Activity Patterns Of Animals Research Articles

Thermal constraints and gender-related differences in the activity patterns of the monomorphic rodent Clyomys laticeps

Abstract The daily activity pattern of animals can be classified as diurnal, nocturnal, crepuscular, and cathemeral reflecting strategic decisions to maximize mating and foraging while reducing predation risks and thermal constraints. Among monomorphic mammals, competition for resources and gender-related differences in physiology and reproductive strategies may translate into different activity patterns of males and females. Therefore, to understand the daily activity pattern both aboveground and belowground of the semifossorial rodent Clyomys laticeps, we tested the following hypotheses: (1) males and females differ in their diel activity patterns; (2) males are active for longer periods than females due to a promiscuous mating system and female site fidelity; and (3) higher maximum temperatures restrain C. laticeps activity. The study was carried out in the Serra de Caldas Novas State Park (Goiás, Brazil) in the Cerrado biome. The activity of C. laticeps was recorded using the telemetry technique over 5 days and nights (twice in each season, rainy and dry, between 2019 and 2021). Clyomys laticeps activity was bimodal, with 2 peaks around dawn and dusk, resembling a crepuscular pattern. Temporal segregation in male and female activity patterns was restricted to the dry season, when female activity was more diurnal than males who were mainly nocturnal. Intersexual competition for resources or male-avoidance behavior by females during the dry food scarcity season could contribute to this pattern, although it may also be explained by gender-related differences in thermal tolerances. Overall, males were active for longer periods than females, probably as a strategy to increase mating opportunities among the former and site fidelity in the latter. Finally, temperature imposed major constraints on C. laticeps activities who preferred milder temperatures and avoided being active in temperatures above their thermoneutral zone.

Assessing the potential of camera traps for estimating activity pattern compared to collar‐mounted activity sensors: a case study on Eurasian lynx Lynx lynx in south‐eastern Norway

The diel activity patterns of animals convey information about physiology, ecological niches and animal behaviour relevant for both applied conservation and more theoretical research. However, these patterns are challenging to study in the field. The current gold‐standard approach to quantify movements and activity patterns of medium to large wildlife species is to use global positioning systems (GPS) collars equipped with activity sensors (e.g. accelerometers). A more recent approach consists of inferring activity patterns from the time‐stamped pictures of wildlife obtained from camera traps now routinely used in wildlife monitoring projects. However, few studies have attempted to validate estimates of activity patterns obtained from camera traps against those obtained from activity sensors. In this study, we compared the diel activity pattern of the Eurasian lynx Lynx lynx inferred from detections by a network of over 300 camera traps active between 2010 and 2020, to activity patterns obtained from 18 GPS‐collared lynx (8 females, 10 males) equipped with 2‐axis accelerometer sensors, in the same area of southern Norway. Our results suggest that camera traps can be used to estimate diel activity curves that are comparable to those obtained from accelerometers. In our study, 75 detections were sufficient to approximate the diel activity pattern obtained from accelerometer. Subsampling indicated that a low number of detections results in a coarser approximation of the diel activity pattern.

Natrix natrix after dark: citizen science sheds light on the common grass snake's nightlife.

Activity patterns in animals are often species-specific, and can be generally categorized as diurnal, crepuscular, or nocturnal. Understanding these patterns provides insight into ecological adaptations and behaviors. The common grass snake (Natrix natrix), one of the most common and widespread European snake species, is traditionally considered diurnal, with scarce evidence of its crepuscular and nocturnal activity. We aimed to document the distribution, environmental conditions, and potential phenotype associations of nighttime activity in N. natrix. We used citizen science data from iNaturalist (1992-2022), Observation.org (2012-2022), together with personal field observations (2010-2023) to collect 127 crepuscular and nocturnal activity records. Most observations occurred between May and August, coinciding with the peak activity period of grass snakes across their distribution range. Statistical analyses revealed no significant difference in mean daily temperatures between crepuscular and nocturnal observations. However, striped individuals displayed nocturnal activity at higher temperatures, consistent with their distribution in warmer regions, but failed to register any difference when tested on a geographic subsample, that accounted for sympatry of the phenotypes. Surprisingly, we found no significant impact of moon presence or moonlight on nighttime activity or age class, contrary to expectations based on other snake species' responses. While our study reveals that nocturnal activity in the common grass snake is geographically widespread, further research is warranted to understand its drivers and ecological implications. This study highlights the value of citizen science platforms for biological and ecological research, offering unparalleled spatial and temporal coverage by their users. In conclusion, our work extends the knowledge of nocturnal behavior in N. natrix and underlines the critical role of citizen science in discovering behavioral aspects of common and widespread species.

Comparing daily, circalunar and seasonal activity patterns of cheetah Acinonyx jubatus in response to livestock presence in Botswana

Animal activity patterns vary on a daily, circalunar and seasonal scale in response to abiotic (e.g. light availability and temperature) and biotic factors (e.g. predation and competition). In the presence of humans and their livestock, carnivores, for example, have been found to become more nocturnal. The aim of this paper is to compare daily, circalunar and seasonal activity patterns of cheetah Acinonyx jubatus in the western Kalahari of Botswana between areas where there is no livestock present (i.e. game farms with a relatively low risk of cheetah mortality) and areas where livestock is present (i.e. cattle farms with a higher risk of cheetah mortality). Using two years of camera trap data, we recorded 88% of cheetah observations on game farms and 12% on cattle farms. Our results showed that cheetahs were more nocturnal in the absence of cattle and more crepuscular on cattle farms compared to game farms. Overall, cheetah activity on cattle farms showed a peak in activity after inferred cattle activity and before human activity during the day, specifically during the dry season. We recommend management strategies on a local scale such as temporal zoning of grazing activities during the different seasons or keeping cattle in an enclosure at night. This study sheds new light on our understanding of the impact of land use on free‐ranging carnivores in the face of livestock expansion on the African continent.

Midnight siesta: Bimodal temporal activity observed in an endangered marsupial predator

AbstractUnderstanding animal behavioural patterns can provide insight into how populations and communities are adapting to broader environmental shifts. The northern quoll (Dasyurus hallucatus), an endangered marsupial predator, has traditionally been classified as nocturnal. However, evidence is emerging that such simple classifications belie the complexity of animal activity patterns. Using time‐stamped camera trap imagery and fine‐scale accelerometer data, our study explores the diel activity patterns of northern quolls across their range in northern Australia. Contrary to the conventional nocturnal classification, we found that the northern quoll used bimodal activity patterns in four of the five populations examined in this study. Activity and accelerometer data showed two nightly movement peaks, with a distinctive lull around midnight, a pattern similar to one displayed by other marsupial predators. We found no consistent effect of season or lunar phase on temporal activity. Instead, its possible temporal activity patterns are primarily influenced by factors not accounted for here, such as prey availability, climate, predator avoidance, or energy expenditure related to digestion. We suggest further research incorporating these factors will improve our understanding of northern quoll behaviour.

Comparison of daily activity patterns across seasons using GPS telemetry and camera trap data for a widespread mammal

AbstractDaily activity patterns of animals can be dynamic across seasons in response to changing environmental conditions. Daily activity, though, has rarely been evaluated in relation to multiple factors (e.g., seasons, demographics, and data collection methods), which could be important for understanding what drives activity patterns. Here, we evaluated the daily activity patterns of a widespread invasive species, wild pigs (Sus scrofa), across two ecologically different study areas at Buck Island Ranch, FL, and Tejon Ranch, CA, from 2015 to 2018. Using GPS telemetry data (62 individuals in FL, 21 individuals in CA) and detections from grids of systematically placed motion‐activated cameras (44 cameras in FL, 48 cameras in CA), we compared activity patterns among seasons, sexes, and data collection methods (GPS and camera traps). Overall, wild pigs were mostly active during crepuscular and nocturnal periods, with their lowest activity during diurnal periods; however, activity patterns varied due to several factors. Daily activity patterns were similar between methods, among seasons, and between sexes in the subtropical climate of Florida. In contrast, daily activity patterns exhibited greater differences between methods and among seasons in California, where seasonal differences in temperature and precipitation were more pronounced. Overall, daily activity patterns estimated using GPS telemetry and camera‐based methods not only exhibited a high degree of overlap in several comparisons but also exhibited marked differences that should be recognized. Given the increasing evaluation of daily activity patterns of animals using multiple types of datasets, our study provides ecologists with valuable information to consider when designing ecological studies, interpreting their results, and comparing research across systems and studies.

Accelerometer-based predictions of behaviour elucidate factors affecting the daily activity patterns of spotted hyenas.

Animal activity patterns are highly variable and influenced by internal and external factors, including social processes. Quantifying activity patterns in natural settings can be challenging, as it is difficult to monitor animals over long time periods. Here, we developed and validated a machine-learning-based classifier to identify behavioural states from accelerometer data of wild spotted hyenas (Crocuta crocuta), social carnivores that live in large fission-fusion societies. By combining this classifier with continuous collar-based accelerometer data from five hyenas, we generated a complete record of activity patterns over more than one month. We used these continuous behavioural sequences to investigate how past activity, individual idiosyncrasies, and social synchronization influence hyena activity patterns. We found that hyenas exhibit characteristic crepuscular-nocturnal daily activity patterns. Time spent active was independent of activity level on previous days, suggesting that hyenas do not show activity compensation. We also found limited evidence for an effect of individual identity on activity, and showed that pairs of hyenas who synchronized their activity patterns must have spent more time together. This study sheds light on the patterns and drivers of activity in spotted hyena societies, and also provides a useful tool for quantifying behavioural sequences from accelerometer data.

Horizontal viewsheds of large herbivores as a function of woodland structure.

There is great potential for the use of terrestrial laser scanning (TLS) to quantify aspects of habitat structure in the study of animal ecology and behaviour. Viewsheds-the area visible from a given position-influence an animal's perception of risk and ability to respond to potential danger. The management and conservation of large herbivores and their habitats can benefit greatly from understanding how vegetation structure shapes viewsheds and influences animal activity patterns and foraging behaviour. This study aimed to identify how woodland understory structure influenced horizontal viewsheds at deer eye height. Mobile TLS was used in August 2020 to quantify horizontal visibility-in the form of Viewshed Coefficients (VC)-and understory leaf area index (LAI) of 71 circular sample plots (15-m radius) across 10 woodland sites in North Wales (UK) where fallow deer (Dama dama) are present. The plots were also surveyed in summer for woody plant size structure, stem density and bramble (Rubus fruticosus agg.). Eight plots were re-scanned twice in winter to compare seasonal VC values and assess scan consistency. Sample plots with higher densities of small stems had significantly reduced VC 1 m from the ground. Other stem size classes, mean percentage bramble cover and understory LAI did not significantly affect VC. There was no difference in VC between summer and winter scans, or between repeated winter scans. The density of small stems influenced viewsheds at deer eye height and may alter behavioural responses to perceived risk. This study demonstrates how TLS technology can be applied to address questions in large herbivore ecology and conservation.

Cathemerality: a key temporal niche.

Given the marked variation in abiotic and biotic conditions between day and night, many species specialise their physical activity to being diurnal or nocturnal, and it was long thought that these strategies were commonly fairly fixed and invariant. The term 'cathemeral', was coined in 1987, when Tattersall noted activity in a Madagascan primate during the hours of both daylight and darkness. Initially thought to be rare, cathemerality is now known to be a quite widespread form of time partitioning amongst arthropods, fish, birds, and mammals. Herein we provide a synthesis of present understanding of cathemeral behaviour, arguing that it should routinely be included alongside diurnal and nocturnal strategies in schemes that distinguish and categorise species across taxa according to temporal niche. This synthesis is particularly timely because (i) the study of animal activity patterns is being revolutionised by new and improved technologies; (ii) it is becoming apparent that cathemerality covers a diverse range of obligate to facultative forms, each with their own common sets of functional traits, geographic ranges and evolutionary history; (iii) daytime and nighttime activity likely plays an important but currently neglected role in temporal niche partitioning and ecosystem functioning; and (iv) cathemerality may have an important role in the ability of species to adapt to human-mediated pressures.

Morphobiometry of the scleral ossicle rings in Chelonia mydas sea turtles.

Scleral ossicle rings of reptiles have endoskeletal functions that are not completely understood. Moreover, descriptive reports on the anatomy of those rings are scarce. We tried to make an anatomical description that could contribute to a better understanding of their functions. We quantified, histologically characterized and evaluated the morphobiometry of the scleral ossicles, and measured the aditus orbitae of 25 sea turtle (Chelonia mydas) heads. The aditus orbitae represented about one-third of the total head length and the mean area of the internal opening of each ring was up to 8.37% of the aditus orbitae area. The mean internal diameter of the rings (6.32 mm) was characteristic of scotopic species and the most frequent number of ossicles per ring varied between 11 and 12. Two new classifications were proposed for the ossicle types: plus-Verzahnung (+V) and minus-Verzahnung (-V). The bone tissue revealed a lamellar arrangement typical of compact and resistant bones. The obtained data may be used to support and expand the understanding of functions, animal activity patterns, distinctions between taxa and taphonomic interpretations.

Telemetry and Accelerometer Tracking of Green Toads in an Urban Habitat: Methodological Notes and Preliminary Findings.

Advancements in tracking technologies provide an increasingly important tool in animal monitoring and conservation that can describe animal spatial behavior in native habitats and uncover migratory routes that otherwise may be difficult or impossible to map. In addition, high-resolution accelerometer sensors provide powerful insights into animal activity patterns and can help to identify specific behaviors from accelerometer profiles alone. Previously, such accelerometers were restricted to larger animals due to size and mass constraints. However, recent advances make it possible to use such devices on smaller animals such as the European green toad (Bufotes viridis), the focus of our current study. We deploy custom made tracking devices, that consist of very-high-frequency transmitters and tri-axial accelerometers, to track toads in their native urban environment in Vienna (Austria). A total of nine toads were tracked, ranging from three to nine tracking days per individual during the post-breeding season period. We demonstrate that our devices could reliably monitor toad movement and activity during the observation period. Hence, we confirmed the predominantly nocturnal activity patterns and recorded low overall movement at this urban site. Accelerometer data revealed that toads exhibited brief but intense activity bursts between 10 pm and midnight, resting periods during the night and intermittent activity during the day. Positional tracking alone would have missed the major activity events as they rarely resulted in large positional displacements. This underscores the importance of and value in integrating multiple tracking sensors for studies of movement ecology. Our approach could be adapted for other amphibians or other animals with mass constraints and may become standard monitoring equipment in the near future.

A narrative review on the use of camera traps and machine learning in wildlife research

Camera trapping has become an important tool in wildlife research in the past few decades. However, one of its main limiting factors is the processing of data, which is labour-intensive and time-consuming. Consequently, to aid this process, the use of machine learning has increased. A summary is provided on the use of both camera traps and machine learning and the main challenges that come with it by performing a general literature review. Remote cameras can be used in a variety of field applications, including investigating species distribution, disease transmission and vaccination, population estimation, nest predation, animal activity patterns, wildlife crossings, and diet analysis. Camera trapping has many benefits, including being less invasive, allowing for consistent monitoring and simultaneous observation (especially of secretive or aggressive animals even in dangerous or remote areas), providing photo/video evidence, reducing observer bias, and being cost effective. The main issues are that they are subject to their environment, dependent on human placements, can disrupt animal behaviour, need maintenance and repair, have limitations on photographic data, and are sensitive to theft and vandalism. When it comes to machine learning, the main aim is to identify species in camera (trap) images, although emerging technologies can provide individual recognition as well. The downsides in- clude the large amount of annotated data, computer power, and programming and machine learning expertise needed. Nonetheless, camera trapping and machine learning can greatly assist ecologists and conservationists in wildlife research, even more so as technology further develops.

What’s Black and White and Pink All Over? Lesser Flamingo Nocturnal Behaviour Captured by Remote Cameras

The study of animal behaviour is important for the development of husbandry and management practices for zoo-housed species. Yet, data are typically only collected during daylight hours, aligning with human work schedules rather than animal activity patterns. To remedy this, 24 h data collection is needed. This study investigated the behaviour of a captive flock of lesser flamingos to understand temporal changes in their time-activity patterns. Two remote camera traps were placed around the birds’ outdoor enclosure and one within the indoor house. Counts of birds visible within specific enclosure zones were recorded from photographic data. Behaviour was defined as active or inactive, and modified Spread of Participation Index (SPI) was used to calculate enclosure zone occupancy. Results indicated that lesser flamingos are active overnight, and to a similar amount as in the daytime. Proportions of birds observed as active were significantly higher at later times of the day (i.e., dusk) when compared to the number of active birds in the morning. Enclosure usage was diverse and indoor and outdoor zones could be used by different numbers of birds at different times of the day. Variation in enclosure usage may indicate the changing needs of the flamingos when housed indoors overnight and when they have night-time access to an outdoor enclosure. This research has identified the need for further research into the nocturnal behaviour and space use of lesser flamingos and suggests the need for 24 h research in captive birds, and other zoo-held species, especially when species are locked indoors or face behavioural restriction overnight due to biosecurity measures surrounding zoonoses outbreaks, e.g., Avian Influenza.

Shift work-like patterns effect on female and male mouse behavior

Shift work (work outside of standard daylight hours) is common throughout the Western world. However, there are notable health consequences to shift work, including increased prevalence of mental health and sleep disorders in shift worker populations. Therefore, the health and wellbeing of shift workers is a public health concern that needs to be addressed. Here we investigate the effects of two separate light induced shift work-like patterns on male and female mouse behaviour (anxiety-like, exploration, marble burying, startle reflex and circadian rhythms). After 6 weeks of shift-like disruptions patterns, animals displayed no behavioral differences in exploration, marble burying and startle reflex. Interestingly however, we identified sex specific and disruption specific effects in light aversion and wheel running activities. Notably, analysis of the activity patterns of animals in disruptive conditions demonstrated that they maintained a degree of rhythmicity through the disruption period, which may explain the lack of behavioral differences in most behavioral tests.

Temporal overlap of human and apex predator activity on wildlife trails and forest roads

The daily activity patterns of animals are modulated by external factors such as habitat selection, temporal niche selection, prey availability and predation risk. Furthermore, different species show a variety of responses to human disturbance; therefore, to understand the effects of human activities on wildlife, it is crucial to consider the disturbance characteristics (e.g. type, frequency, timing and location of human activity). Our objective was to evaluate whether vehicles on forest roads altered the daily temporal activity patterns of three apex predators; Eurasian lynx (Lynx lynx), the grey wolf (Canis lupus) and brown bear (Ursus arctos), using an extensive camera trap data set collected across a gradient of forest roads and wildlife trails in the Croatian part of the Dinaric mountains. We expected a low temporal overlap between humans and apex predators but predicted this even lower at sites where vehicles are present. Consistent with our expectations, the general overlap in temporal activity of all three apex predators and humans was low, the former being primarily active at night/dawn/dusk hours and the latter during daylight hours. In contrast, our results showed similarity in the temporal activity of all three predators on wildlife trails and forest roads where human activity was more frequent and diverse.

Analysis of animal-related electric outages using species distribution models and community science data

Animal-related outages (AROs) are a prevalent form of outages in electrical distribution systems. Animal-infrastructure interactions vary across species and regions, underlining the need to study the animal-outage relationship in more species and diverse systems. Animal activity has been an indicator of reliability in the electrical grid system by describing temporal patterns in AROs. However, these ARO models have been limited by a lack of available species activity data, instead approximating activity based on seasonal patterns and weather dependency in ARO records and characteristics of broad taxonomic groups, e.g. squirrels. We highlight available resources to fill the ecological data gap limiting joint analyses between ecology and energy sectors. Species distribution modeling (SDM), a common technique to model the distribution of a species across geographic space and time, paired with community science data, provided us with species-specific estimates of activity to analyze alongside spatio-temporal patterns of ARO severity. We use SDM estimates of activity for multiple outage-prone bird species to examine whether diverse animal activity patterns were important predictors of ARO severity by capturing existing variation within animal-outage relationships. Low dimensional representation and single patterns of bird activity were important predictors of ARO severity in Massachusetts. However, both patterns of summer migrants and overwintering species showed some degree of importance, indicating that multiple biological patterns could be considered in future models of grid reliability. Making the best available resources from quantitative ecology known to outside disciplines can allow for more interdisciplinary data analyses between ecological and non-ecological systems. This can result in further opportunities to examine and validate the relationships between animal activity and grid reliability in diverse systems.

Influence of Moon Luminosity, Seasonality, Sex and Weather Conditions on the Activity Levels of the Nocturnal Javan Slow Loris

The activity patterns of mammals depend on environmental changes (e.g., moon luminosity, food availability, weather) and endogenous rhythms. Behavioral observations are traditionally used to estimate the activity patterns of animals, but low visibility and the cryptic nature of some species entail that, in certain conditions, the animal is visible only for around 60% of the time. Recent advances in technology allow automatic data collection on the activity levels of animals. We used five years of data collected via accelerometers to understand how moon luminosity, seasonality, sex, and weather conditions influence the activity levels of the nocturnal and cryptic Javan slow loris. We collected 9589 h on six females and 7354 h on six males. Via Generalized Additive Mixed Models, we found that lorises are lunarphobic; they reduce activity levels during cold nights, they have higher activity levels when the relative humidity is close to 100%, and they have high peaks of activity between December and February and between June and August. The activity levels are thus influenced by avoidance of predators, food availability, consumption of insects and nectar, physiological, and behavioral adaptations to cold temperatures and energy requirements during reproductive stages. We highlight the importance of using bio-loggers for cryptic animals as with behavioral observations only, and the observer might underestimate active behaviors and overestimate inactivity.

Evolution of diel activity patterns in skinks (Squamata: Scincidae), the world's second-largest family of terrestrial vertebrates.

Many animals have strict diel activity patterns, with unique adaptations for either diurnal or nocturnal activity. Diel activity is phylogenetically conserved, yet evolutionary shifts in diel activity occur and lead to important changes in an organism's morphology, physiology, and behavior. We use phylogenetic comparative methods to examine the evolutionary history of diel activity in skinks, one of the largest families of terrestrial vertebrates. We examine how diel patterns are associated with microhabitat, ambient temperatures, and morphology. We found support for a nondiurnal ancestral skink. Strict diurnality in crown group skinks only evolved during the Paleogene. Nocturnal habits are associated with fossorial activity, limb reduction and loss, and warm temperatures. Our results shed light on the evolution of diel activity patterns in a large radiation of terrestrial ectotherms and reveal how both intrinsic biotic and extrinsic abiotic factors can shape the evolution of animal activity patterns.

Even generalist and resilient species are affected by anthropic disturbance: evidence from wild boar activity patterns in a Mediterranean landscape

Humans have negatively impacted most ecosystems on Earth, altering how species use habitats and resources available to them, but also their circadian rhythms. Among many factors affecting animal activity patterns, conversion of native habitat into production forests and hunting are critical, and their impacts may be exacerbated by seasonal weather conditions. Both these factors are issues in Mediterranean Europe, especially in Portugal. Nevertheless, their impact on native species behavior remains largely unknown, even for generalist species often resilient to human disturbance such as wild boar (Sus scrofa). Therefore, we assessed temporal activity patterns of wild boar in Portugal to explore differences between habitats (native forest versus Eucalyptus plantations), hunting and non-hunting periods, or between seasons. We found that wild boars were primarily nocturnal, with greater nighttime activity more evident during the dry season and within plantations. Furthermore, they appeared to avoid dusk during the hunting season. Together, these patterns indicate that even a species typically resilient to disturbance and environmental change, such as wild boar, tends to avoid adverse weather conditions and disturbance factors, namely high daytime temperatures in summer and probability of encountering forestry workers or hunters. Accordingly, other more sensitive or resource-demanding mammals may also be affected, so evaluating the impacts of the studied anthropic drivers on other mammals should be prioritized to provide information for sustainable plantation management and hunting.

Seasonal and diel activities of the Yangtze finless porpoise in natural and highly disturbed habitats: Implications for conservation planning of freshwater cetaceans

Abstract Knowledge of fine‐scale seasonal and diel activity patterns of animals provides insights into habitat utilization dynamics and informs conservation action planning against potential human impacts. Such information is particularly important for riverine cetaceans, such as the Yangtze finless porpoise, which is threatened by habitat loss and disturbances by a variety of human activities. Passive acoustic monitoring (PAM) techniques were used to survey the seasonal and diel activities of the Yangtze finless porpoise in two natural habitat patches of the Anqing Yangtze Finless Porpoise Natural Reserve, and in one highly disturbed area adjacent to the reserve. In the two natural habitat patches, significantly higher detection rates of porpoises were observed during autumn and winter. The detection rates during autumn and winter were significantly higher at night than during daytime, whereas during spring and summer the diel difference in porpoise detection rates was not statistically significant. In the highly disturbed habitat, the porpoise detection rates were significantly lower than those in the two natural habitats. Although seasonal differences in porpoise detection rates were not statistically significant, diel detection rates were significantly different in autumn and winter. Information on seasonal patterns of porpoise activities suggested strengthening monitoring and law enforcement during autumn and winter, during the period in which diel activity patterns implied a potential conservation gap during nighttime. Extremely low levels of porpoise activities in port areas implied an ecological impact of coastal engineering on megafauna viability through the alteration of habitat functionality. To provide information on animal occurrences and activities and to minimize the bias of ‘false‐absence’ from visual surveys, the census survey design should consider both visual and PAM techniques. In seasons when occurrences of river cetaceans and habitat use are increasing, heightened conservation monitoring and law enforcement efforts are required, particularly during nighttime.