I love an adventure. I've climbed cliffs on Kauai and stripped down to my skivvies to swim in a Mexican cenote. But the challenges that I pursue are a danger only to me. Those who participate in the annual Running of the Bulls can't say the same. Most tourists who travel to Pamplona for the July event suffer from nothing more than a hangover, but the bulls they run with lose their lives.

Few tourists know that at the end of every day's run, the bulls they used to cross an item off their bucket list will be killed in the bullfighting arena.

After slipping and sliding along the cobbled streets as hordes of people brandishing rolled-up newspapers scream at them, the exhausted, confused bulls must fight to the death. Men on horses circle them while repeatedly piercing them with sharp sticks called banderillas until they are dizzy, weakened from blood loss and in agonizing pain. The horses, who are blindfolded, can also sustain serious injuries if they can't avoid a charging bull.

When the bleeding bull is spent and losing the will and strength to charge, the matador (Spanish for "killer") makes his entrance to administer the death blow. In a sickening twist to an already sadistic spectacle, the crowds often cheer as the animal's ears are cut off as "trophies."

But condemnation of this bloody pastime is growing worldwide, and those few people still clinging to it are finding themselves in increasingly empty arenas. In 2007, some 3,651 bullfights were held in Spain, according to figures from its Ministry of Education, Culture and Sport. In 2015, that number had declined to 1,736. An online poll by Ipsos MORI last year found that just 19 percent of Spanish adults supported bullfighting, compared to 58 percent who opposed it.

Bullfighting is already banned in many parts of Spain, and more and more areas are following suit. In 2015, one town decided to divert funds usually reserved for propping up the local bullfighting industry into buying books for schoolchildren instead. Another swapped tormented bulls for giant polystyrene balls in its annual running festival. Madrid's mayor has eliminated public subsidies for bullfights, and earlier this year, thousands marched through the Spanish capital to demand an end to this cruel spectacle.

Further afield, the Mexican states of Coahuila, Guerrero, and Sonora have all imposed bans, joining Argentina, Cuba, Italy, and others. When the Portuguese city of Viana do Castelo banned bullfighting in 2009, its mayor stated, "The defence of animal rights is not compatible with spectacles that torture and impose unjustifiable suffering."

Since most Spaniards shun bullfights, it's unwitting tourists who are keeping the killing going. Some buy a ticket out of curiosity. Others just go along with the events laid out for them in their package deal. By the time an appalled spectator rushes out of the arena in horror, the damage has already been done.

It's hard to believe that bulls are still being stabbed to death for entertainment in 2017.

Would those who participate in the Running of the Bulls still do it if they knew that the bulls are being forced to run toward their own death? Let's hope not.