Does a bacterial infection lead to a nutritional deficiency in foraging Allenby’s gerbils?

Abstract

Bacterial infections can have both direct (physiological) and indirect (ecological) costs for their hosts. The direct costs of infection may include nutritional deficiencies, which reduce body condition over time, and result in the hosts modifying their foraging behaviour to compensate for any losses. Allenby’s gerbils are commonly infected with the Mycoplasma haemomuris-like bacteria, which may induce choline (essential vitamin) and arginine (amino acid) deficiencies. Gerbils should therefore alter their behaviour to make up for any shortfalls in nutrient production and retention. We tested two predictions. 1) infected gerbils would compensate for nutrient losses by spending more time foraging in patches, including, during riskier periods of owl presence, and in riskier open microhabitats. Furthermore, infected gerbils would preferentially forage from patches supplemented with choline and arginine enriched food over control food. 2) Alternatively, if infection did not create a nutrient deficiency, then infected individuals would display a similar pattern of patch use to uninfected individuals, and harvest similar amounts of food from supplemented and control patches. Our findings supported the second prediction. There was no observed difference in foraging behaviour between infected and uninfected individuals. Moreover, infected gerbils did not selectively forage more intensively from food patches enriched with either choline or arginine seed over the control patches. These results suggest that this bacteria-gerbil interaction does not result in a nutrient deficiency as observed for other Mycoplasma-rodent systems.