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| Author |
Vasquez, R A |
Title  |
Assessment of predation risk via illumination level: facultative central place foraging in the cricetid rodent Phyllotis darwini |
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Journal Article |
| Year |
1994 |
Publication |
Behavioral Ecology and Sociobiology |
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34 |
Issue |
5 |
Pages |
375-381 |
| Keywords |
animals; rodents; foraging behaviour |
| Abstract |
It is well known that the risk of predation affects prey decision making. However, few studies have been concerned with the cues used by prey to assess this risk. Prey animals may use indirect environmental cues to assess predation hazard since direct evaluation may be dangerous. I studied the assessment of predation risk, manipulated via environmental illumination level, and the trade-off between foraging and predation hazard avoidance in the nocturnal rodent Phyllotis darwini (Rodentia: Cricetidae). In experimental arenas I simulated dark and full moon nights (which in nature correlate with low and high predation risk, respectively) and measured the immediate responses of animals to flyovers of a raptor model. Second, varying illumination only, I evaluated patch use, food consumption, central place foraging, and nocturnal variation of body weight. During flyover experiments, animals showed significantly more evasive reactions under full moon illumination than in moonless conditions. In the patch use experiments, rodents significantly increased their giving-up density and decreased their total food consumption under moonlight. On dark nights, rodents normally fed in the food patch, but when illumination was high they became central place foragers in large proportion. Moreover, the body weight of individuals decreased proportionately more during bright nights. These results strongly suggest that P. darwini uses the level of environmental illumination as a cue to the risk of being preyed upon and may sacrifice part of its energy return to avoid risky situations. |
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LoNNe @ schroer @ |
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1604 |
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Ikeda, Masayuki; Sagara, Masami; Inoué, Shojiro |
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Continuous exposure to dim illumination uncouples temporal patterns of sleep, body temperature, locomotion and drinking behavior in the rat |
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Journal Article |
| Year |
2000 |
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Neuroscience Letters |
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279 |
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3 |
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185-189 |
| Keywords |
animals; rodents; animal behaviour |
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Dissociable circadian rhythms of sleep and body temperature in primates are thought to be regulated by independent oscillators whereas the uncoupling of circadian rhythms has not been well described in other mammals. Therefore, we made simultaneous recordings of non-rapid-eye-movement-sleep (NREMS), rapid-eye-movement-sleep (REMS), brain temperature, intraperitoneal temperature, locomotion and drinking activity under light-dark (LD) and continuous dim illumination (dim LL) and analyzed their interrelations. The rhythmic patterns of body temperature, locomotion and drinking were modified on the 12th circadian day of dim LL, while the mean body temperature as well as mean occurrence of drinking and locomotor activities did not change significantly. In contrast, dim LL exposure significantly increased the total time spent in NREMS during the resting phase of dim LL and increased REMS episodes during the active phase of dim LL. The diverse effects of dim LL exposure on the recorded phenomena suggest that temporal patterns of sleep were the most sensitive to perturbations of lighting and that differential oscillatory mechanisms may regulate sleep and other circadian rhythms in the rat. |
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1591 |
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Gorman, M. R.; Elliott, J. A. |
| Title |
Dim nocturnal illumination alters coupling of circadian pacemakers in Siberian hamsters, Phodopus sungorus |
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Journal Article |
| Year |
2004 |
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Journal of Comparative Physiology A |
Abbreviated Journal |
Comp Physiol A |
| Volume |
190 |
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8 |
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631- |
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animals; rodents; seasonal timing |
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The circadian pacemaker of mammals comprises multiple oscillators that may adopt different phase relationships to determine properties of the coupled system. The effect of nocturnal illumination comparable to dim moonlight was assessed in male Siberian hamsters exposed to two re-entrainment paradigms believed to require changes in the phase relationship of underlying component oscillators. In experiment 1, hamsters were exposed to a 24-h light-dark-light-dark cycle previously shown to split circadian rhythms into two components such that activity is divided between the two daily dark periods. Hamsters exposed to dim illumination (<0.020 lx) during each scotophase were more likely to exhibit split rhythms compared to hamsters exposed to completely dark scotophases. In experiment 2, hamsters were transferred to winter photoperiods (10 h light, 14 h dark) from two different longer daylengths (14 h or 18 h light daily) in the presence or absence of dim nighttime lighting. Dim nocturnal illumination markedly accelerated adoption of the winter phenotype as reflected in the expansion of activity duration, gonadal regression and weight loss. The two experiments demonstrate substantial efficacy of light intensities generally viewed as below the threshold of circadian systems. Light may act on oscillator coupling through rod-dependent mechanisms. |
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1590 |
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Hoffmann, J.; Schirmer, A.; Eccard, J.A. |
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Light pollution affects space use and interaction of two small mammal species irrespective of personality |
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Journal Article |
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2019 |
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BMC Ecology |
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BMC Ecol |
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19 |
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1 |
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26 |
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Animals; Animal personality; Hirec; Interspecific interactions; Nighttime illumination; Outdoor enclosure; Rodents |
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BACKGROUND: Artificial light at night (ALAN) is one form of human-induced rapid environmental changes (HIREC) and is strongly interfering with natural dark-light cycles. Some personality types within a species might be better suited to cope with environmental change and therefore might be selected upon under ongoing urbanization. RESULTS: We used LED street lamps in a large outdoor enclosure to experimentally investigate the effects of ALAN on activity patterns, movement and interaction of individuals of two species, the bank vole (Myodes glareolus) and the striped field mouse (Apodemus agrarius). We analyzed effects combined with individual boldness score. Both species reduced their activity budget during daylight hours. While under natural light conditions home ranges were larger during daylight than during nighttime, this difference vanished under ALAN. Conspecifics showed reduced home range overlap, proximity and activity synchrony when subjected to nighttime illumination. Changes in movement patterns in reaction to ALAN were not associated with differences in boldness score of individuals. CONCLUSIONS: Our results suggest that light pollution can lead to changes in movement patterns and individual interactions in small mammals. This could lead to fitness consequences on the population level. |
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Animal Ecology, University of Potsdam, Maulbeerallee 1, 14469, Potsdam, Germany |
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1472-6785 |
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PMID:31215409; PMCID:PMC6582560 |
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GFZ @ kyba @ |
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2584 |
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Fonken, Laura K; Weil, Zachary M; Nelson, Randy J |
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Mice exposed to dim light at night exaggerate inflammatory responses to lipopolysaccharide |
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Journal Article |
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2013 |
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Brain, Behavior, and Immunity |
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34 |
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159-163 |
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animals; rodents; metabolism; health |
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The mammalian circadian system regulates many physiological functions including inflammatory responses. Appropriately timed light information is essential for maintaining circadian organization. Over the past ∼120 years, urbanization and the widespread adoption of electric lights have dramatically altered lighting environments. Exposure to light at night (LAN) is pervasive in modern society and disrupts core circadian clock mechanisms. Because microglia are the resident macrophages in the brain and macrophages contain intrinsic circadian clocks, we hypothesized that chronic exposure to LAN would alter microglia cytokine expression and sickness behavior following LPS administration. Exposure to 4 weeks of dim LAN elevated inflammatory responses in mice. Mice exposed to dimly lit, as compared to dark, nights exaggerated changes in body temperature and elevated microglia pro-inflammatory cytokine expression following LPS administration. Furthermore, dLAN mice had a prolonged sickness response following the LPS challenge. Mice exposed to dark or dimly lit nights had comparable sickness behavior directly following the LPS injection; however, dLAN mice showed greater reductions in locomotor activity, increased anorectic behavior, and increased weight loss than mice maintained in dark nights 24 h post-LPS injection. Overall, these data suggest that chronic exposure to even very low levels of light pollution may alter inflammatory responses. These results may have important implications for humans and other urban dwelling species that commonly experience nighttime light exposure. |
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LoNNe @ schroer @ |
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1588 |
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