Diel Activity Research Articles

ILAM: Imaging Locomotor Activity Monitor for circadian phenotyping of large‐bodied flying insects

Abstract Historically, most insect chronoecological research has used direct observations, cameras or infrared beam‐based monitors to quantify movement across timed intervals. Although some alternative DIY systems are cheaper than the current standard locomotor activity monitor, these options remain complicated to build and/or computationally intensive. We developed the imaging Locomotor Activity Monitor (iLAM), an affordable (~$75 USD/unit) system for activity quantification. The iLAM utilizes a Raspberry Pi Zero W computer and night‐vision camera inside a flight cage to photograph a population of insects at user‐defined intervals. Open‐source, modular R‐scripts process the images and output a file containing the number, size, coordinate location and timestamp of all movements (blobs) identified between consecutive images. Output can be analysed directly or converted into the standard TriKinetics DAM format. We demonstrated the flexibility and power of the iLAM system by comparing diel and circadian activity of different insect species (fireflies: Photinus marginellus, P. greeni, P. obscurellus), ecotypes (moths: Ostrinia nubilalis) and sexes (moths: O. nubilalis). Data captured by only six iLAMs ($450) identified that peak activity of O. nubilalis females (AZT: 19.2 h) occurs significantly earlier than males (22.0 h). Additionally, male moths from a univoltine population exhibited a significantly shorter endogenous period length (AZT: 21.3 h) than males from a bivoltine genetic background (22.7 h). The iLAM will serve as a valuable tool for researchers seeking to measure locomotor activity across diverse species, sexes and populations in constant and changing environments.

A survey of nocturnality and risk for savanna chimpanzees at Assirik, Senegal.

Chimpanzees (Pan troglodytes) in Senegal may use nocturnality to mitigate hyperthermia risk in semi-arid environments but the degree of nocturnality for such chimpanzees also in sympatry with large carnivores remains uncertain. We compared diel activity among chimpanzees and their potential predators at Assirik in Niokolo-Koba National Park and contextualized these findings relative to other unit-groups in savanna landscapes. From 2015-2018, we generated a predator inventory using multi-modal methods and monitored the diel activity of chimpanzees and predators with camera traps [ N = 2092 camera trap (CT) days]. From 2015-2023, we also surveyed for evidence of predation during recce walks. Six potential nonhuman predators occur at Assirik, including lions (Panthera leo), leopards (Panthera pardus), spotted hyenas (Crocuta crocuta), African wild dogs (Lycaon pictus), Nile crocodiles (Crocodylus niloticus), and rock pythons (Python sebae). We documented one suspected case of a predator killing a chimpanzee. Nocturnality comprised 12.7% of CT events for chimpanzees and these events were more concentrated at twilight. Chimpanzees were more active during the day, predators were more active at night, and there was substantial temporal overlap among chimpanzees and potential predators during twilight intervals. Our findings support the hypothesis that savanna chimpanzees in Senegal are active at night in response to the extremely hot environment. We hypothesize that Assirik chimpanzees experience a tension between decreasing hyperthermia and increasing predation risk during nocturnality.

Behavior and Activity Patterns of the Critically Endangered Mangshan Pit Viper (Protobothrops mangshanensis) Determined Using Remote Monitoring.

This study focuses on understanding the behavior and activity patterns of the critically endangered Protobothrops mangshanensis in China in order to better provide scientific data for upcoming artificial breeding and propagation efforts. We conducted a long-term observation of 15 Mangshan pit vipers at different sites in Hunan Province during the summer and autumn of 2021. Our methods involved analyzing the influence of environmental factors such as temperature, relative humidity, and light condition on the snakes' day and night activity and behaviors. The results revealed that the wild behaviors of Protobothrops mangshanensis include resting, sunbathing, crawling, and exploring, with distinct rhythms in their diel behavior. The snakes' diel activity exhibits three peak periods which may be related to food activity and sunbathing. This study also highlights the complex interplay of environmental factors on the activity of Protobothrops mangshanensis. Relative humidity was identified as a critical factor accounting for the difference in activity between observation groups. There was little inter-individual variation among the 15 Protobothrops mangshanensis, even though these snakes used terrestrial and arboreal habitats under different environmental conditions. These findings enhance our understanding of Protobothrops mangshanensis behavior and provide a basis for effective conservation measures for this rare and critically endangered species.

Phototrap‐assessed diel activity of Cerambyx cerdo and Cerambyx welensii sympatric populations in the wild: Does extreme drought boost diurnality?

Abstract Longhorn beetles (Cerambycidae) are a very diverse group whose species vary greatly in morphology and behaviour, particularly in diel activity. The type genus Cerambyx includes two large oak‐ling sympatric species (Cerambyx cerdo and Cerambyx welensii) that exhibit a crepuscular/nocturnal (dim‐light) lifestyle, but their actual diel activity remains largely unclear. We used phototraps in the wild to assess if diel activity depended on either species, sex or annual meteorology. Phototraps were highly effective, and the imaged activities were representative of beetles' life, including interactions with some vertebrate species. Both longhorns exhibited roughly similar crepuscular/nocturnal behaviour, with daytime activity being usually residual or erratic. Diel activity increased sharply just before dusk, peaked between dusk and early dark night (23:00–2:00 h), and then dropped progressively until disappearing at dawn. Diel activity was sexually dimorphic in C. welensii, as in some years females tended to be active earlier than males. Distinctly, in 2022, the warmest and driest year recorded in the study area, diel activity curves were flatter and wider, with C. cerdo activity increasing in the late afternoon (19:00–21:30 h) and C. welensii in the second half of the night (3:00–6:00 h). Furthermore, both species boosted daytime activity (diurnality) by more than three times, and diurnality also increased over the season that year. We finally hypothesise that, under the current climate change scenario, extreme droughts impact diel activity in these species, particularly boosting diurnality, in an attempt to locate water/food sources to counteract body dehydration.

The Diel Activity Pattern of Haemaphysalis longicornis and Its Relationship with Climatic Factors.

Haemaphysalis longicornis is one of the most medically important carriers of various pathogens. Although H. longicornis is an important vector, only basic ecological and biological information has been obtained, primarily focusing on its abundance and distribution. This study determined the most active time and meteorological conditions for the diel activity of H. longicornis. The diel activity pattern of H. longicornis was the highest between 10:00 and 14:00, and the lowest between 22:00 and 02:00. The major activity temperature of H. longicornis was between 25 °C and 40 °C, with the highest activity at 35 °C. The relative humidity was between 30% and 70% during the active period. Temperature had the highest correlation with diel activity (R = 0.679), followed by humidity (R = -0.649) and light intensity (R = 0.572). Our results provide basic information for the development of tick-borne disease vector control programs and tick surveillance.

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.

Insights into the evolution of photoreceptor oil droplets in frogs and toads.

Photoreceptor oil droplets (ODs) are spherical organelles placed most commonly within the inner segment of the cone photoreceptors. Comprising neutral lipids, ODs can be either non-pigmented or pigmented and have been considered optically functional in various studies. Among living amphibians, ODs were only reported to occur in frogs and toads (Anura), while they are absent in salamanders and caecilians. Nonetheless, the limited understanding of their taxonomic distribution in anurans impedes a comprehensive assessment of their evolution and relationship with visual ecology. We studied the retinae of 134 anuran species, extending the knowledge of the distribution of ODs to 46 of the 58 currently recognized families, and providing a new perspective on this group that complements the available information from other vertebrates. The occurrence of ODs in anurans shows a strong phylogenetic signal, and our findings revealed that ODs evolved at least six times during the evolutionary history of the group, independently from other vertebrates. Although no evident correlation was found between OD occurrence, adult habits and diel activity, it is inferred that each independent origin involves distinct scenarios in the evolution of ODs concerning photic habits. Furthermore, our results revealed significant differences in the size of the ODs between nocturnal and arrhythmic anurans relative to the length of the cones' outer segment.

Fine-tuning coexistence: Wildlife's short-term responses to dynamic human disturbance patterns

Anthropogenic disturbance elicits adaptive responses in wildlife, generally aimed at risk-avoidance, ultimately imposing constraints on their spatial and temporal niches. Previous studies have largely focused on long-term adaptive responses to stable human pressure, but rapid adjustments in wildlife’s diel and habitat use patterns in response to fine-scale variations in human presence have so far been overlooked. In this study we estimate short-term spatio-temporal deviations in local habitat use and diel activity of medium and large mammal species in response to rapid variations in human disturbance. We employed a year-long camera-trapping within a small private reserve, and recorded spatio-temporal information on all sources of anthropogenic disturbance in the area. By controlling for the average habitat use and diel activity, we explored fine-scale spatiotemporal adjustments in seven mammal species. We found evidence of spatial and/or temporal avoidance across all species, except wild boar, with variations in magnitude and direction coherent with species traits and expected levels of human-tolerance. Most species exhibited temporal avoidance of human activities, with porcupine and roe deer eliciting particularly strong responses. Notably, foxes concurrently displayed temporal avoidance and spatial attraction, likely driven by the presence of anthropogenic trophic resources. Our study underscores the role of behavioral plasticity in enabling wildlife to adjust daily habitat use and activity patterns to varying levels of human pressure across space and time. Understanding these nuanced behavioral strategies can help to promote wildlife-human coexistence and mitigating the adverse impacts of human presence on wildlife fitness.

Seasonal activity patterns and home range sizes of wolves in the human‐dominated landscape of northeast Türkiye

Gray wolves Canis lupus comprise one of the most widely distributed carnivore species on the planet, but they face myriad environmental and anthropogenic pressures. Previous research suggests that wolves adjust their time‐ and space‐use seasonally to mitigate risks from humans, conspecifics, and other predators while maximizing their hunting and reproductive success. With many populations of wolves resettling in areas with dense human populations, understanding how wolves may adjust their temporal and spatial patterns in these more human‐dominated landscapes is of high conservation importance. Typically, human presence causes wolves to increase their nocturnality and home range size. Here, we look at how seasonal home range size and diel activity patterns among resident and non‐resident wolves differ in an ecosystem that experiences significant differences in human activity between seasons. While non‐resident wolves had larger home ranges than resident wolves, there were no differences in home range sizes within residents and non‐residents between seasons, suggesting that seasonal changes in human presence had no effect on home range size. The activity patterns of wolves were similar between seasons, but resident wolves had greater overlap with humans and were more active than non‐resident wolves when humans were less present in the landscape. Both resident and non‐resident wolves showed increased nocturnality, with both groups selecting for nocturnality more strongly in the nomadic season. This is the first study of tracking Türkiye's wolves and offers the first descriptions of the temporal and spatial trends of GPS‐collared wolves in this highly human‐dominated environment.

Artificial light at night drives diel activity patterns of synanthropic pipistrelle bats and their prey

The use of artificial light at night (ALAN) has increased drastically worldwide over the last decades. ALAN can have major effects on nocturnal communities, including insects and bats. Insects are attracted to street lights and few bat species take advantage of this by foraging on the attracted insects. ALAN potentially affects the temporal patterns of insect abundance and thereby bat foraging behaviour. In a natural dark environment, these patterns are usually bimodal, with an activity peak in the early evening and the morning. Little is known about how ALAN affects insect presence throughout the night, and whether the light spectrum plays a role. This is important, as these temporal changes may be a key driver of disturbances in bat-insect interactions. Here, we studied how white and red light affect insects' and bats' nightly activity patterns. The activity of insects and bats (Pipistrellus spp.) was recorded throughout the night at seven experimentally illuminated sites in a forest-edge ecosystem. ALAN disrupted activity patterns, with both insects and bats being more active throughout the night. ALAN facilitated all-night foraging in bats especially near white light, but these effects were attenuated near red light. The ability to forage throughout the night may be a key advantage causing synanthropic bats to dominate in illuminated environments, but this could also prove detrimental in the long term. As red light reduced disturbing effects of ALAN on insects and bats diel activity pattern, it opens the possibility of using spectral composition as a mitigation measure.

A global dataset of diel activity patterns in insect communities

Insect activity powers ecosystems and food production globally. Although insect activity is known to vary with the rise and setting of the sun, there is surprisingly limited empirical information on how insect abundance and richness varies across the 24-hour day–night (diel) cycle. Moreover, commonly used methods for sampling insects such as light traps do not provide suitable comparisons of community properties between diel periods. We present a dataset of 1512 observations of abundance and richness during diurnal and nocturnal periods in insect communities worldwide. The data were collected from 99 studies that systematically sampled insect communities during day and night, using sampling methods minimally influenced by diel variation, such as movement-based interception traps. Spanning six continents, 41 countries and 16 insect orders, the data can support investigations into the factors influencing insect diel preferences as well as the causes and consequences of temporal changes in insect biodiversity. The data also provides key baseline information on the diel activity patterns of insect communities for long-term ecological monitoring. These pursuits take on added significance considering contemporary ‘insect declines’ and increasing anthropogenic impacts on diurnal and nocturnal biodiversity.

Habituation of wildlife to ecotourism: A COVID‐19 lockdown experiment in Corcovado National Park, Costa Rica

AbstractCorcovado National Park (CNP) in Costa Rica is an important destination for ecotourism. However, the effects of increasing human visitation on wildlife needed evaluation and the global COVID‐19 pandemic lockdown provided a scenario to test the effects of tourist activity on wildlife presence and activity. We performed a camera trap survey initiated during the COVID‐19 lockdown and continuing when tourism resumed (Oct 2020–May 2021). We deployed camera traps on walking trails, including those that remained closed to tourists at all times (control) and those open to tourists after the lockdown was lifted (experimental). With an effort of 2312 trap nights, we assessed the photo rates and diel activity patterns of humans, 11 other species of mammals, and two species of birds. Our results suggest that wildlife species were already habituated to tourists in this area, and thus their behavior and activity did not change after the lockdown was lifted.

Human avoidance, selection for darkness and prey activity explain wolf diel activity in a highly cultivated landscape

Wildlife that share habitats with humans with limited options for spatial avoidance must either tolerate frequent human encounters or concentrate their activity into those periods with the least risk of encountering people. Based on 5259 camera trap images of adult wolves from eight territories, we analyzed the extent to which diel activity patterns in a highly cultivated landscape with extensive public access (Denmark) could be explained from diel variation in darkness, human activity, and prey (deer) activity. A resource selection function that contrasted every camera observation (use) with 24 alternative hourly observations from the same day (availability), revealed that diel activity correlated with all three factors simultaneously with human activity having the strongest effect (negative), followed by darkness (positive) and deer activity (positive). A model incorporating these three effects had lower parsimony and classified use and availability observations just as well as a ‘circadian' model that smoothed the use‐availability ratio as function of time of the day. Most of the selection for darkness was explained by variation in human activity, supporting the notion that nocturnality (proportion of observations registered at night vs. day at the equinox) is a proxy for temporal human avoidance. Contrary to our expectations, wolves were no more nocturnal in territories with unrestricted public access than in territories where public access was restricted to roads, possibly because wolves in all territories had few possibilities to walk more than few hundred meters without crossing roads. Overall, Danish wolf packs were 6.5 (95% CI: 4.6–9.6) times more active at night than at daylight, which make them amongst the most nocturnally active wolves reported so far. These results confirm the prediction that wolves in habitats with limited options for spatial human avoidance, invest more in temporal avoidance.

Comparing the effectiveness of adulticide application interventions on mitigating local transmission of dengue virus

AbstractThe southern US has a large presence of mosquito vector species for dengue virus (DENV) and experiences thousands of DENV importations every year, which have led to several local outbreaks. Adulticide spraying targeting active mosquitoes is one of the most common insecticide strategies used as a response to an outbreak. The aim of this study is to evaluate the effectiveness of adulticide spraying conducted at different times of the day to curb DENV transmission. Based on unique dataset of Aedes aegypti diel activity patterns in Miami-Dade County, Florida, and Brownsville, Texas, we developed a mechanistic model of DENV transmission, which simulates adulticide spraying interventions. We estimated that spraying adulticide for 14 consecutive days at 7am or 8 pm was highly effective in reducing DENV outbreak probability from 10% in the absence of interventions to 0.1% for Miami-Dade County, and from 7.8 to 0.1% for Brownsville. Moreover, in case of a local outbreak in Miami-Dade County, we estimated the median number of symptomatic infections after the identification of a local outbreak to be reduced from 67.0 (IQR: 25.5–103.0) in the absence of interventions to 1.0 (IQR: 0.0–2.0) when spraying adulticide for 14 consecutive days at 8 pm. In Brownsville, the same intervention is estimated to lead to a decrease from 15.0 (IQR: 7.0–33.0) cases to 1.0 (IQR: 0.0–2.0). Our study highlights the importance of considering diel activity patterns of vector mosquito species in arbovirus preparedness and response planning and provide quantitative evidence to guide the decision-making of mosquito control authorities.

Diel activity patterns of a canopy-inhibiting beetle community (Coleoptera) in a Neotropical rainforest

Diel activity is one main feature of animal‘s behavior and is often an intrinsic trait characterizing distinct taxonomic groups. Abiotic conditions such as temperature may influence the diel activity patterns of arthropod communities associated with a particular ecosystem or habitat. Similarly, biotic factors, such as resource availability, affect arthropod activity. In addition, diel activity is thought to be an important factor in niche partitioning of arthropod communities. As part of a larger beetle survey in a lowland tropical rainforest in southern Venezuela, I analyzed the diel activity of an arboreal beetle community collected from 23 canopy-tree species over a cumulative year. Diel activity was observed in 535 beetle species, comprising 5,948 individuals, using a canopy crane installed in the study area. Of the 535 beetle species, 198 (37%) showed diurnal activity, and 281 (52.5%) showed nocturnal activity. In contrast, the proportions of nocturnal (n = 2,024, 34%) and diurnal (n = 1,983, 33.3%) individuals were balanced. Most of the observed beetles occurred only during the activity phase in their host trees. This particularly applies to extrafloral nectary- and flower-visiting beetle species. Flowering trees attracted different proportions of diurnal and nocturnal species according to flowering syndrome, whereas extrafloral nectaries were mainly visited at night. Thus, the beetle communities associated with single tree species showed distinct compositions of nocturnal and diurnal species.

The evolution of body coloration in dung beetles: diel activity and sexual dimorphism

The evolution of body coloration in dung beetles: diel activity and sexual dimorphism

Diel and Vertical Niche Differentiation of Frugivore Communities Feeding on Ficus nota (Blanco) Merr.

Ficus species are keystone species in tropical ecosystems for frugivores. Nonetheless, ecological aspects of fig frugivory such as niche differentiation are understudied, leading to huge gaps in the knowledge of fig-frugivore interactions. We used camera traps to monitor the vertical and diel activity of frugivores feeding on a Ficus nota tree in Cavite, the Philippines for 70 d to determine vertebrate species feeding on Ficus nota and their niche differentiation mechanisms. We observed several mammalian taxa (pteropodid fruit bats, Rattus sp. and Paradoxurus philippinensis) and several avian taxa (Hypsipetes philippinus, Pycnonotus goiavier, Lanius cristatus, and Centropus viridis). All of the detected species were observed to be perching on, inspecting, or eating fruits. However, based on existing literature, two of the four bird species detected (L. cristatus and C. viridis) are known to be carnivorous. Diel niche differentiation was evident from the diurnal and nocturnal activity patterns of birds and mammals, respectively. We also detected temporal activity differences between pteropodids and P. philippinensis, hence suggesting temporal niche differentiation. Pteropodids were also more active in the terrestrial stratum, whereas non-pteropodids were more active in the arboreal stratum, hence suggesting vertical niche differentiation. Diel niche differentiation may be attributed to differences in food acquisition adaptations, whereas vertical niche differentiation may be attributed to differences in tree morphology between strata and in frugivore adaptations for mobility. These results show that Ficus nota acts as a food source and habitat for frugivores and non-frugivores and that interspecific interactions are mediated by niche differentiation. Our findings underscore the potential of Ficus nota as a species in restoration efforts to support seed-dispersing frugivores and other wildlife species, as well as the utility of camera trapping to survey frugivores in understudied habitats.

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.

Complex evolution in thin air: Investigating female flightlessness and diel behaviour in geometrid moths (Lepidoptera)

AbstractMany unique high‐altitude mountain ecosystems have been declining due to climate change, posing a threat to flora and fauna that have adapted to these ecosystems. This study explores the evolution of high‐altitude adaptations, focusing on female flightlessness and diel activity, in geometrid moths (Lepidoptera: Ennominae, Gnophini) within the European Alps. We constructed a phylogeny of Gnophini moths using a dataset of 157 taxa, with up to seven genetic markers and traced the evolutionary history of diel activity and wing length reduction in females. Analysis of divergence times suggested that female flightlessness has evolved at least three times independently between the early and late Miocene. The evolution of wing length reduction is likely correlated with elevation, indicating adaptations to cold and windy conditions in high altitude. The evolutionary events leading to shifts in adult diel activity, from ancestral nocturnality to diurnality, have occurred independently at least three times and may also be a consequence of adaptations at high elevations. Strikingly, among diurnal Sciadia, two species have evolved further to become nocturnal like their ancestors. Our findings highlight how phylogenies can provide new insights into evolutionary patterns in moths. We provided a robust basis for resolving taxonomic ambiguities in Alpine Gnophini, leading us to propose 10 changes to the current classification: Scrupodes Lee & Sihvonen gen. n., Elophos Boisduval (type species Geometra operaria Hübner) is considered a junior synonym of Sciadia Hübner syn. n., Yezognophos dilucidaria (Denis & Schiffermüller) and Y. sproengertsi (Püngeler) are transferred to Parietaria Leraut comb. n., Yezognophos serotinaria (Denis & Schiffermüller) is transferred to Scrupeus Lee & Sihvonen comb. n., Elophos caelibaria (Heydenreich), E. zirbitzensis (Pieszcek), E. operaria (Hübner) and E. andereggaria (De La Harpe) are transferred to Sciadia Hübner comb. n. and Dichrognophos Wehrli (type species Gnophos orthogonia Wehrli) is transferred from Ennominae: Cassymini to Ennominae: Gnophini.

Ultrasound and ultraviolet: crypsis in gliding mammals.

Gliding is only present in six extant groups of mammals-interestingly, despite divergent evolutionary histories, all mammalian gliders are strictly nocturnal. Gliding mammals also seem to have relatively high rates of ultrasound use and ultraviolet-induced photoluminescence (UVP) in contrast with their close relatives. Therefore, we hypothesized that, despite diverging lineages, gliding mammals use similar modes of cryptic communication compared to their non-gliding counterparts. We developed two datasets containing the vocal range (minimum-maximum of the dominant harmonic; kHz) and UVP of 73 and 82 species, respectively; we report four novel vocal repertoires and 57 novel observations of the presence or absence of UVP. We complemented these datasets with information about body size, diel activity patterns, habitat openness, and sociality to explore possible covariates related to vocal production and UVP. We found that the maximum of the dominant harmonic was significant higher in gliding mammals when vocalizing than their non-gliding relatives. Additionally, we found that nocturnality was the only significant predictor of UVP, consistent with the previous hypothesis that luminophores primarily drive UVP in mammal fur. In contrast, however, we did not find UVP ubiquitous in nocturnal mammals, suggesting that some unknown process may contribute to variation in this trait.