Sick animals struggle to problem solve and adapt to changing environments

"Cognitive impairment could contribute to population declines, particularly for species that rely heavily on learning and memory for foraging or other important functions," say the authors, including professors Dana Hawley and Kendra Sewall of Virginia Tech and Anne Leonard of the University of Nevada. "Impaired cognitive performance could compromise the ability of some animals to exploit urbanized and other rapidly changing habitats, where problem solving may be particularly important."

The impact of disease on cognitive abilities can vary widely from animal to animal, depending on the animal's survival strategy and how the pathogen or parasite manifests in the body. For example, social animals such as ants and humans might miss out on learning opportunities because of avoiding high-risk areas or individuals, a behavior termed "landscape of disgust."

Infections early in life could also make animals more susceptible. For example, young canaries that are infected with Plasmodium when they are learning songs might have a reduced song repertoire and complexity as adults. Impairment might also arise indirectly as a result of malnutrition or from the animal's own immune response.

"One challenge in all studies of cognitive ecology is the scarcity of comparable data across taxa," say the authors. "Understanding how infection affects specific cognitive abilities will require research across a wider breadth of hosts and pathogens, targeting analogous aspects of cognition (e.g., spatial learning; problem solving; general versus specialized cognitive abilities), and standardizing experimental paradigms to the extent possible."