The recent criticism of those who sell online tickets to attractions that are accused of mistreating animals has forced City Discovery to make a policy change.
The France-based tours and activities website, now in its 13th year, says it has removed around 40 sightseeing activities that "feature cruelty to animals".
Its CEO, Emmanuel Issaurat, says the sector has to "show leadership on this important issue".
The decision to end sales of such tickets comes a month after TripAdvisor was on the receiving end of a barrage of criticism for not removing listings for the products.
The campaign is being fronted by World Animal Protection (WAP), a global movement to eradicate cruelty to animals which singled out TripAdvisor (and its tour brand Viator) for not taking a stronger stance against such activities.
TripAdvisor says the "best catalyst" to highlight any unfair practices comes from the travellers themselves, by virtue of the reviews they share.
Issaurat says the City Discovery has "hidden behind the argument" that it should not be the service to make judgements on behalf of its customer base (one million customers per year).
"That's a very weak argument; we should have our own standards and ethics, and naturally, they should be high.
"If we can do something to help these defenceless elephants, lions, tigers and dolphins, we must do it. Our only regret today is that we did not move earlier."
WAP has praised City Discovery's decision as "fantastic result for animals".
Global head of wildlife, Julie Middelkoop, adds:
"We hope other travel companies will follow their lead by reaching out to World Animal Protection to discuss how they can help to keep wildlife in the wild, where they belong."
City Discovery has called out Expedia, Viator and GetYourGuide to follow its lead, saying each is large enough to "ignore the loss of revenue".
"We will now see if their management takes a decision based on what's right, rather than what's most profitable."
GetYourGuide says its general policy is to follow local rules and regulations.
Speaking during the Phocuswright Europe conference in Dublin, Ireland, in early-May, Viator CEO Barrie Seidenberg says it is currently reviewing the issue.