Investigating primate densities and human-primate conflict in Tembaro Community Conserved Forest, Omo River Basin, Ethiopia

Abstract

Background

Human-primate conflict is a global conservation challenge, particularly in densely populated, low-income countries like Ethiopia. The Omo River Valley forest belt, spanning across the Omo River in Ethiopia to Lake Turkana in Kenya, harbors a diverse array of African primate species. An investigation on non-human primate population density and human primate conflict was carried out from January 2022 to December 2023 in the Tembaro Community Conserved Forest, Omo River basin, South Central Ethiopia. The population density of non-human primates was estimated using distance sampling method, and the intensity of conflict among human-primate was quantified by a questionnaire survey and focus group discussions.

Results

The study revealed some interesting results which include the presence of black colobus monkeys (Colobus satanas) in Ethiopia. The mean density of Anubis baboons (Papio anubis) was 10.06 ± 2.93, grivet monkeys (Chlorocebus aethiops) 17.09 ± 4.53, black colobus monkeys (Colobus satanas) (vulnerable primate species in Africa) was 8.3 ± 1.20, and mantled guerezas (Colobus guereza) was 14.76 ± 3.57 individuals/km². Crop damage and livestock predation were prevalent issues in the present study area. Majority of the local village respondents (51.96%, n = 146) reported that crop damage was the common cause of human-primate conflict, followed by livestock predation and crop damage (33.5%, n = 94). Majority of the conflict was caused by Anubis baboon (Papio anubis) (41%, n = 115), followed by grivet monkeys (Chlorocebus aethiops) (33.1%). The most common cultivated crop by farmers in the study area and the most damaged by the non-human primates was maize (Zea mays) (33.5%, n = 94). The average estimated loss of crops was US$ 6544.50 per year. The average annual loss incurred by each household due to primates predation on their small animals was 94.19 US$. Physical guarding (33%, n = 93) was chosen as the most effective strategy to prevent crop damage and livestock predation.

Conclusion

This study provides valuable insights into primate ecology and the challenges they pose to local communities. The findings reveal varying primate population densities, with Grivet monkeys exhibiting the highest densities. These primate densities contribute significantly to human-wildlife conflict, primarily through crop foraging and livestock predation. While traditional mitigation methods are currently in place, a more sustainable and integrated approach is urgently needed to ensure the harmonious coexistence of primates and local communities. The findings of this study are crucial for developing effective conservation and conflict mitigation strategies that will safeguard the long-term survival of both primates and the livelihoods of local people.

Clinical trial number

Not applicable.

Background

Primates are charismatic mammals inhabiting many of the world’s tropical forests [1]. Africa stands out as a continent of exceptional primate diversity and abundance [2]. According to [3, 4], global primate species richness ranges from 326 to 550, with Africa harboring approximately 32% of these species. Notably, nine of the fifteen countries globally with the highest primate species richness are located in Africa, including Cameroon, the Democratic Republic of Congo, Nigeria, the Republic of Congo, Equatorial Guinea, and the Central African Republic [4]. Historically, African forests have exhibited dynamic patterns, experiencing cycles of expansion and contraction. In many regions, forests persist in fragmented forms. These historical processes have significantly shaped the current distribution of primate populations across the continent [5].

Anthropogenic pressures have intensified over millennia, profoundly altering the global environment [6]. Human population growth, agricultural expansion, urbanization, and increasing resource demands have led to significant declines in ecosystem complexity [7]. Human-wildlife conflict have also become more frequent, ranging from benign to antagonistic [8, 9]. These interactions contribute to species declines, extinctions, and biodiversity loss [10]. Therefore, collaborative efforts among science, policy, and society are crucial to mitigate the adverse consequences of human-wildlife conflict and reduce the risks associated with these interactions [11].

Primates are highly vulnerable to forest loss, habitat degradation, and hunting due to their strong reliance on forested environments. According to [12, 13], approximately 60% of primate species face extinction, with 75% experiencing population declines globally. Habitat fragmentation and human disturbance pose significant threats to primate survival, impacting species diversity, abundance, distribution, group size, and population density [13]. Human-primate conflict is more likely to occur in areas with high human population density and significant reliance on agriculture and livestock farming for livelihoods [14]. Research on human-primate conflict has been extensively conducted across Africa, with notable studies in Tanzania [15], Uganda [16; 17; 18], Guinea-Bissau [19], Rwanda [20], South Africa [21] and Ethiopia [14]. These studies provide valuable insights into the complexities and challenges of human-primate coexistence across diverse African landscapes.

Ethiopia boasts a diverse wildlife assemblage, encompassing 325 mammalian species within 52 families, including 57 endemic species [22]. The country’s diverse climates, shaped by altitudinal variations, influence the distribution and diversity of both flora and fauna. The Great Rift Valley, the Omo River Valley, and the western lowlands harbor unique and diverse wildlife populations. However, Ethiopia’s wildlife habitats and biodiversity are facing significant threats due to human activities. Poverty, rapid population growth, livestock expansion, and political instability are major drivers of habitat degradation, destruction, and fragmentation [22].

There are 216 species and sub-species of primates in Africa [3]. Among them, 13 species of primates are found in Ethiopia excluding Homo sapiens [22, 23]. Species and sub-species of primates that occur in Ethiopia are black and white colobus monkey (Colobus guereza), gelada baboon (Theropithecus gelada), grivet monkey (Cercopithecus aethiops aethiops), Hamadryas baboon (Papio hamadryas), olive baboon (Papio anubis), bushbaby or Senegal lesser galago (Galago senegalensis) and Somali lesser galago (Galago gallarum) [24], Black faced vervet (Cercopithecus aethiops pygerythrus), Bale monkey (Cercopithecus aethiops djamdjamensis), De Brazza’s monkey (Cercopithecus neglectus), Patas monkey (Erythrocebus patas), Sykes’ Monkey (Cercopithecus albogularis) [25], and two subspecies of blue monkeys (Cercopithecus mitis boutourlinii and Cercopithecus mitis stuhlmanni) [26]. However, due to anthropogenic activities, the majority of these primate species are facing local extinction as well as decreasing population sizes [27].

While primates play important ecological roles within their environment, their interactions with human agricultural practices can lead to conflict. In some contexts, they may cause significant crop damage, impacting local livelihoods. Understanding primate population status and their interactions with humans is therefore crucial for effective conservation management. Although some research has addressed ecological aspects of primate populations living in contact with human populations and their conflict in Ethiopia [14], specific data are scarce for the Tembaro Community Conserved Forest, located within the Omo River Basin. This forest represents a potentially important area for primate conservation because the ecosystem have diverse habitat types (forest, woodland, grassland, bush land, riverine forest and water source) that support primate species, but limited ecological research hinders our understanding of their species’ population sizes and interactions with local communities. Establishing baseline data in this relatively unexplored location is therefore crucial for informing effective conservation management. Specifically, there is limited information on diurnal primate densities and their interactions within the human-dominated ecosystem of the Tembaro Community Conserved Forest. This study addressed this knowledge gap by investigating the population densities of four primate species and their associated conflicts with humans over a 24-month period within and around the Tembaro Community Conserved Forest, Omo River Basin, South Central Ethiopia. We hypothesized that the frequency and severity of human-primate conflict would be positively correlated with the proximity of primate habitat to agricultural fields. By providing baseline data on primate densities and conflict patterns in this area, this study contributes essential information for developing effective conservation strategies that mitigate conflict and promote human-primate coexistence.

Results

Population estimates of primates

The average population size for Anubis baboons, grivet monkeys, black colobus monkeys, and white colobus monkeys in the present study area was 1108.5 ± 311.3, 1425.5 ± 412.94, 678.5 ± 92.23, and 1643 ± 397.2, respectively, and the average estimated density of individuals/km² for Anubis baboons was 10.06 ± 2.93, grivet monkeys was 17.09 ± 4.53, black colobus monkeys was 8.3 ± 1.20, and mantled guereza was 14.76 ± 3.57. The detection probabilities of Anubis baboon, grivet monkey, colobus monkey, and mantled guereza were 0.15 ± 0.40, 0.63 ± 0.14, 0.46 ± 0.52, and 0.36 ± 0.81, respectively (Table 1). A minimum AIC value was taken for each species using the model hazard rate and uniforms with different key functions (Figs. 1 and 2).

Table 1.

Density estimates of primate species in Tembaro Community Conserved Forest (D = density, N = population, ESW = effective strip width, P = Detection probability, %CV = Percentage Coef. Variation, CI = Confidence Interval, SE = Standard Error, HR/Sps = Hazard Rate/Simple polynomials, NE/Cos = Negative Exponential/Cosines, NE/SPs = Negative Exponential/Simple polynomials, HR/Sps = Hazard Rate/ Simple polynomials, UF/Cos = Uniform/Cosines)

Primate species	Year	Parameter	Estimate	SE	%CV	95% CI	AIC	Model
Anubis baboon	2022	p	0.18	0.43	23.47	0.12–0.29	674.61	HR/Sps
		ESW	7.03	1.65	23.47	4.44–11.13
		D	8.74	2.2	25.19	5.35–14.28
		N	920	295.85	32.16	492.00–1722
	2023	p	0.12	0.37	30.63	0.66 − 0.22	112.36	HR/Sps
		ESW	4.9	1.5	30.63	2.69–8.93
		D	11.38	3.66	32.16	6.08–21.29
		N	1297	326.69	25.19	794.00–2119.0
Grivet monkey	2022	p	0.33	0.12	34.24	0.17–0.65	1062.33	NE/Cos
		ESW	20.38	6.98	34.24	10.53–39.45
		D	11.53	4.09	35.44	5.83–22.79
		N	1140	219.47	19.25	780.00–1667.0
	2023	p	0.92	0.15	6.50	0.66–1.13	1243.47	NE/Sps
		ESW	3.78	0.62	16.5	2.72–5.25
		D	14.098	2.71	19.25	9.64–20.61
		N	1711	606.41	35.44	865.00- 3381.0
Black colobus monkey	2022	p	0.33	0.29	8.88	0.28–0.39	1006.97	HR/Sps
		ESW	12.63	1.12	8.88	10.59–15.05
		D	5.08	0.65	12.73	3.95–6.55
		N	603	88.49	14.67	451.00–807.00
	2023	P	0.58	0.74	12.65	0.45–0.75	994.89	NE/Cos
		ESW	35.35	4.47	12.65	27.53–45.38
		D	7.37	1.15	15.61	5.42–10.02
		N	754	96	12.73	586.00–971.00
Mantled guereza	2022	p	0.43	0.96	22.62	0.27–0.66	1112.41	UF/Cos
		ESW	25.89	5.86	22.62	16.63–40.33
		D	9.61	2.34	24.39	5.97–15.46
		N	1426	347.86	24.39	886.00–2294.0
	2023	p	0.29	0.66	22.16	0.19–0.46
		ESW	18.16	4.03	22.16	11.77–28.04	853.73	HR/Cos
		D	12.53	3.01	24.01	7.85–20.02
		N	1860	446.53	24.01	1164.0–2971.0

Fig. 1.

Number of sightings of Anubis baboon (A) and Grivet monkey (B) at different distances from the transect centerline during two survey periods (2022−2023) in Tembaro Community Conserved Forest

Fig. 2.

Number of sightings of Black colobus (C) and Mantled guereza (D) at different distances from the transect centerline during two survey periods (2022−2023) in Tembaro Community Conserved Forest

Human-primate conflict

In the study area, human-primate conflict manifested primarily as crop damage (51.2%, n = 144), followed by combined crop damage and livestock depredation (33.8%, n = 95), livestock depredation (8.9%, n = 25), and human attacks (6.1%, n = 17) (Table 2). A statistically significant difference (χ² = 10.64, df = 2, p < 0.05) was observed in the reported consequences of conflict across the three study villages.

Table 2.

Consequences of conflict between humans and primates in Tembaro community conserved forest. The number in the bracket represents percentage of respondents in each village

Villages	Consequences of conflict					Percentage (%)
	n	Crop damage	Livestock depredation	Livestock depredation & crop damage	Human casualties
Gaecha	108	58(53.7)	9(8.3)	34(31.5)	7(6.5)	38.4
Waro	91	48(52.8)	8(8.8)	31(34)	4(4.4)	32.4
Belela	82	38(46.3.)	8(9.8)	30(36.6)	6(7.3)	29.2
Total	281	51.2%	8.9%	33.8%	6.1%	100

Primate species involved in crop foraging

Four primate species were identified as crop foragers based on respondent reports. The Anubis baboon (Papio anubis) was the most prevalent crop raider across all villages (41.0%, n = 115), followed by the grivet monkey (Chlorocebus aethiops) (33.1%, n = 94), the black colobus monkey (Colobus satanas) (14.9%, n = 42), and the mantled guereza (Colobus guereza) (10.7%, n = 30). All four species were reported as diurnal crop foragers within the study area. A significant difference in the frequency of crop damage was observed among these primate species (χ² = 24.64, df = 3, P < 0.05) (Fig. 3).

Fig. 3.

Percentage of respondents that manifested primate species foraging on crops in Tambaro community conserved forest (the boxes shows the mean number)

The respondents stated that the major crops grown and frequently damaged by primates were: maize (Zea mays) (33.5%, n = 94), followed by haricot beans (Phaseolus vulgaris) (18.1%, n = 51) and potato (Solanum tuberosum) (14.6%, n = 41). Barely (Hordeum vulgare), red kidney beans (Phaseolus vulgaris), pea (Pisum sativum), teff (Eragrostis tef) and sorghum (Sorghum bicolor) are also common crops grown in the area (Table 3). Different fruits and vegetables, including papaya, avocado, and mango, as well as onions and cabbage, were also grown in the study area, and damaged by primates. This situation may intensify the conflict issue.

Table 3.

The most frequently foraged crops by primate and their rank (n = 281)

Crops types preferred by primate	Frequency	Percentage	Rank
Maize(Zea mays)	94	33.5	1
Haricot beans (Phaseolus vulgaris)	51	18.2	2
Potato(Solanum tuberosum)	41	14.6	3
Wheat (Triticum aestivum)	23	8.2	4
Red kidney bean (Phaseolus vulgaris)	18	6.4	5
Pea (Pisum sativum)	16	5.7	6
Barely(Hordeum vulgare)	14	4.9	7
Teff (Eragrostis tef)	13	4.6	8
Sorghum (Sorghum bicolor)	7	2.5	9
Banana (Musa acuminate)	4	1.4	10
Total	281	100

Estimated economic loss of crops by primates

A majority of respondents reported experiencing crop damage caused by primates. An estimated 12,795 kg of various crops were lost over two years, translating to an annual loss of 6397.5 kg. Across three study villages, the total economic losses due to crop damage amounted to US$13,088.99 over two years. This equates to an average annual estimated loss of US$6,544.50 and an average annual loss of US$23.29 per household head. The frequency of crop damage varied significantly among villages. The degree of conflict was reported to be more intense within 0.0 to 1.0 km of the forest edge compared to villages located further away (r = 0.06, p < 0.05). According to respondent reports, Anubis baboons were the primary perpetrators of crop damage, followed by grivet monkeys (Table 4).

Table 4.

Estimated economic loss of various crop types due to primates in Tembaro community conserved forest (2022–2023) (1 US$ amount is 54.757 Ethiopian Birr during the study period)

Distance of villages to the forest and estimated loss of crops in kg &US$				Total loss in kg	Average Price per kg in US$	Total loss in US$
Crop type	Gaecha (0–1.5 km)	Waro (1.5–2.5 km)	Belela (2.5–3.5 km)
Maize	643	583	443	1669	0.86	1435.34
Harricot beans	592	463	436	1491	0.58	864.78
Potato	687	546	416	1649	0.58	956.42
Wheat	774	523	401	1698	0.97	1646.06
Red kidney beans	561	483	394	1438	1.16	1668.08
Peas	455	394	382	1231	1.73	2129.63
Barley	511	481	363	1355	0.97	1314.35
Teff	393	365	453	1211	1.93	2337.23
Sorghum	371	349	333	1053	0.7	737.10
Total loss in kg	4987	4187	3621	12,795		13,088.99
Percentage	38.98	32.72	28.3	100

Small sized livestock loss by primates and its economic valuation

A total of 962 small-sized livestock were lost to primate predation over two consecutive years (2022 and 2023). This included 765 individual livestock and 197 eggs (Table 5). Anubis baboons were responsible for the majority of livestock losses (73.98%, n = 566), followed by grivet monkeys (23.40%, n = 179) and black colobus monkeys (2.61%, n = 20). Grivet monkeys were the primary culprits in the loss of chickens (55.39%) and eggs (79.19%) (Table 5).

Table 5.

The number of livestock depredated by primates in the last two years (2022–2023) in Tambaro community conserved forest

Domestic animals	Predation by primate species				Total kill
	Anubis baboon	Grivet monkey	Black colobus	Mantled guereza
Poultry	109	154	15	0	278
Lamb (age under 5 months)	217	12	2	0	231
Immature goat (age under 4 months)	214	13	3	0	230
Calf of domestic cow (under 6 months old)	26	0	0	0	26
Eggs	41	156	0	0	197
Total	607	335	20	0	962
Percentage (%)	63.09	34.82	2.08	0	100

The total economic losses due to primate predation on small livestock over two years amounted to US$52,934.19. This translates to an average annual economic loss of US$26,467.09. Furthermore, each farmer experienced an average annual loss of US$94.19 due to primate predation (Table 6).

Table 6.

Economic loss due to domestic animals’ depredation in the last two years (2022–2023) around Tambaro community conserved forest. (1 US$ amount is 54.757 Ethiopian Birr during the study period)

Economic loss (US$) due to livestock depredation and distance of villages (km)				Total  kill	Average price per	Total loss in US$
Livestock type	Gaecha (0–1.5 km)	Waro (1.5–2.5 km)	Belela (2.5–3.5 km)		livestock in US$
Poultry	122	96	60	278	16.55	4600
Lamb	109	82	40	231	93.19	21526.89
Immature goat	98	86	46	230	94.89	21824.70
Calf of domestic cow	11	9	6	26	189.82	4935.32
Eggs	88	74	35	197	0.24	47.28
Total	428	347	187	962		52,934.19
Percentage (%)	44.49	36.11	19.4	100

Mitigation methods practiced by local farmers

During the present study, respondents were used different traditional methods to deter crop damage and livestock predation by primate. Most respondents guarded their crops throughout crop growing season and livestock predation (33%, n = 93), followed by chasing (27%, n = 76), fencing (17.4%, n = 49), scarecrow (14.6%, n = 41), killing of animals and hung ups (6%, n = 17) and smoking (2%, n = 5) to repeal the crop foragers from their farms.

Guarding method typically involves physically watching, noise-making, creating smoke by burning materials such as dry leaves, grass, or dung near the crop fields (Figs. 4 and 5). The respondents did not use only one method alone; they combined and integrated traditional methods to prevent crop foraging.

Fig. 4.

Traditional mitigation methods used by the respondents to protect crop damage

Fig. 5.

Villagers adopted different traditional approaches to minimize crop damage and livestock predation by primates in the study area (A & B = different types of fences; C = cage for killing and hanging primate, D = Watch tower)

Discussions

Population density of primate

Accurate assessment of animal status and distribution is fundamental for effective population size monitoring. As emphasized by [28], this constitutes a critical ecological parameter for understanding species ecology and conservation status. Previous studies in Ethiopia have documented that the majority of primates inhabit fragmented forest patches embedded within a matrix of agricultural lands, plantations, and human settlements [27; 23; 29]. Despite the persistence of primate populations within these human modified landscapes, our understanding of their ecology in Ethiopia remains limited. Crucially, data on key ecological parameters, including density, distribution, population abundance, genetic variation, feeding ecology, reproductive behavior, social structure, and activity patterns, remain largely unavailable for most primate species in Ethiopia. Reliable density estimation is paramount for effective primate conservation and management. This study provides valuable data on the ecology of primates within the Tembaro forest, contributing essential information for the development of targeted conservation plans.

Our study in the Tembaro Community Conserved Forest revealed significant variations in the population densities of different primate species. Grivet monkeys emerged as the most abundant, with a mean density of 17.09 ± 4.53 individuals/km². Anubis baboons followed, with a density of 10.06 ± 2.93 individuals/km², while black colobus monkeys exhibited the lowest densities. Grivet monkeys, with their generalist diet and adaptability to a range of habitats, may have a competitive advantage in resource acquisition, supporting their higher population densities. In contrast, black colobus monkeys, which have a highly specialized leaf-based diet, are likely more restricted by the availability of specific food resources, leading to their lower densities. When comparing the density of Anubis baboons in our study to other regions, our estimate (10.06 ± 2.93 individuals/km²) was higher than those reported by [30], in Konasa Pulasa, Ethiopia (3.66 and 5.35 individuals/km²) and [31] in Kainji Lake National Park, Nigeria (0.04 ± 0.00 individuals/km²). However, it was lower than the densities reported by [32] in the Humbo Community Managed Forest, Ethiopia (14.6 individuals/km²), and [33] (132.5 individuals/km²). Similarly, the density of grivet monkeys in our study area was significantly lower than those reported by [34] in the Arba Minch forest, Ethiopia (133.1 individuals/km²), and [35] in Zegie Peninsula, Ethiopia (438.8 individuals/km²). For mantled guereza, we recorded a density of 14.76 individuals per square kilometer, which is higher than the average group encounter rate of 5.5 groups per square kilometer reported by [14] in Borena Sayint National Park, Ethiopia. This aligns with observations by [36], who noted that C. guereza is capable of resilience to habitat degradation and can maintain medium to high population densities. However, it is important to note that the population densities of many primate species are heavily influenced by the availability and quality of food resources [36]. In our study area, factors such as limited food resources (edible leaves and fruits), a scarcity of small prey animals, and significant human impact likely contribute to the observed variation in primate densities.

Understanding the ecological factors that limit primate populations is critical for effective conservation efforts. Future research should focus on resource availability, niche partitioning, human impact and interspecific competition to provide insights into how these primate species coexist. Such studies will be instrumental in developing effective management strategies to ensure the long-term survival of primates within the Tembaro Community Conserved Forest.

Human-primate conflict

One critical conservation concern within this context is addressing human-wildlife conflicts, particularly those arising from crop foraging and livestock predation. These issues constitute a major global challenge in human-primate conflict [37]. In the present study area, primates significantly impact local communities by raiding crops and preying on small livestock. Given that livestock rearing and subsistence agriculture are the primary income sources for most residents, these losses can have severe financial repercussions for individual farmers. Even minor livestock predation by primates can significantly impact the livelihoods of these farmers [38]. [39, 40] and [41] have documented the primates’ remarkable skill and ingenuity in crop foraging strategies. Four primate species are implicated in human-wildlife conflicts within this study area: Anubis baboons, grivet monkeys, black colobus monkeys, and mantled guerezas. Most respondents reported crop damage as the primary cause of human-primate conflict, followed by small livestock predation. While there were a few reports of primate-related injuries to humans, these were not life-threatening. Anubis baboons are the most notorious crop foragers among these primate species. Their prominent role in human-primate conflicts can be attributed to their complex social structure and strict dominance hierarchies. Within these large social groups, intense competition for resources, including access to preferred foraging sites, drives their foraging behavior and increases the likelihood of crop raiding. Villages located closer to the forest experience higher levels of crop and livestock damage. This proximity increases the frequency of primate-human encounters and facilitates easier access to crops for these primates.

Studies elsewhere have shown that communities residing near protected areas experience higher crop damage rates compared to those living farther away [37, 41, 42], aligning with findings by [43] who identified Anubis baboons as the primary crop foragers in Southern Ethiopia. Similarly [21], reported Anubis baboons and vervet monkeys as the leading crop raiders in South Africa. Grivet monkeys pose a significant threat beyond crop damage, stealing food from humans, particularly children and the elderly, and preying on poultry [44]. Furthermore, respondents reported an increasing frequency of crop damage by foragers, consistent with [45] observations in the Gera district of Ethiopia. Several factors contribute to this human-primate conflict: food availability, including the proximity of cultivated crops to protected area boundaries [45], declining availability of natural food sources within primate habitats due to habitat degradation and climate change [46], and the higher nutritional value and ready availability of cultivated crops compared to natural foods [16]; habitat loss and fragmentation, with agricultural expansion, deforestation, and infrastructure development shrinking primate habitats, forcing them into human-dominated areas [47, 48] and traditional mitigation strategies, some of which may inadvertently increase human-primate interaction [18]. This conflict poses a major threat to primate conservation [17]. However, in the Omo River Basin, the issue is complex, with significant social and ecological implications. Addressing this challenge requires a comprehensive understanding of the historical, political, and land-use context, alongside the ecological and behavioral needs of both humans and primates. Collaborative efforts among local communities, government agencies, and conservation organizations are crucial for developing and implementing effective and sustainable solutions.

Our results indicated that maize, haricot beans, wheat, and potatoes were the most frequently foraged crops by primates. This behavior may be attributed to several factors, including a scarcity of natural food within the forest due to the reduction of foraging areas, inadequate farm protection measures, or the cultivation of highly palatable and nutrient-rich crop varieties along the edges of primate habitats. Similar research has shown that primates strongly prefer crops such as maize, beans, wheat, potatoes, cassava, bananas, and sorghum in various study areas [39, 41, 49]. Group discussions revealed that Anubis baboons and grivet monkeys caused damage to crops at all stages, from germination to harvest, while colobus monkeys primarily affected crops after ripening. Not all crops were equally affected; maize was identified as the most vulnerable to primate foraging pressure. This preference can be attributed, in part, to the ease with which primates can handle and consume maize cobs compared to other cultivated crops. From an optimal foraging perspective, maize offers a combination of high caloric content and easy accessibility, making it a potentially more profitable food source than natural alternatives. This is particularly true in fragmented habitats where natural food resources may be scarce or of lower nutritional value, further incentivizing primates to exploit agricultural fields. The economic losses incurred from primate maize foraging were substantial, significantly impacting the livelihoods of local people. These findings align with those of [50], who reported that maize was the most frequently eaten crop by crop-foraging animals in West Africa. Primates often target crops located close to forests due to their accessibility and safety [47]. Farms situated closer to the forest boundary are consequently more vulnerable to primate crop foraging. Living in close proximity to protected areas not only imposes costs such as crop and livestock losses due to primate incursions, but it also necessitates significant time and resource allocation for property protection against wildlife attacks, as reported by [41].

Estimated economic losses

Within the TCCF, crop foraging by primates is considered a significant problem, posing a substantial threat to the food security of smallholder farmers. An estimated average loss of 12,795 kg of crops, equivalent to US$13,088.99, was reported from three villages within two years, significantly impacting household income. The average economic loss caused by primates was US$23.29 per year per household. Several studies have documented similar economic losses due to primate crop raiding [51]. reported a loss of approximately US$154 per household in Northern Tanzania’s Kwakuchinja Wildlife Corridor [52]. reported a comparable loss of approximately US$155 per household in the western Serengeti. Our findings indicate that distance to the forest is a major determinant of the intensity of economic loss from primate crop damage. Economic losses were significantly higher in areas closer to the forest. Crop damage was most severe in Gaecha villages. Focus group discussions corroborated these findings, revealing that local people residing near the forest edge were more economically vulnerable to crop foraging and livestock depredation. This aligns with findings from other studies worldwide, demonstrating that communities living in proximity to protected areas are more susceptible to crop damage and livestock predation [41, 53].

Livestock predation by primates

During the two-year period (2022–2023), respondents reported losing 962 small livestock, including chickens, eggs, lambs, young goats, and calves, to Anubis baboons, grivet, and black colobus monkeys. This resulted in an annual average economic loss of US$26,467.09. Anubis baboons were identified as the most significant threat to small livestock in the study area. Previous studies have also documented similar predation patterns by baboons in the Wonchit Valley, Ethiopia [27], and the Pendjari Biosphere Reserve in Benin [54] where they were observed preying on young goats, sheep, and calves. Grivet monkeys were primarily responsible for attacking chickens and eggs. This behavior might be linked to seasonal food scarcity [55]. suggested that during the dry season, when young leaves and fruits become scarce in the forest, grivet monkeys may increase their reliance on small animals. Furthermore [56], observed that these primates utilize discarded human food sources near villages as an alternative food source during this period. Several factors likely contribute to the increased predation of small livestock in the study area. Habitat degradation, weak livestock husbandry practices, and the decline of natural wild food sources (fruits, leaves, and small prey) for primates may be driving this trend. This aligns with the findings of [57] and [58]. Focus group discussions revealed that primates were perceived as the primary cause of economic losses from small livestock depredation, surpassing the impact of large predators such as spotted hyenas, black-backed jackals, leopards, and common jackals. However, further observational studies are crucial to validate these perceptions and confirm primates as the dominant predators of small livestock in this specific study area. The economic impact of small livestock depredation on subsistence farmers is significant [38]. Our findings indicate that villages located closer to forest boundaries experienced higher rates of livestock depredation incidents compared to those situated further away. The highest livestock losses due to predation occurred in the Gaecha village.

Traditional mitigation methods

Numerous crop protection and livestock loss mitigation methods have been proposed, but few have undergone comprehensive evaluations in real world settings. For instance [59], demonstrated the effectiveness of electric fencing in deterring Japanese macaques (Macaca fuscata) from fruit crops in Japan. However, its high cost renders it inaccessible to many small-scale or subsistence farmers, particularly in developing countries with limited access to electricity. The effectiveness of hedges in preventing primate crop raids remains contentious. Field trials in Uganda revealed that jatropha hedges reduced baboon and guenon crop foraging by 85% when strategically placed to obstruct primate views of escape routes. Barbed wire fences exhibit varying degrees of success in deterring primate access to fields [18].

In this study area, local communities primarily relied on traditional mitigation approaches, with guarding being the most common method followed by chasing and fencing. Respondents generally perceived guarding as effective and cost-effective, although it demands significant time and effort. Effective guarding requires vigilant patrolling of field boundaries, noise-making, and the immediate chasing away of approaching animals [18, 60]. However, guarding can be labor-intensive and may interfere with other household tasks [61]. Several non-lethal mitigation strategies can be employed to minimize human-primate conflict. Creating buffer zones involves establishing strips of primate-unpalatable vegetation between natural habitats and agricultural areas. While effective in deterring wildlife, this approach can significantly reduce the land available for food and cash crop production in smallholder farming systems. Careful consideration must be given to the selection of buffer crops, taking into account their market value, harvesting costs, and compatibility with existing labor schedules [62]. Avoiding the cultivation of primate-preferred crops can also reduce human-primate conflict. However, this strategy can be challenging in small-scale farming systems due to limited land availability and the need to maintain soil fertility through crop rotation and fallowing. Furthermore, primates are adaptable and may shift their dietary preferences over time, expanding their consumption to previously unpreferred crops [63]. Shifting the location of preferred crops within the farm to less vulnerable areas can minimize encounters with primates. These mitigation strategies can be implemented individually or in combination to effectively reduce human-primate conflict in agricultural landscapes. Enrichment planting and diversionary feeding has shown varying degrees of success. In Costa Rica, planting fruit trees successfully diverted capuchin monkeys from commercial crops [64]. Similarly, in South Africa, feeding urban baboons at alternative sites proved effective in reducing human-wildlife conflict [65]. However, in Japan, diversionary feeding failed to reduce crop raiding by Japanese macaques, leading to population increases and increased crop foraging due to habituation [66].

Conclusions

This study provides valuable insights into the estimated numbers of primate species, the extent of their conflicts with humans, and the resulting economic losses. Accurately estimating primate population size is crucial for effective wildlife management. Our findings reveal that primates pose significant challenges to local communities in the study area, causing crop damage, predation of small livestock, and impacting livelihoods. Traditional methods are currently employed by farmers to mitigate these conflicts. However, a more sustainable approach is needed to foster harmonious coexistence between humans and primates. To achieve this, collaborative efforts are essential. Local communities and stakeholders should work together to identify alternative crops that are less attractive to primates. Planting highly palatable crops like maize, wheat, and potatoes near forest edges should be avoided to minimize losses. To increase the availability of natural food sources for primates and discourage them from venturing into human settlements, planting fruit trees within and around forest areas is crucial. This can help reduce reliance on agricultural crops and livestock. Furthermore, compensating local communities for crop losses and livestock predation may significantly reduce human-primate conflicts. The findings of this study highlight the importance of for primate conservation. It boasts a unique terrain, an artificial lake, and the potential to support a diverse range of wildlife species. As such, it can play a vital role in conserving the nation’s natural resources and developing sustainable tourism. Further research is necessary to comprehensively understand human activities within the study area and their impact on local biodiversity. This will provide valuable information on how human actions affect primate habitats and enable the development of effective mitigation strategies to minimize conflicts and ensure the long-term conservation of primate populations.

Methods

Description of the study area

This study was conducted in the Tembaro Community Conserved Forest (TCCF), located in Tembaro Special Woreda, within the Omo Valley of Ethiopia, approximately 405 km south of Addis Ababa (Fig. 6). The TCCF (262 km²) lies between 07°7′30” to 7°18′02” N latitude and 37°21′0” to 37°42′0” E longitude, with an altitudinal range of 959 to 1834 m.a.s.l., decreasing from northwest to southeast. The topography is characterized by highly undulating and rolling terrain interspersed with valleys, gorges, and bottomlands punctuated by hills. The general pattern consists of rolling to steep hills with relatively narrow, flat to undulating bottomlands that collect runoff water from the uplands. The area is drained by several rivers and their tributaries, including the Lammo, Gonjo, and Sana rivers, which ultimately flow into the Omo River, the largest Rift Valley River in southern Ethiopia. Olido hot spring is also located within the study area. The climate is characterized by a mean annual rainfall ranging from 900 to 1400 mm, with the wettest period occurring between June and September and the driest between March and May. Annual temperatures range from 22 °C to 30 °C, with an average of 25 °C [67]. The Omo River Basin is characterized by a diverse range of soil types. The dominant soil types are litisol and alfisols, with clay and loam texture and reddish to dark pale brown color [68]. The Omo River Basin possesses a rich history shaped by diverse indigenous communities and their traditional land-use practices. These communities have traditionally relied on a mix of livelihoods, including pastoralism, shifting cultivation, and fishing, fostering a profound understanding of the local ecosystems. However, recent decades have witnessed significant transformations, primarily driven by large-scale development projects, including hydroelectric dam construction, road construction, mining, deforestation, and agricultural expansion. These interventions have dramatically altered the landscape and livelihoods of local communities, leading to increased human-wildlife conflict and destabilizing the delicate balance of the ecosystem [69, 70]. Historically, the basin was predominantly covered by natural forests 50 years ago, but has since been largely converted to smallholder farmland [71]. This transformation has significantly impacted local livelihoods in the Omo River Basin.

Fig. 6.

Map of the study area

The district has a total population of 372,750 (182,648 males and 190,102 females) [71]. The study area was known by its dense natural forest mainly found in the periphery of Omo River. The dominant plant species such as Croton macrostachyus, Strychnos spinosa, Albizia gumifera, Clematis longicauda, Prunus africana, Millettia ferruginea, Juniperious procera, Acacia bervispica, Combretum molle, Terminalia brownie, Syzygium guineense, Cordia Africana, Allophylus abyssinicas, Olea europaea, Cupressus lusitanica Ficus sycomorus, Ficus sur and Ficus vasta are common tree species in the area [69]. The study area is home to four diurnal primate species, such as olive baboons (Papio anubis), grivet monkey (Cercopithecus aethiops), black colobus monkey (Colobus satanas) (Vulnerable), and the Abyssinian black-and-white colobus or Mantled guereza (Colobus guereza). It also hosts a variety of large and medium-sized mammals, such as common duiker (Sylvicapra grimmia), common bushbuck (Tragelaphus scriptus), Guenther’s dikdik (Madoqua guentheri), hippopotamuses (Hippopotamus amphibius), Nile crocodiles (Crocodylus niloticus), porcupine (Hystrix cristata), hare (Lepus timidus), bush hyrax (Heterohyrax brucei), aardvark (Orycteropus afer), and predators include golden jackals (Canis aureus), black-backed jackals (Canis mesomelas), white tailed mongoose (Ichneumia albicauda), lion (Panthera leo), leopards (Panthera pardus), serval cat (Leptailurus serval), caracal (Caracal caracal), African civet (Civettictis civetta), spotted hyenas (Crocuta crocuta). In addition, the area is believed to possess ample diversity of birds, fish, reptiles, and also amphibians. The diverse wildlife of the area includes species known to cause crop damage and livestock losses, contributing to human-wildlife conflict.

The majority of residents are of the Tambaro ethnic group, with small family farms ranging from 0.5 to 2.5 hectares. Land scarcity often forces farmers to cultivate at the forest edge, using traditional methods that combine perennial and annual crops with livestock rearing. As most households rely on subsistence farming, crop raiding and livestock predation by primates pose a significant threat to their food security. Farmers typically follow a two-season planting regime, coinciding with the onset of rains in late March and August. The main crops are cereals such as common bean (Phaseolus vulgaris), maize (Zea mays), teff (Eragrostis tef), beans (Faba vulgaris), pea (Pisum sativum), wheat (Triticum aestivum), barley (Hordeum vulgare), cash crops like coffee (Coffea arabica), Ginger (Zingiber officinale), oat (Avena sativa), banana (Musa sp.), Taro (Colocasia esculenta), yam (Dioscorea spp.,) false banana (Ensete ventricosum), sweet potato (Ipomoea batatas) and fruits like avocado (Persea americana), papaya (Carica papaya) and mango (Mangifera indica) are cultivated in the present study area. Stimulants such as Khat (Catha edulis), Tobacco (Nicotiana tabacum) are also cash crops in the area. Cattle, sheep, goats, horses, mule, donkeys, and poultry are the common domestic animals in the area [71].

Data collection

To ensure efficient and effective data collection, a preliminary survey was conducted in November 2022. This initial phase gathered critical logistical information, such as site accessibility, topography, vegetation types, fauna present, the number of villages bordering the forest, and preliminary reports of human-primate conflict. This information informed the subsequent design of the main data collection phase, which employed a mixed-methods approach. Questionnaire interviews were chosen to provide quantifiable data on the extent of human-primate conflict, while focus group discussions were used to explore the nuances and complexities of these interactions. The line transect method was selected as the most appropriate technique for estimating non-human primate population densities within the study area’s diverse habitats.

Population density of non-human primate

Primate population censuses (hereafter, primates) were conducted from January 2022 to December 2023, following preliminary reconnaissance surveys. The study area was stratified into forest and farmland habitats, and parallel line transects were established in each, following the methodology of [72]. A total of 21 transects were established using a stratified random sampling approach, considering variations in topography and habitat type. Due to accessibility constraints, existing tracks and roads were occasionally used as transects. Of the 21 transects, 13 were located in forest habitat and 8 in farmland. Transect lengths ranged from 2 to 3 km, with consecutive transects spaced 400 m to 1 km apart to minimize double counting of individuals. Transect width varied from 40 to 60 m on either side of the transect line, depending on vegetation and topographic conditions affecting visibility. Transect lines were marked using natural markers and poles. Surveys were conducted twice daily, from 06:00 to 10:00 and 14:00 to 18:00, coinciding with peak primate activity periods [73]. Transects were walked at an average speed of 1 km/h, with regular pauses to scan the canopy and listen for vocalizations and movements [74]. Thirty four trained and experienced local individuals assisted with simultaneous surveys of transects at a consistent pace during both the dry (January–March) and wet (June–August) seasons. Each transect was counted two times per month, during both the wet and dry seasons. The survey design employed line-transect distance sampling methodology [75]. Population estimation from line transect sampling depends on the following assumptions: animals on the transect are never missed, animals do not move before being seen or flushed, and no animal is counted twice [76]. When primates (individuals or groups) were encountered, the following data were recorded: GPS location, group size, estimated animal-observer distance (r_i), sighting angle (θ), perpendicular distance from the transect to the first animal detected, height of the animal at initial detection, and dominant habitat type [73, 74, 77]. Animal-observer distances were estimated using normal vision, GPS, 7 × 35 binoculars, a Nikon 550 rangefinder, and a laser meter, while sighting angles were measured using a Suunto A-10 compass [75]. All surveys were conducted on foot, employing a silent detection method to minimize disturbance [74].

Human-primate conflict

To assess the extent of human-primate conflict, data were collected through questionnaire interviews with households and focus group discussions. Six villages bordering the forest (the smallest administrative unit within a district in Ethiopia) were initially identified. From these, six villages, Gaecha, Waro, and Belela were purposively selected based on information from the preliminary survey, considering their proximity to the forest and reported problems with crop damage and livestock losses. Household numbers for each village were obtained from the district agriculture office, and sample sizes for the questionnaire survey were subsequently determined. The questionnaire included both open and closed ended questions designed to gather comprehensive information on human-primate conflict in the study area. Prior to the main survey, the questionnaire was pre-tested with 35 randomly selected individuals from all three villages. These individuals, representing a range of ages, sexes, and backgrounds within the local communities, were not included in the final sample. This pre-testing phase allowed for refinement of the questionnaire, estimation of interview duration, and optimization of the interview process for the main study. A questionnaire survey was prepared and administered to 281 local households from 946 households in the three villages [78]. Of the total households, 208 male and 73 female were selected.

Households were randomly selected using a systematic sampling method, skipping one household between each interview. Interviews were conducted with 281 randomly selected participants from the households in the three villages, between January 2022 and December 2023. To facilitate communication and minimize misinterpretations, the questionnaire was developed in English and translated into Tembarssa. Following the methodology of [79], questionnaires were distributed randomly to available household residents on a first-come, first-served basis. Household representatives included both males and females across a range of age groups. Nine local residents (three from each village) were recruited and trained for two days to administer the questionnaires. Using the same trained translators and standardized interview questions across seasons ensured consistency and accuracy in data collection. Each interview lasted approximately 35–45 min. The selected villages were categorized based on their proximity to the TCCF: near (0–1.5 km), medium (1.5–2.5 km), and far (2.5–3.5 km). The questionnaire explored human-primate conflict, focusing on four key areas: (1) participant demographics (e.g., age, gender, education level); (2) the nature and extent of human-primate conflict; (3) the primate species involved; and (4) mitigation methods employed by local communities. Data on the species and number of livestock lost were also recorded to quantify the economic impact. The economic value of crop and livestock losses was estimated based on prevailing market prices at the time of the study, converted to US dollars using the corresponding exchange rate. While precise cost estimates for primate-related damage are inherently difficult to obtain, these approximations provide a valuable illustration of the economic burden faced by local farmers.

Focus group discussion

Focus group discussions (FGDs) were conducted to gather qualitative data on the intensity of human-primate conflict experienced by local communities, perceived benefits derived from primates, and recommendations for mitigating future conflicts. This method also served to corroborate the quantitative data collected through the questionnaire interviews. Two FGD sessions were held in each of the three study villages, with each group comprising 9 to 13 participants. Participants included village leaders, elders, religious leaders, a local primary school teacher, and other local government employees of both sexes, selected to represent a diverse range of perspectives on human-primate interactions. A discussion guide checklist was used to facilitate the FGDs. The information gathered from the discussions was then collated, summarized using text analysis, and presented narratively. This triangulation of data from questionnaires and FGDs enhanced the robustness of the study’s findings.

Data analysis

DISTANCE (Version 6.0, Release 2). DISTANCE (Version 6.0, Release 2) Software was used for density and abundance estimation of primate population. Density of primate within the area surveyed (D_g) was estimated as:

where ‘L’ denotes the aggregate length of the transects, ‘n’ is the number of primate individual observed and is the probability density function of observed, Then, the perpendicular distance from the transect line to the animal is calculated as x = ri sin (θ) [75]. Statistical Package for Social Sciences (SPSS) software version 21 was also used to compare the degree of conflict in different villages. Data analysis consisted of descriptive and inferential statistics. Descriptive statistics (percentages and frequencies) were used to analyze the demographic and socioeconomic profiles of the respondents. A chi-square test was used to determine significant differences among villages regarding crop damage caused by primates and the protective techniques employed. Pearson’s correlation coefficients were calculated to assess the correlation between village proximity to the forest (independent variable) and both crop damage and livestock losses (dependent variables). All statistical tests were two-tailed, with 95% confidence intervals and a significance level (α) set at p = 0.05.

Abbreviations

FGDs

Focus group discussions

GPS

Global positioning system

TCCF

Tembaro community conserved forest

Author contributions

Meselech Anshebo, Aberham Megaze and Taye Dobamo, proposed the research idea and collected the data, organized the data in computer, did the analysis, interpretation, and identification, and wrote the manuscript. Aberham Megaze and Taye Dobamo revised the manuscript for scientific content and did the language check. All authors read and approved the final manuscript.

Funding

Not funding available.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethical approval

This study was approved by the Institutional Review Board (IRB) of the College of Sciences at Wolaita Sodo University, Ethiopia, adhering to their guidelines and regulations. We also obtained necessary permissions from the Tembaro District Administration before commencing the study. To ensure participants fully understood the study’s objectives, we explained the purpose in their native language. For adult participants, we prioritized informed consent. Before initiating each questionnaire or group discussion, we obtained verbal informed consent from every individual. We were meticulous in protecting their privacy by refraining from collecting any personally identifiable information. For participants under 18 years of age, we obtained informed consent from their parents or legal guardians. All participants, regardless of age, were informed about the study’s objectives, the strict confidentiality and anonymity of their data, and their absolute right to withdraw from the study at any time without facing any repercussions. This information was carefully explained to each participant before their involvement, and their informed consent was obtained. We diligently assessed the potential risks associated with the study and determined them to be insignificant. We ensured that participants’ responses would not have any personal, social, or political consequences. The IRB approved the proposed verbal consent procedure.

Consent for publication

This manuscript does not contain any identifiable individual data, and therefore, no further consent for publication is required.

Competing interests

The authors declare no competing interests.