How did artificial night light affect two desert spiny mice?

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Researchers studied ecological light pollution in a rocky desert community, focusing on two related species: the nocturnal common spiny mouse (Acomys cahirinus) and the diurnal golden spiny mouse (Acomys russatus). They hypothesized that artificial light would reduce A. cahirinus activity and increase A. russatus activity, potentially increasing overlap in their active hours and competition between the species.

The study used four field enclosures. The first and third months were natural-light controls; during the second month, artificial illumination simulated low levels of light pollution for the first three hours of the night. The researchers implanted temperature-sensitive radiotransmitters to monitor activity and used individual identification tags with automatically monitored foraging patches to track foraging behavior.

Under artificial light, A. cahirinus reduced its activity and foraging and restricted its movement particularly in less-sheltered microhabitats, probably because of increased predation risk. With both its activity time and space restricted, encounters between A. cahirinus at foraging patches increased during and after the illuminated hours. A. russatus did not expand its activity into the illuminated hours, possibly because competing A. cahirinus were present or because environmental conditions were unfavorable. Overt competition between the species was therefore not affected by the experimental light pollution.

The researchers concluded that light pollution had negative effects: it reduced overall activity and created a relatively underexploited temporal niche that might promote invasion by alien species less sensitive to light. It also increased overlap among foraging A. cahirinus.