Blog Details

This information details the findings from a targeted population census and a drone-based disturbance test on the Common Hippopotamus (Hippopotamus amphibius) population residing in the Dadin Kowa Dam Reservoir, located on the Gongola River in Gombe State, Nigeria. The reservoir represents an important habitat for the species in the region, which faces significant conservation challenges outside of protected areas. The objective of the survey was to establish a current baseline population estimate and to assess the sensitivity of the local hippo population to novel survey technologies, specifically Unmanned Aerial Vehicles (UAVs/drones).

Methodology

The census was carried out in October 2021, employing innovative technologies, including the use of drones, to improve accuracy over traditional land-based counts.

The reservoir represents an important habitat for the species in the region, which faces significant conservation challenges outside of protected areas.

Population Census

• Technique: The census utilized drone surveys to count individuals, estimate hippo abundance, and record distribution across the reservoir area.
• Conditions: The survey was conducted during a period of notably high water levels following the rainy season.

Disturbance Test

• Technique: As part of the drone survey protocol, specific tests were conducted to monitor the behavioral response of the hippos to the presence and noise of the drone operating at various altitudes. This test was crucial for ensuring that the census itself did not bias the count results by causing submerged or concealed individuals.

Result

Population Census Estimate

The preliminary results from the October 2022 survey indicated a confirmed minimum population count for the Dadin Kowa Dam Reservoir:

Estimated Population: 107–112 individuals.

The high water levels present during the survey significantly complicated the effort, as hippos were often widely dispersed across the large body of water and adjacent flooded farmlands. Verifiers suggested that this figure likely represents a minimum count and that the actual population is potentially higher. A subsequent dry-season survey was planned to leverage reduced water levels for a more comprehensive count.

Disturbance Test Findings

The disturbance tests yielded significant findings regarding the localized behavior of the Dadin Kowa hippos
: • High Sensitivity: Unlike other hippo populations surveyed in similar Nigerian reservoirs (e.g., Kiri Dam), the Dadin Kowa hippos appeared to react notably to the presence of the drone at relatively high altitudes.
• Behavioral Implications: This heightened sensitivity suggests a population less habituated to artificial noise and human activity in the water environment.

Context and Threats

The Dadin Kowa hippo population is subject to extreme pressures from human activities, creating a high-conflict environment.
• Human-Hippo Conflict: The area surrounding the reservoir is extensively farmed, particularly with crops like guinea corn, maize, and rice. Due to a lack of sufficient natural grass forage, hippos frequently leave the water to forage in farmlands, leading to severe crop destruction and financial losses for local farmers.
• Negative Attitudes: This damage has resulted in extreme negative attitudes towards the animals, exacerbating the precarious relationship between the local communities and the hippo population.
• Conservation Note: Despite the challenges, the observation of a female hippo with twins (a rare occurrence) was recorded in 2022, highlighting the potential reproductive success and conservation value of this site.

Conclusion and Recommendations

The Dadin Kowa Reservoir supports a significant population of Common Hippopotamus in Nigeria, with an estimated minimum of 107–112 individuals in 2022. The disturbance test confirmed that the behavioral responses of hippo populations to technology are site-specific. The observed sensitivity of the Dadin Kowa hippos to drone noise necessitates caution and adaptive methodology for future monitoring efforts at this location.
Key Recommendations:
1. Site-Specific Protocol: Future surveys utilizing drones at Dadin Kowa must employ conservative flight protocols (higher altitudes and quieter models) to minimize disturbance and ensure accurate counts.
2. Conflict Mitigation: Conservation efforts must prioritize strategies to mitigate human-hippo conflict, focusing on alternative livelihood support for affected farmers, and exploring methods for enhancing natural hippo forage sources around the reservoir perimeter.
3. Long-Term Monitoring: The planned dry-season survey should be executed to provide a more precise population count and establish a robust baseline for long-term population trend monitoring.