Research

INTRODUCTION

Human-wildlife conflicts are increasingly becoming one of the major challenges affecting global conservation efforts. The problem is especially prominent in Africa and Asia, where many countries are host to a rich biological resources base, but are crippled with many challenges, among which include an ever-increasing human population (World Bank 2022; Suzuki 2019, World Bank blog, https://blogs.worldbank.org/opendata/worlds-population-will-continue-grow-and-will-reach-nearly-10-billion-2050), contention for space (Shaffer et al. 2019), struggles to balance economic development and nature conservation (El-Ashry 1993, Alexander and Whitehouse 2004, Cao et al. 2021), coupled with insufficient capacity to manage these resources (Hussain 2023). Large mammals like elephants (Loxodonta africana) have been shown to be at the heart of most of these conflicts (Naughton-Treves 1997, Quirin 2005, Wang et al. 2006a, Warren 2009), because their foraging behavior is characterized by expansive home-range needs (Karanth and Sunquist 2000, Fernando et al. 2008a, b), forcing them to compete directly with humans for limited space and resources (Goswami et al. 2014, Hoare 2015, Youldon et al. 2017, Shaffer et al. 2019).

Human-elephant conflicts are further heightened by human activities that encroach on elephant habitat (Leimgruber et al. 2003, Acharya et al. 2017, Di Minin et al. 2021, Gobush et al. 2021), such as farming either close to the boundaries of protected areas or along wildlife migration corridors (Wang et al. 2006b, Linkie et al. 2007, Strum 2010, Fungo 2011). Over the years, these interactions have resulted into either the decimation of the mammal’s populations or destruction of their habitats by humans (Hance 2013). For example, the population of African elephants is said to have declined from 3–5 million to between 470,000 and 690,000 over the last 100 years, while that of the Asian elephant declined from 100,000 to between 35,000 and 50,000 in the same period, mainly due to habitat loss and conflicts with humans (WWF 2002). In countries such as India, Kenya, and Sri Lanka, up to 100, 120, and 200 annual elephant mortalities have been reported, respectively, resulting from conflicts with humans (MOEF 2010, Santiapillai et al. 2010, Fernando and Pastorini 2011, Shaffer et al. 2019).

Human fatalities of varying proportions have also been reported across several countries (e.g., see Mariki et al. 2015, Köpke et al. 2024). With the projected further increase in human population (World Bank 2022; Suzuki 2019, World Bank blog), this will increasingly draw both elephants and humans closer to each other, and will potentially escalate the incidences of human-elephant conflicts (Leimgruber et al. 2003, Shannon et al. 2009, Das and Chattopadhyay 2011, Montez and Leng 2021). Therefore, unless a tangible solution is in place, this will continue to undermine elephant conservation efforts and may reciprocally result into substantial damage to human grown crops, threatening livelihoods, human life and property by elephants (Acharya et al. 2017, Shaffer et al. 2019, Eustace et al. 2022). However, addressing human-elephant conflicts also calls for the examination of evidence from a growing body of studies suggesting that these, often fatal, interactions are somehow triggered by the variation in the nutritional quality of food between agricultural crops and the vegetation in the mammals’ natural habitats (Sukumar 1990, Rode et al. 2006, Pokharel et al. 2019, Vogel et al. 2020; Vogel et al. 2019, unpublished manuscript). Generally, agricultural crops have been shown to have superior nutritional quality compared to the natural vegetation in the wild. This observation has been made in both Africa (e.g., Rode et al. 2006, Branco et al. 2019, Vogel et al. 2020; Vogel et al. 2019, unpublished manuscript) and Asia (e.g., Sukumar 1990, Pokharel et al. 2019), potentially suggesting that food nutrients composition (henceforth referred to food quality) is likely to be an important factor in driving the elephant’s optimal foraging behavior and patterns of habitat use, including the raiding of agricultural crops (Pretorius et al. 2012; Vogel et al. 2019, unpublished manuscript).

Establishing the key drivers of human-elephant conflicts is essential if the future of these animals and the livelihoods of affected communities are to be ascertained. Certainly, food quality is critical in defining the fitness of wild animals (Nyambe et al. 2017). For example, some studies have shown that poor food quality could reduce the growth rate of an organism or even cause failure to reproduce or premature death (Chapman and Reiss 1992, Bolen and Robison 1995). Many wild herbivores in particular have long been shown to be largely limited by the availability of protein in their diet (Bell 1969), especially during non-growing seasons (Schmidt and Snyman 2010).

Given that food quality of plants can be influenced by environmental parameters such as geographical location, climate, soil type, fertility, and moisture (Yang et al. 2018), it remains unclear as to what extent the food quality of agricultural crops will remain higher than that of wild vegetation. The influence of food quality could particularly be true in a country like Zambia, given that the raiding of human grown crops by elephants is more prominent in the growing season (Nyirenda et al. 2011), during which there is a comparable availability of food resources in both human farms and the elephant’s natural habitats (Clegg and O'Connor 2017). In this case, crop raiding is unlikely to be driven by the scarcity of food in the wild. Thus, studies on human-wildlife conflicts should not only focus on the location of agricultural fields away from the boundary of protected areas or wildlife migration corridors, but also on parameters of food quality and the role they could potentially play in driving elephants toward the raiding of crops. This may help generate information that could contribute toward finding a lasting solution to meaningfully reduce these conflicts.

Food nutrients such as protein, energy, ash, moisture, vitamin C, and fiber have been shown to be particularly critical in the diet of elephants. For example, elephants tend to select foods that are high in protein, energy, and ash, albeit wild plants have been shown to be lower, especially in protein and minerals than agricultural crops (Sukumar 1989, Osborn 1998). Thus, as Rode et al. (2006) suggested, these differences in nutrient composition could be used by elephants to raid agriculture crops to supplement deficient diets in the wild (McDowell 1997). Moisture content of the food determines its quality prior to consumption, especially in the context of texture, taste, appearance, and freshness (AOAC 1995, Isengard 2001, Nyambe et al. 2017). Thus, its presence enhances the palatability of animal food. And adequate dietary vitamin C has been shown to act as an immunomodulatory agent, a critical prophylaxis especially for the prevention of several viral infections (e.g., Elephant endotheliotropic herpesvirus hemorrhagic disease) that often affect elephants (Mousavi et al. 2019). Further, Carr and Maggini (2017) have shown that vitamin C is important for stimulating neutrophil migration to sites of infection, where it enhances phagocytosis, oxidant generation, and microbial killing, whilst simultaneously protecting the host tissue from excessive damage, i.e., by enhancing neutrophil apoptosis and clearance by macrophages, and decreasing neutrophil necrosis and NETosis. Thus, the presence of vitamin C in the diet is necessary for the immune system to mount and sustain an adequate response against pathogens (Carr and Maggini 2017, Colunga et al. 2020). Obviously, dietary fiber plays an important role in the health of animals (Adiotomre et al. 1990, Prosky 2000, Montagne et al. 2003, Cummings et al. 2004, DeVries 2004). However, the overly disproportionate increase in fiber composition has been shown to trigger a significant decrease in the quality of animal food in the wild, as it leads to low moisture, protein, energy, and vitamin C composition (Pei et al. 2001, Nyambe et al. 2017). Thus, a higher dietary fiber diet could potentially lead to deficiencies in these critical nutrients (Schmidt and Snyman 2010) and has been shown to reduce subjective appetite, energy intake, and body weight in some animals (Wanders et al. 2011).

The aim of this study is to increase understanding of the key drivers of human-elephant conflicts for enhanced conservation and ascertaining the livelihoods of affected or vulnerable communities. We tested if there is a difference in the incidences of crop raids by elephants at three distances (of farming) away from the boundaries of protected areas (namely, Kasanka National Park and the nearby wildlife migration corridor). Further, we compared the food quality of agricultural crops to the natural vegetation in the mammals’ habitat in and around Kasanka National Park in Zambia. We predicted that (1) the incidences of crop raids by elephants remained a major problem in our study area, potentially compromising the livelihoods of the majority of households and undermining elephant conservation efforts, (2) the escalation of human-elephant conflicts is not necessarily driven by the location of farming activities in proximity to either the boundary of protected areas or elephant migration corridors, as has been suggested by some studies, and (3) the food quality of agricultural crops is superior to that of the natural vegetation in the elephant’s habitats and this is likely to trigger the raiding of crops by elephants (McDowell 1997, Rode et al. 2006, Pretorius et al. 2012, Branco et al. 2019).

METHODS AND MATERIALS

Study area

The study was undertaken in and around Kasanka National Park, a protected area located in the Central province of Zambia (12° 30′S, 30° 14′E; Fig. 1). The park, which hosts a population of approximately 50 elephants, is completely surrounded by the Kafinda Game Management Area (KGMA). The KGMA (3491 km²) shares boarders with the Bangweulu wetlands and Lavushi Manda National Park in the north, the Muchinka Chiefdom in the south, Mpika district in the east, and an international boundary with the Democratic Republic of Congo in the west. Both Kasanka National Park and Lavushi Manda National Park are currently under public-private partnership management regimes. Moreover, the two national parks share an elephant migration corridor. Situated at an elevation of 1200 m (approximately) above sea level, the area occurs in a predictably high rainfall region (1000 and 1300 mm annually). The rainfall activities are largely triggered by the Congo air-mass that moves south into Zambia. The area is characterized by a series of highly connected natural forest habitats stretching far-beyond the boundaries of the park into human farming areas. The vegetation is predominantly Miombo woodland, the largest forest type in Zambia, characterized by thin, nutrient-poor, and acidic soils, overlaying an iron-rich lateritic rock (Kennedy et al. 2008). The Miombo is dominated by leguminous trees, notably those of the genera Brachystegia, Julbernardia, and Isoberlinia. Traces of Chipya woodland also occur on deep soils in a few places (Smith et al. 2000, Smith and Fisher 2001). The area is also characterized by patches of evergreen swamp forest and is host to abundant wetland habitats, including perennial rivers as well as seasonal, permanent, and floodplain wetlands and lakes, especially toward the Chambeshi and Luapula Rivers further north (Byng 2008, Kennedy et al. 2008). These wetland habitats are partly connected or linked to the Bangweulu swamps, one of the largest marshes in the world and internationally recognized as a Ramsar site (Fig. 1). The most important water bodies in the KGMA are the Luapula and the Lulimala rivers, both sharing boarders with the Bangweulu wetlands. The Luapula River is the main source of water for the Congo River (Kennedy et al. 2008). Thus, the area is an important catchment area, endowed with a rich freshwater resource base. Effectively, this suggests that access to naturally existing water may not be a nutritional challenge for elephants and other animals existing within this ecosystem.

The local people and livelihoods

Host to a few clusters of sparsely populated human settlements, the area is home to the Bemba-Lala speaking people of Chief Chitambo’s chiefdom (Chama et al. 2023). The Chief owns the land and he is the supreme leader of the people locally, but subject to the President of the Republic of Zambia. The traditional leadership is decentralized into village clusters. Each cluster is led by a Chilolo (i.e., Chief’s cabinet minister representing each cluster) while villages are led by Village heads. The area is one of the remotest and most socioeconomically isolated in the country. Small-scale agriculture is the main occupation and source of livelihoods in the area (Eriksen 2004, Kennedy et al. 2008, Chama et al. 2023). Most of these farming activities are undertaken near the boundaries of Kasanka National Park while some occur along the elephant migration corridor linking Kasanka National Park to Lavushi Manda National Park. The distance between the two national parks is approximately 70 km.

Field observations

Between November 2017 and March 2018 and November 2022 and January 2023, fieldwork was undertaken both inside and outside Kasanka National Park.

Monitoring elephants feeding inside Kasanka National Park

In the park, fieldwork was characterized by the observations of elephants during their feeding activities to record and determine their food plant species preferences (i.e., following Chiyo et al. 2005, Koirala et al. 2016). These observations, which lasted for a period of two weeks, were conducted at six different sites, namely (i) Fibwe hide, (ii) Kabwe, (iii) Kafubashi dambo, (iv) Kapabi swamp, (v) Lake Wasa II, and (vi) Songa (Fig. 1). The observations were dependent on the total time that elephants took feeding at each site (lasting between 15 and 40 mins) before they moved out. Observations were repeated at least twice when elephants were seen revisiting each of these sites. Three observers, (accompanied by one game scout) were involved in physically tracking and observing the elephants inside Kasanka National Park. We then collected vegetation samples from all plants on which the animals were seen feeding in each site.

Monitoring elephants feeding outside the park

We repeated the observations outside the park to determine the food preferences of elephants when raiding agricultural crops, i.e., with the aid of camera traps (TOGUARD 2" Mini Trail Camera 20MP 1080P), following Berezin et al. (2023) and Davis et al. (2023). Here, we used camera traps because elephants often raided agricultural crops in late night hours, when most farm owners would be fast asleep, making it practically challenging to observe the mammals. Camera traps have been widely used to either identify individuals (Karanth and Nichols 1998, Silver et al. 2004) or investigate behavior that could be challenging to study using direct observations (Griffiths and van Schaik 1993, Smit et al. 2019). Six camera traps (i.e., three traps at each distance [2 km, 10 km, 20 km] from the protected area boundary) were placed on different days in each of six villages sharing borders with protected areas. Among these (six villages) included three off the boundary of Kasanka National Park (namely, Chalilo, Mapepala, and Mpelembe; Fig. 1) and another three off the boundary of the elephant migration corridor (namely, Chiundaponde, Kasamba, and Musangashi villages; Fig. 1). We used 20 km as the maximum distance because both African and Asian elephants have been estimated to travel an average of 5–10 km each day when living in non-extreme environmental conditions (Rowell 2014). Thus, we only expected this average distance to move to 20 km or beyond in extreme conditions or when elephants are lacking sufficient supplies of resources (e.g., food, water, etc.; Viljoen 1989, Spinage 1994). At each distance across villages, camera traps were placed in three randomly selected crop fields for a period of 72 hours before moving to the next village. We then took note of all crops on which elephants were recorded feeding in each field.

Socioeconomic survey among communities living outside protected areas

We conducted a socioeconomic survey in each of the six villages with the aid of semi-structured questionnaires (Appendix 1), interviewing communities (n = 108 households, comparable to Amwata and Mganga 2014) located at different distances (namely, 2 km, 10 km, 20 km) away from the Kasanka National Park Boundary (KNPB) and the elephant migration corridor (EMC) between Kasanka National Park and Lavushi Manda National Park. In each village, at least 15 farmers or household heads (i.e., ≥ 5 individuals at each distance) were randomly selected and interviewed in this survey. We recruited and trained five community enumerators who helped in administering the questionnaires to all selected household heads across villages. The surveys involved collecting information on the communities’ main sources of livelihoods, incidences of crop raids (i.e., the number of times their fields have been raided), and the type of crops grown. Further (and most importantly), the survey also verified with the local people if the types of crops on which the elephants were captured feeding (by the camera traps) are the most targeted on their respective farms. Similarly, food samples were collected from all crops verified by communities as most targeted by elephant raids.

Handling and analysis of food samples

In both Kasanka National Park and outside, at least 1 kg of vegetation sample was cut and collected with the aid of pruning shears. The samples (n = 48) were packed in kaki paper envelopes and weighed using a digital scale calibrated in grams. They were then stored in a cool box while they were transported from the field to the food chemistry laboratory at the University of Zambia within 48 hours of collection. At the laboratory, collected vegetation samples were subjected to food quality (protein, energy, moisture, ash, vitamin C, and fiber) analysis. Protein was determined by means of the Kjeldahl method and calculated using a conversion factor of 6.25% (Kjeldahl 1883, Levey et al. 2000, Latimer 2016, Mæhre et al. 2018). Energy content (kJ/g) was determined by exposing food samples to combustion at high pressure in bomb calorimetry (Rodríguez-Añón and Proupin-Castineiras 2005). Ash content (% ash) was determined gravimetrically via dry ashing of vegetation samples (approx. 100 g each) in a muffle furnace at 600 °C for 14 hour (Liu 2019). Vitamin C was determined by means of a high-performance liquid chromatography (RP-HPLC) with ultraviolet detection (Gazdik et al. 2008, Mazurek and Włodarczyk-Stasiak 2023), while total dietary fiber was determined by the enzymatic-gravimetric method and liquid chromatography. Here, each vegetation sample was subjected to extended enzymatic digestion at 37 °C to simulate human intestinal digestion followed by gravimetric isolation (Garbelotti et al. 2003, McCleary et al. 2010, McLeary and McLoughlin 2022).

Statistical analysis

During data analysis, we first used linear mixed-effects model fit by REML to test if the incidences of crop raids differed at varying distances (i.e., 2 km, 10 km, and 20 km) away from either KNPB or the EMC. Here, we used incidences of crop raids against distance as fixed effects, while distance nested in village name/location were used as the random effects. Secondly, we used analysis of variance to test if food quality differed among plant types or species (i.e., a variety of food plants on which elephants fed, inclusive of both agricultural crops and the natural vegetation in Kasanka National Park). In this analysis, plant type was used as a predictor while food quality (protein, energy, moisture, ash, vitamin C, and fiber) was used as the response. We then used the post-hoc test with Tukey Honest Significant Difference to tell if and where differences occurred in food quality among individual species of food plants. All the above statistical analyses were performed in R Version 3.0.2 (R Development Core Team 2006, Pinheiro et al. 2012). Socioeconomic data, which was largely centered on assessing the livelihoods and incidences of crop raids by elephants were analyzed with the aid of Microsoft excel (2013) following Amwata and Mganga (2014).

RESULTS

Livelihoods of the local people^[1]

Of the 108 household heads that were interviewed, 44% and 56% were female and male, respectively. The main sources of livelihoods in the area include small-scale crop husbandly (i.e. practiced by 98% [n = 106] of the population). Several crops are grown, but the most common and socioeconomically important crops (selected based on frequency of appearance on the list of crops given by farmers), are grown either as single (monocropping) or part of a cluster of several other crops grown simultaneously (intercropping) by individual households. These crops include maize (Zea mays, henceforth referred to as Agr1 [grown by 98% of the population]), cassava (Manihot spp., Agr2 [94%]), pumpkins (Cucurbita spp., Agr3 [54%]), ground nuts (Arachis spp., Agr4 [67%]), and sweet potatoes (Ipomoea spp., Agr5 [27%]), finger millet (Eleusine spp., Agr6 [25%]), and beans (Phaseolus spp., Agr7 [16%]). The majority (87%, n = 94) of the household-heads interviewed grew most of these crops for both food production and income generation. The income generated from the sale of these crop products is critical for supporting the well-being of these households in the area.

Incidences of crop raids by elephants

The mean frequency of incidences of raids in the EMC (2 ± 1) were similar to those in areas surrounding the KNPB (4 ± 1) during the past five years (F (1, 4) = 1.235; p > 0.05). Seventy-five (69.4%) of the households interviewed experienced incidences of crop raids by elephants on their farms. Among the crops grown by the local people, maize (Agr1; mentioned by 82%, n = 89 of the respondents), cassava (Agr2; 71%, n = 77), and pumpkins (Agr3; 54%, n = 58), respectively, were the most targeted by elephants. The number of individuals in each herd of elephants that was seen raiding crops ranged from 11 to 27 across villages. In the park, elephants were repeatedly seen feeding on four natural vegetation species, namely White thorn (Senegalia [Acacia] polyacantha; henceforth referred to as Wld1; number of elephant feeding visits [n = 14]), Rice grass (Oryzopsis spp.; Wld2; n = 11), Common reed (Phragmites australis; Wld3; n = 5), and Guinea grass (Megathyrsus maximus; Wld4; n = 13). Rice grass (Wld2) plants were particularly highly sought after by the mammals, albeit they could only be found in a couple of small clusters of swamps (Kafubashi and Kapabi areas) located in the middle of Kasanka National Park (Fig. 1).

Effects of distance of farming activities on incidences of crop raid by elephants

No difference occurred in incidences of crop raids across distances of farming activities away from either the KNPB or the EMC (F (2,102) = 1.80; p > 0.05; Fig. 2). Of all the elephant crop raid incidences recorded in the area (69.4%, see above), 29 (26.89%), 30 (27.78%), and 16 (14.81%) occurred within a radius of 2 km, 10 km, and 20 km, respectively, away from either the KNPB or EMC. Of the 26.89% incidences within the 2 km radius, 16 (55%) occurred in the KNPB while 13 (45%) occurred in the EMC areas. Of the 27.78% incidences that occurred in the 10 km radius, 18 (60%) occurred in the KNPB while 12 (40%) occurred in the EMC areas. And of the 14.81% that occurred in the 20 km radius, 9 (56%) occurred in the KNPB while 7 (44%) occurred in the EMC areas.

Food quality across plant types

The mean protein composition differed significantly across plant types (F (6, 41) = 33.39; p <0.0001; Fig. 3a). It was higher (per 100 g wet weight) for maize (Agr1; 4.02 ± 0.58%) than cassava (Agr2; 3.02 ± 0.27%), pumpkin (Agr3; 1.94 ± 0.51%), white thorn (Wld1; 1.61 ± 0.49%), rice grass (Wld2; 2.98 ± 0.17%), common reed (Wld3; 1.42 ± 0.27%), and guinea grass (Wld4; 1.64 ± 0.46%). Protein composition for cassava (Agr2) remained similar to rice grass (Wld2; p > 0.05), both of which were, however, significantly higher than the rest of the plants.

The mean total ash content (per 100 g dry weight) differed significantly across food plant types (F [6, 41] = 21.12; p < 0.0001; Fig. 3b). Generally, it was higher among wild plants than agricultural crops. For example, ash content for white thorn (Wld1; 3.8 ± 0.94%) was higher than maize (Agr1; 1.57 ± 0.89%), cassava (Agr2; 1.43 ± 0.12%), and pumpkin (Agr3; 1.00 ± 0.27%). Similarly, the mean total ash content for rice grass (Wld2; 3.54 ± 0.44), common reed (Wld3; 4.12 ± 0.27%), and guinea grass (Wld4; 3.11 ± 0.40%) were each significantly higher than maize, cassava, and pumpkin. No difference occurred in ash content either among agricultural crops or among wild plants (p > 0.05).

The mean moisture content (per 100 g wet weight) differed significantly across food plants (F [6, 41] = 41.29; p < 0.0001; Fig. 3c). It was higher for pumpkin (Agr3; 86.75 ± 3.26%) than maize (Agr1; 45.02 ± 10.81%), cassava (Agr2; 58.62 ± 2.35%), white thorn (Wld1; 47.42 ± 6.97%), rice grass (Wld2; 59.08 ± 8.91%), common reed (Wld3; 58.74 ± 5.60%), and guinea grass (Wld4; 59.98 ± 4.34%). No difference in moisture content occurred among the rest of the food plants (p > 0.05).

Although the mean fiber content (per 100 g dry weight) for white thorn (Wld1; 3.25 ± 0.51%) and guinea grass (Wld4; 2.77 ± 0.32%) remained similar, both of them were generally significantly higher than the rest of the food plants, namely maize (Agr1; 1.64 ± 0.29%), cassava (Agr2; 1.88 ± 0.12%), pumpkin (Agr3; 1.72 ± 0.45%), rice grass (Wld2; 0.96 ± 0.15%), and common reed (Wld3; 1.76 ± 0.13%; F [6, 41] = 15.89; p < 0.0001; Fig. 3d). Besides being lower than white thorn and guinea grass, the fiber content for rice grass was also significantly lower than maize, cassava, pumpkin, and common reed.

The mean energy content (per 100 g wet weight) differed significantly across food plant types (F [6, 41] = 57.66; p < 0.0001; Fig. 3e). It was higher for cassava (Agr2; 434.67 ± 26.31 KJ/g) than maize (Agr1; 212.32 ± 50.02 KJ/g), pumpkin (Agr3; 41.37 ± 14.78 KJ/g), white thorn (Wld1; 203.94 ± 68.26 KJ/g), rice grass (Wld2; 139.61 ± 21.46 KJ/g), common reed (Wld3; 146.39 ± 23.07 KJ/g), and guinea grass (Wld4; 136.42 ± 15.53 KJ/g). Although lower than cassava, the energy content for maize was significantly higher than both pumpkin and guinea grass. In fact, energy content for pumpkin was also lower than each of the remaining plant types (p < 0.05), i.e., besides cassava. However, no differences in energy content occurred among the rest of the food plant types (p > 0.05).

The mean vitamin C content (per 100 g wet weight) differed significantly across food plant types (F [6, 41] = 27.0; p < 0.0001; Fig. 3f). It was higher for white thorn (Wld1; 113.74 ± 3.96 mg/g) than maize (Agr1; 71.37 ± 20.03 mg/g), cassava (Agr2; 0.77 ± 0.22 mg/g), pumpkin (Agr3; 82.35 ± 14.39 mg/g), and common reed (Wld3; 0.87 ± 0.06 mg/g). However, mean vitamin C content for white thorn remained similar with rice grass (Wld2; 92.65 ± 4.58) and guinea grass (Wld4; 92.30 ± 11.70) (p > 0.05).

DISCUSSION

Our results show that human-elephant conflicts remain a major problem in the study area, as nearly 70% of the households interviewed experienced several incidences of crop raids by elephants on their farms, which agrees with our first prediction. Secondly, the distance of farming activities away from the boundary of protected areas had no effect on the incidences of crop raids by elephants, as elephants raided all farms irrespective of how far they were located relative to the boundary of protected areas, and this is congruent with our second prediction. And although natural vegetation in the park had higher composition of ash, vitamin C, and fiber, our results show that it had comparatively lower composition of protein, energy, and moisture compared to agricultural crops, suggesting that the diet of elephants in the wild had a nutritional deficit in these nutrients. Thus, the elephants’ foraging decisions to raid agricultural crops could be largely driven by the need to increase their uptake of a diet rich in these elements, i.e., in line with our third prediction.

Incidences of crop raids and livelihoods of the local people

Clearly, human-elephant conflicts remain a major problem in the study area, as the majority of farmers still experienced several incidences of crop raids on their farms. Although several crops are grown, the major ones in the context of driving crop raids by elephants and sustaining the well-being of communities including maize, cassava, and pumpkins. The majority of these crops are predominantly grown for both income generation and as food sources by the local communities. The income generated from the sale of these crop products is the only source of income for the majority of households in the area, suggesting that any incidences of crop raids on the community’s fields by elephants could have significantly negative impacts on their livelihoods.

Generally, communities that are dependent upon a single livelihood strategy have been shown to be particularly vulnerable in human wildlife conflict zones because of a lack of alternative income strategies (Dickman 2010, Shaffer et al. 2019, Anoop et al. 2023). For example, human-elephant conflicts were found to reduce household incomes among subsistence farmers by at least 35% in Kenya (Amwata and Mganga 2014), whereas in Tanzania, annual crop damage was equated to two months of household food loss, and reduced household cash income by 1.3% (Kaswamila et al. 2007). Similarly, elephant related conflicts cost communal farmers around US$1 million a year in Namibia, while in some Nepalese communities it can be up to around a quarter of the household incomes of poor farming families (WWF 2008). These and many other risks potentially explain why conflicts with elephants have driven many subsistence farmers (in both Africa and Asia) to either quit their settlements or stop growing food crops that attracts elephants to their farms (Dickman 2010, Barua et al. 2013, Amwata and Mganga 2014, Anoop et al. 2023). However, quitting or relocation of settlements often comes with costs, as farmers have to find or pay for new land to resettle and potentially construct new villages. Thus, unless locals are supported to venture into alternative income-generating activities (e.g., curio shops, village ecotourism, etc.), human-elephant conflicts can lead to socioeconomic deprivation and destitution among the affected communities, i.e., if left unaddressed (Dickman 2010, Barua et al. 2013). Worse still, these conflicts can compromise human appreciation for conservation of local biodiversity and undermine the potential especially for human-elephant coexistence (Hedges and Gunaryadi 2010, Graham et al. 2010, Barua et al. 2013, Anoop et al. 2023). Thus, for as long as the incidences of crop raids by elephants continue to occur in our study area, both the livelihoods (especially food security and household incomes) of the local people and the conservation of the elephants will remain under threat.

Incidences of crop raids across distance of farming from protected areas

Our results show that distance of farming activities away from either KNPB or EMC had no effect on the incidences of crop raids by elephants. These findings are in contrast to those from several previous studies (e.g., Andersson et al. 2013, Parker et al. 2014, Matseketsa et al. 2019) that have shown human-wildlife conflicts to have particularly been prominent among communities that either live or undertook their farming activities close to the boundaries of protected areas. In fact, other studies suggest that the incidences of crop raids by elephants were limited to within 4 to 6 km from the edge of protected areas (Gubbi 2012, Guerbois et al. 2012). However, the fact that these incidences remained similar across distances (i.e., up to 20 km) in our study area raises new questions about the correct radius of high-risk for the occurrence of human-elephant conflicts. On the one hand, our findings suggest that the maximum (20 km) distance threshold used in this study may not have been adequate to detect the effect of distance of farming activities (from the boundaries of protected areas) on crop raids by elephants. For example, elephants can walk up to 195 km per day (Elephants for Africa 2016), albeit they often only average between 5 and 10 km in non-extreme environmental conditions (Rowell 2014) and over 20 km in extreme conditions (i.e., on a daily basis; Spinage 1994, Viljoen 1989, Sukumar 2003, Leighty et al. 2009, Chiyo et al. 2014). Their movements are usually driven by a variety of factors, among which include the need for social groupings and also adjusting their foraging range relative to the distribution and availability of resources (McKay 1973, Whitehouse and Schoeman 2003, Slotow and van Dyk 2004, Leighty et al. 2009). Therefore, the 20 km (maximum) used in this study may fall within the normal daily threshold travelled by the mammals to forage for food resources. Thus, crop raid incidences were expected to remain unchanged within this distance.

On the other hand, our findings could suggest that the distance of farming activities from the boundaries of protected areas may not necessarily be the key driver of human wildlife conflicts in our study area. Instead, other parameters, especially food quality (Osei-Owusu and Bakker 2008) may be responsible, as has been suggested by previous research (Nyhus 2016). In this case, the findings of the current research agree with our prediction that the escalation of human wildlife conflicts was not necessarily driven by the farms’ location relative to the boundary of protected areas, as has been suggested by previous studies (Andersson et al. 2013, Parker et al. 2014, Matseketsa et al. 2019). This may especially be true in our study area, given that it is a game management area that is host to a few clusters of sparsely populated human settlements and a series of highly connected natural forest habitats stretching far beyond the boundaries of protected areas into human farming areas. Potentially, these conditions provide a conducive environment for elephants to traverse and raid nutritious agricultural crops far from the edges of the protected areas. And the fact that these incidences remained similar between KNPB and EMC could be explained by the fact that farming activities by communities in both areas were centered on the growing of nutritionally similar combinations of crops. Thus, there was nothing unique between the two areas to trigger a different foraging behavior from elephants. Overall, our findings suggest that the distance of farming from the edge of protected areas is unlikely to affect crop raid incidences by elephants, as long as there is a connected forest habitat transcending the boundaries of protected areas into human farming areas and that the crops grown on those farms contain nutrients that are either lacking or inadequate in their natural habitats.

Food quality and crop raids by elephants

Although natural plants from the national park contained higher composition of ash, vitamin C and fiber, our results show that they were largely deficient of protein, energy, and moisture, i.e., compared to agricultural crops. Generally, these results seem to suggest that although elephants are able to obtain adequate supplies of minerals, vitamin C, and fiber in the natural habitat, there is a nutritional deficit where access to especially protein and energy was concerned. Thus, it is highly likely that the mammals’ foraging decisions to raid agricultural crops could be largely driven by the need to increase their uptake of a diet rich in these elements. Our findings are similar to those from research suggesting that nutrient deficiency in their natural habitats could be responsible for explaining the elephants’ dietary choices, among which include the behavior of consuming human grown crops (Sukumar 1990, Rode et al. 2006, Pretorius et al. 2012, Branco et al. 2019, Pokharel et al. 2019, Vogel et al. 2020; Vogel et al. 2019, unpublished manuscript).

Although lower in composition among natural plants, protein, energy, and moisture are very critical in defining the survival of wild animals (Barboza et al. 2009). For example, besides being an important energy source (6 kcal/g; Robbins 1983), proteins are polypeptides of amino acids required for building of body tissues, albeit only ruminants (among herbivores) can synthesize a variety of amino acids with the help of symbiotic microbes in their rumen. Given that elephants are non-ruminant herbivores, they are unable to synthesize most of these amino acids. Thus, they need the presence of both qualitative and quantitative protein in their diet to increase their access to all essential amino acids (Branco et al. 2019). Although natural plants such as rice grass (2.98 ± 0.17g) has relatively comparable protein composition to agricultural crops like cassava (3.02 ± 0.27g), elephants still left the park to raid the latter outside the park. This could be explained by the assumption that a combination of both maize and cassava, which are often grown in abundance by the local people, provided a far much high protein composition than what the mammals could obtain from rice grass in the wild. Our findings agree with previous research that found cultivated crops to generally provide significantly more protein than wild vegetation (e.g., Sukumar 1990, Branco et al. 2019), ultimately suggesting that feeding on these crops provided the elephants with substantially more protein. In this case, crop raiding by elephants was an extension of their optimal foraging strategy.

Alternatively, research has shown that several wild plants contain secondary compounds such as tannins that can impact negatively on the digestibility of protein (Barboza et al. 2009). Tannins bind to protein, rendering it unavailable for digestion (Clegg 2008). Therefore, it is highly likely that elephants could be driven to raid agricultural crops to avoid feeding on protein-rich wild plants because they contain secondary compounds, such as condensed tannins that act as chemical deterrents, as they negatively affect the ability of an animal to digest nutrients (Robbins et al. 1987). Elephants have also been shown to generally have poor digestive abilities (Greene et al. 2019). In African elephants, the digestion efficiency can be as low as 22% depending on forage quality (Clauss et al. 2003, Pendelbury et al. 2005, Greene et al. 2019). Given the potential presence of digestion inhibiting chemicals and toxins in their natural forage, elephants strategize their foraging behavior toward consuming a wide variety of plants to either meet their daily nutritional requirements or dilute the chemicals and toxins in some of the plants they feed upon to maximize protein digestion. Thus, this could partly explain their behavior to raid agricultural crops.

Like protein, elephants have a high absolute energy requirement (Branco et al. 2019). The high energy requirement is driven largely by their large body sizes (Demment and van Soest 1985) and shorter gastro-intestinal tracts (GITs; i.e., in relation to their body sizes; Clauss et al. 2003, Clauss et al. 2005a, b), albeit the widths of their GIT are larger than expected (Clauss et al. 2003, Clauss et al. 2005a). These phenological attributes have been shown to effectively result in faster food passage rates, albeit with lower nutritional gains (Clauss et al. 2003, Clauss et al. 2005b, Muller et al. 2013). Clearly, however, elephants still constantly need abundant replenishment of energy to grow, reproduce, sustain metabolic demands, maintain their structures, and respond to changes in the environment (Benedict and Lee 1938, Dierenfeld 1994, Brown et al. 2004, Pretorius et al. 2012). Generally, they have a mixed diet (Cerling et al. 1999), which fluctuates across seasons (Codron et al. 2006, Owen-Smith and Chafota 2012, Shrader et al. 2012). Nonetheless, their high absolute energy requirements have been shown to drive the mammals to select plants of higher quality and digestibility so that energy intake can be maximized (Demment and van Soest 1985, Pretorius et al. 2012). Therefore, elephants may include plant species that are both most abundant and have the highest metabolizable energy value in their diet as in the case of some agricultural crops in our study area.

Our findings are consistent with recent studies on patterns of crop raids by elephants in Africa that found agricultural crops to have exceedingly higher digestible energy than natural-forage diets (Nyhus 2016, Branco et al. 2019). Thus, elephants in our study area likely benefited considerably from crop raiding because of the significantly higher amount of digestible energy present in crops relative to the natural vegetation in protected areas. The above observations further agree with findings from other studies (Simpson and Raubenheimer 1993, Raubenheimer and Simpson 1997, 1999) suggesting that animals could adjust the amounts of food ingested from different food sources to keep the balance between different nutrients and consistently reach their daily nutrient requirements (Pretorius et al. 2012, Branco et al. 2019). Thus, this may explain the observed foraging decisions made by elephants to target and raid agricultural crops such as maize and cassava (outside their natural ecosystem), which are richer in protein and energy, respectively, than wild plants.

Results from this study also show that pumpkin had a significantly higher moisture content than was found in wild plants. Moisture is arguably the most important nutrient in animal diets, as it is the medium through which many physiological process (e.g., metabolic processes, chemical reactions, eliminating waste from the body, etc.) are facilitated. Besides, it regulates temperature and this is particularly critical for large bodied and high-water consuming animals such as elephants (Barboza et al. 2009, Pretorius et al. 2012, Pontzer et al. 2020). Research has shown that the need for moisture or water in animals increases when they forage on a high-protein and high-energy diet, driven largely by a corresponding increase in metabolic waste, urinary excretion of urea, and heat produced by metabolism (Cherian 2020). Interestingly, our results show that besides pumpkins, elephants also targeted both maize and cassava that had significantly higher protein and energy contents, respectively, i.e., among the agricultural crops that they raided. Potentially, this suggests that the mammals feed on pumpkin to ensure that their metabolic processes were adequately supplied with the moisture to effectively break down a high protein and energy diet during crop raid.

Generally, water intake in animals is also expected to increase with higher environmental temperatures and increased physical activity because of water lost through evaporative loss (Barboza et al. 2009, Dunkin et al. 2013, Pontzer et al. 2020). Essentially, water or moisture uptake should not really be a problem for elephants because their natural habitat (Kasanka National Park) has abundant naturally occurring perennial water bodies. Besides, crop raid incidences predominantly occur during the growing season, when most of these water bodies and the vegetation in the park are replenished from high annual mean precipitation (> 1300 mm) in the area. However, as elephants move several kilometers to raid agricultural crops, they possibly lose a lot of water, because most of these crops are located on farms outside protected areas and far from water bodies. Thus, they depend on moisture-rich crops such as pumpkins to compensate for their body water losses and to therefore maintain all water-related physiological functions.

CONCLUSIONS

Generally, human-elephant conflicts still remain a major challenge affecting a predominantly peasant farming-dependent community within Kafinda Game Management Area in Zambia. These conflicts are largely driven by the disparities in the quality of food in the elephant’s natural habitat, seemingly pushing them to raid highly nutritious agricultural crops in our study area. Broadly, these findings suggest that elephants can raid human grown crops, irrespective of the distance the farmland is located away from the boundaries of protected areas, provided such crops contain nutrients that are either lacking or inadequate in their natural habitats. Thus, human-elephant conflicts are likely to continue for as long as humans continue to grow crops whose food quality is higher than wild vegetation.

These results do not necessarily support the practice of farming activities along or closer to the boundaries of protected areas by local farmers, as doing so undermines the integrity of these ecosystems, to the detriment of the wildlife species they host. Thus, farming activities should be undertaken outside the buffer zones (i.e., 10 km immediately after the boundary) of protected areas to promote both elephant conservation and the preservation of livelihoods for the local people. And given that most of the affected communities are farmers whose livelihoods are primarily derived from the raided crops, allowing this problem to continue is detrimental to the survival of these people. Therefore, policy makers should work in collaboration with researchers to identify appropriate measures to address this problem, especially in the face of these findings. Stakeholders (e.g., government, conservation, and charity NGOs, etc.) should especially support and work in collaboration with local communities to identify and introduce crops and livelihood strategies that are not susceptible to attacks by elephants. This will not only enhance the resilience of livelihoods and safety of human life, but also contribute toward the conservation of elephants. Further, we encourage more studies to test the effect of food quality of agricultural crops in driving crop raids by elephants to increase our understanding of the human-elephant conflicts dynamics and thereby be in a stronger position to address this problem for the benefit of both conservation and local communities.

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^[1] All agricultural crops have been named with the letters Agr. (followed by a species’ unique number) while wild plants are named with the letters Wld. (followed by a species’ unique number).

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