It took four years, nine people and countless man-hours, but a team of scientists has finally rediscovered the "giant" Krokosua squeaker frog (Arthroleptis krokosua), a critically endangered species that has not been seen in its native Ghana since 2009. Unfortunately the Sui River Forest Reserve, where a single adult frog was found earlier this month, is itself under threat from logging, illegal mineral mining, agriculture and a particularly nasty invasive plant.
The Krokosua squeaker frog has only been spotted a few times to date. A single adult turned up in 2002. That frog—the only adult seen until this month—was more than 43 millimeters long, much longer than all other Arthroleptis species, making it a "giant" in the genus. Researchers observed 14 much smaller juvenile frogs during an eight-month search in 2009. That expedition was led by Gilbert Adum, then an employee of Ghana's Department of Wildlife and Range Management, who also led the current rediscovery team as executive director of Save the Frogs! Ghana.
With only 16 individuals observed to date, not much is known about this rare species or its behavior. "It is certainly terrestrial, a leaf-litter frog, as are all Arthroleptis frogs," Adum says. "We have not found any breeding habitat yet nor do we know how the frog breeds. But based on the behavior of other Arthroleptis frogs it may be a direct developer, meaning they lay eggs on the leaf-litter and the eggs hatch directly into froglets without passing through the tadpole stage."
That leaf-litter has become more risky for the frogs, however, due to the invasion of a North American plant known as devil weed, or Acheampong weed (Chromolaena odorata). First imported into Ghana during the 1970s as a plant that could supposedly be easily cleared from around power lines, devil weed has since spread throughout the country, choking out native plants, feeding devastating wildfires and causing widespread famine. "The devil weed lives up to its name," Adum says. "Within the frogs' habitat ranges, the weed forms dense thickets that impede the frogs' movement. It also releases chemicals into the soil that prevent the growth of native plants. Additionally, C. odorata depletes the density of leaf-litter that the squeaker frogs utilize for predator escape, breeding activities and protection from desiccation. We suspect its invasion to be one of the causes of the frog's endangerment."
The frogs Adum and his fellow researchers found in 2009 lived at an elevation of about 100 meters. The new frog turned up at the peak of the hill, which has an elevation of 610 meters. Color patterns and other measurements indicate that the adult is probably not one of the juveniles observed in 2009. In fact, Adum says all efforts to locate those frogs again at the original site have been fruitless. "I cannot really say for sure if those frogs still survive," he told me. "I suspect that, apart from the habitat degradation, not many frogs of its kind survive to adulthood, possibly due to natural predators. It may lack certain defensive mechanisms that other large-bodied frogs have." He also says his team found more than 50 deep man-made holes in the area where it spotted the frog, an indication that illegal miners are digging for exploitable minerals there.
Save the Frogs! Ghana has spent some time in the region removing the devil weed and replanting native trees, although Adum says the organization's limited funding prevents them from doing much more. The lack of funds has also exhausted their ability to keep searching for additional frogs. "But we will look for funds to search more at the existing sites and other suitable areas," he says. "We are also planning on establishing a long-term monitoring strategy where we are able to monitor the frogs' status regularly." They also hope to do more advocacy and lobbying to permanently protect the habitat from further logging, agriculture and mining.
Although captive breeding has worked for some other rare amphibians, Kerry Kriger, founder of the U.S.-based parent organization Save the Frogs!, says it would be too risky to the wild population to remove even a single frog from their native habitats. Adum adds, "we would prefer to deal with the insitu threats for now. I think all that matters now is to eliminate the prevailing threats and, more importantly, secure the frogs' habitats permanently from any exploitation."
Photo by and courtesy of Gilbert Adum