes to stop there and remain wrapped themselves around that - and only that - part of the plant. There, they could reach any seed-eating animals that came close. The plant benefited as the seeds matured and dropped.
Lizards work in a similar way, although they tend to mimic the appearances of flowers and eat insects that come close seeking nectar. Their feathers tend to be looser, broader, and bigger than those of snakes, and to come in a wider range of colours.
While lizards and snakes prefer smaller prey, they will tackle larger prey if they can. This includes hornbills, which are equally as partial to nuts and seeds as smaller animals.
Their tendency to hitch-hike on turtles' backs this has allowed lizards and snakes to travel to various islands that the turtles frequent, which they otherwise wouldn't have been able to reach.
Anglerfish
Appearance: Anglerfish have some of the most extravagant feathers in the animal kingdom. They tend to disguise their outlines by bunching their fins close, but some also benefit from having translucent fins (I talk about transparency in the animal kingdom in that colours segment too. Watch this space!)
Feeding: They use their unusual feathers to lure their prey, which can range from insects for the smaller anglerfish, to small animals for the larger ones, like hares and rabbits, and pheasants - which tend to fail to notice them on account of being less acute when it comes to danger.
Predators: (Nothing eats them, but I'd like to comment here on how their numbers are controlled.)
Beneficial relationships: Anglerfish function more or less independently of other Classes, do apart from the species the anglerfish prey on.
Eels and morays
Appearance: Eels bear a close resemblance to snakes so are often confused with them, but are in fact a separate Class. Strictly speaking, they are more inclined to be semi-aquatic and evolved to resemble seaweeds and freshwater plants. An eel will bite the base of a seaweed and hold on, allowing its body to drift with the current or the flow of the river. They are capable or producing a powerful neurotoxin, so that any creature that tries to take a bite out of their fins will be quickly paralysed.
Feeding: The bite of a prey animal on the eel's fins alerts it to the presence of a meal and it lets go of its mooring to drift / swim after its prey, and catch it at its leisure. Hares and rabbits, which eat vegetation, will often confuse such an eel for food and meet its end this way.
Some eels and morays are more inclined to live on land, and these will take pheasants. They are generally unable to catch insectivores but will do so if they can manage it, but they are less well-suited to catch them, and insectivores are highly effective at escaping them. Eels and morays will seek out and catch pelicans if they can. Pelicans are prone to over-confidence due to their size and are unlikely to flee quickly when they see one.There are both salt-and-fresh water eels and morays.
Predators: They are known to seek out hornbill nests to eat their offspring or eggs, as these are an easy meal. This can be dangerous for the eel however, given the strength and aggression of hornbills.
(Hornbills seek out their deserted nests so I think we need a reason for this to be particularly beneficial to hornbills. Perhaps eels and morays leave their scent or other territory markers, which keep other eels and morays away for a greater length of time - long enough to grant the hornbills temporary immunity from risk of attack? The used nests could even be devoid of predators for a while, until the local fauna work out that there are no longer eels there.)
Snakes and lizards are partially immune to eel poison, so they predate on them. The practical implications of this are that a snake may bite an eel and stalk it for a few days until it dies, and then slowly begin to eat its carcass once the eel's venom has ceased to be effective, or the snake may eat only a few bites of the eel. Other snakes will eat, be affected by the toxin, recover, and continue eating.
Beneficial relationships: (None at the moment.)
War'col begla
Most members of this class are two-limbed. The majority lay eggs although a few are live-bearing, and there is no strong trend for warm-bloodedness, cold-bloodedness, or anything in between. The most common trait that the members of this Class share is relatively dull colouration, with shades of orange or black and white being the most colourful you're likely to see.
Pelicans
Appearance: Pelicans are large, somewhat-clumsy animals, and many species have striking black and white markings on their fur. They find life at sea quite easy given their semi cold-bloodedness, and usually float on the surface, using their large, webbed feet to steer, generally close to land where the water is warmer.
Feeding: They prefer to feed on bats' eggs. (I think I'll need to figure out how the bats put themselves in harm's way. EDIT: Having written the bats' segment, I'll guess that the bats generally need to stay in shallow water to aerate their eggs, and this makes them vulnerable. Given that these species are all in a warmer climate with less meaningful seasons, chances are the bats breed all year 'round so this food source won't be seasonal for the pelicans.)
Predators: However, they are not prone to inactivity. Pelicans are known for their over-confident bluster, and generally react to predators by making themselves look big. Their only weapons are their talons and their teeth, and their talons are usually out of the equation when a pelican is in the water.
Beneficial relationships: (Bats share pelican nests, but I'm not sure what pelican nests would look like. I don't think they'd have nests per se since they're effectively amphibians with a slightly stronger tendency towards land than sea, so would be unlikely to be protective of their eggs or young. For them, shelter would be just that - shelter from the elements. So I think they would use rocky caves.)
Pelicans also offer a 'bodyguard' service, so to speak, to passerines. If observed under the surface of the sea, it is common to see dozens of tiny, brightly-coloured passerines swimming around the legs of a pelican. The pelicans do not appear to benefit from this arrangement and choose to ignore them, if they notice them at all.
Pogi'fula
Aquatic, warm-blooded creatures with four limbs. The animals of this Class share a common challenge: to keep warm, and this is why most are limited to the warmer climates. However, their warm-bloodedness is somewhat unique to them. Rather than remaining homeothermic (retaining a constant temperature), they simply aim to remain warmer than their environment.
They all possess gills and textured skin.
Bats
Appearance: Bats are dependant on a warm environment to stay within a temperature range that is tolerable for them. Broad expanses of skin are stretched between all four of their limbs, encompassing their heads and tails. Some species have longer necks which they 'beat' along with their limbs to aid swimming. Their tails have almost evolved away in some species, but remain long in others.
Colours and patterns are usually dark and light greys or browns, and many are subtly striped. When they beat their wings they often resemble the ripples of the ocean. A few species have a green or blue iridescent sheen on their backs.
Breeding: Their eggs are sticky, and adhere to each other in a chain or mass as they are laid. When a female bat is finished laying her eggs, she sticks them to something. Her choice of egg-anchor depends on her species. Some stick their eggs to their tails and swim continuously until they hatch, to allow the female to keep herself warm and her eggs oxygenated. Others stick them to rocks in the shallows where they can benefit from the sun's warmth.
Their eggs are often eaten by pelicans. However, pelicans are messy eaters and often only take the bulk of a chain or float of eggs without bothering to pick off every egg present. It is this safety-in-numbers approach that keeps the population of bats up.
Feeding: Despite them generally being small, bats are ambitious hunters and will catch passerines to eat. One kill will generally feed many bats, and the bats are generally generous about sharing their meals with one another. They are social creatures and this is considered to be one of the ways in which one bat will build trust with others of its kind.
Beneficial relationships: Feeding the pelicans isn't the only relationship the bats have with them. Bats will also co-exist with them in the rocky caves the pelicans shelter in during tropical storms. The arrangement sounds a bitter one, with bats swimming in the shallows of pelican caves, and the pelicans, with their strong tendency to bite or thrash to scare off intruders, reflexively reacting to the bats, but the situation is surprisingly peaceful. Pelicans do not appear to recognise bats as food, and the bats tend to desert their eggs to the mercy of the pelicans.
Passerines
Appearance: The seas and in-land lakes are full of passerines, and many are colourful. Many live in colonies, and each colony develops its own patterning and colouration dependent on species, locally-available food, local predators (and the different spectrums they can or cannot see), and the clarity of the water in which they live. (I think it would be interesting to work out whether these colonies live in any structures and whether they're made by the passerines themselves or something else.)
They are fast-moving but harmless and this makes swimming with them a delightful experience! (A terrestrial person might compare them to little, square, colourful rays. They wouldn't be too far wrong!)
Predators: Their main predators are bats, which find them easy to pick off due to being of a similar size, but the passerines are so numerous that this presents little threat to most populations. They're also generally unaggressive, which makes predating them easier for the bats.
Beneficial Relationships: Passerines, like bats, enjoy a 'bodyguard' service, courtesy of the pelicans. Coastal passerines swim around the pelicans' long legs where they generally go unnoticed, and where no other predators dare come too close.
Passerines also benefit from a cooperative relationship with young catfish. (Now that I look again at my cooperative spot-map, I'm less sure that passerines and catfish larvae need to cooperate, since I've pretty much described passerines as eating phytoplankton or algae here. Unless... Plankton blooms tend to occur in certain areas, and passerines and catfish larvae will gesture to each other to attract one another to such blooms. Quite why they do this is uncertain, perhaps the passerines prefer to have a spiny, hard-to-eat catfish larva around, while the larva prefer to have the more visible, brightly-coloured passerines around as a distraction, but the arrangement seems to work for both Classes.)
O'fur-hai
Awkward on land yet ultimately made to be able to live there at a pinch, o'fur-hai are generally small, moist-furred creatures that breathe air but can absorb oxygen through their skin. They emerge from salt and fresh water as adults after spending their juvenile stage submerged.
O'fur-hai have two limbs, lack teeth, and lay soft eggs.
Gliding tree mammals
Appearance: Odd little gliding creatures that live in the trees in the most humid, forested areas. They strongly prefer high humidity to keep their skins from drying out, and as such are rare. They usually cling to tree-branches but will let go and glide away on a stretchy, thin cape of skin if needed. Their colours vary according to the colours of the bark on the local trees.
Feeding: Gliding tree mammals pick tiny, soft-bodied insects off the leaves of trees; they evolved to eat these from plants that were close to the water they emerged from as adults, and as the plants have evolved into bigger, more land-based trees, the gliding tree mammals have followed them.
Predators: Their worst predators by far are eels and morays. It's the egg-laying and hatching ends of their reproductive cycle that put the gliding tree mammals at most risk: the eels know when it is breeding season and gather at the edges of freshwater lakes and streams to prey on them.
Breeding: They prefer fresh water to lay their eggs in, so return to water to mate.
Beneficial relationships: These creatures tend to occur in the same ranges where insectivores live. While it is uncertain quite why this is, it is thought that they benefit from insectivore vigilance towards predators, and settle on trees in insectivore territory because the insectivores deem it to be safe enough to settle in that location. Their sudden movements tend to startle insectivores, which in turn prompts the occasional false-alarm when the insectivores warn their pheasant hosts into their burrows.
Seals
Appearance: Seals are locally common, with large populations spotted around the globe. Even as adults they generally like to have ready access to the water. Their skin is deep and spongy, and this helps prevent them from drying out. Their flesh is also highly poisonous, so it is not at all recommended to touch them. Their vivid colouration and patterning indicates this to any curious predator.
Feeding: They eat larval, or very young adult, catfish by swallowing them whole, and other relatively helpless animals if they can catch them.
Breeding: The eggs, when found in coastal areas, are huge, and make good eating - unlike the adults, the eggs are not poisonous. This tends to be what keeps their numbers in check.
Predators: Certain species of sharks are immune to the adults' poison and will eat them. Their eggs are more vulnerable than the adults.
Catfish
Appearance: Catfish are squat, dull-coloured, and seek the cover of muddy waters wherever they can.
Feeding: They have huge numbers of offspring and these are the primary food source for seals. Young in the latter phase of their juvenile stage will often emerge from the water to soak up oxygen through their skins or in search of insects to eat, and are rather helpless.
Predators: The natural prey of seals (and quite a few other species too, I'll guess. Catfish play a big part on Earth in the fishing industry, but there are no industries on the planet they're on. Perhaps they're a favourite of many other species. I'll have other species eat these as I develop more.).
Youngsters grow spines as 'fur' to defend themselves while they live in the sea.
Beneficial relationships: The juveniles also tend to seek out shoals of passerines. The two species find a form of safety in contrast: for the catfish young, the passerines distract predators by being brighter-coloured, and for the passerines, the catfish are slower-moving but hard to eat.
Conclusion
If you're following along, good work getting this far! We now have enough information to take your ecosystem's development two steps forward: the next level down in the biological taxonomic system is Family, but we're going to go straight to species and then take a step back.
In part 5 we'll sketch, or commission an artist to sketch, multiple species based on one of the above Orders, and then group their sketches into Families.
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Credits
Title image by Kazenishi as part of an Artfight for giiuu, and used with their kind permission.
