An international response team led by the Greater Virunga Transboundary Collaboration (GVTC) found 'gross lesions' upon post-mortem, however confirmation of the cause of death will be determined in two to three weeks after a histopathology laboratory exam.
The deceased gorillas comprised of three adult females, one of whom was pregnant, and one male infant. The other 13 surviving members of the family, named the Hirwa group, were in general good health and are continuing to be monitored by GTVC and its partners.
The mountain gorilla, one of two subspecies of the eastern gorilla, is estimated to have an overall population of 1000 in the world. Uganda's Bwindi Impenetrable National Park is the habitat of one population of mountain gorillas. Mgahinga National Park, part of the Virunga massif spanning across Rwanda and the Democratic Republic of Congo, is home to the other population.
In 2018, the International Union for Conservation of Nature (IUCN) moved the mountain gorilla from 'critically endangered' to 'endangered' on its Red List of Threatened Species. However, the GVTC have called this incident a "big loss for the species". Andrew Seguya, executive secretary of the GVTC, told the BBC: "The potential of the three females for their contribution to the population was immense."
The preliminary cause of death was determined by post-mortem examination, field assessment observation and history. A Mgahinga Gorilla National Park tracker was reported by Gorilla Doctors to have heard the cries of surviving group members along with the sound of silverback gorillas beating their chest immediately after the lightning strike in the storm. It is likely that the electrical energy passed through the ground where it was struck directly by lightning and was absorbed by the four apes standing nearby.
The report by Gorilla Doctors also states: "This case, while extreme, also highlights the fragility of the endangered mountain gorilla population." Although the loss of the four mountain gorillas through fatal electrocution was a highly unlikely event, the Democratic Republic of Congo, which the National Park encompasses, is a common location for lightning to strike. Five out of the world's ten lightning hotspots are within the Democratic Republic of Congo, according to a study in the Bulletin of the American Meteorological Society.
The long-term survival of the species is endangered by other more immediate threats. According to the International Gorilla Conservation Programme, mountain gorilla populations are most at threat by the loss of habitat, namely deforestation. The other two major reasons are poaching and close-contact exposure to viruses and illnesses which are innocuous to humans.