[3] Born in Milwaukee, Wisconsin, in 1925, Mackal served in the United States Marine Corps during World War II before attending the University of Chicago, where he received his B.S.

"[4] 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.

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.

Mackal's 1980 book Searching for Hidden Animals was negatively reviewed in the BioScience journal as a "reflection of mankind's anxiety in the modern world of science and an obvious extension of current interest in the paranormal.

During this time, the LNIB conducted sonar probes of the waters near Urquhart Bay and installed underwater strobe cameras with the hopes of providing evidence of the Loch Ness Monster.

During the 1980s, Mackal turned his attention to purported creature, the Mokele-mbembe, which figures such as Young Earth creationists claim is a living dinosaur in the Likouala swamp region of the Republic of Congo.

Accompanied by University of Arizona ecologist Richard Greenwell and Congolese biologist Marcellin Agnagna, Mackal undertook two expeditions, the first in 1980 and the second in 1981, to find and photograph the creature.