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When day draws to a close in New Zealand, the forests echo with screeches. There the male lesser short-tailed bat sings up to 100,000 songs a night—more than any other animal—to woo a mate. He serenades from a special singing roost used solely for the purpose of sexual display. But not every one of these Romeos is a one-man show. After a three-year study of the nocturnal mammals' habits, Cory Toth of the University of Auckland found that males in nearly half the 12 singing roosts he observed in North Island turned the stages into time-shares. “One male will be singing, will leave, and as little as three seconds later, another male will enter the roost and start singing,” Toth says. In total, two to five males perform every night in one roost, singing for a few hours each.
Overall, the shared roosts broadcast more songs than those occupied by only one bat all night, increasing the chances that a passing female will stop by. The behavioral ecologist initially hypothesized that the time-share bats were related and worked together to ensure reproductive success for their specific gene pool. But when males in three of four singing roosts turned out to be unrelated or only distantly related, Toth's attention turned to bat size: the males that took turns on the stage were significantly larger than those who sang alone. Larger males expend more energy in the daily tasks of survival and thus might save energy at night by taking shifts singing, Toth says. In fact, DNA testing revealed that the reproductive success for larger and smaller bats within the colony was about the same, suggesting that the joint ownership arrangement helps the big guys compete with little ones.
The lesser short-tailed bat is one of only two remaining endemic land mammals in the country (the second is the long-tailed bat) and is endangered. Knowledge of the reproductive habits of the species could inform conservation efforts.