Biology subjects

Nyaguthii, B.

Publications and source records attributed to Nyaguthii, B..

9 recordsLinked to original sources

bioRxiv2025

Space use fidelity of non-territorial vulturine guineafowl groups is shaped by both environmental and social processes

Animals often use consistent areas. Some are territorial, restricting their space use within territorial boundaries, whereas others at not territorial animals but still restrict their space use despite not being constrained by surrounding conspecifics. Staying within a familiar area can provide a range of benefits, such as using previous knowledge (i.e. memory) to efficiently exploit resources or because they can consistently return to key locations (such as a nest or sleeping site). In group-living animals, consistent space use could reduce the complexity of decision-making time (e.g. by choosing among known foraging sites), facilitating group cohesion. However, to date, little research has explicitly asked what factors determine whether groups use consistent areas. Here we used repeated movements by groups of vulturine guineafowl (Acryllium vulturinum)--leaving and returning back to the same areas in response to seasonal conditions--to examine and disentangle social processes from spatial and ecological factors that might shape the distribution of animals over space. Specifically, we quantified (i) how groups distribute themselves over the landscape, (ii) if their space use is consistent across seasons with similar environmental conditions, (iii) how different social and spatial factors shape the consistency of space use by groups over time, and (iv) how social and spatial factors affect home range overlap between groups. We found that groups were highly consistent in their space use over time and that home ranges were distinct across groups. Fidelity to the core home range area was higher when group composition was more stable, while overall home range fidelity was higher when groups recently experienced milder ecological conditions. Overlap in core areas and the overall home ranges among groups were greater among groups that shared roosts and groups that were fused in the previous season. Home range overlap was also lowest during long intermediate seasons (i.e. a sampling period that immediately follows intermediate season conditions, as opposed to sampling periods that followed dry or wet conditions), suggesting that extended intermediate conditions allow groups to increasingly partition their overall space use. These results provide insights into how the movement decisions by groups, the distribution of animals, and group-level space use emerge, and the role of social and ecological conditions as potential precursors to territoriality.

ecology↗

bioRxiv2025

Group size influences behavioral plasticity in responses to thermoregulation-foraging trade-offs by a socially cohesive bird

Behavioral plasticity, such as changes in habitat use and activity, can be a critical modulator of thermal pressures on endotherms. However, shifts in behaviors can meet diversified costs such as missed feeding opportunities. Individual decision-making should therefore capture the trade-off between the costs and the benefits of thermoregulation. In the case of social species, the decision process could also be facilitated or slowed down by the modulation of costs arising through the social environment. In this study, we tested how vulturine guineafowl (Acryllium vulturinum) change their use of open areas (where they predominately forage) according to heat using GPS data from 105 birds collected every 5 minutes for 6 months. Because animals vary in their sensitivity to risk according to group size--e.g. due to the dilution effect--we compared the responses of individuals depending on the size of the group they belong to. We also analyzed if behavioral responses translate into less precise thermoregulation by recording the body temperature of a subset of birds in two groups. We foundd that birds avoid heat by selectively using open areas and moving to cover, as well as reducing activity when temperature increases, birds use open areas less and move less. Individuals from intermediate-sized groups seemed to be able to use open areas during warmer conditions compared to individuals from small and large groups (10% higher probability of use). However, active birds in the open did not present hyperthermia, suggesting that behavioral changes are efficient or that individuals have other efficient strategies such as physiological cooling. Together, these results indicated that responses to high temperatures are complex, as they included not only a range of environmental constraints but that responses can also vary according to social context.

ecology↗

bioRxiv2024

Moving towards more holistic validation of machine learning-based approaches in ecology and evolution

Machine-learning (ML) is revolutionizing field and laboratory studies of animals. However, a challenge when deploying ML for classification tasks is ensuring the models are reliable. Currently, we evaluate models using performance metrics (e.g., precision, recall, F1), but these can overlook the ultimate aim, which is not the outputs themselves (e.g. detected species or individual identities, or behaviour) but their incorporation for hypothesis testing. As improving performance metrics has diminishing returns, particularly when data are inherently noisy (as human-labelled, animal-based data often are), researchers are faced with the conundrum of investing more time in maximising metrics versus doing the actual research. This raises the question: how much noise can we accept in ML models? Here, we start by describing an under-reported factor that can cause metrics to underestimate model performance. Specifically, ambiguity between categories or mistakes in labelling validation data produces hard ceilings that limit performance metrics. This likely widespread issue means that many models could be performing better than their metrics suggest. Next, we argue and show that imperfect models (e.g. low F1 scores) can still be useable. Using a case study on ML-identified behaviour from vulturine guineafowl accelerometer data, we first propose a simulation framework to evaluate robustness of hypothesis testing using models that make classification errors. Second, we show how to determine the utility of a model by supplementing existing performance metrics with biological validations. This involves applying ML models to unlabelled data and using the models outputs to test hypotheses for which we can anticipate the outcome. Together, we show that effects sizes and expected biological patterns can be detected even when performance metrics are relatively low (e.g., F1: 60-70%). In doing so, we provide a roadmap for validation approaches of ML classification models tailored to research in animal behaviour, and other fields with noisy, biological data. HighlightsEvaluating machine learning (ML) models must go beyond performance metrics Mislabels in validation data leads to underestimation of models performance Underestimated metrics can cause research delays despite models being useful We propose simulations and biological validations to evaluate model performance Models with low standard metrics can still be powerful for hypothesis testing

ecology↗

bioRxiv2024

Low-cost animal tracking using Bluetooth low energy beacons on a crowd-sourced network

O_LIAnimal tracking has opened the door to address many fundamental questions in ecology and conservation. While historically animals have been tracked as a means to understand their large-scale movements, such as migration, there is now a greater focus on using tracking to study movements over smaller scales, individual variation in movement, or how movements shape social network structure. With this shift in focus also comes different tracking needs, including the need to track larger numbers of individuals. C_LIO_LITracking studies all face some technological limitations. For example, GPS and other active tracking solutions can collect fine-scale movement data, but have a high cost per tag, limiting the number of individuals that can be followed. They also have high energy costs of data acquisition and download, limiting time periods over which data can be collected. Low-energy passive (e.g. PIT) or active (e.g. reverse GPS) tags can overcome these limitations, but instead require animals to remain within a bounded study area or to come into close proximity to detectors. C_LIO_LIHere we describe one solution that can overcome many current limitations by employing the massive global network of personal mobile phones as gateways for tracking animals using Bluetooth low energy (BLE) beacons. In areas with medium to high density of people, these simple-to-make beacons can provide regular updates of position over long time periods (battery life 1-3 years). We describe how to use off-the-shelf components to produce BLE beacons that weigh c. 5-6 g and cost < $7USD. Using field testing, we then show that beacons are capable of producing high-frequency tracking data that can be used to build home ranges or to detect spatio-temporal co-occurrences among individuals. C_LIO_LIBLE beacons are a low cost, low energy solution for studying organisms (e.g. birds, mammals, and reptiles) living and moving in urban landscapes. Their low weight and small size makes them particularly well-suited for tracking smaller species. When combined with fixed gateways, their use can also be extended to non-urban habitats. Their high accessibility is likely to make them an attractive solution for many research projects. C_LI

animal behavior and cognition↗

bioRxiv2023

Moving as a group imposes constraints on the energetic efficiency of movement.

Movement is a key part of life for both solitary and group-living animals. In solitary animals, the energetic costs of making large displacements can be mitigated by energetically efficient strategies--specifically faster, straighter movements. However, little is known about whether moving as part of a collective enhances or limits the ability for individual group members to express such strategies. Drawing on 6 years of population-level high-resolution (1Hz) GPS tracking of group-living vulturine guineafowl (Acryllium vulturinum), we detected 886 events from 94 tagged individuals where their groups made large displacements, shifting their home ranges in response to changing environmental conditions. We contrasted these movements with data with 94 large displacement events by 19 lone, dispersing individuals. Our results suggest that individuals moving as part of group can significantly reduce their energetic cost of transport when making large displacements (15.5% reduction relative to their normal daily ranging behaviours) by increasing the speed and straightness of their movements. However, even during their most-efficient movements, individuals in groups could not achieve or maintain the same increases in speed that others could when moving alone, resulting in significantly limited efficiency gains (solitary individuals were 34.9% more efficient than individuals in groups). Overall, this study provides evidence for a substantial, and previously hidden, energetic cost arising from collective movement.

ecology↗

bioRxiv2023

The physiological costs of spatial positioning and leadership in collective movements

Individuals can gain substantial benefits from collective actions1-7. However, collective behaviours introduce new challenges, like coordinating actions, maintaining cohesion, and meeting the needs of different individuals. When making collective movements, leaders are typically thought to gain disproportionate benefits through the choice of more beneficial resources3 and/or earlier access to resources8. However, reaping these benefits can also have costs. Being at the front of a group can increase physical exertion4,9,10 and predation risk11,12. Moreover, ending up in a leadership position (i.e., at the front), is a process of negotiation in many animal groups. Within-group differences in directional preferences are typically resolved by some individuals initiating directional movements, after which they are either followed (if they are successful in leading) or return to the group (if they fail)13-30. By combining data on movement initiations (using whole-group GPS tracking31 and individual heart rate from implanted ECG loggers) in wild vulturine guineafowl, we found significant increases in heart rate (and decreases in heart rate variability) during collective movements. We found that attempting--and failing--to initiate directional movement was particularly costly, with the highest costs when consensus among group members was low and when individuals acted against the majority. Increases in heart rate and decreases in its variability can indicate physiological stress, entailing increased energy expenditure and long-term physiological damage. These results suggest that behaviours often thought beneficial to individuals (by influencing group behaviours) are also physiologically costly, representing a constraint on group-living and explaining why sometimes individuals opt out of contributing to leadership.

ecology↗

bioRxiv2023

Breeding alters females' social positions by changing dominance dynamics

Agonistic and affiliative interactions with group members dictate individuals access to resources, and investment in competing for resources is often traded off with other needs. For example, reproductive investment can reduce body condition and, thereby, an individuals ability to win future agonistic interactions. However, group members may also alter their behaviour towards reproductive individuals, such as becoming more or less aggressive. Here, we investigated the social consequences of reproduction in female vulturine guineafowl Acryllium vulturinum, a plural breeder in which females disperse and are subordinate to males. We found opposing patterns for breeders within- and between-sex dominance interactions from before to after breeding. Specifically, while breeding females became far less likely to win dominance interactions with non-breeding females after breeding than before breeding, they received considerably fewer male aggressions than non-breeding females after breeding. Using agent-based models, we then show that hierarchies inferred using the Percolation and Conductance method are robust to such variation in interaction rates, while other common methods may be prone to systematically overestimating or underestimating particular individuals hierarchy positions. Our study highlights reproduction as a driver of dominance dynamics, and illustrates how the study of dominance may benefit from considering variation in interaction rates.

animal behavior and cognition↗

bioRxiv2022

Cooperative breeding in a plural breeder: the vulturine guineafowl (Acryllium vulturinum)

Cooperative breeding is widely reported across the animal kingdom. In birds, it is hypothesised to be most common in altricial species (where chicks are dependent on parental care in the nest after hatching), with few described cases in precocial species (where chicks are more independent immediately after hatching). However, cooperative breeding may also be more difficult to detect in precocial species and therefore has been overlooked. In this study, we investigate whether vulturine guineafowl (Acryllium vulturinum)--which have precocial young--breed cooperatively and, if so, how care is distributed among group members. Using data collected from colour-banded individuals in one social group of vulturine guineafowl over three different breeding seasons, we found that multiple females can attempt to reproduce in the same breeding season. Broods had close adult associates, and most of these associates exhibited four distinct cooperative breeding behaviours: babysitting, within-group chick guarding, covering the chicks under the wings and calling the chicks to food. Further, we found that offspring care is significantly male-biased, that non-mother individuals provided most of the care each brood received, that breeding females differed in how much help they received, and that carers pay a foraging cost when providing care. Our results confirm that vulturine guineafowl are cooperative breeders, which they combine with an unusual plural-breeding social system. Our study also adds to growing evidence that cooperative breeding may be more widespread among species with precocial young than previously thought, thereby providing a counterpoint to the altriciality-cooperative breeding hypothesis.

animal behavior and cognition↗

bioRxiv2021

Costs dictate strategic investment in dominance interactions

Dominance is important for access to resources. As dominance interactions are costly, individuals should be strategic in who they interact with. One hypothesis is that individuals should direct costly interactions towards those closest in rank, as they have most to gain--in terms of attaining or maintaining dominance--from winning such interactions. Here, we show that male vulturine guineafowl (Acryllium vulturinum), a gregarious species with steep dominance hierarchies, strategically express higher-cost aggressive interactions towards males occupying ranks immediately below themselves in their groups hierarchy. In contrast, lower-cost aggressive interactions are expressed towards group members further down the hierarchy. By directly evaluating differences in the strategic use of higher- and lower-cost aggressive interactions towards competitors, we show that individuals disproportionately use highest-cost interactions--such as chases--towards males found one to three ranks below themselves. Our results support the hypothesis that the costs associated with different interaction types can determine their expression in social groups with steep dominance hierarchies.

animal behavior and cognition↗