Status of Hippopotamus, Hippopotamus Amphibius L., in the River Sanaga of the Centre Region of Cameroon

Abstract

Wildlife protection and management structures around the world have used protective enclaves often referred to as protected areas to limit pressure on biodiversity. No attention has been paid to species living in unprotected areas often known as free areas. The aim of this study is to contribute to the sustainable management of hippopotamus population in the river Sanaga that is facing threats of being extinct and to also provide information on their status to decision makers. The survey method used during this study was a total count that was carried out using several techniques including foot walk and waterway counts. The results revealed that four hippos were cited in two out of the seven villages in the area. A distance of 32 km was covered in the river. The site with the highest number of hippopotamus was in the village of Tsang with three hippos seen. The main threats to the survival of hippos are poaching, fishing, sand mining and crop farming along the river bank. To lessen these threats on the hippopotamus population, sensitization and awareness campaigns are needed. It is recommended that a hippo sanctuary and a hippo friendly club be created in the study area.

1. Introduction

Deforestation has increased in recent decades with population growth and agricultural expansion [1, 2]. Habitat destruction and fragmentation constitute a major cause of wildlife extinction with 40% been mammals [3]. Among the potential resources of these natural environments, wildlife has a prominent place [4, 5]. In some regions of Africa and the world, certain socio-cultural groups contribute to the conservation of wildlife species through their religious beliefs [6, 7, 8].

Thus, efforts to conserve wildlife have been motivated by concern over the rarefaction or near-extinction of certain large animals, including the hippopotamus [9]. The main threats to this species are poaching for the meat and ivory/tooth trade and habitat loss. A field survey showed that in the Democratic Republic of Congo, Hippopotamus populations declined by more than 95% during the 8 years of conflict [10, 11, 12].

In Cameroon, as in many other African countries, structures in charge of wildlife protection and management have often used protective enclaves to conserve wildlife. No attention has been paid to species living in free areas [13] and Cameroon is one of these countries where the population trend of Hippopotamus is still unknown. Given the existence of a great spatio-temporal variability leading to the decline of large mammals likely to see their conservation status deteriorate in the near future [14], it seems more than necessary given that the various threats to population of hippopotamus in the Sanaga River is very high and the figures on the state of their population in Africa and in Cameroon in particular is more than alarming [14], it is necessary to carry out this study that has provided information on the status of the hippopotamus population in the Sanaga River and the challenges of their conservation in unprotected areas. These animals also help in plant and nutrient distribution in the ecosystem through excretion and breaking seed dormancy for some tree species [15, 16].

Hippopotamus are amphibians with two species that are known to exist. An adult can weigh slightly above 3 ton depending on the sex [17]. Hippos are social animals and live groups of up 20 animals. It can live up to 40 years in normal conditions. It can give birth once every 2 years with a coup that can weigh up to 50 kg at birth [18]. Hippos graze late in the evenings and early mornings and pass the hold day resting inside shallow waters (Figure 1).

Figure 1.

Three hippos that were cited at Tsang village.

2. Methodology

The study was carried out in the Ebebda sub-division 80 km from Yaounde. This sub-division is located in the Lekié Division of the Centre region. It is bounded to the North, South, East and West by Bokito, Sa'a and Monatélé sub-divisions respectively [19]. Figure 2 shows the map of the study area.

Figure 2.

Map of the study area.

A Guinean equatorial climate prevails in the area with an average annual temperature of 25 ± 2.5°C. The average annual rainfall is 1577 mm [19]. The soils in this area are hydromorphic and ferralitic, characterised by a sandy clay texture. Under forest cover, these soils are sometimes sandy clay, porous, highly permeable, humus-rich and very fertile for crop production. These soils are especially suitable for perennial food crops. Ebebda is watered by the Sanaga River, a fish-filled river (918 km long) with a permanent flow and other small seasonal rivers empting into it such as the river Ngmeh, river Mbe, river Tèt, river Polo, etc. with many streams alike [19]. The area of this basin is estimated to be over 14,000 km², with an average flow rate of 2072 m³/s. It is not really navigable due to many rocks in it.

The vegetation cover is a derived savanna with trees species that are marketable, non-timber forest products (NTFPs) and wildlife species. The flora is very diverse and consists of numerous grasses. The marshy grasslands are mainly colonised by Marantaceae and Zingiberaceae. Wildlife resources in this area are mostly seen in the gallery forests and in the savanna woodlands [19]. The sub-division has 33 villages with an urban centre. The population is estimated at 50,000 inhabitants, including the Eton, Manguissa, Mbamois, Hausa, Bamileke and Fulbe, respectively. The main economic activities of these populations are hunting, fishing, livestock production, trade and sand exploitation.

2.1 Data collection

Based on the following criteria: the presence of hippos in the locality; the accessibility of the villages in relation to the means of travel (canoes); the presence of a sizeable population of hippos, time and financial availability; seven villages were selected for data collection. These were Ebebda I; Ebebda II; Tsang; Mbenega; Ebomzout; Bikogo; Nkolelouga. Data collection was carried out between April and June 2021.

2.1.1 Characterisation of the hippo population

2.1.1.1 Direct observation

This consisted of identifying and assessing the hippos in the different sites along the river banks or Islands. Observations were made early hours of the morning at 5 am to late evenings at 6 pm over a period of 1 week per village along the river site. Canoes were used as a means of transport along the river. At anticipated point along the river with help of a local guide observations were made. The age structure, size of the species and the activities carried out were also recorded.

2.1.1.2 Indirect observation

Hippos can live in the water and on the banks [20, 21]. Indirect observations was based on the walking method, which consisted of following the bank and counting individuals along the river bank [20, 21, 22], and the waterway method, which consisted of sailing along the river in a canoe and counting individuals [22, 23], in the five villages visited. The area was divided into two sectors: the Northern sector, which extended from the village of Benga to the village of Mele-megan, which borders Bigoko, where three out of the five islands were visited. The Southern sector which had 11 islands out of which 5 where visited. For the villages Ebeda II and Ebomzoute, they were explored on the shore because they did not have islands. Observations were not made in Ebeda 1 and Nkolelouga because they are urban centres with much human activities. The coordinates of the signs of presence of hippos such as footprints, droppings and tracks were taken into account and marked into a data collection sheet with an accompanying geographical positioning system (GPS) coordinates.

2.2 Socio-economic surveys (baseline survey)

A semi-structured questionnaire was use to interview household heads in the study area. A total of 150 household heads were interviewed in the 5 village of the study area. The criteria for selecting respondents were longevity in the study area, activity (primary occupation), and relationship or links with the hippos. The questionnaire focused on socio-economic characteristic of respondents, knowledge of the hippos, and perception and attitudes towards the species.

2.3 Strategy for managing threats to hippopotamus

The strategy was developed by identifying the actors involved in the conservation of wildlife, categorising them into roles and level of intervention, as well as possible actions taken to protect hippopotamus from human actions.

2.4 Data analysis

The socio-economic data was analysis using SPSS version 16. The cartographic data were entered into QGIS data sheet 2.14.21 and ArcGIS 10.0 for map production.

2.4.1 Determination of hippo populations

2.4.1.1 Relative abundance of hippos

Relative abundance was got by calculating the kilometric index abundance (KAI), also known as the kilometre count index (KCI), which is the ratio between the total number of observations of each sign of activity recorded (N) along the sites, and the total distance travelled (L) in km.

$$\mathrm{KIA}=\mathrm{Ni}/\mathrm{Lj}$$E1

Where: KIA = kilometric abundance index for species I; Ni = number of individuals/index of the species along the sites; Lj = length of sites j (in km);

Source: [24, 25]

2.4.1.2 Density

It was calculated using the formula:

$$D=\left(\text{number of individuals}\right)/\left(\text{living space area}\right)$$

The surface area of the hippo’s living space is given by:

$$S=L\ast D$$E2

Where: S = home range area; L = total width in km of the hippo home range estimated at 3 km (i.e. 1.5 km on average on each side of the river); D = the length of the watercourse.

For the specific case of this study, D = 32 km.

Source: [26, 27, 28]

2.4.1.3 Propose a management strategy for these threats to hippos in the Sanaga River

In order to develop an effective strategy for the management of hippos in the Sanaga River, a SWOT (Strengths, Weaknesses, Opportunities and Threats) analysis was carried out based on the field results.

3. Results

3.1 Status of Hippopotamus in river Sanaga

The results in Table 1 below revealed that four hippos were seen in two villages out of the five villages that were surveyed. The village of Tsang had 75% which was followed by Bikogo with 25% of the hippos that were seen. The villages of Ebeda11, Ebomzout and Benga respectively had zero sightings.

Village	Number of hippos sighted	Percentage of sighting	Observations
Tsang	3	75	A female, male and young were seen
Ebeda II	0	0
Bikogo	1	25	A solitary male was seen
Ebomzout	0	0
Benga	0	0
Total	4	100

Table 1.

Number of Hippopotamus observed per village.

Table 1 above showed that the villages Tsang and Bikogo have three and one hippopotamus respectively, as they are located downstream of the river. The absence of these mammals in the villages of Ebebda II, Ebomzout and Benga is due to human activities on the banks of the river and in addition to the infrastructural development. On the other hand, the hippos sometimes sense the presence of humans and do not come out of the water, although signs of their

3.2 Relative abundances

A total of 8 out of 16 Islands in the study area were surveyed, including the river banks of the 2 villages that did not have islands. A distance of 32 km was covered. Kilometric index of abundance (KIA) of hippopotamus which were tracks, droppings and footprints were observed (Table 2).

Type of index	D	N	KIA
Footprints	776	32	24.25
Tracks	19	32	0.59
Dung	3	32	0.09
Total	798	32	24.94

Table 2.

KIA of hippopotamus in the study area.

N: number of index; D: distance travelled; KIA: kilometric index of abundance.

Footprints dominant with a KIA of 24.25 index/km. This is due to the fact that hippos are very huge animals and they can crush nearly every herbaceous vegetation in their path. Tracks with a KIA of 0.59 clues/km are lower because hippos use the same paths in and out of their feeding sites. Dung with a KIA of 0.09 index/km is very low because hippos defecate inside the river which is then carried away.

3.3 Human activities

3.3.1 Agriculture

The majority 80% of the respondents are farmers. The farm lands are not sufficient pushing rural to move into islands inside river which happen to be more fertile; as well as these lands are free not clam by communities. Usually these island are considered private domain of the state (state land). This practice not only destroys the habitat of the hippos but sometimes makes the hippos to become aggressive towards invaders, which often leads to injuries or death on both sides (Table 3).

Abundance of signs of human activity
Signs of activity	Number of observations	Distance travelled in km	KIA
Battery powered torches	7	32	0.21
Bush fires	24	32	0.75
Campsites	9	32	0.28
Tree cutting	8	32	0.25
Dugout garage	9	32	0.28
Camp fires	21	32	0.66
Gardening	10	32	0.31
Cocoa farming	3	32	0.09
Scarecrows	4	32	0.12
Total	95	32	2.97

Table 3.

Signs of agricultural activities.

These signs indicate the presences of human activities. These signs include battery-operated torches, bush fires, campsites, tree cutting, dugout landing, campfires, gardening and cocoa crops and scarecrows. The overall KIA for agriculture in general is 2.97 index/km. The majority of the signs are distributed between bush fires, campfires and gardening, with KIA of 0.75, 0.66 and 0.31 index/km respectively. The tree felling observed (KIA = 0.25 index/km) is linked to the creation of new agricultural farms. The landing of Canoes and the camps with (KIA = 0.28 index/km) to allow local people to move from one island to another and find shelter if necessary. Scarecrows (KIA of 0.12 index/km) are used to scare animals from farms.

3.3.2 Abundance of signs of poaching activities

The results in Table 4 revealed the abundance of signs of poaching in the study area.

Sign of poaching	Number of sightings	Distance travelled (km)	KIA
Cartridge shell	38	32	1.19

Table 4.

Abundance of signs of poaching.

The results in Table 4 showed that the local residents are poaching because the number of cartridge shells with KIA of 1.19 index/km showed that hippos are under threats in these localities. Indeed, the hippopotamus is a coveted species in the study area as its meat (bush meat) is a delicacy in the urban centres of Ebada and Yaounde. Respondents said bush meat is a delicacy with hippo carcass that can cost more than a million (1,000,000) CFA francs on the local market.

3.3.3 Sand exploitation

The results in Table 5 showed the abundance of evidence related to sand mining

Sand mining	Number of observations	Distance travelled in km	KIA
Sand depot	38	32	1.19
Canoes	23	32	0.72
Total	61	32	1.91

Table 5.

Abundance of evidence related to sand mining.

The results in Table 5 showed that sand mining activity is abundant in the study area with KIA of 1.91 index/km. This activity is practiced on a large scale in the study area. Indeed, the sand from the Sanaga is of good quality and is much sought after by real estate developers for construction purposes. Thus, the high demand from sand in the market pushes miners to go to the Islands to get it because at this level, it is still of better quality. This activity has led to the degradation and fragmentation of hippo habitats within the Islands.

3.3.4 Fishing

The results in Table 6 shows fishing activities in the study area with a KIA of 1.19 index/km. In fact, fishing here is artisanal. None of the local residents have a fishing licence, although this is requirement by the Ministry of Livestock, Fisheries and Animal Industry (MINEPIA). According to the respondents fishing is practised early in the morning and that disturbs the hippopotamus that are returning from their pastures and this has often leads to conflicts.

Fishing	Number of observations	Distance travelled in km	KIA
Fishing nets	12	32	0.37
Fishing canoes	26	32	0.81
Total	38	32	1.19

Table 6.

Signs of fishing activity.

3.3.5 Abundance of infrastructural activities

The construction of houses and related infrastructure like the bridge over the river Sanaga are the some of the activities seen in the study area. The results in Table 7 show the construction of houses around the river bank with an KIA of 0.78 index/km is the activity responsible for the fragmentation of habitats and the displacement of hippos in the Sanaga river.

Activity	Number of observations	Distance travelled in km	KIA
Houses	24	32	0.75
Bridge	1	32	0.03
Total	25	32	0.78

Table 7.

Shows the infrastructural activities.

3.3.6 Relative abundance of anthropogenic activities

The results in Table 8 summaries the anthropogenic activities identified in the study area.

Activity	Number	Distance (km)	KIA
Agricultural activities	96	32	2.97
Poaching	38	32	1.19
Sand pits	61	32	1.91
Fishing	38	32	1.19
others	25	32	0.78
Total	258	32	8.06

Table 8.

Abundance of anthropogenic activities.

The results in Table 8 revealed that agriculture is the most abundant anthropogenic activity (KIA = 2.97) followed by sand mining, fishing and poaching respectively.

3.3.7 Density

Density here is equal to the living area.

S = 3 × 32 km S = living area (km²)

S = 96 km hence

D = 0.041 individuals ̸ km²

Relationship between anthropogenic activities and hippopotamus Index Figure 3 shows the relationship between these two elements.

Figure 3.

Correlation curve between human activities and hippo presence.

The above graph shows that there are hippopotamus Index within human settlements. The relationship between these two parameters is a straight line on the equation y = −0.0206x + 1.412 whose correlation coefficient R² = 0.0014. The low correlation observed (R²) echoes that human activities have a high influence on hippopotamus’s presence in the study area. Indeed, direct observations in the field revealed that economic activities at community level are on the increase. However, the local populations have also complaint on the destruction of their crops by hippos.

3.4 The presence of hippopotamus

The distribution of hippo and their presence index in space was done with the values of the different Index observed and are summarised in the graph in Figure 3. This graph showed that there are hippopotamus Index within human settlements. The relationship between these two parameters is a straight line with an equation y = −0.0206x + 1.412 whose correlation coefficient R² = 0.0014. The low correlation observed (R²) reflects on the fact that human activities have a high influence on hippopotamus’s presence. Indeed, direct observations in the field revealed that activities at community level are going well.

3.4.1 Distribution of hippopotamus signs

The distribution of hippo presence Index in space was done with the values of the different Index observed in the field and are summarised in the graph in Figure 4.

Figure 4.

Distribution of hippo evidence by village.

Figure 4 showed that Tsang village had the majority of hippo evidence. This is due to its geographical position (downstream) of the locality where the water is calmer and agricultural activity is not intense. The village of Bikogo has considerable evidence of hippopotamus, while the villages of Ebomzout, Ebeba and Benga have lesser numbers.

It should also be noted that the presence of droppings here is very low according to the inventories because the hippos may defecate directly in the water which is them carried downstream. Those that are made on the shore are directly collected by the locals for medicinal purposes. Figure 4 illustrates the layout of the islands along the river and the part of the shoreline where the survey was carried out.

Figure 5 shows the construction of houses and the various sand deposits along the river that putting pressure on the hippopotamus habitat in the study area. The main source of conflicts between humans and hippos along the Sanaga River is that of competition for resources and space.

Figure 5.

Map of islands and hippopotamus presences.

It should be noted that three out of eight sites were mapped because of the similarity of the problems identified. As a result, agriculture on the islands (hippo habitat) is the most common activity followed by sand mining and artisanal fishing.

3.4.2 Identification of threats to hippos

Despite being on the IUCN Red List of Threatened Species, the hippo is still hunted for its meat and ivory. As a result, it should be noted that habitat loss and fragmentation (45%), human-wildlife conflict (26%), poaching (17%) and fishing (12%) are the main threats to the survival of hippos in the Sanaga River.

3.4.3 Period of hippo’s observation

The watching of hippo movements was done using a canoe, which was complicated by the rocky nature of the river bed in the study area, but the field surveys identified footprints of hippos on the river banks.

Figure 6 showed that majority of residents is engaged in farming, fishing and sand mining as their primary economic activity. Majority of these respondents have sighted hippos late evenings (6–8 pm) as seen in the Figure 7, which is also the time when hippos are returning from the pastures. During the rest of the day, sightings are less or almost non-existent and only start again in the evenings, i.e. 16:00–18:00, when the hippos start to search of pasture. Farmers (7.68%) generally see them in this time slot because it is the time when they return from their fields. Fishermen come with a 0.63% sighting because this is the time when they go fishing, while sandmen have no sightings at this time. In the late evening, from 18:00 to 20:00, farmers always have a high rate of observations, which is 32.64%. This can be explained by the fact that they camp in their plantation to carry out crop surveillance against hippos. The fishermen with 3.99% of observations can be explained by the fact that some of them practice fishing at night. Lastly, sandmen with a low rate of sighting 1.8% because their activity is mostly carried out during the day.

Figure 6.

Period hippopotamus observation.

Figure 7.

Map showing human activities and hippopotamus index on the islands of Tsang, Dikogo, Benga villages.

3.4.4 Hippo poaching

The study area is becoming an increasingly dangerous place for hippos, not only in the waterways they inhabit, but also in their feeding grounds. Although the animal has an indifferent neighbourly relationship with the inhabitants of some villages, especially Ebeda II, it is usually the prey for others who hunt it down for food. In reality, hippopotamus hunting is not organised although there individual hunters who have specialised in the hunting of Hippos in the study area.

Respondents said large holes are often dug (trap pits) for poaching of hippos, as well as cable traps with large spikes nailed to boards and placed at the edge of hippo grazing sites that has often been used by hippo hunters in the study area. Guns are a favourable asset for some local people who primary occupation is hunting. A hippopotamus was killed in Tsang village in 1997 by the community even though this was reported on the news no arrest was made by the competent authorities.

3.4.5 Agriculture

Agriculture is one of the biggest threats to hippo populations in the study area because local residents are destroying hippo habitats in search of new land for crop cultivation. This may be due to a reduction in rainfall patterns which is observe in the area recently. In addition, the loss of habitat for hippo populations has reduced their rangelands and has caused them to migrate to unfamiliar sites in search of new grazing lands.

3.4.6 Sand mining

Sand mining is also a threat to hippo populations as it has destroyed the habitats through fragmentation. Thus, the sand miners’ opinion on the conservation of the animal was negative (Table 9).

Villages	Number of miners per village	Protection of hippos
		Yes	No
Bikogo	08	0%	100%
Mbega	10	0%	100%
Ebeda II	01	0%	100%
Ebomzoute	05	0%	100%
Tsang	02	0%	100%
Total	26		100%

Table 9.

The perception of sand miners on the conservation of the species.

3.4.7 Human and hippopotamus conflicts

This animals are known to have destroyed vast crop lands and fishing nets etc. this has created conflicts resulting to the killing of this animals. These people are increasingly doubting whether hippos have become so much more important than people and their livelihoods. There is therefore a call for the conservation of hippos in the river Sanaga.

Figure 8 shows that most of the respondents in the villages of Bikogo, Benga, Tsang and Ebomzout (35%) said they have being troubled by hippos during their activities (fishing and gardening) in the sense that they are scared by their size. To this effect, they have called for the killing of hippos by the conservation services. On the other hand, 33.33% of the respondents (Ebebda 2) believe that hippos are not harmful to their economic activity.

Figure 8.

Residents’ perceptions of hippo disturbance.

3.4.8 Nature of the relationship between people and hippos

The nature of the relationship between humans and hippos can be very beneficial and should allow for sustainable management of the species as hippo dung is used as traditional medicine. Hippos are part of the biological diversity of this area and constitute an asset for man in the regulation of the trophic chain.

3.4.9 SWOT analysis

The Sanaga River has specific bio-ecological, socio-cultural, economic and institutional features that point toward particular considerations (Table 10)

Strengths	Weaknesses
Existence of wildlife laws and regulations; Ratification of international and sub-regional treaties and agreements for the protection of biodiversity; Existence of hippos in the river;	The lack of follow-up or total abandonment of the hippos by the services in charge of their protection; The non-existence of a hippo inventory in the locality; The lack of data on hippos in the river; The presence of the area itself not yet classified;
Opportunities	Threats
The good adaptation capacity of hippos in the river; The presence of many partners for the conservation of the species; The creation of a hippo sanctuary in the river; Easy access to the site	Presence of agricultural activities, fishing and Sand mining on the hippo habitat; Poaching practices; Effect of climate change ; Loss of its habitat; Demographic pressure; Human-wildlife conflict; Deforestation;

Table 10.

STOW analysis.

4. Discussion

The results in Table 1 showed that the villages Tsang and Bikogo have three and one hippopotamus respectively, as they are located downstream of the river. The absence of these mammals in the villages of Ebebda II, Ebomzout and Benga is due to human activities on the banks of the river and in addition to the infrastructural development. On the other hand, the hippos sometimes sense the presence of humans and do not come out of the water, although signs of their presence are visible. This result may show an increase compared to the inventories carried out by the Ebogo site manager [29] where one hippopotamus was seen in the Nyong River precisely in Mbalmayo. This discrepancy may be due to the fact that the along the river Sanaga there are more Islands compare to the river Nyong. In addition, the study took place at the beginning of the rainy season, a period during which the Sanaga River high water level is high which makes navigation and counting difficult compared to the study conducted by Amoussou et al. [13] in (3) villages in Southern Benin regrouping groups of hippos isolated in wetlands in the Mono and Couffo Divisions in the dry season where he saw 30 hippopotamus.

The Sanaga River is rich in fish which is a source of animal protein for majority of residents. Fishing is often at night or early in the mornings when hippos are most often seen (Figure 7). Some fishermen reported that they have been attacked by hippos at least once during fishing expedition because they fish in shallow waters which are often the resting sites of hippos. The hippos often destroy the nets along their path as well as the Canoes and fish traps. Thus creating tensions between the two parties.

In summary, agriculture is the main threat to the hippo in the study area which is in contrast to the findings as observed by [30] in Benue National Park where poaching is the major threat to hippos as they are been hunted for their meat which is a delicacy and their skin is processed into leather for the manufacture of shoes and bags.

5. Conclusion

The present study makes available a previously non-existence of scientific database on hippopotamus in the Sanaga River with the overall objective of contributing to the sustainable management of hippopotamus in the Sanaga River. The results revealed that, four hippos were seen over the 32 km covered in the river. It also appears that the hippopotamus go out in the evening in search of pasture and do return late at night; and the threats these animals are phasing include agriculture, Sand mining, fishing and poaching.

Anthropogenic activities have shown to have a negative but small influence on the hippopotamus presence. Strategies such as: strengthening the various stakeholders in hippopotamus conservation, enforcing anti-poaching laws, monitoring and protecting hippopotamus and conserving habitats, and enhancing the value of the hippopotamus will help in the mitigation of these threats.

Acknowledgments

We are grateful for the material and logistical support provided by the Laboratory of Environmental Geomatic, Department of Forestry, The Faculty of Agronomy and Agricultural Sciences of the University of Dschang, Cameroon. Special thanks go to all those who participated in the focus group discussions for the vital information they provided that enabled us to move forward with this study.

Conflict of interest

The authors declare that there are no conflicts of interest.