Daily ranger-based symptom observations and health monitoring of habituated mountain gorillas (gorilla beringei beringei) in Bwindi impenetrable national park, Uganda
Abstract
It is often hypothesized that transmission of human diseases to apes is a (if not the) major threat to species survival hence the need for a systematic approach to health data collection yielding solid evidence on which to base intervention strategies for reducing disease transmission. This research was aimed at identification and assessment of clinical parameters among habituated mountain gorillas of Bwindi Impenetrable National Park. Basic health data was collected by the UWA rangers (trackers and guides) using daily clinical observation forms.
There were 1825 potential gorilla group observation days for all the five groups of which 1482 (81.2%) gorilla group observation days were recorded. On average, at least 15 people enter the park per day to track Habinyanja, Mubale and Rushegura groups while an average of 11 people enter to track Nkuringo group of which tourists generally form 40%. An average tourist occupancy rate of 80% was observed in Habinyanja, Mubale and Rushegura groups while in Nkuringo group, an occupancy rate of 56.2% was observed. Fluctuations in the number of visitors were observed with November, April, and May registering fewer visitors than other months and throughout the study period, Nkuringo group significantly had fewer visitors than other tourists groups.
A total of 18018 individual gorilla observations were made out of the potential (if every individual gorilla were seen each observation day) 22939 resulting into an overall observability of individual gorillas of 78.5%. Kyaguliro group individuals were seen most with 96.6% and Nkuringo group individuals were seen least with 66.8%. While by age / sex class, silverbacks were seen most at 93.8% and black-backs were seen least at 70.2%.
Based on the gorillas seen, the body system was observed most with 98.6% (n=18018). The general activity was observed in 98.2%, the respiratory system in 96.7%, the skin / hair in 96.8%, head discharge in 87.3%, other discharge in 35.6%, and the stool was observed least in 3.9% of gorillas seen.
During the study period, 86 abnormal observations were made, out of which 68.6% were wounds and cuts on the integumentary system (skin and hair) and mostly in gorillas of Kyaguliro group and in black backs and silver backs. The average percentage of abnormal observations was highest with black-backs at 1.14% (29/2551) and lowest with infants (0.03%, n= 3672). In the different gorilla groups, the percentage of abnormal observations was higher in Kyaguliro group at 0.94% (40/4258) and lowest in Rushegura group (0.12%, n= 3280). Abnormal observations were significantly more in black backs and less in Infants. In all groups, there was less than 1 abnormal observation per 100 individual gorilla observations.
Overall 1/3 of all gorillas had something identified as abnormal during the one year study period. Kyaguliro group had the highest period prevalence of abnormal observations at 66.2% while Rushegura group at 7.7% had the lowest. In the different age / sex classes, black-backs had the highest prevalence and Infants had the lowest at 87.7% and 6.2% respectively.
All the tourist groups (Habinyanja, Mubale, Nkuringo, and Rushegura) at times move out of the park. Kyaguliro group never moved out of the park. Nkuringo group significantly spent more time out of the park than any other group. Habinyanja group had the biggest home range of 32.52 km2 followed by Nkuringo group (25.95 km2) at 95%UD. Mubale group had the smallest home range of 8.05 km2. There was no relationship between group size and home range.
Gorilla health monitoring using symptoms is a good basis for disease outbreak monitoring because it gives an insight of every day happenings in gorilla groups and this study being the first of its kind covering all the habituated groups of BINP is important in providing the baseline monitoring parameters for the these habituated mountain gorilla groups.