How did the wild dogs of Tanzania disappear? Study offers new explanation

The African wild dog is one of the world’s most endangered mammals. About 6 600 are estimated to be left in the wild, according to the World Wildlife Fund. The largest populations remain in southern Africa and the southern part of East Africa. When this predator population that formerly inhabited the grassland plains in Tanzania’s Serengeti National Park declined and eventually disappeared in 1991, scientists examined the reason behind the pack loss.

One controversial study known as the Burrows hypothesis suggested that viral disease induced by stress caused by radio-collaring immobilisation and handling led to this pack’s demise. The research community has been divided over the explanation since then but a group of scientists have recently offered a new perspective. Partially supported by the EU-funded AfricanBioServices project the team published its findings in the journal ‘Ecology and Evolution’.

“Following their disappearance from the Serengeti plains, the wild dog population survived in LGCA [Loliondo Game Controlled Area] and NCA [Ngorongoro Conservation Area]. Locals in LGCA and NCA saw wild dogs regularly for several decades, both before and after their disappearance from the Serengeti plains,” the scientists said. “Using a multifaceted approach and data from the same wild dog population, where disease is still prevalent, we found no support for Burrows’ hypothesis.”

Quoted in a news article on ‘Gemini’ web magazine first author Dr Craig Jackson said: “Although much of the scientific literature referred to the disappearance of the wild dogs from Serengeti National Park as a population ‘extinction’ the population never went extinct within the broader region.” He added that “the wild dog population actually survived in the eastern part of the greater Serengeti Mara Ecosystem.”

Competition and survival

Although the wild dog (Lycaon pictus) is a predator, it can also be vulnerable to competition from lions and hyenas. The same news item noted that the wild dogs could either be killed or bullied by these rivals that might steal food or prey from them, a phenomenon known as kleptoparasitism. “The high risk posed by lions results in wild dogs avoiding them at all times,” the journal article stated. “During the period of the Serengeti wild dog population decline, the spotted hyaena population increased by 150% (from 2,200 to 5,500) and similarly large increases were recorded in the lion population,” it added. This occurred “with concomitant decreases in wild dog pup survival and adult longevity.” The researchers concluded: “We postulate that the disappearance from the Serengeti plains was instead merely a range contraction driven by increasing competitor densities with an outbreak of disease dealing the final blow to the remaining individuals and had little to do with researcher-induced mortality.”

Running until end-August 2019 the AfricanBioServices (Linking biodiversity ecosystem functions and services in the Great Serengeti-Mara Ecosystem (GSME) - drivers of change causalities and sustainable management strategies) project was launched to examine the impact of population growth land-use change and climate change on biodiversity and human well-being. “The ultimate goal of AfricanBioServices is to bring together all existing and new data in a centralized database which is user friendly and can be accessed by the scientific community conservationists and general public in the future” as stated on CORDIS.

For more information, please see:
AfricanBioServices project website