Biology subjects

Samad, I.

Publications and source records attributed to Samad, I..

6 recordsLinked to original sources

bioRxiv2026

Plumage colour structures global patterns of mixed-species bird flocks

Mixed-species groups (MSGs) pose a particular challenge for our understanding of sociality in animals. Though MSGs are widespread social assemblages that form to enhance foraging success and reduce predation risk of participants, the role of traits in mediating grouping has received less attention. In particular, the role of body colour has not been tested quantitatively, despite the fact that visual similarity can reduce individual predation risk. Here, we examine whether plumage colour structures mixed-species bird flocks (MSFs) at a global scale. Using data spanning four continents, we developed a new metric that quantifies colour similarity among flock participants and compared observed flocks to null assemblages constructed from all flocking species at each site. We further examined whether MSF participants represented a colour subset of the available colours in the regional species pool. We found striking evidence that birds in MSFs were more similar in colour than expected by chance across all sites, indicating that plumage colour is a non-random structuring trait that shapes assembly of flocks globally. The strength and prevalence of colour structuring varied across geographies, but not flock size. Within communities, MSF participants differed systematically in colour composition from the regional species pool, occupying a restricted region of colour space dominated by yellow and brown plumage. Thus, plumage colour affects MSFs influencing both overall flock participation as well as species co-occurrence within flocks. Our findings illustrate the importance of visual traits in structuring interspecific social systems, by highlighting that birds of a feather do indeed flock together.

ecology↗

bioRxiv2025

Lower-middle-income countries disproportionately face the burden of the Open Access publication model

While the Open Access (OA) publishing model may promote equity in the readership of scientific publications, its implications for global research authorship remain poorly quantified. We analysed 504,723 publications over the past decade from 350 Scopus-indexed ecology and evolution journals to compare publication rates and institutional diversity a) between Subscription-Based (SB) and OA publishing models, and b) before and after journals transitioned to fully OA, across country income groups. We found that both publication rates and institutional diversity were lower in the OA publishing model, but with variable differences across country groups. These differences were weaker (by [~]140%) in low-income countries (where full waivers on Article Publishing Charges (APCs) are automatically provided) compared to middle-income countries (where only discounts on APCs are provided). For journals transitioning to a fully OA publication model, publication diversity decreased in middle-income countries and increased significantly in low-income countries. Therefore, OA disproportionately concentrates publishing potential within a few institutions, undermining authorship equity. The OA model, despite its egalitarian philosophy, risks amplifying geographic and institutional disparities in ecology and conservation science. Incorporating models that account for individual and institutional-level variations in funding availability, or providing alternative pathways for publishing, may help reduce this disparity.

ecology↗

bioRxiv2025

Human activities drive novel behaviours and transitions in dolphins

Intensifying human activities are reshaping coastal ecosystems, yet their impact on wildlife behaviour and survival remain poorly understood. We conducted drone-based focal-group follows of endangered Indian Ocean humpback dolphin groups in Goa, India, to quantify how tourism and fisheries jointly impact behavioural states and transitions. By integrating machine learning and georeferencing techniques, we found that both human activities triggered distinct behavioural transitions absent in undisturbed groups. Dolphins expressed escape behaviours exclusively near tourist boats and were more likely to transition into foraging near fishing nets (mostly purse-seines). Smaller groups reacted more strongly to tourist boats and interacted more frequently with fishing nets, especially in seasons when fish landing data showed a decline in their prey. These findings offer new insights into the behavioural mechanisms underlying the co-occurrence of coastal dolphins with humans and provide broader guidelines for managing tourism and fisheries to reduce anthropogenic pressure on threatened delphinids.

ecology↗

bioRxiv2025

Integrated deep learning and geo-referencing for drone-based animal tracking with flexible camera angles

O_LIThe ability of drones to provide detailed information on animals and their surroundings makes them ideal for studying animal behaviour at fine scales. While drones can provide high-resolution images of what animals are doing, they should also, in theory, be able to provide data on where they are. However, reconstructing geo-referenced tracks from drone videos that follow animals is challenging, particularly because current methods require specific drone flight patterns and large computational power. C_LIO_LIHere, we combine deep learning and object tracking methods with a novel geo-referencing algorithm which allows us to track individuals across video frames and reconstruct their geo-referenced trajectories. We used a Region-based Convoluted Neural Network to detect animals and a Hungarian tracking algorithm to link detections across video frames, and then geo-referenced each detection in every frame to reconstruct individual trajectories. C_LIO_LIWe tested our geo-refencing algorithm through multiple drone flights with varying flight parameters over known Ground Control Points. The median (95% CI) geo-referencing error was 2.81 (0.74 - 23.23) meters, which reduced by 50% when the drone camera was positioned between -90{degrees} and -40{degrees}. Error increased with drone height and camera angle (-90{degrees} refers to the camera pointing towards the ground) but was not impacted by drone orientation. C_LIO_LIWe then demonstrate the utility of our framework with empirical examples using consumer-level drones. First, we tracked a volunteer carrying a high-resolution GPS unit and overlayed their GPS tracks on our estimated tracks to quantify tracking error. Next, we used drone videos of two delphinid species (Tursiops truncates gephyreus, and Sousa plumbea) representing varying environmental and flight conditions. We were able to successfully infer individual tracks across all conditions except when individuals formed tight clusters, in which case tracks were assigned a group identifier. C_LIO_LIOur framework demonstrates an easy and robust approach to translate drone videos of moving animals into geo-referenced animal tracks which is applicable in many research contexts. A major advance over previous methods is that our algorithm is robust to different camera angles, and provides tracks with accuracy on-par with, or even exceeding, the accuracy from GPS tracking. C_LI HeadlineAutomated drone-based animal tracking

ecology↗

bioRxiv2024

Species rich but data poor: leveraging distribution modelling techniques to map cetacean occurrence in South Asian waters

Cetaceans play important ecosystem roles but are challenging to study since they are highly mobile and spend their entire life at sea. More than a third of all cetaceans occur in South Asian waters where they overlap with several key threats including fisheries, pollution, and high vessel traffic. However, baseline information on their occurrence at the sub-continental scale is lacking even for relatively well studied species. To address this gap, we collated sighting information on cetaceans from the North Indian Ocean region (5-25{degrees}N, 65-95{degrees}E) and used species-tuned distribution models and ensemble modelling approaches with physiographic and oceanographic predictors to map habitat suitability and species richness. We used Multivariate Environmental Similarity Surfaces (MESS) indices and expert reviews to validate our predictions and better infer species distribution. We collated 2329 sighting records for 31 species and modelled the distribution of 18 species. Areas of high species richness, defined by high slope and bathymetric complexity, occurred along the east coast of India, in south Sri Lanka, and around the Lakshadweep and Andaman and Nicobar archipelagos. Species richness patterns were generally consistent with the six identified ecoregions in the area. Most of our predictions were given high scores by the expert reviewers. Our maps underpredicted the occurrence of a few oceanic species, highlighting the need for focused offshore surveys, and overpredicted areas with high MESS indices for all species. We discuss the occurrence patterns and their drivers for these cetacean species while highlighting knowledge gaps and the importance of fine-scale distribution data for conservation planning, especially during the development of regional management plans for cetaceans.

ecology↗

bioRxiv2020

Plasticity after cortical stroke involves potentiating responses of pre-existing circuits but not functional remapping to new circuits

Functional recovery after stroke is thought to be mediated by adaptive circuit plasticity, whereby surviving neurons assume the roles of those that died. This "remapping" hypothesis is based on human brain mapping studies showing apparent reorganization of cortical sensorimotor maps and animal studies documenting molecular and structural changes that could support circuit rewiring. However, definitive evidence of remapping is lacking, and other studies have suggested that maladaptive plasticity mechanisms, such as enhanced inhibition in peri-infarct cortex, might actually limit plasticity after stroke. Here we sought to directly test whether neurons can change their response selectivity after a stroke that destroys a single barrel (C1) within mouse primary somatosensory cortex. Using multimodal in vivo imaging approaches, including two-photon calcium imaging to longitudinally record sensory-evoked activity in peri-infarct cortex before and after stroke, we found no evidence to support the remapping hypothesis. In an attempt to promote plasticity via rehabilitation, we also tested the effects of forced use therapy by plucking all whiskers except the C1 whisker. Again, we failed to detect an increase in the number of C1 whisker-responsive neurons in surrounding barrels even 2 months after stroke. Instead, we found that forced use therapy potentiated sensory-evoked responses in a pool of surviving neurons that were already C1 whisker responsive by significantly increasing the reliability of their responses. Together, our results argue against the long-held theory of functional remapping after stroke, but support a plausible circuit-based mechanism for how rehabilitation may improve recovery of function.

neuroscience↗