The late Betty White was a tireless lifetime advocate for animals, from caring for those without homes to launching her own weekly TV show, The Pet Set, dedicated to her celebrity friends and their pets.

Her most far-reaching contribution, though, may be yet to come: On Monday, fans of White will be poised to donate to animal welfare charities and shelters as part of whats been dubbed the #BettyWhiteChallenge. And animal welfare nonprofits are gearing up to capitalize on the viral tribute to the star of The Golden Girls and Hot in Cleveland on what would have been her 100th birthday.

Ive had many conversations with Betty about animal welfare, and I know shes looking down from heaven and really smiling, said Robin Ganzert, who leads American Humane, an animal welfare organization that White was involved with for more than 60 years.

Shell be smiling on her birthday, she said. And shell be smiling about the lives shes changed.

It isnt exactly clear who started the #BettyWhiteChallenge on social media shortly after Whites death on Dec. 31. However it began, the idea to donate $5 to a local animal rescue organization in Whites name on her birthday quickly took off and drew support from celebrities like actors Mark Hamill and George Takei on Twitter.

Traffic to American Humanes website spiked after Whites passing. Ganzert said donations, too, have increased. The nonprofit is waiting to reveal by how much until more gifts flood in, including sizable donations its expecting from some donors.

During the decades in which White was involved with the organization, she made fundraising appeals and served on its board and as a presenter and judge on its televised show featuring hero dogs. During tapings of The Pet Set in the early 1970s, Ganzert said, White would have American Humane representatives on set to ensure that animals were safe. In 2012, the nonprofit honored her with its highest award, the National Humanitarian Medal.

Ganzert would also give White a photo book each year of the animals the organization helped.

She kept those out on her coffee table, Ganzert said. And (it) always touched me whenever we would visit.

Best Friends Animal Society, a Utah-based animal welfare organization, has raised $25,000 in donations made in Whites name, according to the groups chief mission officer Holly Sizemore. The group has promoted the #BettyWhiteChallenge broadly across its social media channels to drum up support both for its work and other organizations.

Thats the beauty of animal welfare, Sizemore said. Theres something for everyone to support. Theres so much good work happening and so much opportunity, particularly right now, to make the world a better place for people and animals.

Sizemore hopes that Monday will bring plenty of donations and attention for animal welfare.