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. 2026 Mar 23;88(3):e70141. doi: 10.1002/ajp.70141

The Crop Feeding Behavior of Rhesus Macaques in a Forest‐Farm Mosaic in Central Nepal: Implications for Human–Wildlife Coexistence

Sabina Koirala 1,2,3,✉, Bijaya Adhikari 4, Devi Rai 5, Hem Bahadur Katuwal 6, Weikang Yang 1,2,3, Ming Li 7, Paul A Garber 8,9
PMCID: PMC13006775  PMID: 41866931

ABSTRACT

Human‐driven habitat change is forcing nonhuman primates to exploit anthropogenic landscapes, resulting in primate crop feeding, reduced farmer food security, and human–primate conflict. Here, we investigate the crop feeding behavior of a wild group of rhesus macaques in a farm‐forest mosaic in central Nepal. Macaque behavioral data were collected over 12 months using scan‐ and all‐occurrence sampling methods, along with monitoring crop availability. We evaluated the relationship between macaque feeding behavior, crop type, availability, damage, and farmers' actions to reduce crop damage. We found that ~49% of the macaque's annual diet was composed of cultivated crops, with three crops—maize, oranges, and potatoes—accounting for ~52% of macaque crop feeding time. There was a significant positive association between monthly crop productivity and macaque feeding time on these crops. Local farmers attempted to deter macaque crop feeding 83.1% of the time, but their efforts failed to reduce crop damage. During the maize cultivation season, total maize damage caused by macaques was estimated at 1647 kg (~50 kg/ha) of dry kernels, resulting in a loss of 1.5% of total maize yield per hectare. Thus, macaque crop feeding had only a limited effect on farmer food security. We propose a set of practical and low‐cost actions that can be taken to continue the current balance between the dietary needs of the rhesus macaques and the economic needs of farm families in the local community.

Keywords: anthropogenic habitat disturbance, crop feeding, human–primate conflict, Macaca mulatta, primate conservation

Summary

  • Cultivated crops, principally maize, potatoes, and oranges, comprise 49% of the annual feeding time of wild rhesus macaques in Nepal.

  • Human efforts to protect their domesticated crops from rhesus macaques were not effective in reducing the duration of crop raiding events or the extent of crop damage caused by the macaques.

  • Estimated annual maize damage by the rhesus macaques accounted for only 1.5% of crop yield and therefore had only a minimal impact on farmer food security and economic well‐being.

Rhesus macaques in Nepal fed on crops for a longer duration and caused more crop damage when the foraging party was larger. Farmer interventions failed to reduce the duration of crop feeding and the amount of crop damage.

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1. Introduction

Human‐driven modifications of natural landscapes have led to a significant increase in the number of wildlife species, including nonhuman primates (hereafter primates), inhabiting anthropogenic landscapes (Estrada et al. 2012; Hockings et al. 2012). These environments typically consist of a mixture of altered habitats, such as urban settings, agricultural fields, farm‐forest mosaics, regenerating forests, and agroforestry systems, alongside fragments of remaining natural habitat (Estrada et al. 2012; Hockings et al. 2012; McKinney 2015). As suitable habitats for primates decline in these altered landscapes, prosimians, tarsiers, monkeys, and apes increasingly forage for cultivars planted by humans, resulting in human–animal conflict and the potential for pathogen exchange (Altmann et al. 1993; Anand et al. 2021; Corrêa et al. 2018; Kaplan et al. 2011; Koirala et al. 2017; Strum 2010). In this regard, Hill (2018) identified at least 114 primate species or subspecies across mainland Africa, Asia, Madagascar, and the American tropics that are reported to include crops as an integral part of their diet. Increasingly, local farmers retaliate against wildlife and may kill, injure, or harass primates that enter their fields. (Anand et al. 2018). For example, a study by McLennan et al. (2012) found that 10 endangered eastern chimpanzees (Pan troglodytes schweinfurthii) in Uganda's Budongo Forest were severely injured or killed in steel traps set by farmers to deter crop feeding. In Ethiopia, 12% of local farmers (n = 35 of 300 farmers) in the vicinity of Borena‐Sayint National Park reported that they had killed at least one baboon (Papio hamadryas) in retaliation for crop feeding (Ibrahim et al. 2023). Similarly, in the buffer area around Makalu‐Barun National Park, Nepal, 35 of 38 households indicated that they have experienced considerable crop loss due to crop feeding by Assamese macaques (Macaca assemensis) (Ghimirey et al. 2018). In response, over 5 years, eight farmers were reported to have killed some 100 macaques (Ghimirey et al. 2018).

Primate crop feeding is shaped by foraging trade‐offs affected by the size, nutrient content, and availability of natural and cultivated foods. In agricultural mosaics, cultivated foods often function as preferred feeding sites because they are clumped, predictable, nutritious, and relatively easy to process (Hill 2017, 2018). For example, cacao pulp (Theobroma cacao) consumed by Tonkean macaques (Macaca tonkeana) is lower in fiber (5.75% vs. 34.42%) and higher in digestible carbohydrates (87.34% vs. 40.18%) than many wild fruits, resulting in a 20% increase in metabolizable energy (3.79 kcal/g vs. 3.15 kcal/g) (Riley et al. 2013). In the case of Buton macaques (Macaca ochreata brunnescens), when available, storage organ crops such as sweet potatoes (Ipomoea batatas), cassava (Manihot esculenta), and maize (Zea mays), which were more abundant and spatially concentrated, were consumed more often than natural foods (Priston et al. 2012). Similarly, under conditions in which farmers multicrop and plant several cultivars in the same or nearby fields, certain cultivars may be favored over others. In the case of rhesus macaques (Macaca mulatta) in Nepal, foragers were found to select maize over rice (Oryza sativa) when both crops were available. Despite rice having higher caloric content (360 kcal per 100 g compared to 86 kcal per 100 g for maize), it is possible that macaques preferred maize because they can process larger cobs more efficiently, potentially allowing them to consume more calories in less time (Koirala et al. 2021).

Across a range of studies, the extent of primate crop damage has been shown to be positively affected by crop feeding bout duration, foraging party size, and proximity to forest edges, whereas actions taken by farmers to protect their fields contribute to a reduction in crop damage (Wallace and Hill 2012; Koirala et al. 2021; Neves et al. 2024). For example, in Nepal, rhesus macaque crop damage intensity was significantly lower when farmers collectively guarded fields, highlighting the importance of coordinated deterrence (Koirala et al. 2021). In the case of Barbary macaques (Macaca sylvanus) in Morocco, crop damage decreased when farmers used pre‐emptive deterrence strategies such as dogs or slingshots and encountered the macaques prior to arriving in their fields, compared to confrontations that occurred after the macaques had entered their fields (Neves et al. 2024). Guarding remains a widely used and effective deterrent, especially when it involves multiple farmers and is sustained during periods of peak crop production (Hill 2017; Koirala et al. 2021; Tsuji and Ilham 2021).

Primate crop feeding often results in significant losses in annual farmer income (Hill 2017, 2018; Ibrahim et al. 2023). For example, Mona monkeys (Cercopithecus mona) in Nigeria feed on crops such as cocoa, cassava, and maize. A recent study found that this resulted in economic losses per farmer of 78,398 Nigerian Naira (₦) (equivalent to approximately 55 USD per year—based on the exchange rate as of May 14, 2025) or 19% of smallholder farmer income (Farinloye et al. 2024). In Ethiopia, yield losses due to maize crop feeding by olive baboons (Papio anubis) and grivet monkeys (Chlorocebus aethiops) averaged 271.6 kg per hectare (Deneke et al. 2024), leading to a 13.6% reduction in the average annual income per farmer household (1103 Ethiopian Birr). Similarly, Ghimirey et al. (2018) reported an average yearly loss of 602 USD per household (Nepali Rupees [NRs.] 60,199.74) in eastern Nepal in response to the crop feeding activities of Assamese macaques. However, the economic cost of primate crop feeding can vary considerably across nearby regions. In western Nepal, the economic damage caused per household by rhesus macaques was reported to be approximately one‐third (146.5 USD or NRs. 20,000 per year) of that reported for rhesus macaques in eastern Nepal (Sharma and Acharya 2018). In addition, farmers and their families may be forced to devote considerable amounts of time, effort, and money into protecting their crops (i.e., vigilance, hiring guards, and constructing fences or barricades) that could otherwise be invested in other household activities (Hill 2018). Given that many primate populations range outside of protected areas and increasingly encounter human‐modified landscapes, a detailed understanding of primate crop feeding behavior and local farmers' responses to crop losses is essential for developing effective conservation solutions that limit opportunities for human–primate conflict (Hill 2018; Koh and Gardner 2010; Meijaard 2016; Sodhi et al. 2010).

In the current study, we present data on the crop feeding behavior of rhesus macaques inhabiting a forest‐farm mosaic in central Nepal. Rhesus macaques have the widest geographical distribution of any of the currently recognized nonhuman primate species (Cooper et al. 2022; Singh et al. 2024), are synanthropic with humans across disturbed landscapes, and are reported to commonly come into conflict with local human communities (Anand et al. 2021; Koirala et al. 2022). They are listed by the IUCN as Least Concern (Singh et al. 2024). And, although in some cultures rhesus macaques have traditionally been regarded as sacred, particularly in and around temple sites where religious sentiments offer them a degree of protection (Ogawa et al. 2023), with the increasing frequency and intensity of human–macaque conflict, local tolerance towards these primates appears to be diminishing (Anand et al. 2018). Across many parts of their range, rhesus macaques are now considered a pest species because they exploit agricultural fields, garbage dumps, urban centers, temples, and enter houses to acquire food (Hill 2005; Koirala et al. 2021, 2022; Ogawa et al. 2023). In Nepal, rhesus macaques are listed among the top 10 crop feeding species and have been classified as harmful wildlife (DNPWC & CODEFUND 2018). Given the limited research on rhesus macaques in Nepal, however, it has been difficult to implement effective strategies for mitigating human–macaque conflict (HMC) and promoting macaque conservation. This study aims to collect and analyze data on rhesus macaque crop feeding behavior in order to identify an effective set of strategies to minimize macaque crop feeding damage and promote long‐term coexistence between humans and macaques in rural Nepalese communities. To accomplish this, we test the following hypotheses:

Hypothesis 1

Rhesus macaques consumed a greater diversity of crops during months in which crop diversity was higher.

Hypothesis 2

Rhesus macaques feed on individual crops (i.e., maize, potatoes, rice, mustard, and oranges) based on their relative monthly productivity.

Hypothesis 3

The duration of macaque crop feeding events is positively correlated with crop productivity.

Hypothesis 4

The duration of macaque crop feeding events is positively correlated with the number of macaque co‐feeders.

Hypothesis 5

The duration of macaque crop feeding events is negatively influenced by the actions of humans and their dogs in attempting to deter the macaques from their fields and protect their crops.

Hypothesis 6

The amount of crop damage caused by macaques is positively associated with the duration of crop feeding events.

In addition, we estimated the extent to which macaque crop feeding affected farmers' income and food security.

2. Methods

2.1. Study Area

The study was conducted in the Panauti Municipality, Kavrepalanchok district, Nepal (85.3879–85.5688 longitude, and 27.5265–27.6381 latitude). The site covers an area of 11,812 ha and has a human population totaling 56,329 inhabitants (Panauti Municapility, GoN 2024). The municipality is dominated by needle‐leaved forest (4787 ha), broad‐leaved forest (4020 ha), agricultural fields, and human settlements (2921 ha) (ICIMOD 2013). Agriculture and livestock farming are the major sources of income for the local economy (Panauti Municapility, GoN 2024). Maize, potatoes, Asian rice, mustard, and oranges are the primary agricultural products grown. Potatoes and oranges are cultivated principally as a cash crop, while maize, mustard, and rice are mainly cultivated for self‐consumption. The study district ranks first in terms of potato production in Nepal (Banjade et al. 2019).

Our study area is characterized by an annual cropping pattern based on rice production in irrigated fields during May–October and maize production in rain‐fed fields during April–September (Joshi et al. 2021). Although potato production is important in the area (potatoes are harvested in the months of April and May and again in November and December), it does not affect the timing of rice or maize production. The area is characterized by four seasons. Spring is from March to May, summer is from June to September, autumn is from October to November, and winter is from December to February.

2.2. Ethics Statement

The study was purely observational and noninvasive. The macaques were observed from a distance of approximately 5–20 m, and no animals were captured, handled, or experimentally manipulated. During both the habituation and data collection periods, we followed the American Society of Primatologists' Code of Best Practices for Field Primatology and adhered to the American Society of Primatologists principles for the ethical treatment of both human and nonhuman primates. The research adhered to relevant national and institutional animal care guidelines for nonhuman primates in Nepal.

Human data were obtained through interviews with 12 adult individuals. All individuals agreed to be interviewed, and no personal identifiers or sensitive information were collected. Participation was voluntary. Accordingly, a formal human‐subjects ethics review was not required.

2.3. Data Collection

A single group of 52 rhesus macaques, the “OM Group”, inhabited our study area. Prior to data collection (February–May 2019), we habituated our study group using a team of three trained observers. We further identified our sampling area to monitor annual crop productivity. For additional details concerning the study group, habituation process, and sampling area identification, please refer to Supplementary Text 1.

Approximately 45% of the sampling area (286.2 ha) was located within the annual 636 ha home range of the macaque study group (Figure 1). Our sampling area represents 63.9% of the farmland located within the macaque's home range. We randomly selected 160 sample farm plots, each measuring 15 × 15 m (225 m2) and covering a total of 3.6 ha for analysis (Figure 1).

Figure 1.

Figure 1

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Study area, sampling area, and sample plots used to monitor annual crop productivity. The sampling area covered 44.8% of the annual home range of our macaque study group, and was identified based on field observations and information provided by local informants (see text below). Sample plots were established within this area to systematically collect ecological data on crop availability and productivity.

In the study area, crops are cultivated based on a mixed‐cropping system. During the maize‐growing season, farmers inter‐cropped maize with soybeans, cow‐peas, taro, and pumpkins. Additionally, millet and potatoes are planted between the maize rows after the beans and pumpkins are harvested. In total, we recorded 58 cultivated crops in our sample plots. This diverse system of inter‐cropping makes it difficult to calculate the exact area devoted to each crop and to count the total number of plants of each crop type. Therefore, we focused on recording the area cultivated by the five most commonly grown crops: maize, rice, potatoes, oranges, and mustard. These crops were grown in nearly 100% of the study plots, highlighting their economic importance and central role in the livelihoods of the local community. Hereafter, we refer to these five crops as major crops. Maize (April–September) and oranges (fruiting season: September–February) were cultivated in rain‐fed farmland; rice (June–October) was cultivated on irrigated land, while mustard (September–March, with two cultivation and harvest cycles) and potatoes (September–May, also with two cycles) were grown in both rain‐fed and irrigated farmland.

Once per month, from June 2019 to May 2020, we visited each sample plot and recorded the cultivated crop type(s) and the growth stage of each crop. We used these data to estimate monthly crop diversity and crop productivity. The growth stage of each crop was scored as either vegetative (not ready for consumption) or reproductive (ready for consumption), based on the degree of development of the majority of plants in that sample plot.

In June 2019, we began collecting quantitative behavioral data on the macaques. This was completed in May 2020, with two observers collecting behavioral data on the macaques: one observer was responsible for scan sampling and the other for all‐occurrence sampling. Over these 12 months, we collected data on the behavior and ecology of our study group, an average of 8 days per month (SEM ± 0.47, n = 12 months). In total, we collected 721 h of quantitative behavioral data (mean ± SEM = 7.2 ± 0.15 h/day, n = 99 days). Data on the macaques' activity budget, diet, and ranging behavior on the farmland and in the forest were collected using a 10‐min scan sampling procedure followed by a 5‐min pause (Altmann 1974). Data collection started at 07:00 h, or when the macaques were first located, and continued until 18:00 h or until the group settled into a sleeping site for the night. During each 10‐min sample period, the observer positioned herself at the approximate midpoint of the group and recorded the behavior of one of five individually selected macaques (adults, sub‐adults, and juveniles) every 2 min. To avoid observer bias, maximize the representativeness of the group, and keep data collection standardized and replicable, we systematically selected five focal macaques using the following criteria: Individual 1: the macaque closest to the left of the observer; Individual 2: the macaque closest to the right of the observer; Individual 3: the macaque most distant to the right of the observer; Individual 4: the macaque most distant to the left of the observer; and Individual 5: the nearest macaque behind the observer. If there were no macaques behind the observer, we recorded the activity of the second‐most‐distant individual to the left of the observer. At 2‐min intervals during the 10‐min sampling period, we recorded the behavior of the one focal macaque, that is, if Individual 1 was scanned at 8:00, Individual 2 at 8:02, Individual 3 at 8:04, and so on. We never sampled the same individual twice during the same sampling period. Then, after a 5‐min hiatus in data collection, we began the next scan and repeated the same sampling procedure. We did not record the behavior of individuals younger than 2 years of age because these individuals were in proximity to and likely to engage in the same behavior as their mother. No data were recorded for a scan interval if fewer than five macaques in the study group were visible at the beginning of the scan.

We recorded the activity budget of the macaques as feeding, foraging, resting, traveling, socializing, or other activities. If a macaque was engaged in feeding or foraging, we recorded the food type manipulated and/or consumed. We broadly categorized food sources into three categories, that is, crops, wild foods, and garbage (i.e., human discarded food). Crops were defined as foods cultivated by local farmers, as well as harvested crops stored in farmers' homes. The latter was recorded as a “stored crop feeding.” Wild foods included natural plants and their tissues such as leaves, seeds, flowers, and fruits; animal‐based food (insects, mollusks, and eggs); and soil and stone licking, which may occur for the purpose of mineral supplementation, microbial ingestion, or detoxification of plant secondary compounds (Pebsworth et al. 2019). We recorded a total of 2752 behavioral scan sessions (mean ± SEM = 29 ± 1.09 per day, based on a total of 11,306 individual macaque activity records). This included a total of 2833 feeding and foraging records.

We used an all‐occurrence sampling method (recorded by the second observer) to collect data on crop feeding bouts engaged in by the macaques (Altmann 1974; Wallace and Hill 2012). We refer to each occurrence as a “crop foraging and feeding event” (CFE) (Wallace and Hill 2012), defined as one or more macaques searching for and ingesting crops. CFEs ended when the macaques terminated crop feeding and left the area on their own or due to human disturbance. We collected data on CFEs from July 2019 to March 2020 (9 months). During each CFE, we recorded crop feeding/foraging bout duration, defined as the amount of time (in minutes) the macaques first began feeding or foraging on crops until the last individual in that party left the farmland. We also collected data on feeding/foraging party size (the total number of macaques feeding), excluding infants. We estimated the total area of farmland used by macaques during a CFE. This area was estimated immediately after the macaques left, based on visible signs of their movements and crop damage (Hill and Wallace 2012). Finally, we recorded the number of damaged plants, fruits, or corn ears consumed by the macaques during each CFE, immediately after the macaques left the farmland.

During each CFE, we also recorded the behavior of humans towards macaques. We broadly categorized their behavior into three categories: (1) No humans present, referring to the absence of farmers or local villagers who could potentially respond to the macaques and disturb their crop feeding behavior. (2) Humans present but no actions taken, referring to incidents when people were nearby the macaques but ignored them, or when a farmer guarding his field did not intervene when the macaques entered a neighboring field. (3) Active deterrence when nearby humans made noise (banging drums or shouting) to deter the macaques without attempting direct physical contact, or when farmers attempted to forcefully drive the macaques away using objects like mud, stones, sticks, or slingshots, along with aggressively chasing, shouting, or lighting firecrackers. These categories included all of the traditional mitigation measures used by community members to reduce crop damage by macaques in the study area. Given that during each CFE, multiple humans were often present and each may have behaved differently towards the macaques, we recorded the highest intensity of human behavior observed during each CFE as the representative behavior. For example, if farmers were present but no action was taken during the first several minutes of a CFE and then active deterrence occurred, the event was classified as active deterrence. We also recorded the number of humans and dogs (barking and/or actively chasing the macaques) involved in active deterrence during CFEs.

2.4. Data Analysis

To examine Hypothesis 1, whether the macaques consumed a greater diversity of crops during months in which crop diversity was higher, we calculated macaque monthly crop dietary diversity across all sample plots using the Shannon–Wiener Diversity Index (Pielou 1974) following formula: H= −∑pi  ln pi , where H = Shannon–Weiner Diversity Index and pi = the proportion of that individual crop species consumed by the macaques in a particular month (Sengupta and Radhakrishna 2016). We also calculated monthly crop diversity across all sampled plots using the Shannon–Weiner Diversity Index (Pielou 1974). The value of H ranges from 0, indicating no diversity, to higher values such as 3 or 4, reflecting a more diverse crop community (details in Supplementary Text 2). We then used a Spearman's correlation to compare monthly crop diversity and monthly macaque crop dietary diversity.

To test our Hypothesis 2, we estimated monthly crop productivity for each major crop by multiplying the total area devoted to each crop by the average crop yield per hectare. The crop yield data for the study area were obtained from the Statistical Information of Nepalese Agriculture, published annually by the Government of Nepal, Ministry of Agriculture and Livestock Development, for the study year 2019/2020 (Government of Nepal 2021) (Details in Supplementary Text 2). We also calculated the monthly crop‐specific feeding percentages using data based on macaque scan sampling. For each month, we computed total crop feeding records and the percentage contributed by each crop, which we refer to as macaque monthly crop feeding. Then, to examine the effect of relative monthly crop productivity on “macaque monthly crop feeding,” we used a Generalized Additive Model (GAM) in the “mgcv” package in R. We used crop type and monthly crop productivity, measured in metric tons across the macaques' home range, as a predictor variable and macaque monthly crop feeding as a response variable. Given the non‐normal distribution of the “macaque monthly crop feeding” data, we employed the GAM framework with a beta regression family and logit link function (Wood 2017). The feeding data were subsequently transformed into proportions from percentages, bounded between 0 and 1 to accommodate modeling within the (0,1) interval required by beta regression. These data were then back‐transformed to the response scale for interpretability, which involves converting model predictions from the logit scale back into percentages, allowing us to make direct ecological interpretations. Model evaluation was assessed using deviance squared, adjusted R 2, and parametric intercepts.

To address Hypotheses 3, 4, 5, we used a linear model to test how (1) the combined productivity of the five major crops (estimated in metric tons across the macaques home range), (2) feeding/foraging party size, and (3) the number of humans and dogs involved in active deterrence, influenced crop feeding bout duration (in minutes). Given that macaques in larger feeding/foraging parties may perceive a reduced predation risk compared to individuals in smaller feeding/foraging parties (Majolo et al. 2008), we included macaque crop feeding/foraging party size as a predictor in our model. This allowed us to measure the specific impacts of human and dog aggressive actions on macaque crop feeding behavior while controlling for the effect of feeding/foraging party size. Before model fitting, we log‐transformed foraging bout duration with a constant of 1 added to accommodate zero values. These transformations normalized the data distribution and stabilized the variance to meet the data requirements of the models. Finally, we used Kruskal–Wallis χ 2 to test the influence of macaque crop feeding duration on the size of the farmland area accessed.

To test Hypothesis 6, we used generalized linear modeling (GLM) with a negative binomial distribution and a log link function. For this analysis, the response variable used was the number of maize cobs damaged during each maize CFE during the months of July–September (after September, farmers had harvested the entire maize crop from their fields). We focused on maize because macaques drop the maize cob after feeding, allowing us to count the number of freshly discarded cobs as an accurate estimate of crop damage. This was not possible in the case of potatoes, rice, mustard, or oranges. We used the number of humans and dogs involved in active deterrence, feeding party size, and feeding bout duration as predictor variables.

Finally, using the same maize data set, we calculated the economic loss to farmers of macaque maize crop feeding. For each maize CFE, we calculated the number of ears eaten and converted this into kg of dry maize kernels based on data reported by Koirala et al. (2021). That study indicated an average weight of 100 grams of dried kernels per maize ear. To calculate the economic loss to farmers, we used a local market rate of 40 NRs. per kg of dry maize kernels, which is the amount reported from direct farmer‐to‐consumer transactions in the study area (2025 field market survey). To estimate the USD equivalent, we used the April 22, 2025, official exchange rate of 1 USD = NRs. 136.51. In this area of Nepal, maize yields average 3230 kg per ha (Government of Nepal 2021). All analyses were conducted in R (1.5.57), and the significance level was set at p < 0.05 (The R Foundation 2025).

3. Results

3.1. Crop Feeding Patterns of Macaques Across Different Crop Species and Seasons

Based on feeding and foraging records, 49.1% of the macaque annual feeding records included cultivated crops (crops in the field contributed 44.7% and stored crops 4.4%), 6.8% from human garbage, and 44% from wild foods (wild plants contributed for 38.1%, animal‐based foods 4.6%, and soil and stone licking 1.4%). Overall, the study group consumed a total of 41 of 58 available crop species belonging to 34 genera and 16 families (Table S1). The reproductive stages of cultivated crops accounted for 91% of crop feeding records. In the remaining 9% of cases, vegetative parts were consumed (Table 1). The macaques were also observed to consume a total of 50 wild plant species.

Table 1.

Top 12 crop species consumed by rhesus macaques during the study period.

Name Local name Scientific name Annual feeding % of crop diet Feeding % of total annual diet Consumed parts Months consumeda
Maize Makai Zea mays L. 26.1 11.7 Young corn, kernels, seed, stalk Jun–Oct
Oranges Suntala Citrus reticulata Blanco. 14.7 6.6 Ripe fruit Nov–Feb
Potatoes Aalu Solanum tuberosum L. 11.4 5.1 Tuber Nov, Jan, Apr, and May
Chayote Skush Sicyos edulis Jacq. 7.5 3.4 Fruit Sep–Nov
Oats Jai Avena sativa L. 5.6 2.5 Young leaf, seed Dec–Feb
Pumpkin Farsi Cucurbita pepo L. 5.0 2.2 Fruit, leaves Sep–Dec
Plum Aalubakhada Prunus domestica L. 4.8 2.1 Ripe fruit May and Jun
Millet Kodo Eleusine coracana (L.) Gaertn. 3.1 1.4 Spikelet, seed, stem Oct and Nov
Mustard Tori Brassica campestris L. var. toria 2.7 1.2 Flower, leaf, seed Jan and Feb
Radish Mula Raphanus sativus L. 2.6 1.1 Flower, leaf, stem, root, seed Nov and Jan–Mar
Rice Dhan Oryza sativa L. 2.1 0.9 Stem, seed Jun and Jul
Soybean Bhatamas Glycine max (L.) Merr. 1.8 0.8 Seed, sprouts Oct
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a

Includes months in which the food plant accounted for more than 5% of macaque crop feeding time.

The five major crops cultivated by the farmers in the study area, that is, maize (26.1%), oranges (14.7%), potatoes (11.4%), mustard (2.7%), and rice (2.1%), accounted for 57% of annual macaque crop feeding records (Table 1). Maize was consumed principally (62.4% of all maize consumption) during the months of July–September. This coincided with increased maize productivity, which was estimated at 412.3 metric tons across the study group's home range in July and 288.6 metric tons in August (Figure 2). Oranges were consumed principally during the 4 months from December to March (accounting for 87.2% of total orange consumption). Orange production in the study group's home range peaked in January at 580.4 metric tons (Figure 2). Similarly, the macaques principally consumed potatoes during the months of April–June (accounting for 70.6% of potato consumption) (Table 1). In April, potato production reached 1501.8 metric tons.

Figure 2.

Figure 2

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Monthly feeding percentage and crop productivity for the five major crops consumed by the macaques. This figure presents data on the monthly feeding percentage (re‐scaled by a factor of 10, i.e., multiplied by 10 to allow for better visual comparison with that of crop productivity) and crop productivity Each plot represents a different crop, with light blue bars indicating crop productivity (measured in metric tons), and the black points connected by lines indicate the monthly percent of feeding time the macaques spent on that crop.

In contrast, rice and mustard were characterized by a different pattern of consumption. Rice was consumed principally during the 2‐month period from June to July (66.6% of rice consumption). However, rice productivity was highest in September (306.94 metric tons across the macaque home range). In fact, during the period of peak rice productivity, we did not observe the macaques feeding on rice (Figure 2). Similarly, the majority of mustard feeding occurred in the month of February (65.21% of mustard consumption), whereas peak mustard productivity (69.97 metric tons) occurred during the month of October (Figure 2). We note that in the case of mustard, 52% of macaque feeding time was concentrated on the plant's vegetative tissues, that is, leaves, rather than on its reproductive tissues. In the case of rice, 66.6% of macaque feeding occurred on vegetative tissues, that is, leaves, shoots, and stems. Overall, the macaques concentrated their crop feeding on a single or a small number of species during any given 1‐ or 2‐month period.

3.2. Crop Diversity, Relative Crop Availability, and Crop Feeding

Crop diversity, a measure of the richness and evenness of crop species present across the macaques' home range, varied from a low of 0.43 in May (indicating few crop species available to the macaques) to a high of 3.25 in August (indicating a richer and more evenly distributed variety of crop species). Similarly, dietary diversity in crop consumption, which measures the richness and evenness of different crop species consumed by macaques, varied from 0.16 in August (indicating the macaques focused their diet on one or two crop species) to a high of 2.01 in October (indicating a more diverse crop diet) (Figure S1). A Spearman's correlation indicated that macaque dietary diversity was not significantly correlated with crop diversity (ρ = 0.15, p > 0.05, n = 12). For example, during August and September, when the number of crop species available was highest (n = 25), the macaques principally fed on a single crop species, maize, which accounted for between 80% and 88% of total crop feeding time (Figure S1). Thus, Hypothesis 1 was not supported.

The GAM with beta regression identified both crop productivity and crop type as significant predictors of macaque monthly feeding behavior. According to the model prediction, “macaque monthly crop feeding” increased with increasing crop productivity of maize, oranges, and potatoes (maize: effective degrees of freedom [edf] = 1.00, χ 2 = 9.22, p = 0.002; oranges: edf = 14.53, χ 2 = 11.64, p = 0.0001; and potatoes: edf = 1.00, χ 2 = 9.07, p = 0.002) (Figure 3). However, in the case of rice and mustard, there was no relationship between crop productivity and consumption (rice: edf = 1.22, χ 2 = 0.10, p = 0.94, and mustard: edf = 1.00, χ 2 = 1.37, p = 0.24). These findings support Hypothesis 2 for maize, oranges, and potatoes, namely that rhesus macaque consumption of these crops was based principally on their monthly productivity. However, Hypothesis 2 was not supported for rice and mustard, the two other major crops (Figure 3).

Figure 3.

Figure 3

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Predicted monthly rhesus macaque crop feeding (%) as a function of crop productivity (in metric tons) for the five major crops. These results are based on a Generalized Additive Model (GAM) with a beta regression family and logit link. Smooth terms were fitted separately for each crop using the interactions (amount.available, by = crop), allowing for crop‐specific nonlinear responses. Shaded areas represent 95% confidence intervals. Feeding intensity is expressed as predicted monthly feeding percentage, and the figure illustrates that macaque feeding increased with availability for maize, oranges, and potatoes, but not for rice and mustard. The final model explained 64.7% of the deviance, with an adjusted R 2 of 0.53.

3.3. CFEs: Feeding Party Size, Feeding Bout Duration, Area of Accessed Farmland, and Human Deterrence

Based on our sample of 238 CFEs across all crops (average number of CREs recorded per month was 26.44 (SEM ± 4.87; range: 9–52), the mean crop feeding bout duration (hereafter event duration) was 31.6 min (± 2.90 SEM), with a range of from 0.53 to 255 min (n = 226). Mean feeding party size (hereafter party size) was 24.7 individuals (± 1.38 SEM), ranging from 1 to 42 macaques (n = 219). The area of farmland accessed by the macaques (hereafter area accessed) averaged 1436.7 m2 (± 147.28 SEM), and ranged from 15.90 to 15,262.22 m2 (n = 224). CFEs associated with the consumption of maize (n = 81), potatoes (n = 22), oranges (n = 53), mustard (n = 16), and rice (n = 2) accounted for 60.7% of all recorded events. During 9.4% of CFEs, the macaques entered, fed, and left a field with no humans or dogs present. In addition, 7.5% of CFEs, humans, and dogs were present but did not interfere with the macaques' crop feeding. In the remaining 83.1% of cases, farmers and or their dogs acted aggressively to deter the macaques from feeding and attempted to chase the macaques away from their fields. The mean number of humans attempting to deter and chase away the monkeys was 2.8 (± 0.17 SEM, range: 1–15, n = 189). Similarly, on average, 1.35 (± 0.10 SEM, range: 1–7, n = 80) dogs behaved aggressively towards the macaques during CFEs. Our results showed no statistically significant difference in macaque crop feeding duration (Kruskal–Wallis χ 2 = 5.36, df = 2, p = 0.07) and farmland area accessed (Kruskal–Wallis χ 2 = 6.96, df = 2, p = 0.03) based on the presence, absence, and actions of farmers and their dogs.

A linear regression model revealed a significant negative association between the combined productivity of the five major crops (i.e., maize, potatoes, oranges, rice, and mustard) and feeding bout duration (β = −0.0007 ± 0.0003 (SE), p = 0.013). Thus, regardless of overall crop productivity, the macaques targeted their feeding efforts on only one or two crop species per month. Thus, Hypothesis 3 was rejected. However, we found that the number of macaques (β = 0.01 ± 0.003 SE, p < 0.0001) involved in CFEs was positively associated with event duration, and therefore, Hypothesis 4 was supported. Similarly, the number of humans and dogs (β = 0.06 ± 0.02 SE, p = 0.0014) involved in active deterrence did not reduce the duration of crop feeding events (Figure 4). In fact, the presence of people and dogs attempting to prevent the macaques from crop feeding was associated with an increase in the duration of crop feeding events. This may have occurred because, rather than causing the macaques to leave the farmland, active deterrence by humans and dogs resulted in the macaques temporarily relocating to a nearby area and then returning to feed. Based on these results, Hypothesis 5 is rejected.

Figure 4.

Figure 4

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Relationships between rhesus macaque crop foraging and feeding (CEF) duration (minutes) with (a) no. of humans and dogs involved in active deterrence, (b) the feeding party size involved in CFEs, and (c) the availability of the five major crops. The overall model was statistically significant (F(3, 46) = 20.79, p < 0.001; adjusted R 2 = 0.54), indicating that the predictor variables explained approximately 54% of the variation in log‐transformed event duration. The blue shaded areas represent the 95% confidence intervals around the predicted feeding durations.

The results of our GLM indicated that macaque feeding party size and the duration of a crop feeding event were the strongest predictors of the amount of crop damage caused by the macaques (i.e., amount of maize cobs damaged). Crop damage increased with an increase in foraging/feeding party size (β = 0.044 ± 0.012 SE, Z = 3.82, p < 0.0001) and event duration (β = 0.03 ± 0.007 SE, Z = 4.35, p < 0.0001), supporting Hypothesis 6. However, the number of humans and dogs involved in active deterrence showed a non‐significant negative effect on the amount of crop damage (β = −0.114 ± 0.072 SE, Z = −1.58, p = 0.11) (Figure 5).

Figure 5.

Figure 5

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Relationship between number of maize cobs damaged by rhesus macaques and key predictors: (a) number of humans and dogs involved in active deterrence, (b) number of macaques present during maize crop feeding events (CFEs), and (c) duration of maize crop feeding events (in minutes). Each panel shows the model‐predicted relationships with 95% confidence intervals, and is overlain with observed data points. The blue shaded areas represent the 95% confidence intervals around the predicted maize corn damage.

3.4. Damage Resulting From Maize Crop Feeding

Given that maize was the most common crop consumed by the macaques, we estimated the economic cost to farmers of macaque maize crop feeding during the months of July–September. This was the peak period of maize production, with 33.3 ha of maize planted across the study group's home range. The mean amount of maize consumed by the macaques during CFEs was 108.3 ears (± 30.81 SEM; range: 8–500 ears; n = 19), and the area of accessed farmland averaged 768 m2 (± 165.1 SEM; range: 95.4–2543.7; n = 19). The mean macaque maize feeding party size was 31 macaques (± 2.8 SEM; range: 10–45; n = 19), and the mean maize feeding event duration was 29.82 min (± 5.16 SEM; range: 6.2–73; n = 19). The amount of maize damage caused by the macaques was equivalent to 10.83 kg of dry maize kernels per CRE. Given that, on average, the study group engaged in 1.69 maize feeding CFEs per day (±0.24 SEM; range: 1–4; n = 16; calculated based on observation days > 6 h during July–September), we estimate that the macaques consumed the equivalent of 1647.2 kg of dry maize kernels during these 3 months, resulting in the loss to farmers of 1.53% of total maize yield per planted hectare.

4. Discussion

Learning how to incorporate anthropogenic landscapes into an effective conservation strategy represents an essential tool for managing human–wildlife conflict, protecting animal populations, and promoting food security for local farm households (Koh and Gardner 2010; Meijaard 2016; Hill 2018; Sodhi et al. 2010). However, as humans convert ever shrinking natural forests and woodlands into agricultural fields and urban centers, many species of primates are forced to range further into human‐built landscapes and include human garbage and domesticated crops as part of their diet (Amato et al. 2025; Moy et al. 2023), resulting in human–primate conflict and an increased perception of primates as pests (Altmann et al. 1993; Anand et al. 2021; Corrêa et al. 2018; Kaplan et al. 2011; Koirala et al. 2017; Strum 2010; Amato et al. 2025; Moy et al. 2023). Moreover, crop feeding primates have the potential to exchange pathogens with domesticated animals and human communities, as well as threaten the economic sustainability and food security of local farmers, leading to their killing (Anand et al. 2018, 2021; Chaves and Bicca‐Marques 2017; Hansen et al. 2020; Hockings et al. 2012; McLennan et al. 2021). In this study, we examined the crop feeding behavior of rhesus macaque in a farm‐forest mosaic in central Nepal. Specifically, we explored how crop type, monthly crop productivity, and human attempts to deter macaques from farmland affected macaque crop feeding behavior.

We found that our rhesus macaque study group relied heavily on human‐associated foods. Fifty‐four percent of their total yearly feeding records included domesticated crops from farmland, crops stored in farmers' houses, and human garbage. Although local farmers planted 58 different cultivars, the most common crops eaten were maize, oranges, and potatoes, which accounted for 52% of macaque crop feeding time. The macaques were found to concentrate their feeding on one or two crops each month, and in the case of maize, oranges, and potatoes, monthly consumption was positively correlated with crop productivity. Moreover, although people and their dogs attempted to deter macaque crop feeding during 83% of feeding events, in the case of maize feeding (i.e., the most frequent crop consumed), these actions had no significant effect on reducing the duration of crop feeding events or the amount of damage caused by the macaques. Several previous studies of human–macaque conflict indicate that traditional forms of crop guarding (i.e., creating loud noises, presence of dogs) offer only limited success against persistent crop feeding species such as Assamese macaques (Macaca assamensis), rhesus macaques, and pig‐tailed macaques (M. nemestrina) (Linkie et al. 2007; Pebsworth et al. 2025; Regmi et al. 2013). For example, in the Kerinci Seblat National Park, Indonesia, deterrents such as guard dogs and occasional gunshots were commonly used to protect fields from crop feeding by pig‐tailed macaques (Linkie et al. 2007). These strategies were largely ineffective, however, and farms near the forest edge continued to experience frequent crop damage. The authors of this study argued that, rather than farmers and their families, coordinated and persistent communal guarding of farm fields is likely to offer the most effective solution to macaque crop losses (Linkie et al. 2007).

Active guarding and the construction of physical barriers such as fences or trenches to deter crop feeding can be costly and labor‐intensive, contributing to farmer fatigue and resentment (Kyokuhaire et al. 2023; Stevens et al. 2025; Yeshey et al. 2022). For example, Kyokuhaire et al. (2023) found that guarding against elephants and baboon crop feeders often required several family members spending extended periods in the fields every day. In other cases, farmers hired guards during periods when crops were about to be harvested, which cost an average of $25.50 ± $3.10 USD for the season (~15%–20% of farmers' seasonal income from farming) (Kyokuhaire et al. 2023). Similarly, Yeshey et al. (2022) reported that farmers in Bhutan experienced significant psychological stress and livelihood disruptions due to threats associated with wildlife crop feeding and livestock losses. Thus, unless effective and low‐cost deterrence measures can be put in place, retaliatory killings, trapping and translocation, or culling are likely to increase (Barua et al. 2013; Hill 2017; Stevens et al. 2025).

At our research site in central Nepal, rhesus macaques were absent from more than half of the study area before 2010. Today, the density of macaques in this area remains relatively low (~16 individuals/km2). And, although human foods accounted for over 50% of the feeding time of our macaque study group, crop damage to maize, the most frequently eaten crop, represented only a small fraction (1.5%) of the total maize yield per ha. Thus, it appears that local farmers and rhesus macaques can continue to coexist in this part of Nepal, as long as appropriate measures are put in place to avoid additional conflict in response to increased levels of crop feeding. Below, we detail a series of science‐based conservation measures for rural communities in central Nepal that are economically feasible, adhere to local cultural beliefs and practices, align with the local ecology, and promote human–macaque coexistence.

First, vulnerable crops such as maize, potatoes, and oranges should be cultivated in areas where human actions can serve as a strong deterrent to macaque crop feeding. These areas include locations near farmers' houses, high human traffic areas, and locations adjacent to guard huts. It is recommended that farmers should allocate farmland bordering forest edges to crops less preferred by the rhesus macaques, such as rice, mustard, buckwheat, chili, ginger, taro, or turmeric. These domesticates accounted for < 5% of the yearly macaque diet. Alternatively, farmers could devote a portion of their land to planting grasses for fodder like Stylo grass (Stylosanthes guianensis), Napier grass (Pennisetum purpureum cv. Mott), South African pigeon grass (Setaria sphacelata), or signal grass (Brachiaria spp.), which, while rarely consumed by the macaques, provide valuable livestock fodder and improve soil quality (Robertson 2005; Pandey et al. 2013). Second, deterrence must be strategically coordinated. We recommend that farmers and local governments form community guard groups, in which local villagers are assigned rotating field‐monitoring responsibilities using low‐cost alert systems such as whistles, air horns, or mobile phones to increase the number of people actively deterring crop feeding (Koirala et al. 2021; Kyokuhaire et al. 2023). These efforts should be prioritized in areas such as bridges or forest corridors where the macaques commonly pass through to reach farm fields. Limiting macaque access to these choke points would serve to increase the energetic and risk‐related costs to the macaques of entering farm fields (Treves 2008). In order to minimize damage, these efforts should be intensified during the months of April, July, August, and November–January, when the reproductive stages of crops most sought after by the macaques, including maize, oranges, and potatoes, are most available. Strengthening and coordinating deterrence measures during this high‐risk period can significantly reduce crop losses and protect farmers' economic returns (Kyokuhaire et al. 2023). We also recommend that local and regional governments work with communities to use drone technology or remote‐sensing camera technology to surveil the movement and ranging patterns of the macaques. This will help anticipate when and where the macaques enter fields and alert farmers or community guards to potential crop feeding events (Chang et al. 2023; Ullah et al. 2025; Zak and Riley 2017).

Third, local communities and governments should work together to ensure regular garbage collection and transport to designated dumping sites located distant from farm fields, rather than allowing waste to accumulate near farms or settlements. Proper waste management would reduce the availability of anthropogenic food sources for macaques and help limit their presence near agricultural areas. In addition, local conservation organizations and local wildlife authorities should provide education and training to help farmers understand macaque behavior and to use culturally acceptable and effective non‐lethal deterrents to discourage crop feeding. Public outreach and community campaigns to discourage unregulated feeding and tolerance of macaques in domestic areas can reduce human–macaque proximity and promote sustainable coexistence (Anand et al. 2021; Kaplan et al. 2011; Koirala et al. 2017). For example, crops like maize are often stored outside of houses in open or easily accessible areas, making them vulnerable to post‐harvest damage and losses caused by the macaques. Closing off these storage areas represents a relatively low‐cost solution to this problem. Fourth, wildlife managers and conservation officials should work with local community leaders to assess and clearly communicate the actual economic impact of crop losses caused by macaques. In our study area, overall damage caused by macaques was relatively small, amounting to 1.53% of the total maize yield. However, losses can be significant for smallholder farmers or those whose fields are located close to forest edges, where crop feeding pressure is highest. Without alternative sources of income, this can have a significant impact on farmers' food security and perceptions associated with human–wildlife conflict (Kyokuhaire et al. 2023; Yeshey et al. 2022). Creating participatory platforms for farmer feedback and co‐design of mitigation tools can improve the adoption and effectiveness of conflict management strategies, while also enhancing their social and cultural legitimacy (Barua et al. 2013; Hill 2017; Nkansah‐Dwamena 2023). Additionally, crop insurance and compensation programs tailored for wildlife‐related damage provide an important safety net for farmers at higher risk, helping them cope with seasonal losses. Successful pilot programs in India and Sri Lanka highlight the effectiveness of this approach (Karanth et al. 2018; Ravenelle and Nyhus 2017). By framing macaques and other wildlife not as threats but as species requiring shared stewardship, it is possible to improve tolerance and promote biodiversity and long‐term coexistence (Anand et al. 2018; Nkansah‐Dwamena 2023). Finally, to be most effective, all human‐friendly solutions must also account for the behavior, ecology, and group dynamics of the rhesus macaques. Deterrents and spatial interventions must consider macaque group size, population density, their ability to habituate to humans, and seasonal changes in patterns of range use and shifts in their natural diet (Hill and Wallace 2012; Kaplan et al. 2011; Thatcher et al. 2019).

In sum, our findings indicate that rhesus macaques living in anthropogenic landscapes in rural Nepal adjust their foraging strategies to include a large dependence on particular human cultivars such as maize, potatoes, and oranges. At our site, the amount of crop damage caused by the macaques was limited. However, as our findings are derived from a single group of rhesus macaques and did not assess wild food availability, there may be other mitigation solutions that we have not considered. Therefore, additional studies are needed to determine whether increasing natural food abundance through forest restoration programs would reduce crop losses and support coexistence between local communities and macaque populations. We also note that interventions that work in one region may not be directly applicable to other regions due to differences in local ecology, culture, religious beliefs, food security, and the health and economic well‐being of local human communities. Thus, we advocate for a community‐based and site‐specific management model, where local ecological knowledge, partnerships with wildlife conservation NGOs, community norms, and government support coalesce to produce practical and adaptive conservation and economic solutions (Blackwell et al. 2016; Nkansah‐Dwamena 2023).

Author Contributions

Sabina Koirala: conceptualization, methodology, data curation, investigation, formal analysis, project administration, funding acquisition, writing – original draft. Bijaya Adhikari: investigation, project administration, data curation. Devi Rai: investigation, data curation. Hem Bahadur Katuwal: formal analysis, methodology, validation, writing – review and editing. Weikang Yang: funding acquisition, resources. Ming Li: funding acquisition, supervision, resources. Paul A. Garber: conceptualization, methodology, supervision, validation, writing – review and editing.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Supplementary Figure 1: Monthly variation in Shannon‐Weiner Diversity Index (H) for crop diversity and dietary diversity of macaques.

Supplementary Table 1: List of crop plants consumed by the study group of rhesus macaques over a one‐year study period.

AJP-88-e70141-s001.docx (65.7KB, docx)

Acknowledgments

We are grateful to members of the local community, especially household farmers, for their cooperation and assistance during fieldwork. S.K. is grateful to Bimala Guragain, Til Prasad Pangali Sharma, Deepakrishna Somasundaram, Laxmi Devi Koirala, Ramhari Sharma, Shreevidya K. Adhikari, and Nabin Rawal for their support, encouragement, and assistance during her research. P.A.G. wishes to acknowledge Chrissie, Sara, Jenni, Dax, and Saffron for their support, love, and encouragement. We gratefully acknowledge the assigned AJP Editor and the two anonymous reviewers for their insightful comments and constructive suggestions that significantly enhanced this manuscript. We thank the Panauti Municipality and its ward offices for their support and facilitation in carrying out this work. The work was financially supported by the National Natural Science Foundation of China (NSFC), Research Fund for International Young Scientists (Grant No. W2533084), to S.K. and the Strategic Priority Research Program of the Chinese Academy of Sciences, China (XDA19050202), to M.L.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Supplementary Figure 1: Monthly variation in Shannon‐Weiner Diversity Index (H) for crop diversity and dietary diversity of macaques.

Supplementary Table 1: List of crop plants consumed by the study group of rhesus macaques over a one‐year study period.

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