Quantitative Relationships between Fleas and Rodents in a Hawaiian Cane Field

Relative numbers of Xenopsylla vexabilis Jordan on Rattus exultans (Peale) and Mus musculus L. and in their nests were determined monthly in a field of maturing sugar cane at Kukuihaele, island of Hawaii, January 1962-March 1963, in a preliminary study using nest boxes and live traps. Mean numbers of fleas in active rat nests were most closely correlated with mean numbers of fleas infesting rats when they were cage-trapped in the previous month. Mean numbers of fleas in active mouse nests were most closely correlated with mean numbers of mice that had been recorded per mouse nest found occupied in the previous month. Ratios of mean number of fleas on trapped rats to mean number of fleas in rat nests the following month averaged .20 when means increased and .30 when they decreased. When the total flea index was substituted for mean number of fleas in nests, ratios averaged .32 when fleas became more abundant and .36 when they decreased in numbers. Further study of fleas in rat nests is needed before predictions of flea abundance are routinely made from fleas counted on trapped rats