I have sent your request to the U.S. Geological Survey's expert on
the Virunga volcanoes. Hopefully he will contact you.
I have not found a reference to "mazoukus" in the geologic literature
nor have a seen a reference to gas causing animal deaths in Zaire.
Until then here are some other volcano researchers that have worked on Virunga volcanoes:
Ndontoni Zana, Centre de Recherche en Geophysique, B.P. 10336, Kinshasa, Zaire;
Hiroyuki Hamaguchi, Observation Center for Prediction of Earthquakes and
Volcanic Eruptions, Faculty of Science, Tohiku University, Sendai 980 Japan; and,
Jacques Duriex, Groupe D'Etude des Volcans Actifs, 30 rue Henri Barbusse,
69008 Lyon, France. You might try to contact them.
You might contact the Dian Fosse Gorilla Fund in London.
An article in Science (6 July 1973, p. 51-53) describes methane in Lake
Kivu but does not describe any animal deaths by gas or ponding of the gas
in low areas.
Good luck.
Steve Mattox, University of North Dakota
Update:
Reply to the question posted by Jim Enzinna about toxic gas emanations in
the Virunga volcanoes of Zaire. This was documented in the book by Bourliere
and Verschuren (1960) "Enquetes sur les grands mammiferes du parc national
Albert". Published by the Institut National des Parcs Nationaux. In those
days the park had plenty of wildlife; Jacques Verschuren observed animals,
including hyenas and elephants, killed near gaz emananations which were
sporadic and well known by his pygmy guides. Jacques is still alive, 72
years old, and if you can't find his 1960 book with Bourliere you can write
to him at Dr Jacques Verschuren,82 Avenue Atlantique, Bruxelles 1150,
Belgique. His phone No. is Belgium 02-7708636. His book has great photos of
these gaz vents and dead animals around. I suspect all this area has been
deforested and certainly has no wildlife left unfortunately. I could
photocpy this and even scan some pictures if needed and e-mail them to you
if there was a special urgent need.
Cheers
Dr Eric Wolanski
http://ibm590.aims.gov.au