JHR 50: 117-128 (2016) ore JOURNAL OF | *0eerrieve openacoss ural Sicee cnet (f-) Hymenoptera http://jhr.pensoft.net The inserational Society of Hymenoptersts. RESEARCH Foraging behavior and Preferences for Alternative Supplementary Feeds by the African Weaver Ant, Oecophylla longinoda Latreille (Hymenoptera, Formicidae) W. Nene', Gration M. Rwegasira', Maulid Mwatawala', Mogens G. Nielsen’, Joachim Offenberg? I Sokoine University of Agriculture, Department of Crop Science and Production, Box 3005, Morogoro, Tanzania 2 Terrestrial Ecology, Department of Bioscience, Aarhus University, DK-800 Aarhus, Denmark Corresponding author: W. Nene (wilsoninene@gmail.com) Academic editor: Jack Neff | Received 18 February 2016 | Accepted 17 April 2016 | Published 27 June 2016 Attp://zoobank.org/A75885D7-AA17-4FA2-B9A9-6014C50CDCA3 Citation: Nene W, Rwegasira GM, Mwatawala M, Nielsen MG, Offenberg J (2016) Foraging behavior and Preferences for Alternative Supplementary Feeds by the African Weaver Ant, Oecophylla longinoda Latreille (Hymenoptera: Formicidae). Journal of Hymenoptera Research 50: 117-128. doi: 10.3897/JHR.50.8173 Abstract Weaver ants, Oecophylla spp, are effective predators that control a wide range of insect pests in multiple crops when maintained at high population. Supplementary feeding, particularly during reduced food availability is one of the management practices that maintain and boost weaver ants’ populations. Experi- ments were conducted between September and October 2013, January and February, 2014 to determine the type of food preferred by weaver ants, O. longinoda. Twenty colonies of O. longinoda were provided with four types of food to determine their feeding preferences. These include anchovy, chicken intestine, fish intestines and earthworms. We examined food preferred by ants based on weight of the food removed and activity of the ants on foods. Furthermore, we examined foraging behavior of ant workers on anchovy food (fresh-ground and dry-ground) in nine O. longinoda colonies. Thereafter, small and large particles of dried-ground anchovy were tested. The results showed that O. /onginoda preferred anchovy to other foods provided. However, the results of Analytical Hierarchy Process showed that earthworm and fish intestine were the most accessible food types by farmers, as determined by availability, affordability and applicabil- ity. We observed more ants on fresh-ground as opposed to dry anchovy; similarly, large particles were more easily removed than was the case with small particles. Thus, during reduced food availability, farmers in the study area should use earthworms and fish intestines feeds to supplement O. longinoda colonies. Fresh moist anchovy or dry anchovy of large particle sizes can be used where available. Copyright W. Nene et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 118 W. Nene et al. / Journal of Hymenoptera Research 50: 117-128 (2016) Keywords African Weaver Ant, citrus, cashew, food preference, anchovy, Tanzania Introduction Two species of weaver ants, Oecophylla longinoda Latreille and Oecophylla smaragdi- na Fabricius are generalist predators that protect crops against insect pests (Way and Khoo 1991; Peng and Christian 2007; Van Mele 2008; Materu et al. 2014). The use of Oecophylla as a biocontrol can lead to increased fruit yield and quality (Barzman et al. 1996; Peng and Christian 2005; Olotu et al. 2013a). The ants prey directly on in- sect pests and obtain energy from honeydew produced by homopterans or from plant nectaries (Way and Khoo 1992). Crop protection is therefore more successful when there is a high and stable population of weaver ants. For instance, Stathers (1995) re- vealed that cashew trees colonized by high number of O. longinoda (>500 foraging O. longinoda workers) recorded lower damage by coreid bugs (Helopeltis anacardii Miller and Pseudotheraptus wayi Brown) than those with few O. longinoda (1-20). Adequate palm protection is realized when two or more nests of O. /onginoda are found in the palm crown (Way 1953) or when 60-70% of the palms are colonized by O. longinoda (Way and Khoo 1992). As Sporleder and Rapp (1998) reported, the population of P. wayi sinks to zero after a long and stable occupation of palm trees by O. longinoda. In addition to biocontrol, Oecophylla is used as a valuable source of food for humans (Sribandit et al. 2008), contributing directly to food security (Offenberg and Wiwat- witaya 2010) and also serve as a feed for song birds in Indonesia (Césard 2004). Popula- tions of weaver ants in crop fields are, however, not stable, as they can commonly drop to very low levels in the field, resulting in inadequate crop protection. This can be caused by many factors one of which is movement of colonies to non-agricultural fields. Differ- ent management practices are being developed in order to maintain, boost, and expand the existing colonies to optimum levels. These management practices include artificial nests, (Offenburg 2014), the use of pesticides that are less harmful to the ants, protection of ants from competitors like black ant Dolichoderus thoracicus (Smith), facilitation of colony expansion by using strings and poles to connect trees (Van Mele and Cuc 2000; 2007) and maintenance of ground vegetation to control Pheidole spp (Way and Khoo 1992; Seguni et al. 2011). Furthermore, technologies for rearing weaver ants in nurseries are being developed (Peeters and Andersen 1989; Ouagoussounon et al. 2013) Social insect populations are negatively affected when food is scarce (Dusstour and Sympson 2012). Weaver ant colonies may even move among trees in search of forage (Van Mele and Cuc 2007). The goal of biocontrol is to have large and stable colonies thus food supplementation may help to boost population size. The feeding preferences of Oecophylla longinoda are not well known. In Vietnam, farmers provide fish and chicken intestines to O. smaragdina as supplementary foods during scarcity (Van Mele and Cuc 2000). Food supplementation (Van Mele and Cuc 2000; Lim 2007) or feeding (Offenburg and Wiwatwitaya 2010) of weaver ants Foraging behavior and Preferences for Alternative Supplementary Feed... 119 is reported to increase weaver ant populations. Furthermore, population increase of O. longinoda was reported in fed colonies (Abdula et al. 2015). However, weaver ants consume food in order of preference. O. smaragdina prefer mealworm to fish, honey or weaver ant formula (Lim 2007). The practice of food supplementation for O. longinoda is limited by inadequate knowledge on food preference (based on cheap local available feeds), forms or states as well as particle sizes. Therefore, the objective of this study was to determine the type of food preferred by weaver ants in terms of form and size. A good understanding of food preferences by weaver ants and their foraging behavior is essential for effective management of O. longinoda during food scarcity. Materials and methods We conducted experiments at Naliendele Agricultural Research Institute (NARI), Mt- wara Region, in Southern Tanzania (40°09'57.05"E, 10°21'22.49"S, 140 m asl). The region has a unimodal rainfall pattern, starting from November/December to April/ May, with a single peak in January. The annual rainfall ranges from 810 to 1090 mm, whereas mean temperature ranges from 23°C in July to 27°C in December. Relative humidity ranges from 79% in October to 87% in March. The study was approved by the Directorate of Research and Postgraduate Stud- ies (DRPG) of SUA, a body responsible for monitoring and evaluating compliance to ethical conduct of staff and students undertaking research. The research complied with Code of Conduct for Research Ethics of Sokoine University of Agriculture (SUA) available at www.drpgs.suanet.ac.tz. Food preferences were tested for 10 days in or- chards colonized by weaver ants. The tests were conducted for two seasons, between September and October 2013 (dry season), and between January and February 2014 (rainy season). T'wo orchards one of cashew, Anacardium occidentale L. and another of orange, Citrus sinensis L were selected. In each orchard we selected trees with at least 40% of branches occupied by ants (as assessed by as per Peng et al. (2008). Each tree had between 5 and 25 nests. Each colony was provided with four types of foods; (i) earthworm (ii) chicken intestine (iii) fish intestine and (iv) anchovy. Intestines and anchovy were ground by locally made mortar and pestle. Earth- worms were dug out of wet soils (close to water ponds and irrigated fields) and chopped into small pieces (approximately 0.5—1 cm in length) by a kitchen knife. About 6 g of each food type were placed in a 0.01x0.1 m bowl, set on a feeding platform. Ants could access the bowls by crawling through a guiding stick. Feed bowls were placed equidistant from the middle of the feeding platform. Feeds and water were provided ad libitum throughout the experimental period. All the food types were tested in 10 colo- nies in each orchard. Preferences were determined by i) counting all foraging workers observed on food station and inserting their mouths into a food type and ii) weighing the amount of each food removed by the ants. Counting started 60 minutes after more 120 W. Nene et al. / Journal of Hymenoptera Research 50: 117-128 (2016) than one forager had discovered each food type. Thereafter, the weight of the remain- ing food in each bowl was determined. The amount of food type removed by the ants was determined by establishing the difference in weight between the food supplied and the food which remained in the bowl. In each case, the weight loss due to evaporation was deducted. Weight loss due to evaporation was determined in the control food types that were inaccessible by ants. A sample of each food type was analyzed for nutrient compositions at the Uni- versity of Dar es Salaam. ‘The total carbohydrate, crude protein, total lipids (Fat) and vitamin A were determined according to the procedures described by Allen (1989). The total flavonoids were determined based on the procedures described by Bonvehi et al. (2001); the moisture content was determined gravimetrically after oven has dried at 105°C for 24 hours. Furthermore, we used anchovy food to test for food forms and particle sizes that can be preferred by Oecophylla longinoda. Anchovy was used because it is processed in a standard form. We hypothesized that anchovy type (dry and fresh) affected the foraging behavior of workers. We also hypothesized that the particle size of dry anchovy affects the foraging behavior of workers. The experiments were conducted between May and July 2014. The first experiment involved two different forms of anchovy, dried and fresh. This experiment was conducted for 10 days, with the observation starting around 0900 am each day. The anchovy was sun dried (27—29 °C) for 7 days before grinding. We used fresh-ground anchovy of approximately similar size as the dried one. A Y- shaped feeding arena made up of wood was used as a feeding platform. A feeding bowl was placed on top of a board tied at each end of the Y shaped arena. ‘This gave an equal chance for the work- ers to access each of the anchovy food types. Nine colonies were used. Each colony oc- cupied at least two citrus trees. One bowl of each anchovy food was supplied per colony. The foraging behavior was assessed by counting workers carrying food particles from the source. Ihe counting was done ten times at an interval of one minute (ten observations) every day per each colony for 10 days consecutively. In the end, we calculated the average number of foraging workers per minute per colony for a given food form. The second experiment involved dried-ground anchovy of different particle sizes. ‘The particles were measured by using laboratory test sieves (Wagtech International Ltd UK). Two particles sizes were selected; particles ranging from 0.5 to 1 mm in diameter (referred hereinafter as small particles) and; particles of 2 mm d (referred hereinafter as large particles). The experiment was conducted on six weaver ant colonies for 10 days using similar procedures for testing food types (above). Thereafter, Analytic Hierarchy Process (AHP) (Saaty 1980) was used to determine the food type that would be accessed by the farmers. The set of evaluation criteria consisted of affordability, availability and applicability. The set of alternative options among which the decision was made consisted of four food types. The weights for each evaluation criterion were generated. ‘The score for each criterion was assigned accord- ing to the pair wise comparisons of the options (on a scale of 1 — 9). Finally, the criteria weights and the options scores were used to compute the global score for a given op- tion, as a weighted sum of the scores obtained with respect to all the criteria. Foraging behavior and Preferences for Alternative Supplementary Feed... 124 Data analysis The analyses were performed using JMP 10.00 software. A non parametric one way ANOVA was used followed by Multiple Comparison-Wilcoxon Each Pair for count- ing forage workers and the amount of food removed under food preferences. Mann- Whitney tests were performed to compare the number of forage workers on dried and fresh anchovy; similar comparisons were done for small and large particle sizes. Results Nutrients composition of the feeds fed to the ants are presented in Table 1. Crude pro- tein ranged from 47.7% (from fish intestine) to 31.2% (chicken intestine). All tested feeds, except earthworms contained flavonoids. ‘The highest amount of flavonoids was 0.013 mg/g. The numbers of workers foraging on food types were significantly (p=0.05) dif- ferent in both citrus and cashew orchards, during both dry and rainy seasons (Tables 2, 3). Significantly, (p=0.05) more workers foraged on anchovy than they did on other food types. However, in citrus during dry season, the numbers of workers foraging on anchovy and chicken intestine were not significantly (p=0.05) different. The prefer- ence was the highest for anchovy and fish intestine and the least for earthworm and chicken intestine across both seasons and orchards except in citrus during the dry season (Figure la, 1b). The quantities of food types taken by ant workers were signifi- cantly (p=0.05) different in citrus but not in cashew orchard during the dry season (Tables 2, 3). In contrast, the quantities of food taken by ant workers in both orchards were statistically different (p=0.05) during the rainy season. Workers took significantly (p=0.05) more anchovy than they did to other food types. In all situations, the prefer- ence was the lowest for chicken and fish intestine (Fig. 2a, b). The results show further that more workers foraged on fresh-ground than they did on dried-ground anchovy (Fig. 3a). Similarly, more workers foraged on large particles than they did on small particles of ground-dried anchovy (Fig. 3b). The results of the AHP show that of the three criteria, earthworm ranked the highest followed by fish and chicken intestine. Table |. Nutrients composition of the feeds fed to ants. Food coc YPS | Fish intestine | Chicken intestine Earthworm Parameters Anchovy Crude Protein (%) 44.6 31.2 45.6 Total carbohydrate (g/100g) | _0.2 6.21 0.01 Fat content(g/g) 0.059 0.078 0.087 0.005 Moisture content(%) 89.4 S27, 78.4 92.9 Vitamin A(mg/100g) 4.5 3.4 5.6 0 Flavonoids(mg/g) 0.013 0.0002 0.001 0.00 Energy(kj/g 9.711 9.553 7.834 122 W. Nene et al. / Journal of Hymenoptera Research 50: 117-128 (2016) 90 - OCitus GCashew OCitus 8 Cashew ‘A g 80 - n 00 670 - 3 B iy P 50 - = 60 - B iss] = 40 - p20 4 =| ® cH) E40 - a 30 4 od = ‘el ie) 0 30 5 520 320 - . = 10 - 2 10 | Z a 0 = — Zz 0 Anchovy Earthworm Fishintestine = Chicken Anchovy — Earthworm = Fishintestine Chicken intestine intestine a b Food types Food types Figure |. Number of Weaver Ant workers at food sources after 60 minutes foods supplied daily for 10 days between (a) September-October 2013 (dry season), and (b) January-February 2014 (rainy season) at Naliendele Citrus and Cashew orchard, Tanzania. Table 2. The p-values for weaver ant counting and amount of food removed (g)/hour in 20 days between September and October 2013 and January and February 2014 in citrus orchard, Naliendele, Tanzania. (Kruskal-Wallis Multiple Comparison-Wilcoxon Each Pair test). Food types Citrus dry season Citrus rainy season Weaver ant Amount of Weaver ant Amount of Pairwise comparison counting food removed counting food removed (P-values) (g) (P-values) (P-values) (g) (P-values) Anchovy versus Chicken intestine 0.0011 Anchovy versus Earthworm 0.0011 Anchovy versus Fish intestine 0.0011 Chicken intestine versus Fish intestine 0.0011 Chicken intestine versus Earthworm 0.0011 Earthworm versus Fish intestine 0.0011 Table3. The p-values for weaver ant counting and amount of food removed (g)/hour in 20 days between September and October 2013 and January and February 2014 in cashew orchard, Naliendele, Tanzania. (Kruskal-Wallis Multiple Comparison-Wilcoxon Each Pair test). Food types Cashew dry season Cashew rainy season Weaver ant Amount of Weaver ant Amount of Pairwise comparison counting food removed counting food removed (P-values) (g) (P-values) (P-values) (g) (P-values) Anchovy versus Chicken intestine 0.0013 0.0002 0.0002 Anchovy versus Earthworm 0.0006 0.0002 0.0002 Anchovy versus Fish intestine 1.00 0.0002 0.0002 Chicken intestine versus Fish intestine 0.0008 0.0002 0.0002 Chicken intestine versus Earthworm 0.068 0.023 0.0002 Earthworm versus Fish intestine 0.0003 0.005 0.0002 Foraging behavior and Preferences for Alternative Supplementary Feed... 123 z o 14 s Oo las