Yvonnick Le Pendu

Respiration is a key physiological process in cetaceans, closely linked to energy expenditure, behavior, and physiological state. Using drone‐based surveys, we quantified respiration patterns of southern right whale ( Eubalaena australis ) mother–calf pairs in southern Brazil across two reproductive seasons (2020–2021). Based on over 100 h of observation from 43 identified pairs, we found marked differences between classes: respiration rates were 2.6‐fold higher in calves than their mothers, with median respiration rates of 1.8 and 0.7 breaths per minute, respectively. Respiration rates were significantly influenced by behavioral state, surface duration, and individual identity, decreasing during resting behavior and longer surface intervals. No statistically significant seasonal variation in respiration rates was detected. Comparative analyses revealed that lactating females in Brazil and Argentina exhibited similarly elevated respiration rates, both exceeding those reported for Australian females, suggest population‐level differences that are not solely explained by local environmental conditions. In contrast, calf respiration rates were highest in Argentina, potentially reflecting the combined effects of kelp gull harassment and colder water temperatures. Our findings demonstrate the sensitivity of respiration to behavioral, physiological, and environmental drivers and highlight the value of drone‐based observations for advancing physiological and conservation monitoring of baleen whales.

Increasing boat traffic in estuarine environments poses growing challenges for the conservation of coastal cetaceans, yet how these pressures interact with habitat features to shape spatial use remains poorly understood. This study investigated the influence of boat traffic and habitat features on the spatial use and habitat selection of Guiana dolphins ( Sotalia guianensis ) in Pontal Bay, a northeastern Brazilian estuary, using shore‐based observations and theodolite tracking of dolphin and boat trajectories collected between April 2015 and January 2016. Utilization distribution and habitat selection analyses revealed substantial overlap between dolphins and boats, particularly in deeper areas. At finer scales, however, dolphins preferentially used areas with lower boat traffic, greater depths, and proximity to fishing centers, while avoiding shallow zones and river edges. These patterns indicate a scale‐dependent trade‐off between access to foraging opportunities and exposure to anthropogenic disturbance. Our findings highlight the importance of integrating environmental and human‐related factors into estuarine management and support the need for measures that regulate vessel activity within key dolphin habitats.

Light is one of the main synchronizers of circadian rhythm, being essential for the temporal organization of mammalian behaviour. This study investigated in a controlled closed environment the effects of reduced illumination on the activity rhythms of the rodent Thrichomys laurentius. We compared the activity of a control group kept under a natural photoperiod to that of an experimental group exposed to low lighting. The individuals exposed to the low-intensity light showed circadian rhythm disruption, with alteration to the period of rest and activity. In contrast, individuals from the control group kept a rhythm aligned to the light/dark cycle. The circadian patterns varied among pups, including irregular cases of non-rhythmic fluctuations (pseudorhythms) during the 24-hour cycle, indicating still-immature endogenous rhythms. The combined application of actograms, Lomb-Scargle periodograms and the Cosinor model allowed identification of rhythmicity in behavioural activity and evaluation of their plasticity in the absence of zeitgebers. The results reveal that the dimming of the light compromises the robustness and organization of the circadian rhythms in T. laurentius, reinforcing that maintaining a natural photoperiod is essential for preserving consistent physiological and behavioural patterns in experimental environments.

While protective behaviors of baleen whales toward calves have been documented during predator attacks, they have not been observed in response to approach attempts by other males of the same species. We recorded high-resolution aerial drone videos of four competing male of humpback-whales (Megaptera novaeangliae) harassing a lactating female with her post-neonate calf in a breeding ground in Brazil. We document several protective behaviors and highlight a new role for pectoral fins in maternal protection, a function not previously attributed to this anatomical structure. These results confirm the value of using drones to describe new cetacean behaviors, even in well-known species.

BioStudies – one package for all the data supporting a study

This study compared the size and composition of humpback whale groups estimated from boat-based observations and drone video analysis during the 2022 and 2023 breeding seasons in Ilhéus, Brazil. Data from 43 groups showed that drone consistently recorded larger group sizes than boat-based observations, with a strong positive correlation between the two methods (r=0.94, p<0.001). Drone also enabled more accurate identification of group composition, detecting additional individuals and more complex group types - such as large competitive groups - than the boat-based method. A significant association between method and group composition was found (p<0.001), with drones identifying more groups composed of four or more adults or a mother-calf pair with several escorts. These findings underscore the advantages of drone-based surveys for improving assessments of group structure, contributing to more accurate data to monitor and conserve cetacean populations.

Brazil is one of the largest consumers of herbicides in the world, and glyphosate-based herbicides (e.g., Roundup^®) are commonly applied in cropland. Among vertebrates, amphibians are especially susceptible to contamination due to their strong association with freshwater environments. However, our knowledge of how these herbicides affect amphibians is still scarce, mainly regarding the impacts of commercial formulations. In this study, we experimentally evaluated the effects of Roundup Original DI^®, a glyphosate-based herbicide, on tadpoles of Physalaemus cicada and Physalaemus erikae. Spawnings were collected in south and southern Bahia, transported to the laboratory, and kept until the tadpoles reached developmental stage 25. Tadpoles were acclimated for 24 h and subsequently exposed to increasing herbicide concentrations at acute and chronic levels to assess survival, lethal concentration (LC50 96 h), and morphological and ontogenetic responses. Contamination significantly decreased the survival of tadpoles of both species and affected the development of tadpoles of P. erikae. The estimated lethal concentration (LC50) after 96 h for Physalaemus cicada was 5.52 mg a.i./L, and Physalaemus erikae was 3.40 mg a.i./L. Also, at chronic concentrations, morphological changes were observed in the tadpoles of P. erikae, with the changes being mainly in the tadpoles’ tail and body shapes. Therefore, Roundup Original DI^® is considered moderately toxic to both species. Our results extend the knowledge regarding the action of pesticides mainly for species of the genus Physalaemus, which is the best-known genus for glyphosate based-herbicide toxicity.

Any study of this highly endangered fransiscana population is relevant to its conservation. Nevertheless, the description of collection and analysis methods needs to be completed and enriched. The discussion seems relevant and up-to-date. First para...

This study aimed to investigate whether the use of space and movements of Guiana dolphins were altered during the construction of a cable-stayed bridge at the mouth of the Cachoeira River estuary in Ilhéus, Brazil. We described and compared the visitation rate, use of space, and movements of the Guiana dolphins across two periods: before the construction began (2015–2016) and during the construction of the bridge (2017–2020). A theodolite and a total station were used to observe and record the trajectories of the dolphins. From these trajectories, we estimated the Utilization Distribution (UD) using the biased random bridge kernel (BRBK) method, the area of use, and the core area, based on the 95% and 50% BRBK density, respectively. The dolphins did not change their visitation frequency to the estuary. No significant change in area fidelity was identified by comparing the overlap of areas used during two-month periods. No change occurred in the velocity and linearity of the trajectories of the dolphins swimming close to the bridge. However, contrary to expectations, the results indicated an increase in the use of areas close to the bridge during its construction. This may have been caused by the change in the distribution of their prey in the estuary due to the emergence of a sandbank near the bridge. Bridge construction work seems not to have directly affected the Guiana dolphins’ use of the area, but the impact of the construction on the local topography has changed their areas of use and core areas of activity.