Loïc Bollache

Countries have committed to expanding the marine protected area (MPA) network to 30% of the world's ocean by 2030, more than tripling current coverage, and focusing on areas important for biodiversity. For such expansion to translate into effective conservation of marine biodiversity, it must rely on the best available knowledge. Here, we analyze tracking data on > 13,000 individuals (44 species, eight families) to map the distribution of highly mobile seabirds in the Atlantic Ocean and adjacent seas throughout the year. We identify regions important year‐round or seasonally. The High Seas are as important as national waters for highly mobile seabirds but are even less protected. Current Atlantic MPAs hold < 14% of tracked species density, but their expansion to 30% of the ocean could protect up to two thirds. We share this new knowledge layer to support national and international efforts and policies to strategically expand the Atlantic MPA network.

In bird species with precocial development, i.e. chicks acquire abilities to leave the nest soon after hatching, the nestling period during which parents warm their young in the nest by brooding them is short but critical to breeding success. The duration of the nestling period (DNP) depends on the hatching synchrony of eggs and the speed at which chicks acquire these abilities but may be indirectly affected by parental behaviour and temporal variations in temperature and predation. We assessed the effects of incubation strategy (bi- or uniparental), hatching start time, incubation initiation date and predation risk on the DNP in Arctic-breeding sandpipers. We found that the DNP was longer in biparental species (29.75 ± 8.95 h) compared with uniparental ones (25.82 ± 6.87 h) and was extended in nests where chicks began hatching during the colder ‘night’ hours. No effect of incubation initiation date or predation pressure was found on the DNP. We suggest that parental investment strategies and constraints related to circadian variations in temperature in chicks drive the DNP in Arctic-breeding sandpipers. These results help us better understand how different species may exhibit different behavioural responses during nesting to impending climate change.

Large alluvial plain rivers provide a complex mosaic of freshwater habitats characterised by a lateral hydrological connectivity (LHC) gradient between the main channel and floodplains. This connectivity plays a key role in structuring aquatic communities, influencing species distribution, diversity, and ecosystem processes. The aims of our study were to assess the effects of the LHC gradient on both fish taxonomic and functional diversity, and to characterise the effects of this connectivity on the distribution of non‐native species. Community data were gathered through electrofishing at five sites in the main channel of the Saône River (France), and in four permanently (parapotamic) and four occasionally (plesiopotamic) connected oxbows. Functional diversity was investigated using a trait‐based approach as surrogates of ecosystem processes. A total of 28 fish species were identified, including 14 non‐native species. Our results show that main channel and plesiopotamic oxbows exhibited distinct compositional and structural patterns of fish communities, while parapotamic oxbows displayed an intermediate composition and community structure. Taxonomic and functional diversity decreased along the lateral continuum from the main channel to plesiopotamic waterbodies. In contrast, while non‐native species richness was similar between the main channel and floodplains, their densities were higher in floodplain oxbows. These findings highlight the prominent role of hydrological connectivity in sustaining both taxonomic and functional diversity in riverine ecosystems. Fish community variations between habitats may be explained by physical changes resulting from reduced connectivity, primarily characterised by a loss of depth and surface area, which in turn affect a broad spectrum of abiotic and biotic factors. High densities of non‐native species in lentic environments like oxbows can be attributed to specific abiotic conditions (e.g., hypoxia, rapid temperature fluctuations and eutrophication) and the greater tolerance and plasticity of non‐native species compared to native species. Additionally, the absence of predators reduces top‐down control and intensifies competition with native species for resources. Conservation and management strategies should prioritise preserving and restoring connectivity to support native fish communities, limit the dominance of non‐native species, and maintain the ecological integrity of freshwater ecosystems.

Why parental care strategies can vary from uniparental to biparental care across taxa remains unclear, likely because various sets of ecological conditions are at-play. Here we tested ten possible hypotheses to decipher the direct and indirect impacts of critical factors likely to influence the parental care strategy during incubation in Sanderlings (Calidris alba), one of the few species that uses both types of care during that critical time of the breeding cycle. We examined three ecological factors (timing of local snowmelt, regional temperatures, and the North Atlantic Oscillation experienced just before breeding), one trophic factor (predation pressure), and two social factors (relative abundance of Sanderlings and their laying dates). Using long-term data from Greenland (2011–2023), path analyses revealed that laying date and snowmelt influence parental care strategies during incubation, with indirect climatic effects during migration and on breeding grounds. We observed a greater proportion of uniparental nests in years with delayed laying dates, and the reverse in years with delayed snowmelt. These findings underscore the complex interplay between environmental parameters and parental care strategies, offering insights into how these strategies are likely to respond to rapidly changing Arctic ecological conditions driven by climate change.

Parents can abandon their current clutch when reaching a physiological threshold to prioritise their survival and future breeding in the trade-off against current reproduction. Incubation is metabolically costly, and regular recesses are necessary to replenish energy reserves. Thus, an increase in the duration of these foraging trips may signal diminishing reserves and perhaps impending abandonment. Here, we tested the hypothesis that the probability of abandonment of uniparental nest is directly linked to the duration of extended recesses (i.e., recesses > 120 min). Analysing 13 years of breeding behaviour from Sanderlings (Calidris alba) using thermologgers placed in 120 nests, we found that both the frequency and duration of extended recesses were higher in nests that were ultimately abandoned. The probability of nest abandonment increased with time spent in extended recesses during incubation, with the final day before abandonment proving critical in the decision-making. In contrast, short recesses showed no relationship with abandonment probability, and neither recess type changed significantly as nests approached hatching, confirming the specificity of extended recesses as indicators of abandonment. With such results, parents likely remain at the nest until their reserves fall below a physiological threshold, when they have no choice but to leave the nest when the costs-benefits balance becomes unsustainable for the parent. Our study suggests the key link between extended recesses and nest abandonment; it paves the way for quantifying foraging success and variations in energy reserves of individuals to provide deeper insights into the mechanisms driving reproductive decisions and their impact on population dynamics.

The interplay between facultative scavenging and predation has gained interest in the last decade. The prevalence of scavenging induced by the availability of large carcasses may modify predator density or behaviour, potentially affecting prey. In contrast to behavioural mechanisms through which scavenging affects predation, the demographic effects of facultative scavenging on predator and prey populations remain poorly studied. We used the semi-natural experimental opportunity in Hwange National Park, Zimbabwe, where contrasted management measures (culling and artificial supply of water) have led to fluctuations in elephant carrion abundance, to identify the consequences of facultative scavenging on the population dynamics of a large mammalian carnivore, the spotted hyaena ( Crocuta crocuta ), and its prey. Using a 50-year dataset and Multivariate Autoregressive State Space models, we estimated hyaena and prey densities over four periods contrasted in elephant carrion availability due to management practices. Models that allow hyaena and their prey populations’ growth rate to vary depending on these four periods contributed significantly to explain variations in their density, which is consistent with an effect of management measures on the population dynamics of hyaena and its prey. Although our results support a predominant role of bottom-up mechanisms, whereby hyaena density is driven by herbivore density, itself driven by resources availability, some subtle patterns of densities could be interpreted as consequences of changes in predation pressure following changes in scavenging opportunities. We discuss why signals of prey and predator population dynamics decoupling are less likely to be observed in systems with a high diversity of prey, such as African savannas, and why inputs of mega-carcasses as pulsed resources hardly impacted top-down relationships in the long run. This study represents a first investigation of the long-term effects of carrion pulses, whose frequency may increase with climate changes, on the classical predator-prey coupling for large mammals.

Complex incubation strategies have evolved to solve the trade-off between parent survival and care for their eggs with often brief departures (recesses) that maximize egg survival, and infrequent extended recesses maximizing adult condition. Here we examined incubation behaviour of sanderlings ( Calidris alba ), a species that exhibits both biparental and uniparental incubation behaviour. During 11 breeding seasons in Greenland, we have quantified incubation variability with thermologgers placed in nests. We estimated the impact of environmental conditions and individual characteristics on the occurrence and the duration of recesses. We found that extended recesses are a unique feature of uniparentals, and their frequency and duration increased in colder temperatures. The relationship was mediated by body condition, with individuals in poor condition performing longer extended recesses in colder temperatures. This suggests that extended recesses may represent a shift towards self-maintenance at the expense of the egg care, allowing birds to continue incubating under unfavourable conditions. Our study illustrates how extended recesses may be a key breeding strategy to overcome high energetic costs associated with incubation. Quantifying such behavioural flexibility paves the way for tracking future behavioural responses of individuals in the face of changing environments.

The interplay between facultative scavenging and predation has gained interest in the last decade. The prevalence of scavenging induced by the availability of large carcasses may modify predator density or behaviour, potentially affecting prey. In contrast to behavioural mechanisms through which scavenging affects predation, the demographic effects of facultative scavenging on predator and prey populations remain poorly studied. We used the semi-natural experimental opportunity in Hwange National Park, Zimbabwe, where contrasted management measures (culling and artificial supply of water) have led to fluctuations in elephant carrion abundance, to identify the consequences of facultative scavenging on the population dynamics of a large mammalian carnivore, the spotted hyaena ( Crocuta crocuta ), and its prey. Using a 50-year dataset and Multivariate Autoregressive State Space models, we estimated hyaena and prey densities over four periods contrasted in elephant carrion availability due to management practices. Models that allow hyaena and their prey populations’ growth rate to vary depending on these four periods contributed significantly to explain variations in their density, which is consistent with an effect of management measures on the population dynamics of hyaena and its prey. Although our results support a predominant role of bottom-up mechanisms, whereby hyaena density is driven by herbivore density, itself driven by resources availability, some subtle patterns of densities could be interpreted as consequences of changes in predation pressure following changes in scavenging opportunities. We discuss why signals of prey and predator population dynamics decoupling are less likely to be observed in systems with a high diversity of prey, such as African savannas, and why inputs of mega-carcasses as pulsed resources hardly impacted top-down relationships in the long run. This study represents a first investigation of the long-term effects of carrion pulses, whose frequency may increase with climate changes, on the classical predator-prey coupling for large mammals.

Amblypygids display high levels of sexual dimorphism, especially larger pedipalps in males compared to females. This study examines the difference in allometric rates as a potential cause of dimorphism in pedipalps and walking legs in three Heterophrynus species: Heterophrynus batesii (Butler, 1873); Heterophrynus longicornis (Butler, 1873), and Heterophrynus elaphus (Pocock, 1903). Dimorphism is observed in all studied appendages, but higher allometric rates are shown in males more than females for only the pedipalps (for all three species) and the first walking legs (for only H. elaphus), with higher dimorphism in the pedipalp for H. batesii and lower in H. elaphus. Dimorphism in pedipalps appears to be linked to species' mating system: larger dimorphism are observed in polygamous systems, whereas moderate and small dimorphisms are observed in monogamous and solitary species, respectively. Contrary to pedipalps, the evolution of walking legs seems to occur via natural selection rather than sexual selection.