Effects of Ambient Temperature and Cattle Skin Temperature on Engorgement of <I>Dermacentor andersoni</I>

Abstract

Experiments were conducted to determine whether changes in skin temperature of cattle held at ambient temperatures ranging from 10 degrees C to 30 degrees C influenced engorgement of female Dermacentor andersoni (Stiles). Average skin temperature of Angus cattle increased from 29 degrees C to 34 degrees C, whereas skin temperature of Holstein cattle increased from 32 degrees C to 35 degrees C over the range of ambient temperatures. Changes in skin and ambient temperature strongly influenced the proportion of ticks that successfully engorged, the time required for engorgement, and weight of engorged ticks, and they had a weaker influence on the proportion of dead ticks. The relationships between the tick engorgement parameters and ambient temperature differed between the experiments using either Angus or Holstein cattle. The differences between experiments were reduced when expressed in relation to skin temperature, suggesting that the thermal environment of the breeds is an important characteristic determining engorgement success. Results indicate that ticks respond to changes in the thermal environment of the host, and these changes may be important to engorging ticks exposed to fluctuating spring weather.