Animal's smell? Depends on which animal. Ron Anderson can id most all of them.
It is rumoured that love stinks,
but that was before the 1950's; makes my heart flutter, though Bo said it was bumpety bump.
The first pheromone ever identified (in 1956) was a powerful sex attractant for silkworm moths. A team of German researchers worked 20 years to isolate it. After removing certain glands at the tip of the abdomen of 500,000 female moths, they extracted a curious compound. The minutest amount of it made male moths beat their wings madly in a "flutter dance." This clear sign that the males had sensed the attractant enabled the scientists to purify the pheromone. Step by step, they removed extraneous matter and sharply reduced the amount of attractant needed to provoke the flutter dance.