The Itombwe Golden Frog’s Uncertain Future
Towering like a surreal wall of rock into the clouds from the western shores of Central Africa’s Lake Tanganyika, the mountains of the Itombwe Plateau are impressive, beautiful, and unique. Itombwe rises steeply from the lake at about 780 meters to 3,475 meters at its highest point. It contains a diverse trove of habitats from dry grasslands in the east, to marshy bogs, montane forest and elfin woodlands on the plateau, to a gentle decline in the west that tumbles down to the lowland rainforests of the Congo Basin (Greenbaum and Kusamba, 2012). Just after World War II when Itombwe was part of the Belgian Congo, a herpetologist named Raymond Laurent was able to drive into the heart of the plateau via colonial-era mining roads, and he discovered several species of frogs that occurred in the highlands, some of which were never found anywhere else. One of these frogs was the Itombwe Golden Frog (Chrysobatrachus cupreonitens), a hyperoliid treefrog that was described by Laurent in 1951 based on several unique morphological characters and behavior (Laurent, 1951). With a stunning metallic green and brown color pattern, Chrysobatrachus were found in meadows in Itombwe’s highest elevations. Males were so much smaller than females that they were obliged to engage in inguinal amplexus during mating, where the male wraps his arms around the female’s waist, instead of the more typical axillary amplexus where the male clasps the armpits of the female (Laurent, 1964).
Because of Central Africa’s chaotic and violent post-colonial history, including Africa’s World War in the aftermath of the Rwandan genocide in the late 1990s, few biologists have been able to work in Itombwe’s dangerous and remote highlands in recent years. The roads Laurent used to drive into Itombwe were destroyed from neglect long ago, making exploration of the plateau even more difficult. When I began working in modern-day Democratic Republic of the Congo a decade ago, Chrysobatrachus had not been seen since its original discovery, and I had to consider that it might be extinct (Greenbaum, in press). In 2011, my Congolese colleagues Chifundera Kusamba, Mwenebatu M. Aristote, Wandege M. Muninga and I hiked deep into Itombwe, for the third time, in search of Chrysobatrachus and other “lost” species of frogs that hadn’t been seen in decades. Although we made many interesting discoveries, including some new species, Laurent’s unique genus eluded us. Everywhere we witnessed widespread environmental damage to potential Chrysobatrachus habitat from cattle grazing, mining, and fires to clear land for crops. We had only one day left to spend on the plateau when we reached the remote village of Komesha (2,850 m elevation), where the local Banyamulenge militia openly considered kidnapping me to hold me for ransom, but they changed their minds after I bankrolled a party in their honor with plenty of beer.
Hearing buzz-like frog calls in the chilly air, we descended a small hill near the village to discover a flooded meadow full of several species of frogs, including the long-lost Chrysobatrachus! I almost couldn’t believe my eyes as Chifundera brought me a mating pair still embraced in their distinctive inguinal amplexus, and I spent hours photographing the beautiful animals from every angle. When I returned to my evolutionary genetics laboratory in the USA with specimens of these rediscovered frogs, I was able to match their DNA to a strange frog I had collected at Lake Lungwe in another part of Itombwe in 2009. I hadn’t recognized the latter frog as Chrysobatrachus at the time because it had a stark color pattern of yellow with large black blotches that had not been documented by Laurent. The good news continued in 2016 when Aristote found many more Chrysobatrachus near the elfin woodland at Mt. Mohi, Itombwe’s highest point.
It is certainly heartening to know that Chrysobatrachus is alive, well and reproducing, but many worrying concerns about its long-term sustainability remain. The International Union for the Conservation of Nature (IUCN) Red List of threatened species currently lists Chrysobatrachus as endangered, because of the small number of localities where we recorded it recently, the aforementioned threats to its habitat, and a strongly suspected decline in its overall population size. Although the Itombwe Natural Reserve was established in 2006, its borders were not finalized until input from local stakeholders was combined with conservation analyses in June 2016. The nearby Kabobo Plateau, which has many habitats and species in common with Itombwe (Chrysobatrachus has not been recorded at Kabobo but might be present), was officially protected as a reserve in December 2016 (A. Plumptre, in litt.). But like other protected areas in DRC, meager resources to equip Itombwe’s rangers, who are surely struggling to enforce the new laws, are woefully inadequate. Numerous studies have shown that the most important factor to avert biodiversity loss in protected areas is effective law enforcement.
But these daunting threats pale in comparison to the impending doom from climate change that will surely devastate Itombwe’s highland flora and fauna in the coming years. As explained in my forthcoming book Emerald Labyrinth: A Scientist’s Adventures in the Jungles of Congo, Itombwe’s fragile frogs will likely be the first animals to disappear as the region’s climate warms and precipitation patterns shift, because they will have nowhere to go to find optimal conditions (Greenbaum, in press). Given the amphibians’ biphasic life history, where tadpoles spend the first part of their lives as the ecological equivalent of fish before transforming their bodies (via metamorphosis) into a terrestrial life on land, frogs are especially sensitive to changes in their environment. To make matters even worse, the Chrysobatrachus from Lake Lungwe and Komesha tested positive for the amphibian chytrid fungus, which has caused population declines and even extinctions in other parts of the world (Greenbaum et al., 2015).
Unfortunately, we are likely to face a stark choice regarding Chrysobatrachus in the near future. Shall we allow the unstoppable juggernaut of climate change to push the species to extinction, or will we take action, while there is still time, to protect their remaining natural habitat and establish a captive-breeding program? Such actions saved another beautiful African frog, the Kihansi Spray Toad (Nectophrynoides asperginis) from annihilation in Tanzania, and recent reintroduction efforts are promising (Greenbaum, in press). If we want future generations to enjoy the beauty of the Itombwe Golden Frog, as I have been privileged to do, we must make every effort to rectify the environmental damage that humanity has thrust upon this defenseless and beautiful creature.
Greenbaum, E. In press. Emerald Labyrinth: A Scientist’s Adventures in the Jungles of Congo. University Press of New England.
Greenbaum, E., and C. Kusamba. 2012. Conservation implications following the rediscovery of four frog species from the Itombwe Natural Reserve, eastern Democratic Republic of the Congo. Herpetological Review 43:253–259.
Greenbaum, E., J. Meece, K. Reed, and C. Kusamba. 2015. Extensive occurrence of the amphibian chytrid fungus in the Albertine Rift, a Central African amphibian hotspot. The Herpetological Journal 25:91–100.
Laurent, R. F. 1951. Deux reptiles et onze batraciens nouveaux d’Afrique centrale. Revue de Zoologie et de Botanique Africaines 44:360–381.
Laurent, R. F. 1964. Adaptive modifications in frogs of an isolated highland fauna in Central Africa. Evolution 18:458–467.
Eli Greenbaum is associate professor and director of UTEP biodiversity collections, University of Texas at El Paso.