Predator Experience Shapes Behaviour: Comparing Stone Wētā (Hemideina maori) Populations With and Without Weka (Gallirallus australis hectori)

Sheri Johnson, Luke Thompson, Hamish Doogan, Priscilla Wehi

Antipredator behaviour reflects both evolutionary history and individual experience, yet how populations respond to changes in predator exposure remains poorly understood, particularly for large invertebrates. We examined antipredator behaviour in two populations of stone wētā (Hemideina maori Pictet & Saussure, 1891) inhabiting weka-free Mou Tapu and nearby Mou Waho, where weka (Gallirallus australis hectori – a large flightless rail) were translocated in 2004 and persist. Wētā were collected from both islands and assayed under controlled laboratory conditions to quantify refuge use, locomotor activity, exploratory behaviour, and defensive responses to simulated attack. Morphological traits did not differ between islands, aside from a weak trend toward longer hind femora in Mou Waho individuals. Refuge-seeking behaviour and open-field activity did not vary between populations, nor did exploratory tendencies. However, predator-experienced Mou Waho wētā were substantially more defensive: 84% responded aggressively to the first simulated attack compared with 58% of Mou Tapu individuals, and larger wētā showed stronger defensive responses irrespective of origin. Defensive behaviour types (fending, fleeing, rasping) were conserved across populations, suggesting that differing recent exposure to weka altered the threshold at which antipredator behaviours were deployed rather than the underlying behavioural repertoire itself. Field observations revealed striking microhabitat restriction on Mou Waho, where wētā were found only beneath large summit rocks, consistent with sustained predation pressure. Our findings demonstrate that predator experience selectively enhances reactive components of antipredator behaviour without altering proactive behaviours such as refuge-seeking or activity. These results highlight the importance of behavioural assessments in conservation planning, especially when predator-naïve populations may face re-exposure to native predators through restoration or translocation programmes.