By Willem Briers-Louw, 27th January 2025
War has devastating impacts not only on people and human infrastructure, but also on the natural world. Since the 1950s, warfare has plagued over 80% of global biodiversity hotspots, often resulting in steep declines of wildlife populations, and even in local extirpations of species. Mammals are particularly vulnerable to the effects of human conflict, as they are often targeted by hunters for food or profit, and habitat fragmentation caused by armed conflicts affects wide-ranging species. Whether mammals persist in post-war landscapes is largely dependent on their resilience and the extent and intensity of the conflict. But even if species persist, population recovery can be slow as mammals face obstacles such as long-term effects from habitat loss and altered ecosystems.
A spotted hyaena Crocuta Crocuta. Photo: Tiero/Adobe Stock.
Our recent study aimed to investigate the baseline population density of spotted hyaenas in central Mozambique after many years of war, and provide novel insights into the post-war status of this seemingly resilient species. Although we identified significant threats facing this population, there is potential for recovery if management interventions are implemented effectively.
Mozambique suffered from decades of armed and political conflict during 1964–1975 and 1977–1992, with the country’s central region particularly hard-hit. This led to the depletion of wildlife populations in most protected areas, including the well-known Gorongosa National Park and the lesser-known but ecologically significant Zambezi Delta. In the Delta, which is designated as a Ramsar Wetland Site of International Importance, law enforcement was essentially absent during the war. Local people were displaced into the protected landscape and, faced with low employment levels and food insecurity, many were driven to hunting in these areas, leading to unregulated resource extraction and a significant rise in bushmeat poaching. By the end of the war in 1992, the populations of many large mammals had declined by around 95%, most notably the African buffalo, which decreased from 45,000 to only 2,000 individuals, and the waterbuck, which fell from 45,000 to fewer than 1,000 individuals.
Aerial photograph of the Zambezi Delta, a Ramsar Wetland Site of International Importance. Photo: Zambeze Delta Conservation.
However, the end of the war also provided a huge opportunity for nature recovery and marked the start of a remarkable restoration journey. When the war ended in 1992, safari operators and tourism began returning to the Delta. The income generated from these visitors was vital to support the funding of locally-employed anti-poaching units that patrol the landscape with the aim of reducing bushmeat poaching. As a result of these protection efforts and fuelled by the naturally high productivity of the Delta ecosystem, wildlife populations began to bounce back. Today, after more than 30 years of conservation, the Delta boasts a level of ecological restoration that few other places have experienced, with many ungulate populations rebounding to almost pre-war numbers: the African buffalo and waterbuck have now reached c. 70% and 90% of their pre-war population sizes, respectively.
The long-term data that allowed scientists to monitor the dramatic decline and impressive recovery of ungulates, however, were the result of aerial-based surveys that targeted these animals specifically, and no equivalent baseline data are available for the region’s resident large carnivores. Alternative approaches were therefore needed to study these lesser known but equally important components of the Delta ecosystem.
Camera-trap images of spotted hyaenas Crocuta crocuta in our study area. Photo: Zambeze Delta Conservation.
Spotted hyaenas Crocuta crocuta are large carnivores of ecological and socio-economic significance. The species is categorized as Least Concern on the IUCN Red List and is often considered to be abundant, adaptive and resilient, meaning it receives little research attention. Despite purported declines across the continent, there is little baseline data on the hyaena’s population size and status throughout its geographical range.
To address this knowledge gap, in 2021 we conducted a comprehensive camera-trap study using 76 paired camera-trap stations in the central region of the Zambezi Delta. We conducted our fieldwork during the dry season (May-October) because high rainfall during the wet season poses major challenges for vehicle access. As their name suggests, spotted hyaenas are characterized by a conspicuous coat pattern, and like the stripes of tigers or the spots of leopards, these patterns vary between individual animals. Thanks to their unique spot patterns and the pairwise arrangement of the camera traps that enabled us to capture both sides of a passing hyaena simultaneously, we identified 23 individuals from the images captured. Being able to distinguish between individual hyaenas helped us to estimate the species’ population density in the Delta. To our disappointment, this density was unexpectedly low, ranking in the bottom 10% of range-wide population density estimates published to date.
Setting up camera traps. At each of the 76 camera trap stations, we deployed two opposing camera traps to obtain bilateral images of spotted hyaenas. Photos: Zambeze Delta Conservation
To find out why the density of spotted hyaenas in our study area was so low, we examined a few possible causes. Firstly, we looked at prey abundance as a potentially limiting factor, but found prey numbers were actually sufficient to support almost 10 times the current number of hyaenas in the landscape. Next, we explored the impact of trophy hunting on the population. Records of offtake provided by the hunting operators revealed that although trophy hunting does contribute to spotted hyaena mortality, hunting levels were relatively low and income from well-regulated trophy hunting in fact helped to fund anti-poaching efforts in the area. Finally, we evaluated the impact of bushmeat poaching, an unregulated and serious threat to wildlife in the region. Two of the 23 hyaenas captured by our camera traps were visibly affected by poaching snares, and many others may have become trapped in the wires and been unable to escape. Using published lethality rates from snaring, we estimated that these illegal traps could be responsible for fatalities of 4–25% of the hyaena population. Without immediate intervention, both locally (through improved law enforcement) and nationally (through government action plans and more stringent punishments for poaching), this threat is likely to persist and threaten the viability of hyaenas and other large carnivores throughout Mozambique.
Contrasting habitat types in the Delta including dense sand forest (left) and open floodplain (right). Photos: Zambeze Delta Conservation.
Our study clearly highlights that spotted hyaenas are less resilient to severe anthropogenic disturbances than previously believed. The species’ extirpation from Gorongosa National Park and its low density within the Zambezi Delta provide irrefutable evidence of its vulnerability, and warrant improved monitoring and protection efforts. To promote the recovery of the spotted hyaena population in the Delta, we strongly recommend a set of actions based on three complementary approaches, which we have discussed with safari operators and local authorities. Firstly, anti-poaching efforts in the area should be increased to further reduce impacts of bushmeat poaching. Greater pressure from anti-poaching units may make it increasingly difficult for poachers and cause them to move away from poaching. Other efforts carried out by the safari operators, such as community-based projects providing employment, sustainable fishing, meat distribution, bee-keeping, primary schools etc. should be continued, so as to provide tangible benefits to the local people surrounding the landscape and demonstrate the value of wildlife. Secondly, augmenting the population with wild individuals would help promote population resilience and ensure the genetic diversity required for its long-term viability. Based on this, plans are now in place to translocate two hyaena clans from southern Mozambique to the Zambezi Delta this year. And thirdly, hunting offtake quotas should be reduced to minimize pressure on the species. Long-term monitoring will be crucial to evaluate the effectiveness of these proposed intervention strategies and ensure the population grows and re-establishes a stronghold within central Mozambique.
Bushmeat snaring is a major threat to the spotted hyaena population in the Zambezi Delta (left), but there is potential for population recovery. Effective anti-poaching efforts (middle and right) are vital to reduce the impact of this hazard. Photos: Zambeze Delta Conservation.
The article ‘Estimated baseline density of a spotted hyaena population in a post-war landscape’ is available open access in Oryx—The International Journal of Conservation.
