Yes, yes indeed. Buio implied we're getting trolls in there, so let's think: These things are big, so they'll either need a lot of small prey or some big prey. For the former, there can be a lot of open space or an extensive system of underground tunnels, where bats and rats and cats can hide. For the latter, open space is a must. Trolls are most likely to be carnivorous, so they need not be in an extensively vegetative ecosystem, so long as the Tier 1 Consumers can survive. Trolls, again, are large, so they most likely will be Tertiary Consumers, so they'll have lots of defenses, such as tusks, fangs, claws, thick skin, thick fur, superior eyesight, scent, and hearing, as well as speed and strength, and maybe even poison. There will be no natural predators in their ecosystem (maybe outside of the caves). They would reproduce sexually, and be sexually dimorphic. Males are much larger than females, and the tusks are much more prominent (bulls sport curving tusks about a meter in length versus females who only have tusks about a foot in length), and the process of courting involves displays of strength (throwing the largest boulders possible, wrestling rival males), scraping of tusks on cave walls to gather more territory, and flat-out offensives towards other males, locking tusks and fighting to the death. Females produce a litter with an average of six spawn, the gestation period lasting about 12 months, and both parents care for the litter for about six months. The bulls remain with their mate for life to protect the female from rival males, and reproduce every 14 months, the added 2 given to allow each litter time to mature and develop the capability of surviving on their own. It is not unheard of for the offspring to kill each other off before maturity as a sign of dominance, which the parents allow. Trolls are solitary aside from the mating pairs. If a mate is killed, the other flies into a blood rage, and will not stop until the killer is devoured. A big weakness (given they live in caves or underground) may be extensive light, not to mention the weapons of the God Forge. So, with the ecosystem created and the top tier filled, let's move down: Secondary Consumers. I was going along the lines of some sort of reptile, like a serpentine Wyrm. The Wyrms would grow throughout their lives (they could reach massive sizes), but are often eaten by Trolls before they can get too large. They are not sexually dimorphic, and it is impossible to tell males and females apart at the surface. Egg clutches could number from 30 to 50, and Wyrms reproduce every 6 months, gestation lasting for the same period. Wyrms do not care for their young, and are solitary animals. The population is only kept in control by Trolls eating adolescent and adult Wyrms and Chirops cracking the eggs and sucking out the unborn Wyrms. Thus, the numbers allow for the Wyrms to survive. Hatchlings have scales about 1/8 of a centimeter thick, adolescents 1/2 of a centimeter, and adult scales are a full centimeter thick. The scales are slate-gray to pitch-black, acting as camouflage in their environment. They constrict prey or swallow it whole, and are incredibly fast at all ages. They are perfectly capable of swimming. Their only natural predators are Trolls, who are strong enough to rip them apart and suck out the juicy meat and have good enough nocturnal eyesight and smell to spot the serpents in the dark. Noticeable traits are the spine crests along the serpentine heads that grow with maturity. Tier 1 Consumers: Chirops, large (about a foot by a foot), omnivorous bats. They're natural prey would be the Lirn (the producers), a rapidly reproducing species of large night crawler (a big worm for those of you who don't know) that devour the fluorescent lichen that grow in the caverns like a plague, and glow because of their diet. The Chirops are also capable of eating the lichen themselves, as well as eating unborn Wyrms by cracking the eggs, but prefer the taste of the Lirn. They hunt with unbelievably accurate echolocation, have short, flat teeth and razor-sharp talons they use to grip and tear at prey. They have thin, downy fur, and a squashed looking face with milky eyes. They reproduce often (every week), with a gestation period of 4 days. Every litter contains about 100 offspring. The population is checked by Wyrms devouring Chirops by the scores. They are not sexually dimorphic, and gather together in large flocks of up to 1,000. Now, this covers the land-based population. Lying in the waters of the cave systems are the fluorescent fish called Casys, with wide-set eyes and a flat body. They reproduce every three months, with egg clutches numbering up to 50 spawn. They have no true defense mechanisms, relying upon their flashing lights to dissuade predators. Chirops are known to devour hatchlings and eggs, and Wyrms are known to feed on adolescent and mature Casys in place of Chirops if the situation demands it. They feed on lichen and Scorpos, a rapidly reproducing (every 2 weeks, with a clutch of 8 eggs) breed of insect with 16 legs, a stinger tail, 4 pincers connected to 4 of the limbs, fluorescent and extremely poisonous, the Casys being the only who are able and willing to eat them. The stingers are ineffective against Wyrm scales, and Troll skin is usually thick enough to block the stingers.
There I just created an entire ecosystem, and the creatures to populate it. That wasn't too hard, was it?
