Gorillas in the crossfire: population dynamics of the Virunga mountain gorillas over the past three decades

Abstract

Small populations are particularly susceptible or 1.3% annual growth rate since 1972. This is lower than growth estimates made in several population viability to disturbance. Routine censusing to monitor changes is important for understanding both population dynamics analyses, but approximately 5% of the 1989 population is known to have died due to military activity over the and the eCectiveness of conservation strategies. Mountain gorillas Gorilla beringei beringei in the Virunga Volcanoes last decade. DiCerent subsets of the population exhibited diCerent responses to disturbance caused by war. We region of Rwanda, Uganda and the Democratic Republic of Congo have been censused five times since 1970. discuss conservation strategies that are likely to have contributed to an increase in the gorilla population during However, due to war and political unrest in the region since 1990, no census had been conducted since 1989, this time of turmoil. While the population has grown, the results should be viewed with caution, not only because when the population was thought to number 324 gorillas. In 2000 we estimated population size using repeated all known growth during the last decade can be attributed to one subset of the population, but also because the region observations of 17 habituated groups and information on 15 unhabituated groups obtained during patrols. The is still plagued by political unrest. minimum population was 359 gorillas, and a best-case scenario correcting for groups that might not have been Keywords Democratic Republic of Congo, Gorilla beringei beringei, war, population size, Rwanda, Uganda, counted was 395. Using the minimum population and best-case scenario respectively, this represents a 0.9% or Virunga Volcanoes. 1.8% annual growth rate over the last decade and 1.0% could have a critical impact on the ability of such

Socioecological influences on the dispersal of female mountain gorillas—evidence of a second folivore paradox

“…In combination with previous census data and analyses of female reproductive success (Kalpers et al 2003;Robbins et al 2007), this study has provided additional evidence that the second folivore paradox applies to mountain gorillas in the Virunga Volcano Region. Females were not more significantly likely to emigrate from larger groups, and the immigration rate was not significantly greater into smaller groups.…”

“…Juvenile red howler monkeys were more likely to leave larger groups, but those results may reflect infanticide risks more than within-group scramble competition (Crockett and Pope 1993;Crockett and Janson 2000). One potential caveat for this study is that it focused on groups that have better habitat than the rest of the Virungas (McNeilage 1995) and have less reliance on contestable resources than other gorillas (Doran et al 2002;Robbins and McNeilage 2003;Robbins 2008a). Thus, our results may not be representative of other populations of mountain gorillas or of western lowland gorillas.…”

“…Regardless of whether the original folivore paradox applies to mountain gorillas, they are still an interesting species for examining the socioecological influences on female dispersal because both one-male and multimale groups can be observed in the same population (median= 40% multimale groups, range=8-53%, N=6 censuses of the entire population; Kalpers et al 2003). Infant mortality has been nearly twice as high in one-male groups, a significant difference that is at least partly due to infanticide (Fossey 1984;Watts 1989;Robbins et al 2007).…”

Understanding the co-existence of conflict and cooperation: Transboundary ecosystem management in the Virunga Massif

“…In spite of the region's lingering conflicts, collaboration between the three countries in the Greater Virunga made considerable progress through informal and field-level cooperation, including some concrete achievements that have undoubtedly contributed to conservation effectiveness, most notably an increase in the number of mountain gorillas (Kalpers et al, 2003). In institutional terms, the main achievement was the closer collaboration between the three Protected Area Authorities.…”

Long-term research and conservation of the Virunga mountain gorillas

“…It is notable that increases in the Virunga population can be accounted for by one subsection of the population: the Karisoke research groups plus the Susa tourist group. If other groups have not fared so well, this is likely to result from differing levels of protection, human disturbance, and demographic factors (Kalpers et al, 2003).…”