PICT: A low?cost, modular, open?source camera trap system to study plant–insect interactions

? Interactions between plants, their pollinators and herbivores have been key in the evolution of flowering plants (Barrett, 2013; Kergoat et al., 2017; Moreau 2006; Schoen 2019). Despite tremendous progress fields pollination biology, quantitative genetics, comparative phylogenetics genomics, paucity empirical data from natural history studies limits understanding pollinator-driven (van der Niet, 2021). Conventional plant–insect interactions typically involve collection using direct (e.g. Suetsugu, 2019; Tang 2020; Varma & Sinu, 2019) or indirect observations Boyer Johnson 2011). However, because are time-intensive, limited by environmental conditions logistics, they not conducted over large spatiotemporal scales often underestimate importance furtive organisms compared to larger slower ones (Micheneau 2006). Furthermore, presence a human observer need illuminate study organism at night may influence its behaviour (Opp Prokopy, 1986). Camera trap (CT) technology can greatly advance providing convenient replacement classic observations. This technique gained popularity it allows for non-intrusive constant sampling effort (Rovero Zimmermann, 2016; Wearn Glover-Kapfer, Recently, camera trapping insects has become an active field research development but important technical limitations still persist (Pegoraro Preti First, although reported that passive thermal infrared motion sensor commercial CT systems be activated flying (Houlihan Raguso, 2016), most ectotherms, such as reptiles, amphibians invertebrates, do trigger sensors (Hobbs Brehme, 2017). Moreover, initial delay deemed excessive many cases, especially hot environments (Glover-Kapfer Meek Pittet, 2012). To circumvent these problems, researchers developed relying on detection based pattern recognition changes successive frames captured (Barlow O’Neill, 2020). proven efficient obtaining insect visit frequency, duration modelling activity Steen, applying on-the-fly algorithm filter video stream during recording increases power consumption does allow one estimate rate which events fail detected. Second, characteristics limit number taxa accurately identified, when taxonomically relevant traits subtle. Image resolution modulated settings, shutter speed decreases increases, hence decreasing sharpness moving animals. quality is ultimately lens, neither interchangeable cases (Meek 2012; Rovero 2013). Most CTs use wide-angle fixed-focus lens set so depth ranges infinity down few metres. As result, models suited macro-photography. Finally, cost units limiting factor terms deployed simultaneously, therefore, statistical analysis. Currently, mid-range costs 200—500 USD The unit price motion-triggered designed monitoring range 400 EUR 2020) several thousands euros (Danaher Houlihan Here, we propose new system, called (PICT), overcomes above shortcomings. We report results deployment this system under two where manual observation impossible: (a) places cannot remain long periods time (pollinator visitation canopy African ebony tree) (b) scale involved too (low rates epiphytic orchid). PICT contrasts with other solutions increased portability, reduced low energy hardware require heavy bulky lead batteries operate. Low-energy mainly achieved separating analysis steps. By enough memory H264 compression algorithm, record high definition videos continuously computer search interest later lab. consists four main components, single-board computer, micro SD card, USB bank battery (Figure 1). A practical guide detailed instructions constructing well control programs codes available online Supporting Information (Droissart protect components elements, sealed food storage case about 1 L volume. Each component inside fixed place adhesive Velcro® strips. mount standard ¼ screw glued onto mount. At writing, full building operational less than 170 USD. needed functionality comparable retail CT, is, without mount, would 100 (Table operated through picamera Python package (https://picamera.readthedocs.io/) installed Raspberry Pi Zero, credit card-sized, low-cost, high-performance computer. All integrated Wi-Fi controller provide required, recommend model ‘Zero W’ relatively lower consumption, smaller size. card serves hard drive operating stored. It powered 5V mini-USB port supplied lithium-ion used 5-megapixel Module v1 (OmniVision © OV5647 sensor), 2,592 × 1,944 photosites, format sensor. comes customized versions embedded 3.3V output connected near-infrared LED soldering, 3.6-mm diagonal view 75 degrees adjustable focus distance, (c) no filter, improving allowing illumination scene IR light. scene, 850-nm equipped onboard photoresistor decrease light intensity increasing ambient An resistor tuned threshold toggling LED. Near-infrared preferred invisible animals thereby influencing behaviour. Insects’ photoreceptors spectral sensitivity range, maximal observed peak absorption wavelength 630 nm (Briscoe Chittka, 2001). Positive phototaxis wavelengths Grunsven 2014; Wakakuwa 2014), small 850 nm, shown Coleoptera (Meyer, 1976) Hemiptera (Matsumoto 2014). image freely determined user. Because v1, smallest resolvable point actual pixel size (1.4 1.4 µm). For reason, setting 1,296 972 pixels 2 binning applied downsample image. added benefit doubling signal noise ratio. resolution, capture up 42 per seconds (FPS) 90 FPS 640 480 (Barnes, Low essential avoid autonomous operation times exceed targeted phenomenon (the anthesis instance). reduce drawn 0.13W, deactivated our application: HDMI port, Bluetooth LEDs. electronic multimeter (RuiDeng UM25C) measure various conditions. load each different settings given Table 2. found both frame substantial effect 2; Figure S1). 15 second achieve lowest possible needs while affecting ability identify insects. With switched off night, will draw only 0.76 1.87 W, respectively, day night. theoretically permits continuous filming 72 hr 30,000-mAh (111 Wh) bank, was confirmed deployment. able run almost 9 days if recordings performed IRD advocate application algorithms post-processing stage rather situ processing out sequences computationally expensive. additional directly depend complexity. comparison, extra 0.89 0.57 W implemented RPi Cam Web Interface (https://github.com/silvanmelchior/RPi_Cam_Web_Interface) MotionEyeOS (https://github.com/ccrisan/motioneye) respectively 2) increase 24 (with 12 daylight) c. 67% 43% respectively. Once 64 GB 57 free data. saved MP4 files encoded H.264 standard. hour default compression, outdoor take around 700 MB. Therefore, space factor, before media get saturated. noticed artefact reducing file higher level, thus further efficiency needed. Processing pictures time- power-intensive. choice data, detection, processor temperature fine-tuning omission. Motion techniques post-process effective detecting pollinator (Azarcoya-Cabiedes Weinstein, 2015). In study, useful rare brief visits frequent. Two presented (pp. 36–39). assess performance field, studied plant species contrasting habits, ecologies floral characteristics: Ebony tree Diospyros crassiflora Hiern orchid Cyrtorchis letouzeyi Szlach. Olszewski. commercially valuable native rainforests Central Africa reach 25 m height. Until identity unknown (Deblauwe, Staminate carpellate flowers character known dioecy. considered potential all entirely enter narrow opening (c. 5 mm wide) fused petals corolla. PICTs were placed dusk D. trees (4–10 ground), front single flower estimated following 6 14 April 2018 Mbalmayo arboretum, Cameroon. total, observed. Time arrival departure visiting Every entered entirely, head abdomen, independent visit. letouzeyi, sub-endemic primarily Cameroon, remarkable ivory white nectar spur measuring 10 cm length. emit strong lilac/jasmine scent easily growing height 1–3 shrubs bordering grasslands inselbergs Dja Faunal Reserve (East Cameroon). Pollination syndromes suggest could visited long-tongued hawkmoths (Cribb, 1989), had yet six individuals bearing least inflorescences each, consecutive (24 June July) 2019 July). Batteries cards replaced every 48 hr. detect post-processing, own MATLAB routine. same detected open-source cross-platform command-line tool DVR-Scan (https://dvr-scan.readthedocs.io). automatic necessary remove flowers. Videos analysed manually watching 8× VLC player software. recorded total 76.3 stage. occasion non-insect seen interacting squirrel (Anomalurus sp.) predating (Video Flowers fully open midnight dropped 20 later, just after dusk. antheses five (four staminates carpellate) 394 videos. identified three families (two orders) flowers: Thrinchostoma sp. (Halictidae), Ceratina sp., Plebeina hildebrandti Friese, Meliponula (Meliplebeia) nebulata Smith (Apidae) Sphingidae. Up 141 concentrated daytime. nocturnal spp. bees rarely observed, being first flowers, potentially 2). One visitors, Apis mellifera Linnaeus twice, flower. corolla S1) therefore represented 1,447 monitored campaigns 2019. Post-processing resulted 66 summary files. Only 121 166 registered contact ten taxonomic Orders 3). C. Sphingidae Xanthopan morganii Walker Coelonia fulvinotata Butler 13 video. Pollen transfers resulting fecundation showing attachment pollinaria probosces hawkmoth (see example Video S2) daily, fruits. mean 19.6 s (±20.7 s, SE). pollinarium removal 25.3% (84/332 flowers) fruit 6.3% (21/332 entire population (31 individuals) 2-year survey. Our demonstrate resolves commonly associated monitor ectotherms conventional 2013): system. 32 Wh recommended bank. Customizable acquisition quality. proprietary technologies, preventing users modifying specific options acquisition. pixels, provided clear, sharp allowed identifying genus level S1–S3). Modular architecture. Interchangeable lenses permit sizes. Lenses wide focal lengths available, fisheye telephoto lenses. best knowledge, there currently film cm. (d) Portability. weigh 250 g. weighs 450–690 g, 22,000 30,000 mAh tested. weight substantially similar recently proposed literature Clayborn Clayborn, Nazir (e) Remote control. control, live transfer smartphone, tablet laptop facilitate placement difficult access. (f) Low-cost components. 1) suite software operate analyse maximize portability minimize cost. consequence choices. autonomy 3 continuously. depends capacity. Data widely inexpensive sufficient store more (resolution 972, FPS). improved solar panel (a process pass-through charging technology). When external source longer time, then capacity might limiting. case, save media. libraries https://github.com/Motion-Project/motion https://opencv.org/). reduced. absence source, either sacrificed algorithm. durability harsh affected electrostatic damage, flaws sealing mishandling plastic container. Occasional malfunction however posed challenge experiments due ease low-cost acquiring spare parts repair damages. controlled remotely via Wi-Fi. area, smoothly away smartphone emitting network. expect distance obstructed environments, operator probably repeaters wireless supervision required. computers. computational power, versatility connectivity complex tasks performed. If arises, interact (Bluetooth Wi-Fi) any nearby devices, including PICTs, remote machine Internet. minor modifications made present here, believe ex experiments, instance document insects’ social predator–prey interactions, (micro)climate change herbivory phenology. part Congo Basin Institute's Project generously funded UCLA Bob Taylor, owner Taylor Guitars co-owner Crelicam mill Yaoundé, Field investigations materials partly Fondation pour Favoriser la Recherche sur Biodiversité en Afrique (João Farminhão Laura Azandi PI), Leonardo Dicaprio Foundation Aspire Grant Program (Laura PI). express gratitude American Orchid Society (AOS) funding Ph.D. activities Cameroon her stay herbarium Université Libre de Bruxelles. grateful David Roubik identification pollinators. much indebted Fabienne Van Rossum Camille Cornet us sequence Silene nutans L. S3. conservator staff Reserve, local authorities communities support help fieldwork activities. also thank Ruksan Bose anonymous reviewers whose comments helped improve final version manuscript. V.Dr. V.De. conceived idea; V.Dr., V.De., L.A., M.S. E.R.O. collected data; L.A. wrote manuscript input M.S., T.B.S. E.R.O.; authors contributed draft written M.S.; figures; assembled edited clips Information. gave approval publication. declare connection whatsoever brands entities cited text accompanying illustration. peer review article https://publons.com/publon/10.1111/2041-210X.13618. code step PICT, movies archived https://doi.org/10.5281/zenodo.4139839 Please note: publisher responsible content supporting information authors. Any queries (other missing content) should directed corresponding author article.