Diel Activity Research Articles

Temporal activity patterns of bears, wolves and humans in the Cantabrian Mountains, northern Spain

Human-wildlife coexistence is important for a sustainable relationship between humans and the natural environment. However, human activities often act as a disturbance to wild animals, which may show behavioural shifts indicating human avoidance. For large carnivores, which are prone to conflict with many human interests, coexistence with humans can be particularly challenging. We used long-term camera trap data to evaluate seasonal and diel variations in activity of two large carnivores, the brown bear (Ursus arctos) and the grey wolf (Canis lupus), as well as humans in the Cantabrian Mountains, northern Spain. Brown bears were less active in winter than in summer; the opposite was observed for wolves, whereas there was limited seasonal variation in human activity. On a diel scale, both bears and wolves were mostly crepuscular during summer and had less distinct, but generally more nocturnal activity during winter. Humans were strictly diurnal during both seasons. We suggest that the diel activity of bears and wolves was partially caused by human avoidance, but that seasonal variations in both overall and diel activity were mainly caused by ecological and physiological factors. While we suggest that the observed similarity in diel activity of bears and wolves did not have caused strong competition between these two species, it may have influenced interactions with other predators and prey. Since such interactions are likely to be context dependent, we urge for further studies evaluating how humans influence the behaviour of large carnivores across different spatio-temporal scales.

Unclear relationships in interference competition among three sympatric medium-sized carnivores in a heavy snowy environment

Abstract Interference competition, a category of interspecific competition, is a critical aspect of understanding the dynamics of carnivore communities, as it can result in a decline in the health and reduced opportunity for resource acquisition of one or both competing species. Heavy snowfall environments during winter are expected to exacerbate interference competition due to decreased food resources and limited foraging opportunities caused by snow cover. However, knowledge on interference competition in such environments is limited. Using camera traps with baits, we evaluated the interference competition among three sympatric medium-sized carnivores, red foxes, raccoon dogs, and Japanese martens, within a heavy snowfall region of northeastern Japan. As in previous studies, we hypothesized that body weight would serve as a determining factor for superiority in winter snow environments. Diel activity patterns using the visitation time to baits did not reveal any clear differences. Nevertheless, the daytime occurrence frequency of Japanese martens during the snowfall season was higher than that of the other two species, indicating inferiority to the other species. The analysis of time intervals between species visiting baits revealed no clear superiority among the target species. These findings suggest that the interspecific relationships among medium-sized carnivores in winter snowy environments are complex and not easily determined.

Evaluation of multiple behavioral responses of sika deer to human hunting pressures

AbstractSeveral ungulate populations have become overabundant worldwide, resulting in ecological and social effects. Wildlife managers must establish effective population control programs to mitigate these negative influences. Hunting is a significant mortality factor for ungulates, which exhibit sensitive behavioral responses toward hunting activities. Wildlife managers need a comprehensive understanding of the ungulate responses to different hunting pressures across seasons. We developed a conceptual method to evaluate multiple behavioral responses to human hunting pressures and applied this to sika deer (Cervus nippon) in Hokkaido, Japan, during August and November in 2015. We measured flight behavior, spatial avoidance, and temporal activity shift during non‐hunting and hunting seasons in 4 regions with different hunting pressures. Although we did not observe a clear difference in flight initiation distance among study areas or seasons, sika deer showed significant spatial avoidance during the hunting season in areas with high hunting pressure. Furthermore, sika deer were more active at night in areas with higher hunting pressures, regardless of the season. Collectively, these results suggest that sika deer responded to hunting pressure by changing diel activity to nocturnal throughout the year and avoiding risky areas (i.e., around hunting roads) during hunting season, rather than by increasing flight distance when they encounter humans. Our method can be used for a more efficient population control program for wildlife managers, as it considers the spatiotemporal variations of flexible ungulate behaviors in response to hunting pressures.

Assessing spatiotemporal patterns of mesocarnivores along an urban‐to‐rural gradient

AbstractRapid increases in human development and activity are affecting the spatial and temporal dynamics of mammalian mesocarnivore communities. We used 40 motion‐sensitive cameras along an urban‐to‐rural gradient, and single‐season occupancy models, to evaluate the habitat use of a local mesocarnivore guild (coyote [Canis latrans], bobcat [Lynx rufus], red fox [Vulpes vulpes], gray fox [Urocyon cinereoargenteus], and raccoon [Procyon lotor]) near Newburgh, New York, USA, during May–September 2021. Additionally, we fit circular kernel density estimations to assess how mesocarnivores may alter their diel and nocturnal activity patterns in response to human development. Red foxes were positively associated with urban areas and were also significantly more active at night in semiurban areas versus rural and urban locations. Coyotes demonstrated some adaptability to urban areas, being generally more nocturnal as urbanization increased but were also more likely to use higher elevation sites and areas with more natural habitat cover. We did not find support for a spatial shield hypothesis, as red foxes and raccoons were often detected in the same semiurban and urban sites as coyotes. Bobcats generally avoided human‐dominated areas, whereas raccoons were ubiquitous throughout the gradient and exhibited similar daily and nocturnal activity levels in all land cover types. Overall, our results document how anthropogenic disturbance may alter mesocarnivore community structure and landscape use, providing information for managing urban carnivore populations and mitigating human–wildlife conflict, particularly at the local scale.

Temporal partitioning and the potential for avoidance behaviour within South African carnivore communities.

Carnivora occupy many ecological niches fundamental to ecosystem functioning. Within this diverse order, carnivore species compete to establish dominance, ensure survival and maintain fitness. Subordinate carnivores must, therefore, adapt their behaviour to coexist with dominant species. One such strategy is the partitioning of temporal activity patterns. We aim to determine interspecific avoidance patterns among sympatric carnivores by examining coexistence along a temporal axis. We compared the temporal activity patterns of 13 carnivore species using multi-seasonal camera trapping data from four protected areas across South Africa: Associated Private Nature Reserves, Madikwe Game Reserve, Mountain Zebra National Park and Tswalu Kalahari Reserve. Interspecific coefficients of overlap in diel and core activity periods were calculated over the study period and during the wet and dry seasons. Furthermore, interspecific spatiotemporal behaviour was examined using time-to-event analyses. Our results showed that complete avoidance of diel activity patterns was rare among South African carnivore species. Most species were predominantly nocturnal and, therefore, diel activity overlap was high, whereas core activity overlap was significantly lower (p < .001). Diel activity overlap was significantly lower during the dry than wet seasons (p = .045). Lastly, evidence of spatiotemporal aggregation revolved around scavenging species. We show the importance of seasonality in the temporal avoidance behaviours of South African carnivores while highlighting the need for fine-scaled behavioural analyses. Overall, we show that the daily activity patterns of most subordinate South African carnivore species are not influenced by top-down forces in the form of competitional suppression and risk exerted by dominant species. If avoidance is required, it is more likely to manifest as fine-scaled avoidance of core activity periods. We suggest that the focus on core activity periods might be a more suitable tool for interspecific temporal partitioning research.

Spectral sensitivity of retinal photoreceptors of tortricid moths is not tuned to diel activity period.

Leafrollers (Lepidoptera: Tortricidae) are a large family of small moths containing over 10,000 species, many of which are crop pests. Grapholita molesta, Lobesia botrana and Cydia pomonella adults are sexually active before, during and after sunset, respectively. We wanted to determine whether being active at different times of the day and night is associated with differences in their visual system. Spectral sensitivity (SS) was measured with electroretinograms and selective adaptation with green, blue and ultraviolet light. SS curves could be fitted with a triple nomogram template which indicated the existence of three photoreceptor classes peaking at 355, 440 and 525 nm. The retinae showed clear regionalization, with fewer blue receptors dorsally. No differences among species or between sexes were found. Intracellular recordings in C. pomonella also revealed three photoreceptor classes with sensitivities peaking at 355, 440 and 525 nm. The blue photoreceptors showed inhibitory responses in the green part of the spectrum, indicating the presence of a colour-opponent system. Flicker fusion frequency experiments showed that the response speed was similar between sexes and species and fused at around 100 Hz. Our results indicate that the three species have the ancestral insect retinal substrate for a trichromatic colour vision, based upon the UV, blue and green-sensitive photoreceptors, and lack any prominent adaptations related to being active under different light conditions.

The genomic basis of temporal niche evolution in a diurnal rodent

Patterns of diel activity-how animals allocate their activity throughout the 24-h daily cycle-play key roles in shaping the internal physiology of an animal and its relationship with the external environment.1,2,3,4,5 Although shifts in diel activity patterns have occurred numerous times over the course of vertebrate evolution,6 the genomic correlates of such transitions remain unknown. Here, we use the African striped mouse (Rhabdomys pumilio), a species that transitioned from the ancestrally nocturnal diel niche of its close relatives to a diurnal one,7,8,9,10,11 to define patterns of naturally occurring molecular variation in diel niche traits. First, to facilitate genomic analyses, we generate a chromosome-level genome assembly of the striped mouse. Next, using transcriptomics, we show that the switch to daytime activity in this species is associated with a realignment of daily rhythms in peripheral tissues with respect to the light:dark cycle and the central circadian clock. To uncover selection pressures associated with this temporal niche shift, we perform comparative genomic analyses with closely related rodent species and find evidence of relaxation of purifying selection on striped mouse genes in the rod phototransduction pathway. In agreement with this, electroretinogram measurements demonstrate that striped mice have functional differences in dim-light visual responses compared with nocturnal rodents. Taken together, our results show that striped mice have undergone a drastic change in circadian organization and provide evidence that the visual system has been a major target of selection as this species transitioned to a novel temporal niche.

Rain, recreation and risk: Human activity and ecological disturbance create seasonal risk landscapes for the prey of an ambush predator.

Predation risk and prey responses exhibit fluctuations in space and time. Seasonal ecological disturbances can alter landscape structure and permeability to influence predator activity and efficacy, creating predictable patterns of risk for prey (seasonal risk landscapes). This may create corresponding seasonal shifts in antipredator behaviour, mediated by species ecology and trade-offs between risk and resources. Yet, how human recreation interacts with seasonal risk landscapes and antipredator behaviour remains understudied. In South Florida, we investigated the impact of a seasonal ecological disturbance, specifically flooding, which is inversely related to human activity, on interactions between Florida panthers (Puma concolor coryi) and white-tailed deer (Odocoileus virginianus). We hypothesized that human activity and ecological disturbances would interact with panther-deer ecology, resulting in the emergence of two distinct seasonal landscapes of predation risk and the corresponding antipredator responses. We conducted camera trap surveys across southwestern Florida to collect detection data on humans, panthers and deer. We analysed the influence of human site use and flooding on deer and panther detection probability, co-occurrence and diel activity during the flooded and dry seasons. Flooding led to decreased panther detections and increased deer detections, resulting in reduced deer-panther co-occurrence during the flooded season. Panthers exhibited increased nocturnality and reduced diel activity overlap with deer in areas with higher human activity. Supporting our hypothesis, panthers' avoidance of human recreation and flooding created distinct risk schedules for deer, driving their antipredator behaviour. Deer utilized flooded areas to spatially offset predation risk during the flooded season while increasing diurnal activity in response to human recreation during the dry season. We highlight the importance of understanding how competing risks and ecological disturbances influence predator and prey behaviour, leading to the generation of seasonal risk landscapes and antipredator responses. We emphasize the role of cyclical ecological disturbances in shaping dynamic predator-prey interactions. Furthermore, we highlight how human recreation may function as a 'temporal human shield,' altering seasonal risk landscapes and antipredator responses to reduce encounter rates between predators and prey.

Novel in-situ observations on the diel surface activity of the Romanian hamster, Mesocricetus newtoni (Rodentia, Cricetidae), during pup rearing

The Romanian hamster Mesocricetus newtoni is a threatened and cryptic species, with a distribution limited to North-eastern Bulgaria and South-eastern Romania (Dobruja region). Current literature does not provide sufficient data regarding diel activities and behavior of this species, especially under field conditions. In this context, one female M. newtoni, during the rearing period of her four pups, was monitored for ten days using camera traps. For each documented activity, the date, time, age of the individual, type of activity, and duration were recorded. In total, from the 26140 media files, 72968 seconds were recorded as active behaviors. Data analysis revealed that diurnal activity was predominant and documented for all monitored days; however, the animals spent more time per each activity during the night. The nocturnal activity was present but erratic, without significant patterns. No significant differences were observed in the median duration of activities of the adult compared to the immature individuals. Both the adult female and pups spent time exploring the burrow entrance, especially during the day, but immatures were more reserved to leave the burrow than the female. The female used four burrows for rearing the pups. During this time, food storage behaviors and transferring of immatures between burrows, as well as the weaning of the pups were documented. This study demonstrates that M. newtoni exhibits significant diurnal activity, at least in certain ecological and physiological conditions.

An animal movement track segmentation framework for forecasting range adaptation under global change

The methods used for predicting space use and geographic distribution adaptations of animals in response to global change have relied on fitting statistical and machine learning models to environmentally-contextualized movement and spatial distribution data. These predictions, however, are made at particular spatiotemporal scales (from home range to species distribution), but no comprehensive methods have been proposed for predicting how changes to subdiel segments of individual movement tracks may lead to emergent changes in the lifetime tracks of individuals, and hence in the redistribution of species under global change. In this article, we discuss in terms of a hierarchical movement track segmentation framework that, anchored by diel activity routines (DARs), how adaptions in the canonical activity modes (CAMs) of movement can be used to assess space use adaptations to landscape and climate change at scales ranging from subdiel movement segments to the lifetime tracks (LiTs) of individuals.

Assessing the Movements, Habitat Use, and Site Fidelity of the Giant Freshwater Whipray (Urogymnus polylepis) with Acoustic Telemetry in the Maeklong River, Thailand

We used acoustic telemetry to assess site fidelity, movement patterns, and habitat use within the lower Maeklong River, Thailand, by 22 giant freshwater whipray Urogymnus polylepis. This study is the first of its kind for this rare, endangered species, and it begins to fill critical information gaps about its ecology and life history. Study animals were tagged subcutaneously in the dorsal area with acoustic transmitters and tracked for 12 months using a fixed array of eight receivers. Receivers were positioned within an 18 rkm section of the Maeklong, starting approximately 4 rkm upstream from the mouth. We calculated individual residency indices, tracked longitudinal movements, and assessed annual and seasonal patterns of site use. We also investigated spatial use patterns, diel activity patterns, and relationships of temperature and site fidelity. We detected 86% of our tagged whiprays, 53% of which were detected for the majority of the study period. Whiprays exhibited high site fidelity across seasons. Individuals made long longitudinal movements within the site for much of the study period but seemed to remain closer to the estuary during the second half of the rainy season and early winter. All receivers had large numbers of detections, but upstream receivers were visited for longer time durations than downstream receivers. A receiver in the middle of the study area had the highest detection rate, but low detection durations, suggesting that this receiver is in a migration corridor. A mix of immature and mature males and females was present in the site throughout the study period, suggesting that this area is not exclusively a breeding or nursery site. However, the high site fidelity suggests that this is an important aggregation site for the species. Effective conservation measures may include conservation zones and a shrimp reintroduction program upstream, ensuring fish passage through the middle of the site, and regulating traffic and pollution downstream. We found acoustic telemetry to be an effective study method and encourage its use to improve understanding of the giant freshwater whipray.

Keeping cool on hot days: activity responses of African antelope to heat extremes

Long-lived organisms are likely to respond to a rapidly changing climate with behavioral flexibility. Animals inhabiting the arid parts of southern Africa face a particularly rapid rise in temperature which in combination with food and water scarcity places substantial constraints on the ability of animals to tolerate heat. We investigated how three species of African antelope—springbok Antidorcas marsupialis, kudu Tragelaphus strepsiceros and eland T. oryx—differing in body size, habitat preference and movement ecology, change their activity in response to extreme heat in an arid savanna. Serving as a proxy for activity, dynamic body acceleration data recorded every five minutes were analyzed for seven to eight individuals per species for the three hottest months of the year. Activity responses to heat during the hottest time of day (the afternoons) were investigated and diel activity patterns were compared between hot and cool days. Springbok, which prefer open habitat, are highly mobile and the smallest of the species studied, showed the greatest decrease in activity with rising temperature. Furthermore, springbok showed reduced mean activity over the 24 h cycle on hot days compared to cool days. Large-bodied eland seemed less affected by afternoon heat than springbok. While eland also reduced diurnal activity on hot days compared to cool days, they compensated for this by increasing nocturnal activity, possibly because their predation risk is lower. Kudu, which are comparatively sedentary and typically occupy shady habitat, seemed least affected during the hottest time of day and showed no appreciable difference in diel activity patterns between hot and cool days. The interplay between habitat preference, body size, movement patterns, and other factors seems complex and even sub-lethal levels of heat stress have been shown to impact an animal's long-term survival and reproduction. Thus, differing heat tolerances among species could result in a shift in the composition of African herbivore communities as temperatures continue to rise, with significant implications for economically important wildlife-based land use and conservation.

Niche conservatism over deep timescales and diverse niche axes in land vertebrates

AbstractAimThere has been considerable interest in niche conservatism, the idea that ecological variables are similar among related species. Much research has focused on climatic niches of recently diverged species, rather than deeper timescales or non‐climatic niche axes. Furthermore, it has been suggested that conservatism disappears over deeper timescales, and is greater in alpha niche traits (like diet and microhabitat) than beta niche variables (like climate). Here, we test these latter two ideas by comparing patterns of phylogenetic conservatism among 10 niche variables across major clades of land vertebrates.LocationGlobal.Time PeriodPresent to 350 million years ago.Major Taxa StudiedTetrapods, including amphibians, mammals, lepidosaurs (including lizards and snakes), turtles, crocodilians and birds.MethodsThe 10 niche variables included four alpha niche components (diet, diel activity, habitat, body temperature) and six beta niche components (related to climatic temperature and precipitation). We analysed these variables on time‐calibrated phylogenies with similar taxon sampling (~1700 species), using phylogenetic signal (lambda) to estimate conservatism, along with the D statistic and estimates of evolutionary rates.ResultsPhylogenetic signal was generally strong across all variables, with lambda generally &gt;0.80 (with 1.0 representing maximum signal). Nevertheless, mean phylogenetic signal was lower in beta niche traits than alpha niche traits (based on lambda and especially the D statistic), and alpha niche traits showed significantly slower rates of evolution.Main ConclusionsWe address two long‐held views in the literature on niche conservatism, rejecting one but supporting the other. We show that phylogenetic signal does not disappear over deep timescales for many important niche variables, even over 350 million years. We also generally support greater conservatism in alpha niche traits than beta niche traits over hundreds of millions of years, a pattern that was previously suggested (but not explicitly tested) based on closely related species.

Anthropogenic activities and age class mediate carnivore habitat selection in a human-dominated landscape

Human activities increasingly challenge wild animal populations by disrupting ecological connectivity and population persistence. Yet, human-modified habitats can provide resources, resulting in selection of disturbed areas by generalist species. To investigate spatial and temporal responses of a generalist carnivore to human disturbance, we investigated habitat selection and diel activity patterns in caracals (Caracal caracal). We GPS-collared 25 adults and subadults in urban and wildland-dominated subregions in Cape Town, South Africa. Selection responses for landscape variables were dependent on subregion, animal age class, and diel period. Contrary to expectations, caracals did not become more nocturnal in urban areas. Caracals increased their selection for proximity to urban areas as the proportion of urban area increased. Differences in habitat selection between urban and wildland caracals suggest that individuals of this generalist species exhibit high behavioral flexibility in response to anthropogenic disturbances that emerge as a function of habitat context.

Rafting behaviour of albatrosses and petrels at South Georgia

Seabirds often spend time on the water in the vicinity of their breeding colonies at the start or end of foraging trips, which may be for bathing, social interaction, information transfer, or to reduce predation risk for small petrels that prefer to return to land in darkness. Although such behaviour (hereafter rafting) is common, there are few data on variation in its incidence or timing across species, or analyses of relationships with intrinsic or extrinsic factors such as breeding stage (reflecting central-place foraging constraints) or weather. Here, we use GPS and immersion data collected over multiple years at Bird Island, South Georgia, to investigate rafting behaviour of four albatross and one burrow-nesting petrel species. Nearly all tracked birds (89%) landed within 10 km of the colony at the start of foraging trips for ~ 30 min, whereas only 17% did so at the end, suggesting they likely use rafting mainly for plumage maintenance after extended breeding shifts on land. Rafting duration, distance and bearing from the colony varied markedly according to species, wind speeds and period of the day (daylight vs. darkness), which may reflect differences in foraging direction, time constraints, degree of plumage soiling, diel activity patterns, or the requirement for high wind speeds for efficient flight. Given that all the study populations are decreasing, and most individuals make extensive use of nearshore waters during the breeding season, effective marine spatial planning is required that eliminates or mitigates human risks around their colonies.

A noisy neighbour: acoustic competition drives changes in song traits and spatiotemporal behaviour of orthopterans

Competition for acoustic space is key for sound-communicating animals, yet little is known about whether and how it may drive evolutionary pathways, for example signal structure, as well as species distributions or individual spatial behaviour. Here we assessed the occurrence of interspecific acoustic competition in sound-communicating taxa by testing three nonmutually exclusive hypotheses explaining variability of song structure and singing activity, in two sibling species of tree crickets of the genus Oecanthus. By comparing song acoustic parameters, diel activity patterns and relative densities of singing crickets in both sympatry and allopatry, we found that the local co-occurrence of the two species drives changes in all the considered factors of song production. Namely, we report changes in temporal and structural song traits, as well as in singing activity patterns and apparent population density, with strongly asymmetrical effects, only evident for one of the two species considered. Our results highlight the role of acoustic space as a key resource that shapes biotic interactions, and eventually behaviours, in sound-communicating taxa, and represent a replicable approach in the study of acoustic assemblages.

Spatiotemporal overlap with invasive wild pigs (Sus scrofa) varies by species and season in a temperate ecosystem

AbstractWild pigs (Sus scrofa), which are invasive in many regions globally, can alter ecosystems and compete with native species through interference competition and resource exploitation. Wild pig impacts on other species may increase with greater niche overlap, which could vary over time based on environmental conditions, resource availability, or biological traits like diet, especially as seasonal variation in wild pig diet has been widely documented. A limited number of studies have assessed spatial or temporal overlap between native species and invasive wild pigs, with only a handful simultaneously assessing overlap in these niche dimensions. We investigated the potential for interspecific interactions involving invasive wild pigs in the Piedmont region of South Carolina, USA, by examining seasonal spatiotemporal overlap with other wildlife using N‐mixture models and diel activity overlap analyses. Site use by white‐tailed deer (Odocoileus virginianus) and coyote (Canis latrans) was negatively associated with wild pig activity in the fall, when the species had high diel activity overlap, indicating spatial partitioning could reduce interference competition with wild pigs in this season. Conversely, white‐tailed deer site use was positively associated with wild pig activity in the winter, suggesting higher spatial overlap may be necessary if resources are limited. Site use by bobcat (Lynx rufus) and nine‐banded armadillo (Dasypus novemcinctus) in the spring, along with raccoon (Procyon lotor) and wild turkey (Meleagris gallopavo) site use in the summer, was positively associated with wild pig activity. With the exception of diurnal wild turkey, diel activity overlap between these species and wild pigs was high, although temporal partitioning could have occurred at finer spatiotemporal scales than we examined. Our results collectively emphasize the importance of accounting for seasonal spatial and temporal responses by individual species to invasive wild pigs, with special consideration given to species in seasons where high niche overlap with wild pigs is anticipated.

Non-exploitative human disturbance provides shelter for prey from predator.

Human activities can influence behaviors of predators and prey, as well as predator-prey interactions. Using camera trap data, we investigated whether or to what extent human activities influenced behaviors of predators (tigers and leopards) and prey (sambar deer, spotted deer, wild boar, and barking deer), and predator-prey interactions in the Barandabhar Corridor Forest (BCF), Chitwan District, Nepal. A multispecies occupancy model revealed that the presence of humans altered the conditional occupancy of both prey and predator species. Specifically, the conditional occupancy probability of prey was substantially higher (ψ = 0.91, CI = 0.89-0.92) when humans were present than when humans were absent (ψ = 0.68, CI = 0.54-0.79). The diel activity pattern of most prey species overlapped strongly with humans, whereas predators were generally more active when humans were absent. Finally, the spatiotemporal overlap analysis revealed that human-prey interactions (i.e., the probability that both humans and prey species being present on the same grid at the same hourly period) was ~3 times higher (10.5%, CI = 10.4%-10.6%) compared to spatiotemporal overlap between humans and predators (3.1%, CI = 3.0%-3.2%). Our findings are consistent with the human shield hypothesis and suggest that ungulate prey species may reduce predation risk by using areas with high human activities.

Carnivore coexistence in Chicago: niche partitioning of coyotes and red foxes

Mesopredators including coyotes (Canis latrans) and red foxes (Vulpes vulpes) often co-occur in urban environments, but how niche partitioning facilitates their coexistence remains unclear. Highly urbanized areas can be spatial refuges for smaller mesopredators (i.e., spatial human shield effect), however these species also may coexist through temporal niche partitioning. We used camera traps (n = 110 sites) across an urbanization gradient in Chicago to examine coyote-fox interactions from 2011 to 2018. We analyzed spatial partitioning through multi-season occupancy models and structural equation modeling (SEM), and quantified temporal overlap between canids and with humans. Coyotes most often occurred in natural areas, and urbanization reduced their colonization rates and increased their extinction rates. Initial occupancy for red foxes was negatively impacted by urbanization, but their extinction rates depended on a surprising interaction between coyotes and humans. When coyotes were rare, fox extinction was related positively to human activity; but when coyotes were more common, fox extinction was related negatively to human activity. This outcome may reflect a human shield effect at a within-site scale. The SEM further supported the negative impact of urbanization on both canids, and lack of an effect of coyotes on the distribution of foxes. Diel activity of coyotes and red foxes indicated temporal niche partitioning intensified at more urbanized sites. Our results suggest the spatial human shield effect is not operating across sites in Chicago. Instead, coyotes and red foxes may share green spaces, especially in highly urbanized areas, where species coexistence is promoted by temporal niche partitioning.

Human presence and infrastructure impact wildlife nocturnality differently across an assemblage of mammalian species.

Wildlife species may shift towards more nocturnal behavior in areas of higher human influence, but it is unclear how consistent this shift might be. We investigated how humans impact large mammal diel activities in a heavily recreated protected area and an adjacent university-managed forest in southwest British Columbia, Canada. We used camera trap detections of humans and wildlife, along with data on land-use infrastructure (e.g., recreation trails and restricted-access roads), in Bayesian regression models to investigate impacts of human disturbance on wildlife nocturnality. We found moderate evidence that black bears (Ursus americanus) were more nocturnal in response to human detections (mean posterior estimate = 0.35, 90% credible interval = 0.04 to 0.65), but no other clear relationships between wildlife nocturnality and human detections. However, we found evidence that coyotes (Canis latrans) (estimates = 0.81, 95% CI = 0.46 to 1.17) were more nocturnal and snowshoe hares (Lepus americanus) (estimate = -0.87, 95% CI = -1.29 to -0.46) were less nocturnal in areas of higher trail density. We also found that coyotes (estimate = -0.87, 95% CI = -1.29 to -0.46) and cougars (Puma concolor) (estimate = -1.14, 90% CI = -2.16 to -0.12) were less nocturnal in areas of greater road density. Furthermore, coyotes, black-tailed deer (Odocoileus hemionus), and snowshoe hares were moderately more nocturnal in areas near urban-wildland boundaries (estimates and 90% CIs: coyote = -0.29, -0.55 to -0.04, black-tailed deer = -0.25, -0.45 to -0.04, snowshoe hare = -0.24, -0.46 to -0.01). Our findings imply anthropogenic landscape features may influence medium to large-sized mammal diel activities more than direct human presence. While increased nocturnality may be a promising mechanism for human-wildlife coexistence, shifts in temporal activity can also have negative repercussions for wildlife, warranting further research into the causes and consequences of wildlife responses to increasingly human-dominated landscapes.