Oil-eating animal; possible?

Question

I saw a movie where oil companies stumbled upon these fictional underground aquatic deep-sea animals that survived on eating and digesting the oil where they lived. They had squid/octopus-like bodies and were as smart (possibly smarter) than dolphins or apes (not us, though).

These are the conditions:

• very high pressure since they lived in deep underground caves filled with high-pressure water
• very intelligent
• social
• oil (petroleum) eating

Is it possible for an animal to survive and develop the ability to eat oil in these conditions?

Answer 1

The biology of such a creature is plausible - oil is an energy-rich substance and there are bacteria that can digest it. These creatures may have a symbiotic relationship with such bacteria. The real question is why they would be intelligent.

Most intelligent animals eat a wide variety of food sources (they need to learn which are good for eating and which are not, and remember the tricks for eating each kind of food) and many are carnivorous to some degree (they need to outsmart prey). Grazers are rarely very intelligent, and sucking on oil wells seems to be pretty similar to grazing. However, there is one intelligent species that may have evolved with an ecology similar to your oil-eaters: Elephants.

It is theorized that elephants evolved their substantial brains not so much for the sake of finding food, but for finding water. When resources are rare, far apart, clumped together, and tend to vary in how accessible they are (pools appearing and disappearing seasonally), it is important to be able to remember where those resources are in order to migrate between them. It is also important to remember what conditions are associated with the appearance or disappearance of a given pool (heat and rain). A social hierarchy may develop as herds migrate together, and older individuals may remember pools that younger ones do not.

An analogy can be made between elephants searching for water and these sea-creatures searching for oil. Oil wells are rare and far apart, and many are fed from deeper sources or shale that slowly replenish the easily-accessible reservoirs over time, at least until the deeper wells are depleted (presumably the biological mechanisms of these creatures are not quite as effective as the best human equipment, so they are only able to access the most easily-accessible wells). Finding new oil wells is difficult (perhaps the creatures have some kind of natural sonar ability) so being able to remember to return to the old wells decades later will be a major survival advantage, as will judging how quickly each well tends to refill. As with elephants, this will likely result in a complex social hierarchy with elderly leaders that remember the old wells, migrating in huge herds across the ocean floor.

Answer 2

It is totally plausible. You would need commensal microbes to do the metabolic work.

Consider cellulose - loaded with energy but difficult for metazoans to digest. Those that can digest it (e.g. termites, ruminants) have commensal bacteria in their guts which have the metabolic machinery to handle cellulose. The metazoans house these organisms and keep them safe; in exchange the microbes release the nutrition in the cellulose and nourish their hosts.

This same model could work with petrochemicals. There are microbes which can digest these energy rich compounds. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3815313/ and one would expect that just as termites house cellulose-digesting microbes, metazoans in environments rich in petrochemicals would house petrochemical digesting organisms.

Answer 3

Others have covered that biologically this is quite plausible, but the main issue I see is most petrochemicals have a very short life near oxygen, and have no scope for squeezing a little bit more out by some form of anaerobic process.

The problem with large life is that they need oxygen, but oil requires an anoxic environment to be created and persist.

The oil eating organisms are all bacteria because of the lack of oxygen.

Your creature is either going to need to process the most difficult oils (tar) or spend its time traveling between the surface and depths of the sea.

So in summary you have either beasts roaming the land searching and digging for tar or perhaps some deep diving cephalopod consuming methyl hydrates formed on the edges of continental shelves, or drinking from natural seepage above reserves.

Answer 4

It is not only possible, oil eating animals already exist. On top of that, oil is extremely close to fat chemically, as they are chains of hydrocarbons. Essentially, every animal on the planet eats some form of fat from other animals, even from some plants. Oil and petroleum are full of energy. Its no stretch for an animal to evolve to take advantage of that as a good source.