They found no elephants at all, in an area where 350 had been counted just before the war.
Gorilla numbers have been drastically cut as a result of fighting and lawlessness in a game park in the eastern Democratic Republic of Congo.
The results of a recent survey published by a wildlife conservation group also shows that elephants - formerly numerous - have apparently been hunted to extinction.
Kahuzi-Biega National Park became one of the great names in gorilla conservation, with the pioneering American naturalists Diane Fossey and George Schaller both having worked there.
The portrait of one of its gorilla residents - Maheshe - also appeared on Zairean banknotes.
But the park has since been devastated by the war.
It is only in the last year that forest rangers have been allowed to resume work in parts of the reserve and start assessing the state of the animal population.
Depressing survey
The results of the initial survey - done last year with the American Wildlife Conservation Society - make depressing reading.
They found no elephants at all, in an area where 350 had been counted just before the war.
Gorillas had fared slightly better, but their numbers had been reduced by half.
And this was only in the mountainous part of the park, which has seen less violence.
The much larger, lowland area, where there used to be thousands of gorillas, is still too dangerous to attempt a survey.
Primate cooking pot
It is infested with armed groups, and these have now been joined by tens of thousands of illegal miners digging for tantalum, a rare metal used in mobile phones and computer games, the price of which has soared over the past year.
As the price rose towards $300 a pound, diggers flooded into the park, encouraged by the Rwandan army, which controlled the area and its Congolese allies.
Guns are plentiful these days, and the miners have to eat.
Conservationists fear that a large part of the gorilla population may already have been killed for the pot.