Effect of population density on number of leukocytes in domestic cats

Abstract

Leukocytes (white blood cells) are an important part of the mammalian immune system preventing the invasion and colonisation by different pathogens. Many factors may affect the number of leukocytes in mammals, including the population density. The population density in the same species of felines may differ 100–300 times and the aim of this study was to estimate an effect of this factor on the leukocytes number and the ratio for two groups of domestic cats (Felis catus) with different population densities. We sampled 47 cats in the surroundings of Daursky State Nature Reserve, counted the number of leukocytes with a microscope immediately upon sampling and the leukocytes formula in the blood smears later in the laboratory. The population density of cats in the village and at herdsman stations differs approximately by 330 times. Domestic cats in the village (with a denser population) had a higher number of leukocytes and neutrophils, but the same number of lymphocytes and neutrophils/lymphocytes ratio. The number of eosinophils was also higher in village cats. Presumably, the higher number of leukocytes and neutrophils in a cat population with higher density is determined by the higher exchange rate of pathogens/symbionts between cats in the village than at the herdsman stations. These results may give some insight into understanding the changes in wild feline populations at different densities.

Keywords

• eosinophils
• felidae
• immunity
• mating system
• neutrophils
• white blood cell