Birds exposed to toxic metals have demonstrated personality traits inconsistent with common animal behavior, according to new research which warns that the changes could prove deadly.

Scientists at the University of Antwerp in Belgium found that exposure to contaminants could alter an animal’s personality traits to the extent that it may prove dangerous for them when faced with predators.

The study examined 250 birds captured near a smelting and metal refinery center notorious for emitting lead and cadmium into the environment. Five populations of a popular songbird the great tit (Parus Major), located at different distances from the refinery, were analysed at the laboratory.

The birds captured closest to the metal refinery were the least active and the least curious, according to the findings. They also reported that those closest to the smelting plant had the highest levels of the metals in their eggs and feathers.

Lead researcher Dr Andrea Grunst told the New Scientist that the metals could change the chemistry of the brain, resulting in the altered behaviour. Scientists expressed concerns that the slowdown in exploration behavior may reflect impaired neurological or physiological function and could affect fitness levels, potentially putting the creatures at greater risk of becoming prey.

For the second part of the experiment, the captured birds were released in their natural environment and observed as they interacted with decoy intruders such as stuffed birds. Interestingly, aggression and protection of the nest did not vary with proximity to the refinery.

The scientists concluded that the presence of toxic metals appears to affect natural exploration behavior in animals but does not impact other inherent personality traits. Metal poisoning in humans can lead to a wide variety of physical and mental disorders.