I took the picture below at Ka'ena Point, Oahu in January of 2006. In this picture, there are two Hawaiian Monk Seals. (They can be hard to spot, so I've marked the two animals in a second version of the picture below the fold.) Here's the quiz question that goes with this image: without recourse to Google, estimate the percentage of the total population of the species that can be seen in this one picture.
(Click on the pictures to view larger versions.)
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About 0.2%? I seem to remember reading something about a year ago (most likely New Scientist, but who knows!) saying there were only about 1000 Hawaiian monk seals left in the wild.
Apparently, this question calls for some serious assumptions and approximations. Based on my world map, and measuring with a ruler, and rounding to a nice even number, Hawaii appears to have a coastline of about 1000 km (1,000,000 m). I'm assuming that this species is endemic to Hawaii only. Being an isolated island group with many unique species, I don't think this is an unreasonable assumption. Let's estimate the length of the seal in the background as 2 meters. That's about 1/2 inch on my monitor. Sorry for mixing units. Given that the entire width of the photograph is 4 1/2 inches, this represents 9 seal-lengths, or 18 meters of coastline. The entire coast (and presumably the entire seal population along with it) would thus be covered by 55,555 such pictures. Since there are 2 seals in this section, the total population would be 111,111, or about 100,000, and these would represent 0.002% of the total. This of course assumes the density of seals/coastline in the photo is equal to the average density. That's rather unrealistic I know. Most such random photos would have no seals at all.
I?m sure someone else has a much more clever way to get at that number.
This paper says the world population is ~ 1300 (via PubMed, not Google!).
Looks like Colin's right - about 0.2%. And he didn't even have to bend the rules!
Having just done a snorkel survey where I personally counted about 10% of the world's entire population of a very rare fish (won't say what it is but it is the only species in its genus), I know things have to be grim to even ask the question. I'll say 4%. Also, it's great that they are in the same frame. At least there is an opportunity for reproduction.
The answer has been posted.