Abstract

In December 1997, an apparent third-degree rectal prolapse was observed in an active and otherwise healthy-looking juvenile female mountain gorilla in Mubare tourist group in Bwindi Impenetrable National Park (BINP), Uganda. The juvenile gorilla was observed with a 3–4 cm-diameter mass protruding 10–12 cm from the anus. The juvenile would occasionally squeeze the mass, expressing liquid from the distal lumen, but was active. The mass appeared to be slightly dehydrated. A tentative diagnosis was made, and preparations were made for an intervention to further assess and possibly treat the condition. The gorillas of BINP are managed as a population, and the condition was considered to be life-threatening to this individual gorilla, but not to the rest of the group (consisting of 16 members) or to the population.

While preparing for an intervention, observations continued on this gorilla, but within the next 24 hours, the prolapse was not seen again. Forty hours later, a small portion of rectum was seen protruding from the anus, a condition which would be described as a first-degree rectal prolapse and therefore not serious. Following this case, the BINP field staff reported having observed similar conditions on more than one occasion in two other juvenile gorillas straining to defecate. These conditions reportedly resolved without treatment approximately 20 minutes after first being observed. The decision to intervene was canceled, and the gorilla was monitored for further signs, which did not occur in the next 24 hours. To date, no subsequent health problems have been reported in this animal.

Although further investigation is warranted, the limited information available at present would suggest that periodic pronounced rectal prolapse occurs in young gorillas of BINP and spontaneously resolves without serious health effects for the individual. This case study highlighted the fact that there is very limited information on disease conditions in mountain gorillas; therefore, staff training in observation and accurate reporting is essential for successful field diagnosis and subsequent management of cases.