Vessel strikes are a major threat impacting large whales globally. Juvenile whales often represent a high proportion of lethal vessel strikes, but few studies have investigated whether juvenile ...whales show different behaviors that might influence their risk of vessel strike. We evaluated how variability in habitat use and foraging behavior by age class influences the risk of vessel strike for humpback whales
Megaptera novaeangliae
in the New York Bight (NYB), a highly urbanized region with frequent vessel strikes. We used data from unmanned aerial vehicle (UAV) surveys to compare the habitat use and foraging behavior of adult and juvenile humpback whales and compared length measurements of foraging individuals with those confirmed to have been killed by vessel strikes. Further, using Automatic Information System data, we analyzed the speed and density of vessel traffic relative to humpback whale habitat use. The vast majority (93%) of humpback whales confirmed to have been struck by vessels in the NYB were juveniles. Whales foraging in nearshore waters were exclusively juveniles that were surface feeding, while both juveniles and adults foraged cooperatively in offshore waters. Passenger vessel density and speed were highest in nearshore waters. The habitat use and surface foraging behavior of juvenile humpback whales may make them particularly vulnerable to vessel strikes in nearshore waters, and passenger vessels in these waters may be a risk factor. This work highlights the importance of understanding age-specific differences in habitat use to better understand and mitigate the risk of anthropogenic threats to large whales.
Harmful algal blooms (HABs) are becoming increasingly frequent due to the effects of nutrient pollution. Some HABs affect the environment by decreasing light penetration, resulting in die-offs of ...aquatic primary producers. Particularly for species of conservation concern, there is a need to understand how HAB impacts on seagrasses and macroalgae relate to the foraging ecology of marine consumers. Stable isotope analysis (SIA) is a potentially useful tool to study these processes, but typical SIA study designs may not be appropriate due to the unpredictable nature and fast onset of HABs. Our goal was to gain insights into impacts of HABs on juvenile green turtles Chelonia mydas in the Indian River Lagoon, Florida, USA, by comparing long-term patterns in turtle carbon and nitrogen isotopic values to those of pinfish Lagodon rhomboides , a species with high site fidelity that serves as a reference for the lagoon. Mean isotopic values of carbon and nitrogen showed relatively small changes over time in both species. Green turtle stable carbon and nitrogen isotopic variance decreased during and after the 2011-2013 HABs in the Indian River Lagoon, while pinfish isotopic variance largely remained at pre-HAB levels except for an increase in nitrogen variance in 2013. The decrease in green turtle isotopic variance extended through 2018. We discuss potential causes for this decrease, including changes in diet diversity and habitat use. Our study highlights the need to further understand the impacts of nutrient pollution and HABs on protected marine species and the importance of long-term monitoring programs in achieving this understanding.
Physiology and temperature can both have a profound influence on behaviour and metabolism. Despite this, thermal physiology has rarely been considered within the animal personality framework, but ...could be an inherent mechanism maintaining consistent individual differences in behaviour, particularly in species that need to thermoregulate (i.e. ectotherms).
Here, we present evidence for a thermal‐behavioural syndrome and detail how it is linked to variation in habitat selection in an Australian lizard, the delicate skink, Lampropholis delicata.
We predicted that individuals would occur along a cold–hot continuum—analogues to the slow–fast continuum proposed by the pace‐of‐life hypothesis—whereby an individual's placement along a thermal physiological axis will correspond with their placement along a personality axis. We first tested the thermal‐behavioural syndrome by measuring the thermal preferences and optimal performance temperature of individual skinks and linking it to their activity, exploratory, social and boldness behaviours.
In line with our predictions, we found that individuals with a “hot” thermal type performed optimally at higher temperatures, had faster sprint speeds and were more active, explorative and bold relative to “cold” thermal types.
We then monitored each individual's habitat selection within an artificial environment containing three microhabitats differing in their thermal characteristics.
We found that an individual's thermal type mediated their use of habitat, in which “hot” individuals utilized a hotter microhabitat more regularly than both “cold” and “intermediate” thermal types, suggesting that the thermal‐behavioural syndrome could drive ecological niche partitioning in this species.
We envisage that the thermal‐behavioural syndrome concept is likely to extend to other study systems, particularly to ectothermic organisms that rely heavily on behavioural thermoregulation to maintain optimal body temperature.
A plain language summary is available for this article.
Plain Language Summary
In the context of a changing climate, understanding the environmental drivers of marine megafauna distribution is important for conservation success. The extent of humpback whale breeding habitats ...and the impact of temperature variation on their availability are both unknown. We used 19 years of dedicated survey data from seven countries and territories of Oceania (1,376 survey days), to investigate humpback whale breeding habitat diversity and adaptability to climate change. At a fine scale (1 km resolution), seabed topography was identified as an important influence on humpback whale distribution. The shallowest waters close to shore or in lagoons were favored, although humpback whales also showed flexible habitat use patterns with respect to shallow offshore features such as seamounts. At a coarse scale (1° resolution), humpback whale breeding habitats in Oceania spanned a thermal range of 22.3–27.8°C in August, with interannual variation up to 2.0°C. Within this range, both fine and coarse scale analyses of humpback whale distribution suggested local responses to temperature. Notably, the most detailed dataset was available from New Caledonia (774 survey days, 1996–2017), where encounter rates showed a negative relationship to sea surface temperature, but were not related to the El Niño Southern Oscillation or the Antarctic Oscillation from previous summer, a proxy for feeding conditions that may impact breeding patterns. Many breeding sites that are currently occupied are predicted to become unsuitably warm for this species (>28°C) by the end of the 21st century. Based on modeled ecological relationships, there are suitable habitats for relocation in archipelagos and seamounts of southern Oceania. Although distribution shifts might be restrained by philopatry, the apparent plasticity of humpback whale habitat use patterns and the extent of suitable habitats support an adaptive capacity to ocean warming in Oceania breeding grounds.
Reservoirs are subject to artificial water level fluctuations leading to a degradation of the littoral habitats. This often results in reduced productivity and biological diversity, particularly for ...fish. The development of predictive tools of fish population dynamics linked to habitat characteristics can help to optimize management actions such as habitat restoration. We developed a spatially explicit individual-based model, the 3Plake model, which predicts the spatial distribution of three fish species, northern pike, European perch and pikeperch, over seasons and diel cycles according to their habitat use. The model was calibrated with an accurate description of habitat and high spatial and temporal resolution data of fish movements in a French reservoir. The model calibration is only based on a species-specific coefficient of habitat selectivity. It was chosen to (i) match the observed and simulated traveled hourly and daily distances and (ii) minimize a metric quantifying the distance between observed and simulated density maps. The 3Plake model correctly simulated the means of traveled distances and the species distributions along the year on the study reservoir. The minimal input required (HSI maps and maximum distance range) allows its easy implementation on other reservoirs and fish species. It could be used to assess the impact of habitat restoration or water level management scenarios on fish distribution.
Les réservoirs sont soumis à des fluctuations artificielles du niveau de l’eau entraînant une dégradation des habitats littoraux. Elles entraînent souvent une réduction de la productivité et de la diversité biologiques, en particulier pour les poissons. Le développement d’outils prédictifs de la dynamique des populations de poissons, liés aux caractéristiques de l’habitat, peut aider à optimiser les actions de gestion telles que les mesures de restauration ou de gestion des niveaux d’eau. Nous avons développé un modèle individu-centré spatialement explicite, le modèle 3Plake , qui prédit la distribution spatiale de trois espèces de poissons, le brochet, la perche commune et le sandre, au fil des saisons et du cycle diurne en fonction de leur utilisation de l’habitat. Le modèle a été calibré grâce à une description précise de l’habitat et des données à haute résolution spatiale et temporelle des déplacements des poissons dans une retenue française. La calibration du modèle est uniquement basée sur un coefficient de sélectivité de l’habitat spécifique à l’espèce. Ce coefficient a été choisi pour (i) faire correspondre les distances parcourues horaires et journalières observées et simulées et (ii) minimiser une métrique quantifiant la distance entre les cartes de densité observées et simulées. Le modèle 3Plake a simulé correctement les moyennes des distances parcourues et les distributions des espèces tout au long de l’année sur la retenue d’étude. Le minimum de données d’entrée requises permet d’envisager des transpositions sur d’autres réservoirs et espèces piscicoles. Il pourrait être utilisé pour évaluer l’impact de mesures de restauration de l’habitat ou de scénarios de gestion des niveaux d’eau sur la répartition des poissons.
Conservation of apex predators is a key challenge both in marine and terrestrial ecosystems. The white shark is a rare but persistent inhabitant of the Mediterranean Sea and it is currently assessed ...as “critically endangered” in the region. However, the population trends and dynamics of this species in the area are still unknown. Little is known about white shark distribution, habitat use and population abundance trends, aspects that are critical for conservation and management. In this study, we built the most comprehensive database of white shark occurrence records in the region. We collected 773 different records from different sources and used them to characterize the spatial and temporal patterns of abundance of Mediterranean white sharks between 1860 and 2016. We analysed these data by using generalized additive models and used spatially disaggregated information on human population abundance as a proxy of observation effort. Our results suggest a complex trajectory of population change characterized by a historical increase and a more recent reduction (61%, range 58%–72%) since the second half of the 20th century. In particular, analyses reveal a 52% (range 37%–88%) to 96% (range 92%–100%) overall decline in different Mediterranean sectors and a contraction in spatial distribution. Here, we provide the first reconstruction of abundance trends and offer new hypotheses regarding the drivers of change of white sharks in the Mediterranean. Our approach can be broadly applied to data‐poor contexts to reconstruct change and inform the conservation of endangered top predators in the Mediterranean Sea and other intensely used marine regions.
Life history diversity can significantly affect population dynamics and effects of management actions. For instance, variation in individual responses to environmental variability can reduce ...extirpation risk to populations, as the portfolio effect dampens temporal variability in abundance. Moreover, differences in habitat use may cause individuals to respond differently to habitat management and climate variability. To explore the role of life history diversity in population trajectories, population models need to incorporate within-population variation. Integrated population modeling (IPM) is a population modeling approach that offers several advantages for sharing information and propagating uncertainty across datasets. In this study, we developed an IPM for an endangered population of Chinook salmon ( Oncorhynchus tshawytscha) in the Wenatchee River, Washington, USA, that accounts for diversity in juvenile life histories, spawning location, and return age. Our analysis revealed that diversity in the age of juvenile emigration from natal streams had a portfolio effect, resulting in a 20% reduction in year-to-year variability in adult abundance in population projections. Our population viability analysis suggests that management interventions may be necessary to meet recovery goals, and our model should be useful for simulating the outcomes of proposed actions.
Balikpapan Bay is one of the wetlands providing potential foraging habitat for waterbirds in Indonesia. Potential habitat loss due to oil industry expansion, recent waterbird occurrence, and ...co-occurrence of two closely related species with similar foraging characteristics led to habitat selection. Habitat selection could be affected by food as an intrinsic factor and extrinsic factor, for example, accessibility to the physical and biological components of the habitat. This study aimed to measure the foraging habitat selection, identify significant habitat quality parameters for the habitat selection and predict the foraging habitat selection model. We used one-zero sampling for collecting foraging habitat selection data, corer sampling for prey data, and collecting the abiotic environment, and Generalized Linear Modelling (GLM) to build the model. We identified four species as the migrant Little Egret (Egretta garzetta), Great Egret (Ardea alba), Purple Heron (Ardea purpurea), and Lesser Adjutant (Leptoptilos javanicus). All species, except Purple Heron, selected foraging habitats. A simple mathematic model of foraging habitat selection was significantly affected by two factors: water depth and patch area. A large patch area may provide primary prey abundance for waterbirds, while a low water depth level may give easy access to the prey.
1. Ecological trapping implies a preference for low-quality habitats over higher-quality options. Although such a maladaptive decision-making has been shown in a range of organisms, the mechanisms ...that underlie this habitat selection pattern often remain unidentified. We tested in a human-modified environment whether food availability and food use of a migratory species operate as functional drivers of an ecological trap. 2. The Red-backed shrike (Lanius collurio) is a migratory bird that was shown to breed preferentially in forest plantation clearcuts where reproductive performance is however markedly lower than in the traditional farmland habitat. We examined whether differences in food availability between forest and farmland habitats resulted in contrasting food provisioning to the offspring with, in turn, significant impact on the quality of the offspring. 3. Invertebrate prey items for shrikes were 41% more abundant in farmland, and prey size was 6% larger in forest habitat. Opposite to the pattern of prey size availability, larger prey items were delivered to the offspring in farmland than in forest habitat. Feeding visits by the parents were 22% more frequent in farmland, and evidence of strong among-nestling competition for food was found in forest only. 4. This study demonstrates the existence of food limitation for an organism in a habitat type associated with high preference but low reproductive performance. This result offers a functional explanation for the mismatch between habitat preference and quality, and hence, for an ecological trap in the wild. 5. Beyond the case of migratory birds, this study draws attention to the point that human-modified environments may lead to a biased perception of habitat quality relative to food availability and may induce an ecological trap for organisms that allocate only a limited time budget to habitat selection decision-making.
PDF
