Mannix appears to be or have been a professional co-author.  He has dozens of books to his credit all as co-author with folks who appear not to have done other writing.  I'm guessing that Mannix actually did teh typing and editing for just about anyone with a good story but not the inclination or ability to write a book themselves.  Ryhiner was a animal collector for zoos in the 1950s.  But he seems to have dropped out of the public eye after a New Yorker article in 1958.  It was shortly after his divorce, money troubles dogged him through his career, and he drank heavily all the while spending his time in places where you collect things like Indian Rhino and Mountain Gorillas.  So I wondered if he succumbed to a back water fever in an unmarked grave, or retired quietly with a Brazillian bride to run the private zoo he always wanted.....?

I found another board with a European hunting section and reached out to some Swiss hunters there to see if they had any information.  They turned up this page:  here

The page linked above has a link to a film about Peter.  Here is the description in English as translated with an online translator (Babelfish):

“The most beautiful concert hall was for it the jungle, said the Basler Peter Ryhiner. In this enormous free air hall it listened to the music of the wilderness in the fifties-years however not only, but it caught here Nashörner, elephants, apes, birds and all kinds of other majority game, which it sold particularly to zoo-logical gardens in the whole world. Ryhiner, called Pief, was one of the old pellet and grain, one of those men, whom there are not today any longer, like his first wife Mercia in Mike Wildbolz' Documentary film “Ryhiner' s Business” means: Pief was hero, Charmeur, adventurer and drunkard. Actually Peter Ryhiner Zoologie wanted to study, instead he became “a savage Tierfänger” (in such a way appropriate his small daughter in an essay designated him). It not only the money sold the wild animals because of. An animal welfare activist in the today's sense was it surely not, however also no hunter and Wilderer. Ryhiner was convinced of the fact that by the breed in zoos surviving of gefährderter kinds could become secured. He made movies of the animals caught, he held lectures, wrote books, from radio stations was invited. It supplied among other things the two Indian Panzernashörner, which provided world-wide for the first new generation in captivity to the Basler with zoo. But with the increasing preventive measures for game animals in their natural habitats Ryhiner' lost; s Businesses its authorization and his basis. It became from the individualists to the social outsider and separated 1975 voluntarily from this life. Mike Wildbolz does not go it in its documentary film primarily around bringing up for discussion ethical questions around the occupation of a Tierfängers. With the memories of relatives, friends and teammates, with old and new film and pictorial material of the places, at which Ryhiner stayed, with Piefs, the producer of the schillernden personality of the Baslers follows to diary recordings and cutouts from radio interviews and reconstructs in a critical homage stations of a moved life, which summarized Pief ironically on one of its visiting cards: “Peter Ryhiner NO money NO home NO ADDRESS NO of hair dryers”.

Direction Mike Wildbolz Book Hans Rohner, Mike Wildbolz Camera Thomas hard Meier Music Ibo Antognini Production CH 1998 Duration 89 min. Category Doku © Karin Mueller. “

I’m not sure from the translation whether he went into isolation, into an asylum, or committed suicide in 1975 but in any case he was quite a fellow.

His biography on a German language page says "He was hero, adventurer, romantic and drunkard. A kind of modern Allan Quatermain. His journeys led him around the whole world, straight through South America, Africa and Asia. He caught and sold thousands of animals in approximately twenty years."

As a side note his wife Mercia who he found working as a penniless hotel clerk in Singapore, eventually widowed Sir Rex Harrison in her fourth marriage and is still alive.

Peter certainly lived a life of adventure. I suspect that he had few regrets and hope that he was happy in the end. Here's a toast to his memory even though I never met him!