While large avian frugivores are known to be key dispersers for large‐seeded tree species, their role in community‐wide plant‐disperser networks is still poorly known. Large avian frugivores are also among the most threatened due to anthropogenic impacts. We evaluated the role of large avian frugivores in a plant‐disperser community by (a) determining whether the plant‐disperser community was modular, with a distinct community of large frugivores (thereby highlighting their importance), (b) determining relative qualitative and quantitative roles played by large‐bodied frugivores vis‐à‐vis other frugivores and (c) determining impacts of large‐bodied frugivore loss on the plant‐disperser community. The study was carried out at a tropical forest site in north‐east India, which is part of the Eastern Himalaya Biodiversity Hotspot. We collected tree watch data (20:55 hr) from 46 tree species, which represented 85% of tree species that are predominantly bird‐dispersed in the area. We found that the plant‐disperser community was modular, with a distinct module of large‐seeded tree species and large frugivores. Intermediate‐sized frugivores such as barbets and bulbuls were the most connected, while large‐sized frugivores, such as hornbills and imperial pigeons, were moderately well connected. Qualitative and quantitative roles played by different dispersers varied across the gradient of frugivore body size. Hornbills, the largest avian frugivores, consumed a significantly greater number of fruits and swallowed larger proportions of fruits compared with other avian groups. In comparison with similar‐sized frugivores, imperial pigeons fed on larger‐sized fruits, highlighting their importance for dispersal of large‐seeded plants. Under simulated extinction scenarios, larger extinction cascades were not necessarily caused by larger frugivores; however, extinctions of certain large‐bodied frugivores (hornbills, imperial pigeons) caused extinction cascades. Integrating information from networks and seed dispersal effectiveness approaches enabled a better understanding of large frugivore role in a plant‐disperser community. While large‐bodied frugivores may not be playing a central role in plant‐disperser communities, they are crucial as seed dispersal service providers for large‐seeded plants. In conjunction with the reported local extinctions of large frugivores like hornbills from the south Asian region, this study’s findings highlight the irreplaceable quantitative and qualitative impacts that tropical plant communities are likely to experience in the future.
8 91. Video recordings of animals are used for many areas of research such as collective movement, animal 10 space-use, animal censuses and behavioural neuroscience. They provide us with behavioural data at 11 scales and resolutions not possible with manual observations. Many automated methods are being 12 developed to extract data from these high-resolution videos. However, the task of animal detection and 13 tracking for videos taken in natural settings remains challenging due to heterogeneous environments. 14 2. We present an open-source end-to-end pipeline called Multi-Object Tracking in Heterogenous environ-15 ments (MOTHe), a python-based application that uses a basic convolutional neural network for object 16 detection. MOTHe allows researchers with minimal coding experience to track multiple animals in their 17 natural habitats. It identifies animals even when individuals are stationary or partially camouflaged.18 3. MOTHe has a command-line-based interface with one command for each action, for example, finding 19 animals in an image and tracking each individual. Parameters used by the algorithm are well described 20 in a configuration file along with example values for different types of tracking scenario. MOTHe 21 doesn't require any sophisticated infrastructure and can be run on basic desktop computing units.22 4. We demonstrate MOTHe on six video clips from two species in their natural habitat -wasp colonies 23 on their nests (up to 12 individuals per colony) and antelope herds in four different types of habitats 24 (up to 156 individuals in a herd). Using MOTHe, we are able to detect and track all individuals in 25 these animal group videos. MOTHe's computing time on a personal computer with 4 GB RAM and i5 26 processor is 5 minutes for a 30-second long ultra-HD (4K resolution) video recorded at 30 frames per 27 second. 28 5. MOTHe is available as an open-source repository with a detailed user guide and demonstrations at 29 Github (https://github.com/tee-lab/MOTHe).30 1 Introduction 31Video-recording of animals is increasingly becoming a norm in behavioural studies of space-use patterns, be-32 havioural neuroscience, animal movement and group dynamics [1, 2]. High-resolution images from aerial pho-33 tographs and videos can also be used for animal census [3, 4, 5]. This mode of observation can help us gather 34 high-resolution spatio-temporal data at unprecedented detail and help answer a novel set of questions that were 35 previously difficult to address. For example, we can obtain movement trajectories of animals to describe space-36 use patterns of animals, to infer fine-scale interactions between individuals within groups and to investigate 37 how these local interactions scale to emergent properties of groups [6, 7, 8, 9, 10, 11, 12, 13]. To address these 38 questions, as a first step, videos need to be converted into data -typically in the form of positions and trajec-39 tories of animals. Manually extracting this information from videos can be time-consuming, tedious and, often 40 not feasible...
Lekking is a spectacular mating system in which males maintain tightly organized clustering of territories during the mating season, and females visit these leks for mating. Various hypotheses—ranging from predation dilution to mate choice and mating benefit—offer potential explanations for the evolution of this peculiar mating system. However, many of these classic hypotheses rarely consider the spatial dynamics that produce and maintain the lek. In this article, we propose to view lekking through the perspective of collective behaviour, in which simple local interactions between organisms, as well as habitat, likely produce and maintain lekking. Further, we argue that interactions within the leks change over time, typically over a breeding season, to produce many broad-level as well as specific collective patterns. To test these ideas at both proximate and ultimate levels, we argue that the concepts and tools from the literature on collective animal behaviour, such as agent-based models and high-resolution video tracking that enables capturing fine-scale spatio-temporal interactions, could be useful. To demonstrate the promise of these ideas, we develop a spatially explicit agent-based model and show how simple rules such as spatial fidelity, local social interactions and repulsion among males can potentially explain the formation of lek and synchronous departures of males for foraging from the lek. On the empirical side, we discuss the promise of applying the collective behaviour approach to blackbuck ( Antilope cervicapra ) leks—using high-resolution recordings via a camera fitted to unmanned aerial vehicles and subsequent tracking of animal movements. Broadly, we suggest that a lens of collective behaviour may provide novel insights into understanding both the proximate and ultimate factors that shape leks. This article is part of a discussion meeting issue ‘Collective behaviour through time’.
Animals spend a significant amount of time roosting. Therefore, understanding roosting patterns and the processes that influence roosting behaviour and roost site choice is essential. Hornbills exhibit interesting roosting patterns with some species roosting communally in large flocks. They are important seed dispersers and patterns of roost site use can have a significant influence on seed dispersal distributions and thereby on plant recruitment. We documented roost site use by four Great Hornbills (Buceros bicornis) and one Wreathed Hornbill (Rhyticeros undulatus) at a site in north-east India using GPS telemetry. We examined the influence of riverine habitats, nests and foraging range on roost selection. We determined the proportion of seeds that hornbills disperse at roosts and the dispersal distances of seeds dispersed at roosts from the source trees. Through telemetry, we found that roosts of Great Hornbills were generally in forested habitats. Our telemetry data showed that Wreathed Hornbill roosts were close to the river. These results were corroborated by observational data from roost sites where we had regular detections of relatively large flocks of Wreathed Hornbills and occasionally Great Hornbills. The roost sites were not close to the nest sites and were generally within the 95% kernel density diurnal activity ranges. Hornbills dispersed a small proportion of seeds at roost sites. Seeds dispersed at roost sites had almost twice the dispersal distances compared to those dispersed at non-roost sites. This study highlights variation in roost site pattern across individual hornbills and its implications for seed dispersal.
Knowledge about roost selection can have implications for understanding the ecological role played by animals. For example, some frugivorous animals have been reported to clump-disperse seeds at their roosts that are used repeatedly (Datta, 2001;Howe, 1989;Kitamura et al., 2008). Clump-dispersed seeds at communal roosts that are repeatedly used experience high mortality due to negative density dependence (Comita et al., 2014;Datta, 2001;Kitamura et al., 2008). However, if clump-dispersed seeds at roost sites form only a small proportion of seeds that are dispersed by the frugivore, it may not significantly alter the overall contribution of the frugivore to seed dispersal. Relative proportions of seeds that get dispersed at favorable and unfavorable sites by animals are typically not estimated (Naniwadekar et al., 2019b). This is critical for determining the quantitative and qualitative role of frugivores in seed dispersal (Schupp, 1993).Hornbills are key avian seed dispersers with interesting roosting ecology. They may roost as singles, in pairs, smaller flocks, or in large communal roosts (up to 2,000 birds) (Poonswad et al., 2013). A telemetry study on Southern Ground Hornbills (Bucorvus leadbeateri) in South Africa revealed that the birds preferred riverine habitat for roosting and exhibited site fidelity (Zoghby et al., 2016). In northeast India, hornbills roost on isolated trees, in open riverine grassland areas or on cliff faces with lower tree density, and they exhibit
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