1. Once abundant across Africa, the common hippopotamus is threatened owing to habitat degradation and loss, hunting, and negative human-wildlife interactions. West African populations are notably small and fragmented and therefore at greatest risk. 2. In Nigeria, Africa's most populous nation, the IUCN estimates that only 100 hippos remain. They occur in protected areas, such as national parks and game reserves, and outside protected areas in estuarine habitats, inland rivers, lakes, and reservoirs. However, the status of hippos in most sites is poorly known. Reliable data are needed to better ascertain the status of this species in Nigeria. 3. Over five days in December 2018 and May 2019, motorized boats were used to conduct a census of the hippo population in Kiri Dam reservoir, a large-dam reservoir along the Gongola River, a major tributary of the Benue River, in northeastern Nigeria. These findings were compared with data on hippo abundance from several sites across Nigeria and the Benue River basin in North Cameroon. 4. A minimum of 56 hippos (51 adults and 5 calves) were recorded, predominantly in the transitional zone of the reservoir. Based on available data, hippos in Kiri reservoir currently represent the largest recorded population in Nigeria, exceeding individual populations in official protected areas. 5. Research and conservation efforts for hippos in Nigeria should focus on assessing their status and improving protection in key sites and increasing connectivity among populations. Special attention should be paid to populations within the Benue River basin, which is emerging as critical for hippopotamus conservation in west-central Africa.

In a world increasingly affected by human presence and activities, achieving human–wildlife coexistence has become the goal of many wildlife conservation programs. Coexistence requires an understanding of factors that contribute to human tolerance and acceptance of problematic wildlife. In four communities in Nigeria, we used structured and semi-structured interviews to explore local people’s acceptance of the river hippopotamus (Hippopotamus amphibius) at a large reservoir with high human impact and where other conspicuous, damage-causing species are absent. We collected data two years apart to evaluate whether acceptance changed over time. Acceptance was low among respondents (21%). Logistic-regression results showed that attitudes, beliefs related to benefits and risks, behaviors toward hippos, study period, and income source significantly influenced acceptance of hippos. Results from Woolf tests showed that hippo-caused human fatalities most notably modified the observed decline in acceptance between study years. The potential significant impact of rare, yet severe events (in this case, human fatalities) on acceptance of wildlife and thus human–wildlife coexistence was supported in this study, one of few focused on hippo-human relations. For conservation and development interventions to be effective at this site, they should, at a minimum, improve human safety around hippos, emphasize current and potential benefits of hippos, create avenues for off-farm income, and reduce crop losses owing to hippos.