Variable ecological effects of hurricanes: the importance of seasonal timing for survival of lizards on Bahamian islands.

Two recent hurricanes passed directly over the northern Bahamas 2 years apart, allowing a comparison of their effects on lizard populations inhabiting exactly the same islands. The hurricanes differed in two ways: one struck during the reproductive season and was relatively severe; the other struck after most reproduction had taken place and was milder. The late-season hurricane produced a significant relation between population reduction and lowness of the island that lasted at least through two seasons; the earlier hurricane produced no such relationship. The late-season hurricane wiped out populations of lizards on two islands (two of the three lowest) that the earlier hurricane failed to exterminate even though it was stronger. We relate these effects to the fact that the study lizards regenerated from the earlier hurricane only via the egg stage, whereas eggs were unavailable when the later storm struck and regeneration was via hatched lizards. We discriminate and illustrate four kinds of hurricanes, cross-classified by two contrasts: earlier vs. later and stronger vs. weaker. A later, stronger hurricane completely exterminated lizard populations at a second Bahamian site, whereas an earlier, weaker hurricane had no detectable effect at a third Bahamian site. We suggest that, in addition to severity, the timing of a hurricane as it coincides with reproductive scheduling or other phenological aspects may determine the magnitude of its effect on a variety of organisms.