Biology subjects

Bassi, E.

Publications and source records attributed to Bassi, E..

4 recordsLinked to original sources

bioRxiv2026

Early avoidance of human-dominated landscapes by juvenile Alpine golden eagles

O_LIThe expanding human footprint drives profound transformations in species, including not only morphological trait loss but also behavioural trait extinction. In contrast to behavioural trait extinction, which entails a reduction in genetic variability, behavioural plasticity maintains behavioural trait diversity and the associated genetic variability required for evolutionary adaptation. Yet, while behavioural plasticity shaping non-human capacity to coexist with humans has evolved under past, human-modified, environmental conditions, few studies have examined whether species retain a level of behavioural plasticity after past interactions with humans. C_LIO_LIUsing data from 64 juveniles golden eagles (Aquila chrysaetos) from a population demographically recovering after centuries of persecution, yet still restricted to less human-dominated alpine massifs, we tested whether human avoidance is innate or learned through experience during dispersal or parental influences during the pre-dispersal period. We performed a Principal Component Analysis (PCA) on landscape features used during the pre-dispersal and the first fifteen weeks of the dispersal phase, and used Mahalanobis distance as an indicator for quantifying changes in individual spatial behaviour over time. C_LIO_LIThe lower frequency of use of human-dominated landscape features, compared with the more sparsely populated mid- and high-elevation landscape features, resulted from individuals consistent use of similar landscape features across the pre-dispersal and dispersal periods. Avoidance of humans was therefore better explained by a learning or imprinting process prior to dispersal, which predisposed individuals to use landscape features similar to those experienced during pre-dispersal, rather than by learning during dispersal, or by an innate avoidance. C_LIO_LIImprinting on natal habitat features corroborates the observed limited range expansion of the alpine population beyond the massif borders. Differences among European populations in range recolonisation suggest contrasting histories of persecution, which may have left varying degrees of behavioural plasticity across populations. C_LIO_LIAs a guide for future conservation priorities, these findings underscore the need to reconstruct past conditions and/or to document contemporary animal behaviour in order to build a library of behaviours that can be used in the future to track behavioural changes. C_LI

animal behavior and cognition↗

bioRxiv2025

Cascading carry-over effects of early activity phenotypes in golden eagles

1.Early-life conditions are often associated with fitness of animals later in life. Although recent studies show that environmental conditions during development affect the formation of early behavioural phenotypes we have a limited understanding of the cascade of life-history transitions from early phenotypes to fitness relevant behaviours in later life stages. Here, we used GPS and body-acceleration data of 35 juvenile golden eagles (Aquila chrysaetos) to investigate the association between nestling body condition and activity levels (ODBA), the relationship of nestling activity with the timing of fledging and post-fledging activity, and the effects of post-fledging activity on post-fledging movements and the timing of dispersal. We found that nestlings with good body condition also showed increased activity levels. Active nestlings fledged earlier and remained more active after fledging than passive nestlings during early post-fledging. Increased post-fledging activity levels were related to an increased number of pre-dispersal forays and an early timing of dispersal. Even though some effects showed reduced certainty, our results provide evidence for downstream effects of behavioural differences due to early-life conditions. They suggest that early activity phenotypes of nestlings drive the timing of subsequent life-history transitions, thereby representing a key mechanism that links early life conditions with future performance.

ecology↗

bioRxiv2025

Timing of independence is explained by movement ability, but depends on how independence is defined for a long-lived raptor

Many young animals must gain independence from parental care by acquiring the necessary skills for survival. Thus, the rate of skill acquisition can predict how long juveniles remain with their parents before emigrating from the natal territory. Yet in some systems, young animals acquire adult-like skills and the capacity to be independent long before they emigrate. This raises the question of why the timing of emigration decouples from the rate of skill acquisition, resulting in extended parental care. We addressed this by leveraging GPS tracking data from juvenile golden eagles (Aquila chrysaetos), which learn to fly and to hunt while remaining with their parents for 61-283 days after fledging. Young golden eagles often go on excursions without their parents outside of their natal territories before emigration. We expected flight performance to predict the timing of excursions better than the timing of emigration, which should be more influenced by external factors. In a set of time-to-event models, we predicted the rate of excursions and of emigration using metrics of soaring flight performance or of daily movement. Contrary to our prediction, we found that soaring performance failed to predict the rate of either excursions or emigration, whereas daily movement predicted both rates, but inconsistently. This was likely because those coarser metrics captured motivation and weather in addition to flight skills. Thus external factors seem more likely to explain the timing of independence and internal development--in this case of flight skills--may be completed quickly. Juveniles may delay emigration not due to lack of skill, but because the costs of leaving parental care outweigh the benefits. The difference we discovered between when individuals were capable of independence and when they committed to it may obscure the more general link between skill acquisition and the end of parental care in other systems as well.

animal behavior and cognition↗

bioRxiv2023

Gaining proficiency in flight transforms energy landscapes during ontogeny

The heterogeneity of the physical environment determines the cost of transport for animals, shaping their energy landscape. Animals respond to this energy landscape by adjusting their distribution and movement to maximize gains and reduce costs. Much of our knowledge about energy landscape dynamics focuses on factors external to the animal, particularly the spatio-temporal variations of the environment. However, an animals internal state can significantly impact its ability to perceive and utilize available energy, creating a distinction between the "fundamental" and the "realized" energy landscapes. Here we show that the realized energy landscape varies along the ontogenetic axis. Locomotor and cognitive capabilities of individuals change over time, especially during the early life stages. We investigate the development of the realized energy landscape in the Central European Alpine population of the golden eagle Aquila chrysaetos, a large predator that requires negotiating the atmospheric environment to achieve energy-efficient soaring flight. We quantified weekly energy landscapes using environmental features for 55 juvenile golden eagles, demonstrating that energetic costs of traversing the landscape decreased with age. Consequently, the potentially flyable area within the Alpine region increased 2,170-fold during their first three years of independence. Our work contributes to a predictive understanding of animal movement by presenting ontogeny as a mechanism shaping the realized energy landscape.

animal behavior and cognition↗