The official listing of an animal species as endangered triggers the enforcement of legal safeguards designed to protect endangered species, such as tighter animal export and trade restrictions and stronger antipoaching laws. Nevertheless, there have been many cases in which the decline in the wild population of a species was more rapid after that species was listed as endangered than before it was so listed. Which one of the following, if true, does most to account for the increase in the rate of population decline described above? ["Public campaigns to save endangered animal species often focus only on those species that garner the public's affection.", "Poachers find it progressively more difficult to locate animals of a particular species as that species' population declines.", 'Animals are more desirable to collectors when they are perceived to be rare.', 'The process of officially listing a species as endangered can take many years.']