Territoriality in a cannibalistic burrowing wolf spider

Field experiments to test the hypothesis that a cannibalistic species is territorial are rare. We conducted two field experiments to test the hypothesis that adult females of the Mediterranean tarantula, Lycosa tarentula (L.) are territorial. In a relatively long-term experiment we placed a female intruder in an artificial burrow within the hypothesized territory of a resident. The intruders disappeared from their burrows at 7× the rate of spiders in a reference and two control treatments. Residency status, not relative size, determined whether the intruder or the resident remained, and evidence suggests that the winner frequently cannibalized the loser. We also conducted a short-term field experiment in which we induced encounters between females. The results were consistent with territorial defense because escalation was more likely if spiders were similar in size, and cannibalism, the outcome of one-third of the encounters, occurred only after escalation. Thus, adult females of the Mediterranean tarantula are territorial, and cannibalism may be a consequence of territorial defense.