Territorial tuatara? – a hypothesis still to be tested

The term territorial is used in a variety of ways and is rarely defined unambiguously, or tested empirically. Nevertheless, attributing it correctly has far-reaching implications for our understanding and management of populations. Territoriality is commonly attributed retrospectively, as a convenient description of spatial pattern without an a priori and operational definition and tests for territorial behaviour. It is distinguished from female-defence or male-dominance mating systems by the defence of resources, including space. Thus, territories are defined operationally by site-specific dominance and their boundaries are determined by spatial changes in an individual’s success in agonistic interactions with competitors. A number of recent articles describe the reptile, tuatara (Sphenodon punctatus: Rhynchocephalia) as territorial and use Gans et al. (1984) and Gillingham et al. (1995) in support. Neither Gans et al. (1984), nor Gillingham et al. (1995), provided operational definitions of territoriality, or tested for territorial behaviour, however. Gillingham et al. (1995) also confused the concepts of home range and territory by using the former to define the latter. The recent literature on tuatara includes the same errors. Home ranges continue to be used to define territories without measures of spatially dependent, female-independent dominance, and even though body size relates positively to success in male–male competition and access to females, neither of these factors influences ‘territory’ size. Instead, territory-like artefacts such as range dispersion and fidelity have been used as evidence of territoriality, although they can also be products of female-defence and male-dominance mating systems. Measures of the frequency, intensity and outcomes of male–male conflict where proximity of females and a priori territory boundaries vary, or ideally are varied experimentally, are necessary to tease apart the influence of females, resources and male dominance in the tuatara mating system.