Common hippopotamus in Nigeria: New census data and literature review confirm the conservation importance of sites outside protected areas

Abstract

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.

Hippos alter their aggregations to mitigate density‐dependent drought effects

“…For example, Stears et al (2021) observed hippo aggregation in a few remaining pools in response to drought in Tanzania. In such contexts, dammed and impounded water may provide important refugia for hippos when pooled water becomes limited (Baker et al, 2020; Utete et al, 2017). However, increased aggregation during drought can have dramatic consequences for water quality and aquatic ecology within pools and downstream (Dutton et al, 2018; Subalusky et al, 2018).…”

Are hippos Africa's most influential megaherbivore? A review of ecosystem engineering by the semi‐aquatic common hippopotamus

“…Conversely, human exploitation of hippos and their habitat is responsible for their population decline in many areas (Lewison, 2007; Zisadza et al ., 2010; Kanga et al ., 2012; Scholte & Iyah, 2016; Utete, 2020). Hippos often venture outside protected areas because their aquatic habitats render fences less restrictive to their movements, making hippos more prone to encounters with people than many other large mammals (Mackie, Dunham & Ghiurghi, 2013; Post, 2017; Baker et al ., 2020). Furthermore, hippos venturing into human‐inhabited landscapes, often referred to as ‘problem animals’, are routinely shot and killed (Mkanda, 1994; Chomba et al ., 2012; Utete, 2020) without much consideration for their vulnerable conservation status (Lewison & Pluháček, 2017).…”

Economic Consequence of Human - Hippopotamus (Hippopotamus amphibious) Conflicts on Farming Livelihood in Rural Adamawa State, Nigeria

“…Human-Hippo conflict denotes any instance in which the resource demands of humans and Hippos overlap, spurring competition for food, space, and water and thus creating tension between people and Hippos (Messmer, 2000;Seoraj-Pillai & Pillay, 2017). Hippopotamus (Hippopotamus amphibious) are among Africa's most destructive crop raiders (Lamarque et al, 2009;Baker et al, 2020). In Adamawa state, while the exact population of Hippopotamus in the riverine communities is not exactly known, (Baker et al2020) it is estimated to be about 45 animals around Kiri dam reservoir.…”

“…During this time, hippos may travel long distances in search of new water sources or better grazing areas. As they move, they may come into contact with human settlements, which can lead to human-wildlife conflicts and potential attacks (Baker et al, 2020). HWC (human-wildlife conflict) is fast becoming a critical threat to the survival of many globally endangered species (Distefano, 2005;Cromsigt et al, 2013;Manral et al, 2016).…”