Along with ecologist Richard Greenwell and Belgian zoologist Bernard Heuvelmans, he was one of the founding members of the International Society for Cryptozoology, which was created in 1982 at the National Museum of Natural History in Washington, D.C., with the hopes of bringing a degree of respectability to what is often seen as a pseudoscience. The organization published a quarterly newsletter and an annual journal, and members met annually at meetings held at universities throughout the world. Mackal was the ISC’s vice-president for the entirety of its existence, although the organization gradually folded in the early 21st century owing to lack of funding and the deaths of Heuvelmans and Greenwell.