Explore the vast range of titles available.

Diel activity rhythms, representing the behavioral pattern of the sleep–wake cycle, may be adjusted by wildlife in response to changes in environmental conditions. An increase in nocturnality is typically recognized as an adaptive strategy to segregate from humans and mitigate heat stress. Numerous studies have investigated spatial patterns and habitat use of large carnivores in human-modified landscapes, but little research has examined their activity rhythms. We compiled Global Positioning System data (2004–2022) for 139 brown bears Ursus arctos from six populations across Europe, representing a human-modified landscape, and the Greater Yellowstone Ecosystem, U.S.A., representing a landscape with limited human impact, which we used to calculate hourly movement rates as an activity proxy. Using a Bayesian approach to model the temporal autocorrelation of activity data, we tested if the extent of nocturnality in brown bears is modulated by intensity of human encroachment, accounting for primary productivity and maximum ambient temperature. All bear populations exhibited a predominantly bimodal, crepuscular pattern of activity, although Yellowstone bears were proportionally more crepuscular and diurnal. Whereas the effect of primary productivity was variable, all European populations became more nocturnal in response to higher human encroachment and reduced diurnal and crepuscular activity at higher summer temperatures, decreasing overall diel activity levels. Yellowstone bears displayed the greatest shift towards nocturnality among all populations in response to increasing human encroachment, and increased nocturnal activity to compensate for lower diurnal and crepuscular activity at higher summer temperatures. Our research indicates that European bears in human-modified landscapes may be reaching a limit in the behavioral plasticity they can manifest in their activity patterns, being already constrained into increased nocturnality. Our findings enhance the understanding of brown bear adaptive capacity to accommodate future changes, such as urbanization and increasing temperatures, to the ecosystems they inhabit.

Small cats play a vital role in maintaining ecological balances. Inadequate knowledge based on their habitat preference and interspecific competition has hindered the effective conservation initiatives. We studied occupancy and diel activity patterns of two sympatric small cats, i.e., jungle cat (Felis chaus) and leopard cat (Prionailurus bengalensis), in and around Bardia National Park (BNP) using camera trap data. BNP was divided into 344 camera trap grids of 2 × 2 km, and a survey was conducted with a trapping effort of 6307 days. For the occupancy modeling, we applied a single‐species single‐season occupancy model. We analyzed 11 covariates that have the potential to influence the occupancy of jungle cats and leopard cats. The probability of occupancy of the jungle cat was 0.17 (SE: 0.0026, CI: 0.1726, 0.18271). The tiger's index positively influenced the jungle cat's occupancy, while it showed a strong negative association with the terrain ruggedness index and distance to road. Similarly, the probability of occupancy for leopard cat was found to be 0.19 (SE: 0.0022, CI: 0.1829, 0.1916). The leopard cat occupancy was strongly positively correlated with riverine forest habitat type. We used non‐parametric kernel‐density functions on camera trap data to determine diel activity patterns. Sympatric jungle cat and leopard cat showed high temporal overlap with a coefficient (Δ = 0.9), being nocturnal. The distribution of jungle cats and leopard cats in BNP appears to be facilitated by spatial segregation. The study serves as a baseline for further research and conservation initiatives for these two sympatric cats in western Nepal. Camera trap captured photographs from the study area, on the left is the jungle cat, and on the right is the leopard cat.

The Congo basin forests have vast conservation potential but because of their inaccessibility and periodic insecurity there is little formal protection or ecological research occurring there. Community-based conservation efforts in the unprotected forest corridor separating Kahuzi-Biega and Maiko National Parks in eastern Democratic Republic of the Congo aim to protect a unique forest ecosystem and facilitate the development of ecological research. To support this process, we obtained baseline data on the occurrence of terrestrial mammals in the Nkuba Conservation Area by conducting camera-trap (2014–2018) and transect (2013–2018) surveys. From camera-trap images we also extracted diel activity patterns and estimated overlap in these patterns between selected pairs of species. We identified 29 mammal species weighing > 1 kg using camera traps and 22 species in transect surveys, with a total of 33 mammal species, of which seven are categorized as threatened on the IUCN Red List. Among this mammalian community, we recorded nocturnal and diurnal species with short core activity periods, and several cathemeral species with long activity periods, with various degrees of temporal separation of diel activity between species. The presence of threatened species, including the Critically Endangered Grauer's gorilla Gorilla beringei graueri, suggests that the Nkuba Conservation Area harbours a forest community that requires continuous monitoring, further research and investment in protection from the ongoing deforestation and resource exploitation occurring in the surrounding region.

Southeast Asia supports the greatest diversity of felids globally, but this diversity is threatened by the severe forest loss and degradation occurring in the region. The response of felids to disturbances appears to differ depending on their ecology. For example, the largely terrestrial and nocturnal leopard cat (Prionailurus bengalensis) thrives near forest edges and in oil palm plantations where it hunts rodents (Muridae) at night, thereby avoiding human activity peaks. Conversely, we hypothesized that the sympatric and similar‐sized marbled cat (Pardofelis marmorata) would respond negatively to edges and relatively open oil palm plantations as they are more arboreal than leopard cats, rely on tree connectivity for hunting, and are diurnal so have less potential to temporally avoid humans. We used camera trapping from Southeast Asia to test habitat associations at multiple spatial scales using zero‐inflated Poisson generalized linear mixed models and hierarchical occupancy modeling. We found that marbled cats were positively associated with large intact forests and, in contrast to leopard cats, negatively associated with oil palm plantations. Furthermore, we found preliminary evidence suggesting marbled cats may adapt their diel activity to become more crepuscular in degraded forests, likely shifting their activity to avoid humans. These findings suggest that the marbled cat's International Union for Conservation of Nature (IUCN) Red List conservation status should potentially be upgraded from Near Threatened to Vulnerable, matching other forest‐dependent felids in the region. We posit our findings may be generalizable such that semi‐arboreal and diurnal felids could face greater threats from habitat degradation than their terrestrial and nocturnal relatives.

An important resource partitioning strategy allowing dung beetles to coexist in the same habitat, while utilising the same food, is species’ separation of activity times. After establishing the diel activity period of three closely related, co-occurring dung beetles, we examined their eye and wing morphology. Absolute and relative eye size, and facet size were greater in the nocturnal Escarabaeus satyrus, followed by the crepuscular Scarabaeus zambesianus and then the diurnal Kheper lamarcki. The diurnal K. lamarcki had the highest wing aspect ratio (long, narrow wings), followed by the crepuscular S. zambesianus and the nocturnal E. satyrus (short, broad wings), suggesting that dim-light active species fly slower than diurnal species. In addition, the two species active in dim light had a lower wing loading than the diurnal species, indicating the need for greater manoeuvrability in the dark. Analyses of wing shape revealed that the diurnal K. lamarcki wing had a proportionally larger jugal and anal region than both dim light species. Our results show that different species of dung beetles have a combination of optical and morphological wing adaptations to support their foraging activities in diverse light conditions.

Anadromous Arctic charr, Salvelinus alpinus, migrate back to freshwater in late summer to spawn and/or overwinter. While seasonal movement patterns during the freshwater residency period are generally understood, specifics of the short temporal activity patterns remain poorly characterized. This study used temperature and accelerometer sensing telemetry to describe the diel activity patterns of 21 overwintering anadromous Arctic charr in a lake in southern Labrador, Canada. Tagged individuals displayed diurnal activity patterns throughout the overwinter residency period marked by greater activity during the day than at night and distinctive peaks of activity at the beginning and the end of each daylight period. Diurnal patterns were interpreted as driven by prey and light availability in the upper water column because of known linkages between light and foraging efficiency. Movement activity also increased as a function of temperature during the spawning and ice breakup periods, but not during winter when increased movement activity was correlated with colder temperatures. No association was found between movement activity and body size over the size range (36.0–48.5 cm) of fish studied. Our data suggest a complex set of behavioural determinants of overwinter activity, among which temperature and foraging are the most significant.

The European badger is a highly adaptable species, inhabiting a range of environments across Europe, from woodlands to urban areas, with its behaviour influenced by environmental conditions and human activities. This study examines the badger feeding habits, patterns of diel activity, and sett site choice in north-western Italy, assessing how landscape composition affects these behaviours. We conducted our research across seven study areas in northern Italy from December 2020 to November 2022, utilising camera trapping, faeces analysis, and sett surveys. Our findings revealed significant dietary variation, with earthworms being the primary food source in natural landscapes, while fleshy fruits being consumed especially in mixed and heavily modified landscapes, up to constitute the staple of the diet in one agricultural area. Badgers were found to be nocturnal, primarily active between sunset and sunrise. Setts varied considerably in structure and location, with a preference for natural grounds over human-made structures; key factors influencing sett site choice included slope, exposure, and vegetation cover. This study underscores the European badger’s remarkable adaptability, illustrating how its diet, activity patterns, and sett site preferences are shaped by a complex interplay of factors, allowing the species to thrive in both pristine and modified environments across northern Italy.

Examination of environmental DNA (eDNA) is a non-invasive conservation tool that has been used for the detection of aquatic organisms. When coupled with quantitative polymerase chain reaction (qPCR), eDNA sampling may be used to infer seasonal or diel activities of target species. To survey the status of eastern hellbenders (Cryptobranchus a. alleganiensis), fully aquatic cryptic salamanders of conservation concern, through eDNA analyses, we collected water samples monthly from 13 sites across 8 tributaries of the West Branch Susquehanna River in Pennsylvania, USA, from June through October 2014. We also examined the effects of the breeding season, diel activity, and stream environmental variables (e.g., temp, pH) on eDNA concentration estimates. We repeatedly detected hellbender eDNA from all 4 tributaries known to contain hellbenders, and from downstream sites of 2 of the 4 tributaries without known records of hellbenders. In the tributaries known to contain hellbenders, we observed notable increases in eDNA concentrations during the September breeding season, suggesting possible reproductive events. However, such seasonal eDNA signature was lacking from the eDNA positive sites of the tributaries without known records of hellbenders. There was no difference in eDNA estimates between diurnal and nocturnal samples, indicating that diel activity was inconsequential to eDNA estimates. Our statistical analyses of the eDNA positive sites revealed no effects of the stream variables on eDNA estimates. Yet, the presence of hellbenders was positively associated with stream temperature and negatively with pH. The positive association with temperature was likely to be an artifact of the sampling design, whereas the negative association with pH may indicate negative effects of farming and livestock on hellbenders. Our findings concur with recent studies on the importance of temporal sampling in interpreting eDNA signature in relation to life histories of target species. Further studies are needed to characterize the core habitats of newly found populations for future management of the declining hellbender populations.

In nature, nothing is wasted, not even waste. Dung, composed of metabolic trash and leftovers of food, is a high‐quality resource and the object of fierce competition. Over 800 dung beetle species (Scarabaeinae) compete in the South African dung habitat and more than 100 species can colonize a single dung pat. To coexist in the same space, using the same food, beetles divide the day between them. However, detailed diel activity periods and associated morphological adaptations have been largely overlooked in these dung‐loving insects. To address this, we used a high‐frequency trapping design to establish the diel activity period of 44 dung beetle species in their South Africa communities. This allowed us to conclude that the dung beetles show a highly refined temporal partitioning strategy, with differences in peak of activity even within the diurnal, crepuscular, and nocturnal guilds, independent of nesting behavior and taxonomic classification. We further analyzed differences in eye and body size of our 44 model species and describe their variability in external eye morphology. In general, nocturnal species are bigger than crepuscular and diurnal species, and as expected, the absolute and relative eye size is greatest in nocturnal species, followed by crepuscular and then diurnal species. A more surprising finding was that corneal structure (smooth or facetted) is influenced by the activity period of the species, appearing flat in the nocturnal species and highly curved in the diurnal species. The role of the canthus—a cuticular structure that partially or completely divides the dung beetle eye into dorsal and ventral parts—remains a mystery, but the large number of species investigated in this study nevertheless allowed us to reject any correlation between its presence and the nesting behavior or time of activity of the beetles. Dung is the site of fierce competition. To coexist in exactly the same space, using precisely the same food, over 40 species of dung beetles are shown in our paper to finely divide the day between them. This is driven by changes in light, which in turn reflect in morphological adaptations among these species which in many cases override their taxonomic heritage.

Background Many living birds exhibit some nocturnal activity, but the genetic basis and evolutionary origins of their nocturnality remain unknown. Results Here, we used a molecular phyloecological approach to analyze the adaptive evolution of 33 phototransduction genes in diverse bird lineages. Our results suggest that functional enhancement of two night-vision genes, namely, GRK1 and SLC24A1 , underlies the nocturnal adaption of living birds. Further analyses showed that the diel activity patterns of birds have remained relatively unchanged since their common ancestor, suggesting that the widespread nocturnal activity of many living birds may largely stem from their common ancestor rather than independent evolution. Despite this evolutionary conservation of diel activity patterns in birds, photoresponse recovery genes were found to be frequently subjected to positive selection in diverse bird lineages, suggesting that birds generally have evolved an increased capacity for motion detection. Moreover, we detected positive selection on both dim-light vision genes and bright-light vision genes in the class Aves, suggesting divergent evolution of the vision of birds from that of reptiles and that different bird lineages have evolved certain visual adaptions to their specific light conditions. Conclusions This study suggests that the widespread nocturnality of extant birds has a deep evolutionary origin tracing back to their common ancestor.