Sleep, sleeping sites, and sleep-related activities: awakening to their significance

Habitual ground nesting in the Bugoma Forest chimpanzees (Pan troglodytes schweinfurthii), Uganda

We report the presence of habitual ground nesting in a newly studied East African chimpanzee (Pan troglodytes schweinfurthii) population in the Bugoma Central Forest Reserve, Uganda. Across a 2-year period, we encountered 891 night nests, 189 of which were classified as ground nests, a rate of ~21%. We find no preliminary evidence of socio-ecological factors that would promote its use and highlight local factors, such as high incidence of forest disturbance due to poaching and logging, which appear to make its use disadvantageous. While further study is required to establish whether this behavior meets the strict criteria for nonhuman animal culture, we support the argument that the wider use of population and group-specific behavioral repertoires in flagship species, such as chimpanzees, offers a tool to promote the urgent conservation action needed to protect threatened ecosystems, including the Bugoma forest.

Understanding Circadian and Circannual Behavioral Cycles of Captive Giant Pandas (Ailuropoda melanoleuca) Can Help to Promote Good Welfare

Circadian and circannual cycles of behavior regulate many aspects of welfare including metabolism, breeding, and behavioral interactions. In this study, we aim to demonstrate how systematically determining circadian and circannual cycles can provide insight into animals' needs and be part of an evidence-based approach to welfare assessment. We measured and analyzed the observational behavioral data of 13 zoo-housed giant pandas (Ailuropoda melanoleuca), across life stages and between sexes, each month for one year using live camera footage from six zoos across the world. Our results indicate that life stage was associated with changes in overall activity, feeding, locomotion, and pacing, and that sex influenced scent anointing and anogenital rubbing. Overall, the circadian rhythms showed three peaks of activity, including a nocturnal peak, as seen in wild giant pandas. We also found associations between sexual-related, stereotypical/abnormal, and feeding behavior, which are possibly linked to the timing of migration of wild pandas, and elucidated the relationship between a mother and cub, finding that they concentrate maternal behaviors to mainly after closing hours. Understanding these cycle patterns can aid animal care staff in predicting changing needs throughout the day, year, and life cycle and preemptively provide for those needs to best avoid welfare concerns.

The influence of vegetation structure on sleeping site selection by chimpanzees (Pan troglodytes troglodytes)

Sleep is an important aspect of great ape life; these animals build sleeping platforms every night. In a community of chimpanzees, each subgroup selects a sleeping site where each individual builds a sleeping platform, mostly on a tree. Previous studies have measured the heights of sleeping platforms and sleeping trees to test the predation avoidance and thermoregulation hypotheses of sleeping site selection. However, it remains unclear how components of vegetation structure (vertical and horizontal) together determine the selection of sleeping sites by chimpanzees. Using botanical inventories around sleeping sites in a tropical rainforest of Cameroon, we found that chimpanzees preferentially sleep in trees measuring 40-50 cm in diameter. Regarding height, on average, sleeping trees measured 26 m and sleeping platforms were built at 16 m. To build sleeping platforms, chimpanzees preferred four tree species, which represent less than 3% of tree species in the study area. We demonstrate that the variation in abundance of tree species and the vertical and horizontal structure of the vegetation drive chimpanzee sleeping site selection. It was previously thought that preference for vegetation types was the driver of sleeping site selection in chimpanzees. However, results from this study indicate that the importance of vegetation types in sleeping site selection depends on their botanical characteristics including the variation in tree size, the abundance of all trees, the abundance of sleeping trees, and the occurrence of preferred sleeping tree species, which predict sleeping site selection. The height and diameter of trees are considered by chimpanzees when selecting a particular tree for sleeping and when selecting a site with a specific vertical structure. In addition to tree height, the abundance of smaller neighboring trees may also play a role in the chimpanzee antipredation strategy. Our results demonstrate that chimpanzees consider several vegetation parameters to establish sleeping sites.

Promoting Good Nonhuman Primate Welfare outside Regular Working Hours

Promoting good primate welfare outside of daylight hours is an important task. The responsibility to provide a complex environment and environmental enrichment is an essential element of primate wellbeing programs that should be approached from a 24-h perspective and planned according to the species and individual needs, including giving animals the ability to interact with and control their environment during hours when animal care staff are not present. One must be aware, however, that their needs may differ at night-time from their care needs during the day when staff are present. Assessing welfare and providing enrichment during times when staff are not on hand can be achieved through the use of a variety of technologies, such as night-view cameras, animal-centred technologies, and data loggers. This paper will address the relevant topics concerning the care and welfare of primates during off-hours, and the use of related technologies to facilitate and assess wellbeing at these times.

Listening to Their Nights: Sleep Disruptions in Captive Housed Chimpanzees Affect Their Daytime Behavior

Chimpanzee's nocturnal sleep is a dynamic and complex process, still not fully understood. As in humans, not getting enough quality sleep due to frequent or lasting disruptions may affect their physical and mental health, hence wellbeing, which may be reflected in their daytime behavior. This study aims to understand the impact of abiotic factors, such as temperature and humidity on the nocturnal activity as well as the impact of nocturnal awakening events on daytime behavior in sanctuary-housed chimpanzees. We monitored noisy nocturnal activity through audio recordings for one year, documenting the number and duration of sound events produced by chimpanzees to indicate sleep fragmentation and disruption intensity, respectively. Our results indicate that indoor temperature and humidity indeed influence the chimpanzee's nocturnal activity. Furthermore, sleep fragmentation and intensity of nocturnal events significantly influenced the following day's behavior. After nights marked by frequent and/or intense sleep disruptions, higher levels of inactivity, and abnormal and self-directed behaviors were observed, and chimpanzees spent more time on affiliative interactions and in social proximity. These findings highlight the importance of controlling factors influencing nocturnal sleep quality. Furthermore, we demonstrated that economic audio recordings used to monitor nocturnal activity, provide insights into the chimpanzee's behavior and wellbeing.

Adaptive Solutions to the Problem of Vulnerability During Sleep

Sleep is a behavioral state whose quantity and quality represent a trade-off between the costs and benefits this state provides versus the costs and benefits of wakefulness. Like many species, we humans are particularly vulnerable during sleep because of our reduced ability to monitor the external environment for nighttime predators and other environmental dangers. A number of variations in sleep characteristics may have evolved over the course of human history to reduce this vulnerability, at both the individual and group level. The goals of this interdisciplinary review paper are (1) to explore a number of biological/instinctual features of sleep that may have adaptive utility in terms of enhancing the detection of external threats, and (2) to consider relatively recent cultural developments that improve vigilance and reduce vulnerability during sleep and the nighttime. This paper will also discuss possible benefits of the proposed adaptations beyond vigilance, as well as the potential costs associated with each of these proposed adaptations. Finally, testable hypotheses will be presented to evaluate the validity of these proposed adaptations.

Seasonal changes in the parasite prevalence of a small Malagasy lemur species (Lepilemur edwardsi)

Parasitic infections can impact the fitness of individuals and can have influence on animals' population dynamics. An individuals' parasite prevalence often changes depending on external or seasonal changes, e.g., rainfall and ambient temperatures, but also on internal changes, e.g., changes in body condition. In this study we aimed to identify the environmental factors that may influence the intestinal parasite and ectoparasite prevalence of the folivorous Malagasy primate species, Lepilemur edwardsi, living in a seasonal dry deciduous forest. Species living in this habitat have to adapt to seasonal changes of ambient temperature, with almost no precipitation during the dry season and hence strong fluctuations of resource availability throughout the year. We sampled the feces and ectoparasites of L. edwardsi throughout the year. Intestinal parasite prevalence increased from the wet to the dry season and was highest in the late dry season, which might be due to the accompanying decrease in diet-quality. Conversely, ectoparasite prevalence decreased in the dry season, presumably due to the prevailing unfavorable environmental conditions for the development of ectoparasites (i.e., mites and ticks). Paired with the higher resting metabolism and stress level of L. edwardsi during the late dry season, it seems that this species may struggle when dry seasons intensify in its habitat. This article is protected by copyright. All rights reserved.

Lateral hypothalamic neuronal ensembles regulate pre-sleep nest-building behavior

The transition from wakefulness to sleep requires striking alterations in brain activity, physiology, and behavior, yet the precise neuronal circuit elements facilitating this transition remain unclear. Prior to sleep onset, many animal species display characteristic behaviors, including finding a safe location, performing hygiene-related behaviors, and preparing a space for sleep. It has been proposed that the pre-sleep period is a transitional phase in which engaging in a specific behavioral repertoire de-arouses the brain and facilitates the wake-to-sleep transition, yet both causal evidence for this premise and an understanding of the neuronal circuit elements involved are lacking. Here, we combine detailed behavioral observations, EEG-EMG recordings, selective targeting, and activity modulation of pre-sleep-active neurons to reveal the behaviors preceding sleep initiation and their underlying neurobiological mechanisms. We show that mice engage in temporally structured behaviors with stereotypic EEG signatures prior to sleep and that nest-building and grooming become significantly more prevalent with sleep proximity. We next demonstrate that the ability to build a nest promotes the initiation and consolidation of sleep and that the lack of nesting material chronically fragments sleep. Lastly, we identify broadly projecting and predominantly glutamatergic neuronal ensembles in the lateral hypothalamus that regulate the motivation to engage in pre-sleep nest-building behavior and gate sleep initiation and intensity. Our study provides causal evidence for the facilitatory role of pre-sleep behaviors in sleep initiation and consolidation and a functional characterization of the neuronal underpinnings regulating a sleep-related and goal-directed complex behavior.

Where to sleep next? Evidence for spatial memory associated with sleeping sites in Skywalker gibbons (Hoolock tianxing)

Finding suitable sleeping sites is highly advantageous but challenging for wild animals. While suitable sleeping sites provide protection against predators and enhance sleep quality, these sites are heterogeneously distributed in space. Thus, animals may generate memories associated with suitable sleeping sites to be able to approach them efficiently when needed. Here, we examined traveling trajectories (i.e., direction, linearity, and speed of traveling) in relation to sleeping sites to assess whether Skywalker gibbons (Hoolock tianxing) use spatial memory to locate sleeping trees. Our results show that about 30% of the sleeping trees were efficiently revisited by gibbons and the recursive use of trees was higher than a randomly simulated visiting pattern. When gibbons left the last feeding tree for the day, they traveled in a linear fashion to sleeping sites out-of-sight (> 40 m away), and linearity of travel to sleeping trees out-of-sight was higher than 0.800 for all individuals. The speed of the traveling trajectories to sleeping sites out-of-sight increased not only as sunset approached, but also when daily rainfall increased. These results suggest that gibbons likely optimized their trajectories to reach sleeping sites under increasing conditions of predatory risk (i.e., nocturnal predators) and uncomfortable weather. Our study provides novel evidence on the use of spatial memory to locate sleeping sites through analyses of movement patterns, which adds to an already extensive body of literature linking cognitive processes and sleeping patterns in human and non-human animals.

Sleeping Site and Tree Selection by Bale Monkeys (Chlorocebus djamdjamensis) at Kokosa Forest Fragment in Southern Ethiopia

Although selecting advantageous sleeping sites is crucial for nonhuman primates, the extent to which different factors contribute to their selection remains largely unknown for many species. We investigated hypotheses relating to predator avoidance, food access, and thermoregulation to explain the sleeping behavior of Bale monkeys (Chlorocebus djamdjamensis) occupying a degraded fragmented forest, Kokosa, in the southern Ethiopian Highlands. We found that the study group reused 11 out of 20 sleeping sites used during the 42 study days over a 6-month period. Sleeping sites were usually close to the last feeding trees of the day (mean distance =15.2 m) and/or the first feeding trees of the next morning (mean distance = 13.5 m). This may reflect an attempt to maximize feeding efficiency and reduce travel costs. Compared to the mean trees in the study area, sleeping trees were significantly shorter. Bale monkeys selected sleeping places in trees with high foliage density above and below them, lending support to the hypothesis that they select sleeping places that can conceal them from predators and at the same time offer shelter from cold weather. The monkeys also frequently huddled at night. Our results suggest that predator avoidance, access to food resources, and thermoregulation all likely influence the selection of sleeping sites by Bale monkeys.

Enriched sleep environments lengthen lemur sleep duration

Characteristics of the sleep-site are thought to influence the quality and duration of primate sleep, yet only a handful of studies have investigated these links experimentally. Using actigraphy and infrared videography, we quantified sleep in four lemur species (Eulemur coronatus, Lemur catta, Propithecus coquereli, and Varecia rubra) under two different experimental conditions at the Duke Lemur Center (DLC) in Durham, NC, USA. Individuals from each species underwent three weeks of simultaneous testing to investigate the hypothesis that comfort level of the sleep-site influences sleep. We obtained baseline data on normal sleep, and then, in a pair-wise study design, we compared the daily sleep times, inter-daily activity stability, and intra-daily activity variability of individuals in simultaneous experiments of sleep-site enrichment and sleep-site impoverishment. Over 164 24-hour periods from 8 individuals (2 of each species), we found evidence that enriched sleep-sites increased daily sleep times of lemurs, with an average increase of thirty-two minutes. The effect of sleep-site impoverishment was small and not statistically significant. Though our experimental manipulations altered inter-daily stability and intra-daily variability in activity patterns relative to baseline, the changes did not differ significantly between enriched and impoverished conditions. We conclude that properties of a sleep-site enhancing softness or insulation, more than the factors of surface area or stability, influence lemur sleep, with implications regarding the importance of nest building in primate evolution and the welfare and management of captive lemurs.

The ecology of sleep in non-avian reptiles

Sleep is ubiquitous in the animal kingdom and yet displays considerable variation in its extent and form in the wild. Ecological factors, such as predation, competition, and microclimate, therefore are likely to play a strong role in shaping characteristics of sleep. Despite the potential for ecological factors to influence various aspects of sleep, the ecological context of sleep in non-avian reptiles remains understudied and without systematic direction. In this review, we examine multiple aspects of reptilian sleep, including (i) habitat selection (sleep sites and their spatio-temporal distribution), (ii) individual-level traits, such as behaviour (sleep postures), morphology (limb morphometrics and body colour), and physiology (sleep architecture), as well as (iii) inter-individual interactions (intra- and inter-specific). Throughout, we discuss the evidence of predation, competition, and thermoregulation in influencing sleep traits and the possible evolutionary consequences of these sleep traits for reptile sociality, morphological specialisation, and habitat partitioning. We also review the ways in which sleep ecology interacts with urbanisation, biological invasions, and climate change. Overall, we not only provide a systematic evaluation of the conceptual and taxonomic biases in the existing literature on reptilian sleep, but also use this opportunity to organise the various ecological hypotheses for sleep characteristics. By highlighting the gaps and providing a prospectus of research directions, our review sets the stage for understanding sleep ecology in the natural world.

Gibbon sleep quantified: the influence of lunar phase and meteorological variables on activity in Hylobates moloch and Hylobates pileatus

Sleep in the primate order remains understudied, with quantitative estimates of sleep duration available for less than 10% of primate species. Even fewer species have had their sleep synchronously quantified with meteorological data, which have been shown to influence sleep-wake regulatory behaviors. We report the first sleep duration estimates in two captive gibbon species, the Javan gibbon (Hylobates moloch) and the pileated gibbon (Hylobates pileatus) (N = 52 nights). We also investigated how wind speed, humidity, temperature, lunar phase, and illumination from moonlight influence sleep-wake regulation, including sleep duration, sleep fragmentation, and sleep efficiency. Gibbons exhibited strict diurnal behavior with little nighttime activity and mean total average sleep duration of 11 h and 53 min for Hylobates moloch and 12 h and 29 min for Hylobates pileatus. Gibbons had notably high sleep efficiency (i.e., time score asleep divided by the time they spent in their sleeping site, mean of 98.3%). We found illumination from moonlight in relation to lunar phase and amount of wind speed to be the strongest predictors of sleep duration and high-quality sleep, with increased moonlight and increased wind causing more fragmentation and less sleep efficiency. We conclude that arousal threshold is sensitive to nighttime illumination and wind speed. Sensitivity to wind speed may reflect adaptations to counter the risk of falling during arboreal sleep.

Sleepiness as motivation: a potential mechanism for how sleep deprivation affects behavior

STUDY OBJECTIVES

To determine how sleepiness and sleep deprivation drive the motivation to engage in different behaviors.

METHODS

We studied the sleepiness of 123 participants who had been randomized to sleep deprivation or normal sleep, and their willingness to engage in a range of everyday behaviors.

RESULTS

Self-reported sleepiness was a strong predictor of the motivation to engage in sleep-preparatory behaviors such as shutting one's eyes (OR = 2.78, 95% CI: 2.19-3.52 for each step up on the Karolinska Sleepiness Scale) and resting (OR = 3.20, CI: 2.46-4.16). Sleepiness was also related to the desire to be cared for by a loved one (OR = 1.49, CI: 1.22-1.82), and preparedness to utilize monetary and energy resources to get to sleep. Conversely, increased sleepiness was associated with a decreased motivation for social and physical activities (e.g. be with friends OR = 0.71, CI: 0.61-0.82; exercise OR = 0.65, CI: 0.56-0.76). Sleep deprivation had similar effects as sleepiness on these behaviors. Neither sleepiness nor sleep deprivation had strong associations with hunger, thirst, or food preferences.

CONCLUSIONS

Our findings indicate that sleepiness is a dynamic motivational drive that promotes sleep-preparatory behaviors and competes with other drives and desired outcomes. Consequently, sleepiness may be a central mechanism by which impaired alertness, for example, due to insufficient sleep, contributes to poor quality of life and adverse health. We propose that sleepiness helps organize behaviors toward the specific goal of assuring sufficient sleep, in competition with other needs and incentives. A theoretical framework on sleepiness and its behavioral consequences are likely to improve our understanding of several disease mechanisms.

Something Scary Is Out There: Remembrances of Where the Threat Was Located by Preschool Children and Adults with Nighttime Fear

Young children frequently report imaginary scary things in their bedrooms at night. This study examined the remembrances of 140 preschool children and 404 adults selecting either above, side, or below locations for a scary thing relative to their beds. The theoretical framework for this investigation posited that sexual-size dimorphism in Australopithecus afarensis, the presumed human ancestor in the Middle Pliocene, constrained sleeping site choice to mitigate predation. Smaller-bodied females nesting in trees would have anticipated predatory attacks from below, while male nesting on the ground would have anticipated attacks from their side. Such anticipation of nighttime attacks from below is present in many arboreal primates and might still persist as a cognitive relict in humans. In remembrances of nighttime fear, girls and women were predicted to select the below location and males the side location. Following interviews of children and adult questionnaires, multinomial log-linear analyses indicated statistically significant interactions (p < 0.001) of sex by location for the combined sample and each age class driven, in part, by larger frequencies of males selecting the side location and females selecting the below location. Data partitioning further revealed that males selected the side location at larger frequencies (p < 0.001) than the below location, whereas female selection of side and below locations did not differ significantly. While indicative of evolutionary persistence in cognitive appraisal of threat locations, the female hypothesis did not consider natural selection acting on assessment of nighttime terrestrial threats following the advent of early Homo in the Late Pliocene.

Deciding Where to Sleep: Spatial Levels of Nesting Selection in Chimpanzees (Pan troglodytes) Living in Savanna at Issa, Tanzania

To understand how animals select resources we need to analyze selection at different spatial levels or scales in the habitat. We investigated which physical characteristics of trees (dimensions and structure, e.g., height, trunk diameter, number of branches) determined nesting selection by chimpanzees (Pan troglodytes) on two different spatial scales: individual nesting trees and nesting sites. We also examined whether individual tree selection explained the landscape pattern of nesting site selection. We compared the physical characteristics of actual (N = 132) and potential (N = 242) nesting trees in nesting sites (in 15 plots of 25 m × 25 m) and of all trees in actual and potential nesting sites (N = 763 in 30 plots of 25 m × 25 m). We collected data in May and June 2003 in Issa, a dry and open savanna habitat in Tanzania. Chimpanzees selected both the site they used for nesting in the landscape and the trees they used to build nests within a nesting site, demonstrating two levels of spatial selection in nesting. Site selection was stronger than individual tree selection. Tree height was the most important variable for both nesting site and tree selection in our study, suggesting that chimpanzees selected both safe sites and secure trees for sleeping.

Postural behavior of howler monkeys (Alouatta palliata, A. macconnelli, and A. caraya) during sleep: an assessment across the genus range

Sleep is the longest and most continuous behavioral phase in the 24 h cycle of mammals. However, selection of postures, substrates, and tree parts during sleep has not been adequately explored, as well as their evolutionary consequences. The present study investigates postural behavior, substrate, and tree part use during sleep in three howler species (A. palliata, A. macconnelli, and A. caraya) in Nicaragua, French Guiana, and Argentina. All three species were consistent in the use of a crouched ball-like sit-in posture on large, horizontal, unramified, or bifurcated substrates, and in avoiding the periphery of tree crowns. The regularities of these sleeping patterns are very likely functionally associated with protection from potential predators and extreme weather conditions, biomechanical stability, thermoregulation, and enhancement of the digestive process of hard-to-decompose plant material.

Factors influencing riverine utilization patterns in two sympatric macaques

Many species of terrestrial animals, including primates, live in varied association with the aquatic (e.g., riverine or coastal) environment. However, the benefits that each species receive from the aquatic environment are thought to vary depending on their social and ecological characteristics, and thus, elucidating those benefits to each species is important for understanding the principles of wild animal behaviour. In the present study, to gain a more complete picture of aquatic environment use, including social and ecological factors in primates, factors affecting riverine habitat utilization of two macaque species (Macaca nemestrina and M. fascicularis) were identified and qualitative comparisons were made with sympatric proboscis monkeys (Nasalis larvatus), which have different social and ecological characteristics. Temporal variation in sighting frequency of macaques at the riverbanks was positively related to the fruit availability of a dominant riparian plant species and negatively related to the river water level which affects the extent of predation pressure. Riverine utilization of macaques was greatly influenced by distribution and abundance of food (especially fruit) resources, possibly in association with predation pressure. Additionally, qualitative ecological comparisons with sympatric proboscis monkeys suggest that the drivers of riverine utilization depend on the feeding niches of the species, and different anti-predator strategies resulting from their differing social structures.

Being hunted high and low: do differences in nocturnal sleeping and diurnal resting sites of howler monkeys (Alouatta nigerrima and Alouatta discolor) reflect safety from attack by different types of predator?

Predation risk is important in influencing animal behaviour. We investigated how the choice of nocturnal sleeping and diurnal resting sites by two species of primates was influenced by the most likely forms of attack (diurnal raptors and nocturnal felids). We recorded vertical and horizontal patterns of occupancy for 47 sleeping and 31 resting sites, as well as the presence of lianas or vines on trees. We compared the heights of trees used as resting or sleeping sites by the monkeys with those of 200 forest trees that the monkeys did not use. Trees used as nocturnal sleeping sites were taller than those used as diurnal resting sites, and taller than trees that the monkeys did not use. However, while trees used as diurnal resting sites were not significantly taller than non-used trees, diurnal resting sites were located on branches closer to the ground, closer to the main trunk of the tree and in trees with more lianas/vines than nocturnal sleeping sites. The differences in site location can be explained by the type of predator most likely to attack at a particular time: raptors in the day and felids at night.

Sleeping trees and sleep-related behaviours of the siamang (Symphalangus syndactylus) in a tropical lowland rainforest, Sumatra, Indonesia

Sleeping tree selection and related behaviours of a family group and a solitary female siamang (Symphalangus syndactylus) were investigated over a 5-month period in northern Sumatra, Indonesia. We performed all day follows, sleeping tree surveys and forest plot enumerations in the field. We tested whether: (1) physical characteristics of sleeping trees and the surrounding trees, together with siamang behaviours, supported selection based on predation risk and access requirements; (2) the preferences of a solitary siamang were similar to those of a family group; and (3) sleeping site locations within home ranges were indicative of home range defence, scramble competition with other groups or other species, or food requirements. Our data showed that (1) sleeping trees were tall, emergent trees with some, albeit low, connectivity to the neighbouring canopy, and that they were surrounded by other tall trees. Siamangs showed early entry into and departure from sleeping trees, and slept at the ends of branches. These results indicate that the siamangs’ choice of sleeping trees and related behaviours were strongly driven by predator avoidance. The observed regular reuse of sleeping sites, however, did not support anti-predation theory. (2) The solitary female displayed selection criteria for sleeping trees that were similar to those of the family group, but she slept more frequently in smaller trees than the latter. (3) Siamangs selected sleeping trees to avoid neighbouring groups, monopolise resources (competition), and to be near their last feeding tree. Our findings indicate selectivity in the siamangs’ use of sleeping trees, with only a few trees in the study site being used for this purpose. Any reduction in the availability of such trees might make otherwise suitable habitat unsuitable for these highly arboreal small apes.

Potential use of actigraphy to measure sleep in monkeys: comparison with behavioral analysis from videography

Sleep is indispensable for human health, with sleep disorders initiating a cascade of negative consequences. As our closest phylogenetic relatives, non-human primates (NHPs) are invaluable for comparative sleep studies and exhibit tremendous potential for improving our understanding of human sleep and related disorders. Previous work on measuring sleep in NHPs has mostly used electroencephalography or videography. In this study, simultaneous videography and actigraphy were applied to observe sleep patterns in 10 cynomolgus monkeys ( Macaca fascicularis) over seven nights (12 h per night). The durations of wake, transitional sleep, and relaxed sleep were scored by analysis of animal behaviors from videography and actigraphy data, using the same behavioral criteria for each state, with findings then compared. Here, results indicated that actigraphy constituted a reliable approach for scoring the state of sleep in monkeys and showed a significant correlation with that scored by videography. Epoch-by-epoch analysis further indicated that actigraphy was more suitable for scoring the state of relaxed sleep, correctly identifying 97.57% of relaxed sleep in comparison with video analysis. Only 34 epochs (0.13%) and 611 epochs (2.30%) were differently interpreted as wake and transitional sleep compared with videography analysis. The present study validated the behavioral criteria and actigraphy methodology for scoring sleep, which can be considered as a useful and a complementary technique to electroencephalography and/or videography analysis for sleep studies in NHPs.

Spider Monkeys Rule the Roost: Ateline Sleeping Sites Influence Rainforest Heterogeneity

: The sleeping site behavior of Ateline primates has been of interest since the 1980s, yet limited focus has been given to their influence upon other rainforest species. Here, we use a combination of arboreal and terrestrial camera traps, and dung beetle pitfall traps, to characterize spider monkey sleeping site use and quantify the impact of their associated latrines on terrestrial vertebrate and dung beetle activity. We also characterize the physical characteristics of the sleeping sites and the floristic and soil composition of latrines beneath them. Spider monkey activity at sleeping sites peaked at dawn and dusk and group composition varied by sex of the adults detected. The habitat-use of terrestrial fauna (vertebrates and dung beetles) differed between latrine sites and non-latrine controls, underpinned by species-specific changes in the relative abundance of several seed-dispersing species (such as paca and great curassow). Seedling density was higher in latrines than in non-latrine controls. Although most soil properties were similar between latrines and controls, potassium and manganese concentrations were different. These results suggest that spider monkey sleeping site fidelity leads to a hotspot of ecological activity in latrines and downstream impacts on rainforest floristic composition and diversity.

Effects of cold weather on the sleeping behavior of Skywalker hoolock gibbons (Hoolock tianxing) in seasonal montane forest

Considering the high energetic costs of maintaining constant body temperature, mammals must adjust their thermoregulatory behaviors in response to cold temperatures. Although primate daytime thermoregulation is relatively well studied, there is limited research in relation to nighttime strategies. To investigate how Skywalker hoolock gibbons (Hoolock tianxing) cope with the low temperatures found in montane forests, we collected sleep-related behavior data from one group (NA) and a single female (NB) at Nankang (characterized by extensive tsaoko plantations) between July 2010 and September 2011, and one group (BB) at Banchang (relatively well-managed reserve forest) between May 2013 and May 2015 in Mt. Gaoligong, Yunnan, China. The annual mean temperature was 13.3°C at Nankang (October 2010 to September 2011) and 13.0°C at Banchang (June 2013 to May 2015) with temperatures dropping below -2.0°C at both sites, making them the coldest known gibbon habitats. The lowest temperatures at both sites remained below 5.0°C from November to March, which we, therefore, defined as the "cold season". The hoolock gibbons remained in their sleeping trees for longer periods during the cold season compared to the warm season. Sleeping trees found at lower elevations and closer to potential feeding trees were favored during cold seasons at both sites. In addition, the gibbons were more likely to huddle together during cold seasons. Our results suggest that cold temperatures have a significant effect on the sleeping behavior of the Skywalker hoolock gibbon, highlighting the adaptability of this threatened species in response to cold climates.

Eulerian videography technology improves classification of sleep architecture in primates

Sleep is a critically important dimension of primate behavior, ecology, and evolution, yet primate sleep is under-studied because current methods of analyzing sleep are expensive, invasive, and time-consuming. In contrast to electroencephalography (EEG) and actigraphy, videography is a cost-effective and non-invasive method to study sleep architecture in animals. With video data, however, it is challenging to score subtle changes that occur in different sleep states, and technology has lagged behind innovations in EEG and actigraphy. Here, we applied Eulerian videography to magnify pixels relevant to scoring sleep from video, and then compared these results to analyses based on actigraphy and standard infrared videography. We studied four species of lemurs (Eulemur coronatus, Lemur catta, Propithecus coquereli, Varecia rubra) for 12-h periods per night, resulting in 6480 1-min epochs for analysis. Cramer's V correlation between actigraphy-classified sleep and infrared videography-classified sleep revealed consistent results in eight of the nine 12-h videos scored. A sample of the infrared videography was then processed by Eulerian videography for movement magnification and re-coded. A second Cramer's V correlation analysis, between two independent scorers coding the same Eulerian-processed video, found that interobserver agreement among Eulerian videography increased sleep vs. awake, NREM, and REM classifications by 7.1%, 46.7%, and 34.3%, respectively. Furthermore, Eulerian videography was more strongly correlated with actigraphy data when compared to results from standard infrared videography. The increase in agreement between the two scorers indicates that Eulerian videography has the potential to improve the identification of sleep states in lemurs and other primates, and thus to expand our understanding of sleep architecture without the need for EEG.

Environment shapes sleep patterns in a wild nocturnal primate

Among primates, the suborder Haplorhini is considered to have evolved a consolidated monophasic sleep pattern, with diurnal species requiring a shorter sleep duration than nocturnal species. Only a few primate species have been systematically studied in their natural habitat where environmental variables, including temperature and light, have a major influence on sleep and activity patterns. Here we report the first sleep study on a nocturnal primate performed in the wild. We fitted seven wild Javan slow lorises (Nycticebus javanicus) in West Java, Indonesia with accelerometers that collected activity data, and installed climate loggers in each individual’s home range to collect ambient temperature readings (over 321 days in total). All individuals showed a strictly nocturnal pattern of activity and displayed a striking synchronisation of onset and cessation of activity in relation to sunset and sunrise. The longest consolidated rest episodes were typically clustered near the beginning and towards the end of the light period, and this pattern was inversely related to daily fluctuations of the ambient temperature. The striking relationship between daily activity patterns, light levels and temperature suggests a major role of the environment in shaping the daily architecture of waking and sleep. We concluded that well-known phenotypic variability in daily sleep amount and architecture across species may represent an adaptation to changes in the environment. Our data suggest that the consolidated monophasic sleep patterns shaped by environmental pressures observed in slow lorises represent phylogenetic inertia in the evolution of sleep patterns in humans.

Nesting, sleeping, and nighttime behaviors in wild and captive great apes

The past few decades have seen a burgeoning of scientific studies on great apes' use of nests for sleeping in the wild, as well as their nesting behavior and sleep in captivity. We review recent advances in knowledge of these topics, with the aim of promoting information exchange between people working in the field and with captive great apes. We trace developments in research into nest-building techniques in adults and immatures, factors that influence selection of general sleeping sites and specific locations, social aspects of sleep, postures, and nighttime activities. We argue that exchanges of information deriving from studies of captive and wild apes are valuable for obtaining a better understanding of sleep-related adaptations in our nearest evolutionary neighbors, and conclude by making some recommendations regarding sleeping arrangements in captivity from a welfare perspective.

Sleeping site and tree selection by Sichuan snub-nosed monkeys (Rhinopithecus roxellana) in Baihe Nature Reserve, Sichuan, China

For non-human primates to optimize their survival chances, sleeping site selection is crucial as they spend much of their time sleeping. We studied sleeping site and tree selection by a group of wild Sichuan snub-nosed monkeys (Rhinopithecus roxellana) in the temperate forests of Baihe Nature Reserve, Sichuan, China, to assess if certain site and tree characteristics were selected. We identified a total of 39 sleeping sites and 111 sleeping trees over a period of 1 year. We compared nine sleeping site and six sleeping tree variables related to the environment, habitat, and vegetation structure. We found that certain characteristics of sleeping sites and sleeping trees predicted their selection by R. roxellana. On a larger spatial scale, sleeping sites were selected based mainly on four factors: canopy height, slope direction, slope gradient, and vegetation type. They also selected sites with trees that were taller and larger, had larger crown diameters and higher bole branches. On a smaller spatial scale, they selected larger trees with larger crown diameters. The selection of these characteristics could be explained in terms of predator avoidance and thermoregulation efficiency, although it was difficult to delineate which was more important. This could be due to some characteristics of R. roxellana, that is, large groups living in temperate climates, which required a balanced strategy for sleeping site and tree selection in order to optimize their survival chances.

Behavioural thermoregulation via microhabitat selection of winter sleeping areas in an endangered primate: implications for habitat conservation

Strategic microhabitat selection allows animals in seasonally cold environments to reduce homeostatic energy costs, particularly overnight when thermoregulatory demands are greatest. Suitable sleeping areas may therefore represent important resources for winter survival. Knowledge of microhabitat use and potential impacts of anthropogenic habitat modification can aid species conservation through development of targeted habitat management plans. Wild, endangered Barbary macaques (Macaca sylvanus) in logged cedar-oak forest were studied to investigate (1) the hypothesis that macaques select winter sleeping areas with microhabitat characteristics that may reduce thermoregulatory costs, and, if so, (2) how to minimize damage to sleeping areas from logging. Macaques slept only in Atlas cedars (Cedrus atlantica). Consistent with predictions, macaques preferred sleeping in sheltered topography and dense vegetation, which may reduce exposure to wind, precipitation and cold, and preferred large trees that facilitate social huddling. This suggests that Barbary macaques employ strategic nocturnal microhabitat selection to reduce thermoregulatory costs and thus suitable sleeping areas may influence winter survival. To minimize negative impacts of logging on macaque sleeping areas, results suggest avoiding logging in topographical depressions and maintaining cedar densities greater than 250 ha-1 with average breast height greater than 60 cm. This study demonstrates how animal behaviour can be used to guide species-specific habitat management plans.

The Effects of Climate Seasonality on Behavior and Sleeping Site Choice in Sahamalaza Sportive Lemurs, Lepilemur sahamalaza

Temperature, rainfall, and resource availability may vary greatly within a single year in primate habitats. Many primate species show behavioral and physiological adaptations to this environmental seasonality, including changes to their diets and activity. Sahamalaza sportive lemurs (Lepilemur sahamalaza) inhabit the northwest of Madagascar and have been studied only during the dry, colder period of the year. We investigated potential effects of climate seasonality on this species by collecting behavioral data between October 2015 and August 2016, encompassing both the warmer wet and the colder dry seasons. We collected 773.15 hours of behavioral data on 14 individual sportive lemurs to investigate year-round activity budgets, ranging behavior, and sleeping site locations. Additionally we recorded temperature and rainfall data at our study site to describe the environmental conditions during the study period. The study individuals significantly decreased their time spent traveling and increased their time spent resting in the dry season compared to the wet season. Although home range size and path lengths did not differ over the study period, sleeping locations were significantly different between seasons as the lemurs focused on more confined areas in colder periods. Overall, the results indicate that Sahamalaza sportive lemur behavior varies with season, in line with reports for other primates.

Are sleeping site ecology and season linked to intestinal helminth prevalence and diversity in two sympatric, nocturnal and arboreal primate hosts (Lepilemur edwardsi and Avahi occidentalis)?

BACKGROUND

Various factors, such as climate, body size and sociality are often linked to parasitism. This constrains the identification of other determinants driving parasite infections. Here, we investigate for the first time intestinal parasites in two sympatric arboreal primate species, which share similar activity patterns, feeding ecology, body size and sociality, and cope with the same climate conditions, but differ in sleeping site ecology: the Milne-Edward's sportive lemur (Lepilemur edwardsi) and the Western woolly lemur (Avahi occidentalis). Comparison of these two species aimed to test whether differences in sleeping sites are related to differences in parasite infection patterns. Additionally, gender and seasonal factors were taken into account. Animals were radio-collared to record their sleeping site dynamics and to collect fecal samples to assess intestinal parasitism during both the dry and the rainy season.

RESULTS

Only low parasite diversity was detected, which is attributable to the strict arboreal lifestyle of these lemurs, limiting their contact with infective parasite stages. L. edwardsi, which sleeps in tree holes and repeatedly uses the same sleeping site, excreted eggs of strongyle and oxyurid nematodes, whereby strongyles always occurred in coinfection with oxyurids. In contrast, A. occidentalis, which sleeps on open branches and frequently changes sleeping sites, only excreted eggs of strongyle nematodes. This difference can be attributed to a potential favorable environment presented by tree holes for infective stages, facilitating parasitic transmission. Additionally, Strongylida in A. occidentalis were only observed in the rainy season, suggesting an arrested development during the dry season in the nematodes' life cycle. Males and females of both lemur species showed the same frequency of parasitism. No differences in body mass of infected and non-infected individuals were observed, indicating that the animals' body condition remains unaffected by the detected gastrointestinal parasites.

CONCLUSIONS

The comparison of two primate hosts with a very similar lifestyle suggests an influence of the sleeping site ecology on intestinal parasites. In A. occidentalis there was a clear seasonal difference in strongyle egg excretion. These results improve our understanding of the parasite ecology in these endangered primate species, which may be critical in the light of species conservation.

Intermittent pair-housing, pair relationship qualities, and HPA activity in adult female rhesus macaques

Laboratory rhesus macaques are often housed in pairs and may be temporarily or permanently separated for research, health, or management reasons. While both long-term social separations and introductions can stimulate a stress response that impacts inflammation and immune function, the effects of short-term overnight separations and whether qualities of the pair relationship mediate these effects are unknown. In this study, we investigated the effects of overnight separations on the urinary cortisol concentration of 20 differentially paired adult female rhesus macaques (Macaca mulatta) at the California National Primate Research Center. These females were initially kept in either continuous (no overnight separation) or intermittent (with overnight separation) pair-housing and then switched to the alternate pair-housing condition part way through the study. Each study subject was observed for 5 weeks, during which we collected measures of affiliative, aggressive, anxious, abnormal, and activity-state behaviors in both pair-housing conditions. Additionally, up to three urine samples were collected from each subject per week and assayed for urinary free cortisol and creatinine. Lastly, the behavioral observer scored each pair on four relationship quality attributes ("Anxious," "Tense," "Well-meshed," and "Friendly") using a seven-point scale. Data were analyzed using a generalized linear model with gamma distribution and an information theoretic approach to determine the best model set. An interaction between the intermittent pairing condition and tense pair adjective rating was in the top three models of the best model set. Dominance and rates of affiliation were also important for explaining urinary cortisol variation. Our results suggest that to prevent significant changes in HPA-axis activation in rhesus macaque females, which could have unintended effects on research outcomes, pairs with "Tense" relationships and overnight separations preventing tactile contact should be avoided.

The use of a mixed rubber landscape by tufted-ear marmosets

With the loss and fragmentation of tropical forests, the survival of primates depends on their ability to adapt to human-introduced modifications in their habitat. Marmosets are known for their ecological and behavioral plasticity and have been registered in various agricultural landscapes. Our goal was to describe the ecology of tufted-ear marmosets (Callithrix sp.) in a rubber/forest landscape, monitoring their use of habitat and diet. We followed two groups using radio telemetry and visual observations for nine months at the Michelin plantation Ltd. in Bahia, Brazil. Both groups used mainly pioneer forest and rubber with pioneer vegetation more than expected according to availability, even though they explored all types of vegetation. Rubber monocultures act as corridors for marmoset locomotion among more suitable habitats. Feeding, gummivory and socialization were mainly performed in the pioneer forest (with or without rubber), in which most sleeping sites and food sources were found. Groups of marmosets can incorporate agroforest matrixes to their area of use and activity patterns. Maintenance of marmosets in fragmented landscapes might be favored by their diet flexibility, with the use of resources such as gum and fruit, including exotic plants. Although known for their ecological flexibility, marmosets do require certain resources to be present in native habitat to adapt to agricultural landscapes. Patches of forest within a rubber landscape and pioneer vegetation in the rubber inter-rows should be considered to maintain populations of Callithrix in rubber landscapes.

Bed site selection by a subordinate predator: an example with the cougar (Puma concolor) in the Greater Yellowstone Ecosystem

As technology has improved, our ability to study cryptic animal behavior has increased. Bed site selection is one such example. Among prey species, bed site selection provides thermoregulatory benefits and mitigates predation risk, and may directly influence survival. We conducted research to test whether a subordinate carnivore also selected beds with similar characteristics in an ecosystem supporting a multi-species guild of competing predators. We employed a model comparison approach in which we tested whether cougar (Puma concolor) bed site attributes supported the thermoregulatory versus the predator avoidance hypotheses, or exhibited characteristics supporting both hypotheses. Between 2012-2016, we investigated 599 cougar bed sites in the Greater Yellowstone Ecosystem and examined attributes at two scales: the landscape (second-order, n = 599) and the microsite (fourth order, n = 140). At the landscape scale, cougars selected bed sites in winter that supported both the thermoregulatory and predator avoidance hypotheses: bed sites were on steeper slopes but at lower elevations, closer to the forest edge, away from sagebrush and meadow habitat types, and on southern, eastern, and western-facing slopes. In the summer, bed attributes supported the predator avoidance hypothesis over the thermoregulation hypothesis: beds were closer to forest edges, away from sagebrush and meadow habitat classes, and on steeper slopes. At the microsite scale, cougar bed attributes in both the winter and summer supported both the predator avoidance and thermoregulatory hypotheses: they selected bed sites with high canopy cover, high vegetative concealment, and in a rugged habitat class characterized by cliff bands and talus fields. We found that just like prey species, a subordinate predator selected bed sites that facilitated both thermoregulatory and anti-predator functions. In conclusion, we believe that measuring bed site attributes may provide a novel means of measuring the use of refugia by subordinate predators, and ultimately provide new insights into the habitat requirements and energetics of subordinate carnivores.

The 24/7 approach to promoting optimal welfare for captive wild animals

We have an ethical responsibility to provide captive animals with environments that allow them to experience good welfare. Husbandry activities are often scheduled for the convenience of care staff working within the constraints of the facility, rather than considering the biological and psychological requirements of the animals themselves. The animal welfare 24/7 across the lifespan concept provides a holistic framework to map features of the animal's life cycle, taking into account their natural history, in relation to variations in the captive environment, across day and night, weekdays, weekends, and seasons. In order for animals to have the opportunity to thrive, we argue the need to consider their lifetime experience, integrated into the environments we provide, and with their perspective in mind. Here, we propose a welfare assessment tool based upon 14 criteria, to allow care staff to determine if their animals' welfare needs are met. We conclude that animal habitat management will be enhanced with the use of integrated technologies that provide the animals with more opportunities to engineer their own environments, providing them with complexity, choice and control.