Light Pollution: Disrupting Animal Behavior And Ecology

Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It has been shown to have harmful effects on wildlife and ecosystems. For billions of years, all life on Earth has relied on the planet's predictable rhythm of day and night. This daily cycle of light and dark governs life-sustaining behaviours in plants and animals, such as reproduction, nourishment, sleep, and protection from predators. Artificial light at night has been found to negatively impact many creatures, including amphibians, birds, mammals, insects, and plants.

This paragraph will discuss the effects of light pollution on animals in detail, exploring how it disrupts their natural behaviours and threatens their survival.

Disrupts feeding and hunting patterns

Light pollution has a significant impact on the feeding and hunting patterns of animals, particularly those that are nocturnal or crepuscular. These species, which include moths, bats, frogs, and cats, rely on the cover of darkness to hunt for prey or search for food without being exposed to predators. Artificial light reduces the time they have to find food and makes them more visible to predators, thus increasing their risk of becoming prey themselves.

For predators, light pollution can make hunting more challenging as their prey may become more dispersed or difficult to locate in altered environments. This can result in a decrease in successful hunts and impact their ability to survive.

In addition, artificial light can attract certain organisms, such as moths, frogs, and sea turtles, leading them away from their natural habitats and concentrating them in areas where they are more vulnerable to predation or exhaustion. This not only affects their feeding and hunting patterns but also increases their mortality rates.

The disruption of day/night patterns caused by artificial light can also impact the feeding and hunting behaviours of both diurnal and nocturnal species. For example, diurnal songbirds may have their breeding cycles altered, causing them to breed too early or too late, which can affect their foraging and hunting activities. Nocturnal species, such as bats and rodents, may have their sleep disrupted, resulting in reduced energy for hunting and feeding.

Furthermore, light pollution can affect the hormone production of certain animals, such as frogs and humans. Prolonged exposure to bright lights can alter hormone levels, which in turn can impact feeding and hunting behaviours. For example, reduced melatonin production in rats has been linked to an increased rate of tumours, which may impair their ability to hunt and feed.

Interferes with reproduction

Light pollution has a significant impact on wildlife, with one of the most notable effects being the interference with reproduction.

Frogs and Toads

The nighttime croaking of frogs and toads is part of their breeding ritual. Artificial light disrupts this nocturnal activity, interfering with reproduction and reducing populations.

Sea Turtles

Female sea turtles nest on beaches around the world, and about two months later, the hatchlings start scrambling towards the brightest horizon. On a natural beach, this is towards the moon and starlight glimmering off the water. However, artificial lights on beaches and in nearby towns disorientate the hatchlings, drawing them away from the safety of the ocean and towards danger.

Birds

Migratory birds depend on cues from properly timed seasonal schedules. Artificial light can cause them to migrate too early or too late and miss the ideal climate conditions for nesting, foraging, and other behaviours.

Mammals

Research has shown that light pollution can lead to changes in movement patterns and individual interactions in small mammals, which could have fitness consequences on the population level. For example, in one study, small mammals changed their activity patterns as an anti-predatory response when subjected to artificial light as dim as moonlight.

Insects

Artificial light at night (ALAN) is also associated with insect declines. Insects are drawn to light, and even one artificial light source can disrupt normal flight activity, long-distance migrations, or attract insects that don't usually move from their habitat. Insects that are trapped by the light may be killed directly by the lamp's heat or become easy prey for predators.

Causes exhaustion and starvation

Light pollution has a detrimental impact on wildlife, and one of the consequences is that it causes exhaustion and starvation.

Effects on Birds

Migratory birds that travel or hunt at night rely on moonlight and starlight to navigate. Artificial light can cause them to veer off course and towards dangerous, illuminated landscapes in cities. The bright lights of buildings can also confuse birds, causing them to circle them endlessly, leading to exhaustion and the depletion of energy reserves needed for their journeys. This can ultimately result in death.

Effects on Insects

Light pollution can be a fatal attraction for nocturnal insects, such as moths, which are drawn towards bright lights. The powerful lure of artificial lights may be due to the instinctual tendency of these insects to orient themselves by moonlight. Insects can find themselves trapped, circling lights until they are caught by predators or dying from exhaustion. This can also cause them to miss courtship cues from potential mates.

Effects on Sea Turtles

Light pollution poses a significant threat to sea turtles, particularly hatchlings. On beaches near roads and buildings, artificial lights can disorient them, causing them to move inland instead of towards the ocean. This leads them away from the safety of the water and towards potential dangers such as dehydration, predators, and vehicle collisions.

Effects on Bats

Slow-flying bats, such as little brown, mouse-eared, and long-eared bats, tend to avoid illuminated areas as the light exposure increases their vulnerability to predators like owls and other birds of prey. Light pollution can also delay their emergence at dusk, when their prey, insects, are most active, impacting their foraging behaviour and food sources.

Increases exposure to predators

Light pollution has a drastic effect on nocturnal ecology, with predators using light to hunt and prey species using darkness as cover.

Light pollution radically alters the nighttime environment for nocturnal animals, turning night into day. This has a significant impact on their ability to hide from predators. For example, the western snowy plover avoids roosting on beaches where artificial light is brighter than the light of a half-moon. When the operators of a power plant in California agreed to dim the lights, the following year, 10 snowy plover nests appeared on the previously barren beachfront.

Light pollution can also lead to the proliferation of invasive species. For instance, cheatgrass has been observed to grow in urban areas where more streetlights are present. This can lead to further exposure to predators as food webs are affected in unanticipated ways.

Light pollution can also directly increase exposure to predators by acting as a lure. For example, on beaches adjacent to roads and buildings, many sea turtle hatchlings are drawn inland towards artificial lights instead of heading towards the ocean. This results in millions of hatchling deaths each year.

Light pollution also affects the behaviours of predators. For example, bats, a type of predator, avoid feeding in or passing through illuminated areas as it exposes them to their own predators such as owls and other birds of prey.

Disrupts migration

Light pollution can have a significant impact on the migration patterns of animals, particularly those that migrate at night, such as birds.

The glow from cities and urban areas can powerfully attract migratory birds, drawing them away from their intended path and towards potential dangers. This attraction to artificial light has been observed in hunters and fishers who have used torches, lamps, and other light sources to attract their prey. Nocturnal migration has many benefits, such as better weather conditions and fewer active predators, but it also makes migratory birds highly susceptible to light pollution.

Research has shown that light pollution acts as an amplifying agent, drawing songbirds into urbanized areas. This can lead to birds becoming trapped in areas where food is scarce and they face other threats such as colliding with buildings. It is estimated that up to 1 billion migrating birds die each year from collisions with buildings in North America alone.

Birds that migrate at night navigate by moonlight and starlight, and artificial light can cause them to wander off course and towards the dangerous landscapes of cities. The light pollution within geographic ranges was found to be relatively greater during the migration season, for shorter-distance migrants, and for species with smaller ranges.

Light pollution can also impact the timing of migration and other seasonal behaviors by disrupting the biological clocks of birds. Birds may misinterpret artificial light at night as a longer period of daylight, causing them to migrate earlier or later than usual. This mistiming can put birds at risk if the necessary environmental conditions and resources are not available during their journey or upon arrival at their destination.

Additionally, light pollution can lead to unnatural light-induced behaviors, causing migratory birds to deplete their energy reserves and putting them at risk of exhaustion, predation, and lethal collisions with man-made infrastructure.

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