The study also indicates that when the senses relay information on these environmental factors, it can influence daily activity and, in the case of a particular monkey species, may have even produced evolutionary change. It is possible, according to the study results, that changes in sensitivity to specific environmental stimuli may have been an essential key for evolutionary switches between diurnal and nocturnal habits in primates. The study also provides data to better understand all life cycles.
Researchers set out to examine the hypothesis that masking, the chronobiology term for the stimulation or inhibition of activity, was largely caused by changing environmental factors that affected the Azara's owl monkeys' internal timing system, or synchronized circadian rhythm. Put simply, changes in temperature and light make Azara's owl monkeys the only anthropoid primate (monkeys, apes and humans) with a propensity for both early bird and night owl behavior.
The observational nature of field studies has generally limited science's understanding of the mechanisms responsible for the change in activity patterns of these species, whose behavior traditionally takes place in the dimmest of light. Researchers monitored the activity of these wild owl monkeys continually for as long as 18 months using actimeter collars fitted to them.
The results represent the first long-term study of wild primates providing direct evidence for environmental masking, according to researchers.
The data indicate that, although regular daytime activity is represented by the output of a circadian clock, nocturnality is the result of fine-tuned masking of circadian rhythmicity by environmental light and temperature.
Specifically, date showed that nocturnal activity was more consolidated during the relatively warmer months of September to March than during the colder months of April to August, when temperatures in the Argentine province of Formosa regularly fall below 10ºC. Throughout the year, nocturnal activity was higher during full-moon nights than during new-moon ones, and these peaks of nocturnal activity were consistently followed by mornings of low activity. Conversely, new-moon nights were usually followed by mornings of higher diurnal activity than mornings following full-moon nights.
"The behavioral outcome for these owl monkeys is nocturnal activity maximized during relatively warm, moonlit nights," said Eduardo Fernández-Duque, lead investigator and an assistant professor in the Department of Anthropology in Penn's School of Art and Sciences.
"While laboratory studies have pointed to the importance of masking in determining the environmental factors that cause animals to switch from nocturnal activity patterns to diurnal ones or vice versa, our study underscores the importance of masking in determining the daily activity patterns of animals living in the wild. It also suggests that moonlight is a key adaptation for the exploitation of the nocturnal niche by primates," he said.
Conclusive evidence for the direct masking effect of light was provided when three full lunar eclipses completely shadowed moonlight, coinciding with diminished monkey activity. Temperature also negatively masked locomotor activity, and this masking was manifested even under optimal light conditions.
"If there was a biological clock that they were depending on to regulate this activity, you could expect the activity to continue even in the absence of lunar light," said Horacio de la Iglesia of the Department of Biology at the University of Washington.
Primates — even humans — conduct their daily tasks in patterns ranging from nocturnality to diurnality, with a few species showing activity both during day and night. Among anthropoids (monkeys, apes and humans), nocturnality is only present in the Central and South American owl monkey genus Aotus. But unlike other tropical Aotus species, the Azara's owl monkeys (A. azarai) of the subtropics, and this study, have actually switched their activity pattern from strict nocturnality to one that also includes regular daytime activity. The phenomenon led researchers to question the causes of such a behavioral change.
"Harsher climate, food availability and the lack of predators or daytime competition have all been proposed as factors favoring evolutionary switches in primate activity patterns," Fernández-Duque said.
"The lunar day has not been a stable force as much as the solar day to evolutionarily select for a clock," de la Iglesia said. "We still have to prove it in the lab, but the evidence in this paper points to a lack of a lunar biological clock."
The article appears in the current issue of the journal PLoS ONE.
The study was conducted by Fernández-Duque, de la Iglesia and Hans G. Erkert of the University of Tübingen.
The research was funded by the Zoological Society of San Diego, Leakey Foundation, Wenner-Gren Foundation and National Geographic Society. It was authorized by the Ministerio de la Producción, Subsecretaría de Ecología y Recursos Naturales and Dirección de Fauna from Formosa Province.
Jordan Reese | EurekAlert!
Drone vs. truck deliveries: Which create less carbon pollution?
31.05.2017 | University of Washington
New study: How does Europe become a leading player for software and IT services?
03.04.2017 | Fraunhofer-Institut für System- und Innovationsforschung (ISI)
Computer scientists use wave packet theory to develop realistic, detailed water wave simulations in real time. Their results will be presented at this year’s SIGGRAPH conference.
Think about the last time you were at a lake, river, or the ocean. Remember the ripples of the water, the waves crashing against the rocks, the wake following...
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
29.06.2017 | Physics and Astronomy
29.06.2017 | Life Sciences
29.06.2017 | Health and Medicine