Frohoff described Wildlife Safari as "an antiquated zoo" because it uses bullhooks - sharp, poker-like weapons - to train and subdue its elephants. She said the park offers elephant rides, which the Humane Society considers cruel, in part because of the inhumane training methods that are often involved.
Wildlife Safari was unable to respond to questions before this piece was published.
Wildlife Safari is accredited with the Association of Zoos and Aquariums, which says its members have the highest facility standards in the industry.
Liz, 51, and Valerie, 33, were the last resident elephants remaining at Six Flags Discovery Kingdom. Company officials say the transfer means the two elephants will be able to socialize with more pachyderms - but they will be missed nonetheless: "Liz and Valerie are beloved members of our family and their departure marks the end of a truly remarkable era."
Zoos and circuses continue to face public pressure for reform and criticism from animal welfare organizations. Earlier this month, news reports say two employees with the UniverSoul Circus are facing animal abuse charges after sticking a bullhook in an elephant's mouth to move it off stage.
Below, see footage from the elephant show at Six Flags and the Wildlife Safari elephant car wash.