Manipulative females: intra-sexual interactions in nest site choice, nest guarding, and nest defence in tuatara.

Females of many reptile species engage in colonial nesting. Proposed advantages to colonial nesting include breeding synchrony, predator satiation and nest site copying by young or inexperienced females. However, nest site copying may also present costs to individual females in that previously laid nests may be intentionally or unintentionally destroyed by females that nest later at the same site. Conspecific nest destruction may be prevented if females guard their nests following oviposition, although nest guarding presents additional costs. Nesting by female tuatara, Sphenodon punctatus, was investigated in seven rookeries over 5 years on Stephens Island. Nest site copying appeared to be common, with approximately 30% of nests being constructed at sites showing evidence of a previous nest, e.g., old eggshells, recent eggs, or the previous year's hatchlings. The majority of copied nests were constructed by a female digging up eggs laid earlier in the season, and replacing them with her own. Nests constructed earlier in the season were more likely to be dug up than those laid later in the season. Twenty-two percent of nests were guarded by females following oviposition, with length of time spent guarding ranging from 1 to 10 days. Half of the observed nests were destroyed by conspecific females, but 92% of destroyed nests were unguarded. Inter-female interactions in tuatara nesting appear to involve a tradeoff between individuals using the nest site of other females as a cue in nest site choice, and guarding their own nest against other females making the same choice. [ABSTRACT FROM AUTHOR]