Unusual risks

The title of Sal Mercogliano's latest "What's Going on With Shipping?" vlog offers two idiom extensions: "Understanding Global Shipping Risks: Black Swans, Black Jellyfish & Black Elephants".

The "black swan" metaphor starts from Juvenal (Satire VI, line 165), who described a virtuous wife as "Rara auis in terris, nigroque simillima cycno ("a rare bird on earth, and very like a black swan"). This made sense in 1st-century Rome, because the only swans the Romans knew were white.

Actual black swans are found in Australia, first reported to Europeans by the Dutch around 1697, and described scientifically in 1790. But the "black swan" idiom has continued to be used up to the present day, in the sense of (what Wiktionary calls) "Something believed impossible or not to exist, especially if an example is subsequently found". Thus a book published in 1847 asserted that "Among the most refined of the ancients, an educated woman was a sort of black swan, an object of curiosity and amazement".

A version of that interpretation was codified by Nassim Nichalas Taleb's 2007 book The Black Swan: The Impact of the Highly Improbable.

Mercogliano glosses his extensions this way:

• Black Swan Events: Rare, unpredictable events with catastrophic impacts, such as the Ever Given Suez Canal blockage and the Baltimore bridge collapse involving the Dali.
• Black Jellyfish Events: Small, known risks that accumulate to create a massive disruption, highlighted by the impact of global tariffs and the persistent Houthi attacks in the Red Sea.
• Black Elephant Events: Large-scale, highly probable threats that are often ignored until they "trample" the system, exemplified by the tensions and potential chokepoint in the Strait of Hormuz.

Thus he's generalized the idiom beyond swans, to "black ANIMAL", in the sense of something that people didn't expect, with the nature of the unexpected event metaphorically linked to the stereotypical characteristics of the named animal. (And maybe algae or seaweed would work better than jellyfish for his second category?)

No other examples of this style of metaphor extension come to mind, though I'm sure they're Out There.