NIGHT SKY AND DARK ENVIRONMENTS: BEST MANAGEMENT PRACTICES FOR ARTIFICIAL LIGHT AT NIGHT ON BLM-MANAGED LANDS TECHNICAL NOTE 457 32 A study in the Mojave Desert (Bouskila 1995) shows that snake predation on desert rodents decreased under higher levels of nighttime illumination from moonlight because the rodents were better able to see the snakes (which do not rely on vision for hunting). Perry et al. (2008) suggest that exposure to artificial light might have similar effects. 3.5.1.5 Effects on Fish It is well established that fish are attracted to artificial light at night. Research shows that predaceous fish and their prey species are attracted to light near the water surface (Becker et al. 2013). In some fish species, hatching is photoperiod-dependent (McAlary and McFarland 1993). Artificial light at night can have various effects on development of freshwater fish species (Brüning et al. 2011) and can affect the dispersal of juvenile salmon and the swimming depth of mature salmon (Nightingale et al. 2006). Tabor et al. (2004) found that artificial light at night delayed migration of sockeye salmon fry and increased predation by sculpins. Observations show nonfish predators taking advantage of lighting to prey on migrating salmon (Nightingale and Simenstad 2002). 3.5.1.6 Effects on Amphibians Many amphibians are nocturnal, at least seasonally, and some have vision systems adapted for living in extremely dark environments. Research suggests that these species may be extremely sensitive to artificially lit areas (Buchanan 2006). Amphibians generally use vision to capture their prey, so altering light in their environment may change their predatory behavior. Some frogs and toads appear to be attracted to lit areas, presumably to feed on insects and other animals drawn to the light (Wise 2007). Dark adaptation is the process of the eyes adjusting to dark conditions after exposure to light, and vision is impaired until the eyes are fully adapted. In humans, dark adaptation may take as long as 50 minutes (Ruseckaite et al. 2011). Evidence from various studies show that, for certain frogs, dark adaptation after exposure to light as dim as a headlamp may take hours, and during the period of dark adaptation, frogs were less able to locate prey, potentially affecting their foraging success. Difficulty with dark adaptation may also make them more susceptible to becoming prey or being killed by vehicles after being blinded by automobile headlights while crossing roadways (Buchanan 2006). In certain species of frogs, artificial light at night can affect mating behavior, including the calling behavior and movement of male frogs (Baker and Richardson 2006), mate selection by female frogs (Rand et al. 1997), and nest locations (Tárano 1998). Some of this behavior is believed to result from avoidance of predation in illuminated areas. Dias et al. (2019) found that artificial light at night affected the calling season length and timing as well as the daily calling behavior of various frogs in Brazilian wetlands. Artificial light at night can affect toads as well. Dananay and Benard (2018) show that exposure during the larval stage of the American toad affected development and behavior. Touzot et al. (2019) demonstrate that artificial light at night reduced activity levels and changed energy allocation in the common toad in the breeding season. In a separate study, Touzot et al. (2020) show that artificial light at night affected mating behavior and fertilization success of the common toad. In certain species of frogs, artificial light at night can affect mating behavior.
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