Canada's Bighorn sheep have long been a favorite target among trophy hunters, prized for their massive, curling horns which can weigh up to 30 pounds. But according to new research, all this hunting aimed at bagging the biggest of the bighorn has caused the species to adapt in response -- not surprisingly, by becoming smaller.
Biologist Marco Fest-Bianchet, who studied records of 7,000 bighorn sheep gathered in Alberta between 1974 and 2010, found that gun-totting humans have changed the what "fitness" means in terms of the iconic animals' evolutionary process.
"The hunt is actually selecting in a direction that is opposite to what natural selection would be," Festa-Bianchet tells CBC News. "Normally, a large-horned ram would do very well, but in a hunted population he is more likely to get shot."
Hunters are required to only kill rams whose horns grow to a least four-fifths of a circle -- but bighorns typically achieve that growth prior to their peak reproduction age. This selective hunting therefore favors smaller or slower-growing rams for survival and mating. Their offspring, in turn, are smaller as well, better suited to avoid being hunted.