"Sometimes ticks attach themselves to rabbits and feed on their blood for several days. Once fully engorged, the ticks will drop off naturally, but they cannot be pulled off whole while still alive. The head remains firmly embedded in position. They can be killed by cutting off their air supply for about thirty minutes with a smear of vaseline, fat or butter. Afterwards it is possible to pull them away cleanly using a pair of tweezers." - http://www.mismatch.co.uk/rabbithealth.htm