The Humane Society financed research for a prototype of her famous double-rail restrainer system. “That system is in use in half the slaughterhouses in the country, and it probably would not have existed if not for John Hoyt,’’ she said in an interview Friday. “He took the practical approach - ‘If we’re going to eat meat, well, let’s make sure the animals don’t suffer needlessly.’ ’’

Mr. Hoyt was also an early proponent of laws against organized dogfighting. Lobbying efforts by the Humane Society beginning in the 1980s were instrumental in persuading 40 states to adopt laws making deliberate animal cruelty a felony rather than a misdemeanor. Those laws were considered instrumental in the passage of the 2007 Virginia law under which Michael Vick, the NFL quarterback, was prosecuted for dogfighting.

By its own accounting, the Humane Society grew to more than 5 million members during Mr. Hoyt’s tenure from 100,000. Its annual budget, which was under $1 million when he became president in 1970, had grown to about $50 million by the time he retired.

When confrontational animal rights organizations like People for the Ethical Treatment of Animals emerged in the 1980s - criticizing organizations like the Humane Society for being too focused on fund-raising and for not recognizing the inherent equal rights of humans and animals - Mr. Hoyt vigorously defended his group’s approach, which he described as “pragmatic idealism.’’

He dismissed staff members he considered too sympathetic to the animal liberation movement and in a speech at the society’s 1988 annual conference refused to accept “censure for our willingness to accept compromise’’ or for the society’s “organizational growth and financial success.’’