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 north‐eastern 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.

中文翻译：

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尼日利亚常见的河马：新的人口普查数据和文献回顾证实了保护区以外地区的保护重要性

1. 曾经遍布整个非洲的普通河马由于栖息地退化和丧失，狩猎和人类与野生生物的消极互动而受到威胁。西非人口特别少，人口零散，因此风险最大。
2. IUCN估计，在非洲人口最多的国家尼日利亚，仅剩100个河马。它们发生在国家公园和野生动物保护区等保护区，以及河口栖息地，内陆河流，湖泊和水库中的保护区之外。但是，在大多数地方，河马的状况鲜为人知。需要可靠的数据来更好地确定该物种在尼日利亚的地位。
3. 在尼日利亚东北部贝努河的主要支流贡戈拉河沿岸的大型水库-基里大坝水库中，在2018年12月和2019年5月的五天内，使用机动船进行了人口普查。 。将这些发现与尼日利亚和喀麦隆北部贝努河流域的多个地点的河马丰度数据进行了比较。
4. 至少记录了56个河马（51个成年牛和5个小牛），主要在水库的过渡带。根据现有数据，基里水库中的河马目前代表了尼日利亚记录的最大人口，超过了官方保护区的单个人口。
5. 尼日利亚对河马的研究和保护工作应着重于评估其状况，并在关键地点改善保护，并增强人群之间的联系。应特别注意贝努河流域内的人口，这对于非洲中西部的河马保护至关重要。