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Representative views of the immobilization hypothesis for the function of sleep. Shown is the probability of death (D) given an encounter with a predator as a function of the intensity of sleep (s). D is the product of the probability of being detected and attacked by a predator (d (s)) and the probability of capture given attack (c (s)). Quiet wakefulness is represented by s Z 0, and deep sleep by s Z 1. The large dots indicate the value of s minimizing D (or s*). (a) Case in which both d (s) and c (s) are linear. Here, s* occurs at one of the extremes of 0 or 1; s* Z 1 for the functions shown. (b) Case in which both d (s) and c (s) are concave-downward functions of s. Here, s* also occurs at one of the extremes of 0 or 1; s* Z 0 for the functions shown. (c) Case in which both d (s) and c (s) are concave-downward functions of s. Here, s* may occur at an intermediate value of s.
Source publication
Every studied animal engages in sleep, and many animals spend much of their lives in this vulnerable behavioural state. We believe that an explicit description of this vulnerability will provide many insights into both the function and architecture (or organization) of sleep. Early studies of sleep recognized this idea, but it has been largely over...
Contexts in source publication
Context 1
... optimal sleep intensity (s*) depends strongly on the form of the functions chosen to describe the probabilities d(s) and c(s). For instance, if both d(s) and c(s) are linear in s, then D will be minimized at one of the extremes (Fig. 3a). That is, the animal would be either quietly awake (s* Z 0) or deeply asleep (s* Z 1). These two extreme solutions also hold when d and c are both concave-downward functions of s (Fig. 3b). The extreme favoured is determined by the details of the functions. Furthermore, an intermediate value of s* is possible when both d and c are ...
Context 2
... chosen to describe the probabilities d(s) and c(s). For instance, if both d(s) and c(s) are linear in s, then D will be minimized at one of the extremes (Fig. 3a). That is, the animal would be either quietly awake (s* Z 0) or deeply asleep (s* Z 1). These two extreme solutions also hold when d and c are both concave-downward functions of s (Fig. 3b). The extreme favoured is determined by the details of the functions. Furthermore, an intermediate value of s* is possible when both d and c are concave-upward functions of s (Fig. ...
Context 3
... animal would be either quietly awake (s* Z 0) or deeply asleep (s* Z 1). These two extreme solutions also hold when d and c are both concave-downward functions of s (Fig. 3b). The extreme favoured is determined by the details of the functions. Furthermore, an intermediate value of s* is possible when both d and c are concave-upward functions of s (Fig. ...
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Citations
... Indeed, many ectoparasites such as blood-feeding flies and mites have been classified as micropredators (39,40), and differences in sleep have been associated with predation levels (41)(42)(43), such that animals with increased exposure to predators have reduced or lighter sleep (42,44). Here, we showed that reduced sleep-like behavior in D. ...
Parasites harm host fitness and are pervasive agents of natural selection. Host defensive traits in natural populations typically show genetic variation, which may be maintained when parasite resistance imposes fitness costs on the host coupled with variability in parasite prevalence in space and/or time. Previously we demonstrated significant evolutionary responses to artificial selection for increasing behavioral immunity to Gamasodes queenslandicus mites in replicate lines of Drosophila melanogaster. Here, we report transcriptional shifts in metabolic processes between selected and control fly lines based on RNA-seq analyses. We also show decreased starvation resistance and increased use of nutrient reserves in flies from mite-resistant lines. Additionally, mite-resistant lines exhibited increased behavioral activity, reduced sleep and elevated oxygen consumption under conditions of darkness. The link between resistance and sleep was confirmed in an independent panel of D. melanogaster genetic lines exhibiting variable sleep durations, showing a positive correlation between mite resistance and reduced sleep. Experimentally restraining the activity of artificially selected mite-resistant flies during exposure to parasites under dark conditions reduced their resistance advantage relative to control flies. The results suggest that ectoparasite resistance in this system involves increased dark-condition activity and metabolic gene expression at the expense of nutrient reserves and starvation resistance.
... If survival occurs, it is commonly assumed that the animal resumes its normal activities [9] and physiological equilibrium is restored. However, studies on commercial strains of rats and mice have shown that non-lethal, long-lasting effects of predators, such as fear, anxiety, or post-traumatic responses, can have a significant impact on individual morphology, behavior, and reproductive success [10][11][12][13][14]. A fundamental question is thus the extent to which experimental findings using a commercial strain of rats or mice can be generalized to real-world situations. ...
In the wild, animals face a highly variable world full of predators. Most predator attacks are unsuccessful, and the prey survives. According to the conventional perspective, the fear responses elicited by predators are acute and transient in nature. However, the long-term, non-lethal effects of predator exposure on prey behavioral stress sequelae, such as anxiety and post-traumatic symptoms, remain poorly understood. Most experiments on animal models of anxiety-related behavior or post-traumatic stress disorder have been carried out using commercial strains of rats and mice. A fundamental question is whether laboratory rodents appropriately express the behavioral responses of wild species in their natural environment; in other words, whether behavioral responses to stress observed in the laboratory can be generalized to natural behavior. To further elucidate the relative contributions of the natural selection pressures influences, this study investigated the bio-behavioral and morphological effects of auditory predator cues (owl territorial calls) in males and females of three wild rodent species in a laboratory set-up: Acomys cahirinus; Gerbillus henleyi; and Gerbillus gerbillus. Our results indicate that owl territorial calls elicited not only “fight or flight” behavioral responses but caused PTSD-like behavioral responses in wild rodents that have never encountered owls in nature and could cause, in some individuals, enduring physiological and morphological responses that parallel those seen in laboratory rodents or traumatized people. In all rodent species, the PTSD phenotype was characterized by a blunting of fecal cortisol metabolite response early after exposure and by a lower hypothalamic orexin-A level and lower total dendritic length and number in the dentate gyrus granule cells eight days after predator exposure. Phenotypically, this refers to a significant functional impairment that could affect reproduction and survival and thus fitness and population dynamics.
... LHD is the typical REM sleep posture and thus can be used to estimate REM sleep. This is based on the fact that due to postural atonia, the animal's head needs to be rested in REM sleep (Lima et al., 2005;Zepelin et al., 2005). It is a common method for estimating REM sleep by the LHD position; recent studies using this method include studies of Cetartiodactyla, like the common eland (Zizkova et al., 2013), the giraffe (Seeber et al., 2012), the dromedary camel (El Allali et al., 2022), and cattle (Ternman et al., 2014). ...
Introduction
The nocturnal behavior of many ungulate species has currently not been sufficiently studied. However, the behavioral patterns of large herbivores vary greatly between day and night, and knowledge about species’ behavior is not only scientifically interesting, but also required for successful animal management and husbandry.
Material and methods
In the current study, the nocturnal behavior of 196 individuals of 19 ungulate species in 20 European zoos is studied, providing the first description of the nocturnal behavior of some of the species. The importance of a wide range of possible factors influencing nocturnal behavior is discussed. Specifically, the behavioral states of standing and lying were analyzed, evaluating the proportion and number of phases in each behavior. The underlying data consist of 101,629 h of video material from 9,239 nights. A deep learning-based software package named Behavioral Observations by Videos and Images Using Deep-Learning Software (BOVIDS) was used to analyze the recordings. The analysis of the influencing factors was based on random forest regression and Shapley additive explanation (SHAP) analysis.
Results
The results indicate that age, body size, and feeding type are the most important factors influencing nocturnal behavior across all species. There are strong differences between the zebra species and the observed Cetartiodactyla as well as white rhinos. The main difference is that zebras spend significantly less time in a lying position than Cetartiodactyla.
Discussion
Overall, the results fit well into the sparse existing literature and the data can be considered a valid reference for further research and might help to assess animal's welfare in zoos.
... By switching to a predominantly nocturnal pattern of activity in human-dominated landscapes, wild boars chose to expose their resting phase to a higher risk of anthropic disturbance. This likely is a successful strategy for risk mitigation, as resting is a well-known and efficient anti-predator strategy (Lima et al., 2005). However, this also means that the daily choice of a resting site is critical for minimizing the risk of encountering people. ...
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... LHD is the typical REM sleep posture and thus can be used to estimate REM sleep. This is based on the fact that due to postural atonia the animal's head needs to be rested in REM sleep(Lima et al., 2005;Zepelin et al., 2005). It is a common method to estimate REM sleep by the LHD position, recent studies using this method include studies of Cetartiodactyla, like CommonFigure 1: The three observed behavioral poses: standing (first column) and lying (second and third column). ...
This study analyzed the nocturnal behavior of 196 individuals of 19 ungulate species in 20 zoos in Germany and the Netherlands. To the best of our knowledge, this is the first description of nocturnal behavior for some of the species. The importance of a wide range of possible factors influencing nocturnal behavior is discussed. Specifically, the behavioral states of standing and lying were analyzed, evaluating the proportion and number of phases in each behavior. The underlying data consists of 101,629 hours of video material from 9,239 nights. BOVIDS, a deep learning-based software package, was used to analyze the recordings. The analysis of the influencing factors was based on a random forest regression and a SHAP analysis. The results indicate that age, body size and feeding type are the most important factors influencing nocturnal behavior across all species. There are strong differences between the zebra species and the observed Cetartiodactyla as well as White Rhinos. The main difference is that zebras spend significantly less time in a lying position than Cetartiodactyla.
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... Alternatively, the risk of inactivity, especially sleep [67,68], is possibly equal to that of activity and thus may create opposing patterns that mask any relationship between foraging and predation that does exist. Although inactivity such as hibernation has been reported to increase prey survival potentially through reduced predation risk [69], sleep requires individuals to enter a state of reduced neural activity and suspension of consciousness that results in a lack of awareness of, and responsiveness to, the environment [68]. ...
... Alternatively, the risk of inactivity, especially sleep [67,68], is possibly equal to that of activity and thus may create opposing patterns that mask any relationship between foraging and predation that does exist. Although inactivity such as hibernation has been reported to increase prey survival potentially through reduced predation risk [69], sleep requires individuals to enter a state of reduced neural activity and suspension of consciousness that results in a lack of awareness of, and responsiveness to, the environment [68]. Some organisms minimize the dangers of sleep by relying on communal resting [70,71] or using safe places or refuges for sleep [72], but not all environments provide refuges that completely eliminate risks. ...
The assumption that activity and foraging are risky for prey underlies many predator-prey theories and has led to the use of predator-prey activity overlap as a proxy of predation risk. However, the simultaneous measures of prey and predator activity along with timing of predation required to test this assumption have not been available. Here, we used accelerometry data on snowshoe hares (Lepus americanus) and Canada lynx (Lynx canadensis) to determine activity patterns of prey and predators and match these to precise timing of predation. Surprisingly we found that lynx kills of hares were as likely to occur during the day when hares were inactive as at night when hares were active. We also found that activity rates of hares were not related to the chance of predation at daily and weekly scales, whereas lynx activity rates positively affected the diel pattern of lynx predation on hares and their weekly kill rates of hares. Our findings suggest that predator-prey diel activity overlap may not always be a good proxy of predation risk, and highlight a need for examining the link between predation and spatio-temporal behaviour of predator and prey to improve our understanding of how predator-prey behavioural interactions drive predation risk.
... In addition to tree sleeping platforms, chimpanzees also build their sleeping platforms on the ground (Koops et al., 2007;Tagg et al., 2013). Understanding what motivates great apes to choose a site for sleeping may shed light on sleep quality and ecological determinants of sleep (Furuichi & Hashimoto, 2004;Lima et al., 2005). ...
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.
... The main causal factor for this is not established. Are individuals with more protectively biased emotional states, already more likely to show problem behaviours, achieving only vigilant states of sleep due to the perception of risk in the environment [45]? Are individuals with an engaging emotional bias being woken from deep (non-vigilant) sleep by significant stimuli (such as nearby fireworks or a household baby crying) and therefore sleep deprived and showing problem behaviours as a result? ...
Excessive emotional arousal has been shown to impact physiological health in both veterinary species and human animals. The focus of work in many models of veterinary behavioural medicine has predominantly been associated with reducing activation of the protective emotional systems; in particular, fear-anxiety. The management of the engaging emotional systems of desire-seeking, social play, care and lust has not traditionally been considered in the treatment of physiological health of veterinary species. This article reviews the literature in both veterinary and human fields on the relationship between emotional arousal of both protective and engaging emotional systems and physical health conditions. The current literature describing the regulatory control of sleep on emotional arousal is also discussed. An exemplary case report of a seven month old male entire Cocker Spaniel showing fly-snapping behaviour which had been non-responsive to leviteracetam (Keppra) is presented. The emotional health assessment and treatment of this case is described along with the short and long term (fourteen month follow up) outcomes to demonstrate that some patients presenting in this way can be effectively managed with an appropriate behavioural medicine treatment plan. The authors put forward the argument that an emotional health assessment should be considered an essential component of the work up of all such cases.
... Sleeping sites can also provide protection against predators. Because mammals spend a large portion of their lives resting and sleeping, they can be easily accessible to predators during such activities (Lima et al., 2005). Small mammals are often preferred as prey in tropical forests, making their vulnerability even increased when sleeping (Lutermann et al., 2010;Maher & Lott, 2000). ...
Current incessant threats of environmental changes, such as habitat fragmentation, may disrupt vital mutualistic plant-frugivore networks, threatening the whole ecosystem. To advance our knowledge of the magnitude of the impacts of such disruption, we need a better understanding of its structure and robustness. We addressed this by comparing several aspects of plant-frugivore networks in the forest edge and interior habitats of a fragmented forest, using field data on fruit removal by a community of frugivorous birds and lemurs from 40 tree species over 30 months. While the plant-frugivore networks in both habitats were significantly less nested than random expectations, the network in the forest edge habitat had higher value of nestedness compared to the network in the forest interior. Also, the networks in both habitats were highly modular compared to random expectations, with a dominance of species that are highly interactive within its modules. We also found that fruit size, weight, and color as well as tree height predicted the structural role of plants in the networks and their degree of specialization. Finally, the removal/loss of best-connected plants or animals resulted in a weak robustness of the networks in both habitats; this vulnerable pattern is more pronounced in forest edges than interior habitats. Interestingly, the loss of large-bodied seed dispersers from either habitat did not affect much the robustness of the networks; in contrast, when small-sized species were eliminated first, the network became less robust, especially for the edge community. These findings highlight the need to preserve species interactions in forest edges to avoid the collapse of the network, mitigating the impacts of species extinctions on ecosystem equilibrium.
