&gt;  Well, the article is about the occurrence of homosexual behavior in some populations of greylag geese. I don&#x27;t know how this turned into &quot;so many animals&quot;. According to Wikipedia, homosexuality has been observed in anywhere from 500 to 1500 species -- out of an estimated 8.7 million currently living (estimate from 2011).<p>Comparing the 500–1500 number (of presumably well-observed species) with an estimated total number of species is not really a good comparison. Setting aside the accuracy of the estimate of the number of species and how many of those have actually been seen&#x2F;classified, what fraction of those have been observed well enough to make a reasonable determination of the occurance of homosexual activity? Certainly the fraction of well-characerized species who exhibit homosexual behavior is much higher than the 1-in-1000 rate your numbers imply.