Light Pollution Affects Mammals in the Environment
This page covers:
Light pollution's impact on other species in the environment are found here.
Effects of Artificial Night Lighting on Terrestrial Mammals.
Source: Ecological Consequences of Artificial Night Lighting. Catherine Rich & Travis Longcore (eds). 2006. Island Press. Covelo, California. Pages 15-42.
Northern Arizona University School of Forestry
Beier first cites Walls' 1942 paper saying that all species of bats, badgers and most smaller carnivores,
most rodents (besides squirrels), 20% of primates, and 80% of marsupials are nocturnal, and many more are active both night and
day. (Walls, G. L. 1942. The vertebrate eye and its adaptive radiation. Cranbrook Institute of Science Bulletin No. 19,
Bloomfield Hills, Michigan.)
Few studies exist that have focused on artificial night lighting on wild mammals; however, some papers do describe the moonlight's effect on nocturnal behavior and biological clocks. Using these and other papers regarding light and vision, Beier's paper covers likely effects of artificial lighting on mammals, such as foraging patterns changes, predation risk increases, biological clock disruptions, road mortality increases, and disruption of dispersal movements through artificially lit landscapes.
Disruption of Foraging Behavior and Increased Risk of Predation
Disruption of Biological Clocks
The light regime and the circadian clock also influence production of some hormones, notably melatonin,
which mediates almost every physiological or behavioral rhythm in mammals (Bartness and Goldman. 1989. Mammalian pineal
melatonin: a clock for all seasons. Experientia 45:939-945). In all species, melatonin production is high at night and
suppressed during daytime, although reaction to melatonin often differs between diurnal and nocturnal species. Among its many
roles, melatonin suppresses tumor growth by regulating production and tumor use of linoleic acid. In a laboratory experiment,
Dauchy et al. (1997) (Light contamination during the dark phase in
This clock adaption is not a surprising finding for the length of the night varies year round. Adapting to the variation should benefit any animal. However, in winter, the nights are longer, it is colder out and there is less food available. Those animals that do not hibernate probably need more time to find food for their survival. Lights at night, therefore, should reduce the number of hours that they have to find food, leading to hungrier animals.
Effect of Street Lighting on Roadkill of Mammals
So, if you are a driver at night, in such a situation, and you have stopped your car without hurting the animal, I would suggest that you then turn your headlights off, while leaving your parking lights on. The animals are now effectively night blind. Your parking lights, however, should enable them to use enough of their cone vision to see into the road sides to travel there and no longer be completely blind.
Disruption of Dispersal Movements and Corridor Use
In several instances, the animal would bed down until dawn, selecting a location where it could see the terrain beyond the highway after sunrise. The next evening, the puma would attempt to cross the road if wild land lay beyond or would turn back if industrial land lay beyond. (Beier, P. 1995. Dispersal of juvenile cougars in fragmented habitat. Journal of Wildlife Management 59:228-237.)
This wait it out approach just so the animal can see, obviously means that the puma has less time to hunt and so goes hungry, which decreases its chance for survival. The co-editor of the book Ecological Consequences of Artificial Night Lighting and co-director of the Urban Wildlands Group, Travis Longcore says that "If the corridors aren't dark, the animals they're protected for aren't going to use them."
Artificial light puts ecosystem services of frugivorous bats at risk.
Source: Journal of Applied Ecology, April 2014, Volume 51, Issue 2, pages 388-394. doi: 10.1111/1365-2664.12206.
Daniel Lewanzik1,2 and Christian C. Voigt1,2
1 - Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
2 - Animal Behaviour, Freie Universitšt Berlin, Berlin, Germany
To appreciate this report, here is some background information. Nocturnal bats have poor visual acuity, generally night vision rods cells in their retinas, seeing in shades of grey. No species of bats are truly blind (they do have eyes), but can be blinded by bright lights. Hence they are highly sensitive to lights.
Each year, large swaths of tropical rain forests are cleared and converted to farm land. And then roads with streetlights are built to connect these farms to cities to move their crop yields. However, tropical rain forest is a poor soil to grow crops in and when their soil fertility fails, they become uneconomical to grow crops there and this converted land is often abandoned. However, the roads and the streetlights remain.
Lewanzik & Voigt found that the remaining streetlights repel the seed dispersing, fruit-eating bats that naturally live there. While the bats rank second only to birds in seed-spreading, no other animal tends to do so out into the open lands of a former now destroyed forest. Bats have less to fear from predators when flying out in the open lands at night. But, these streetlights repel the bats in doing so, and in turn inhibit the regrowth of the rain forest.
Thus, the artificial light pollution can retard and inhibit the regeneration of one of our planet's largest "sinks" for the greenhouse gas CO2, a tropical rain forests, by disrupting the behavior of the fruit-eating bats that help rain forest plants re-colonize the land from their "seed-rain".
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