Conservation of endemic lizards in New Zealand cities

Abstract

Globally, biodiversity is in crisis. One contributing factor is the rapid urbanisation of the world’s population. Land cover change associated with urbanisation radically alters ecosystems, making them uninhabitable for many species. Additionally, people who live in cities often have reduced contact with nature and there are fears that a lack of nature experience may diminish concern for the environment and biodiversity among urbanites. For these reasons, people in cities are increasingly being encouraged and empowered to reduce environmental impacts and connect with nature through urban restoration and backyard conservation. Internationally, lizards are a common feature of urban biodiversity but in New Zealand, where many species are threatened, little is known about populations of endemic skinks and geckos in cities. In order to effectively manage urban lizard populations, greater knowledge is needed about where and how lizards are surviving in cities, and what potential exists for their restoration. I investigated species diversity and abundance of lizards in New Zealand cities, making comparisons with historical species distributions to inform urban restoration and investigating the potential role that participatory conservation might play in their protection.

To collate current knowledge about past and present distributions of urban-dwelling lizards, I reviewed records for six New Zealand cities from published and unpublished literature and databases. Little research was identified from cities and the majority of lizard records were of one-off sightings, or surveys related to salvage or biosecurity operations. Comparing current species records with historical species distributions, it found that the diversity of lizards in all of the cities has declined dramatically since human colonisation.

To begin to fill the identified knowledge gap and to provide baselines for future monitoring, I carried out skink surveys in four cities and trialled a citizen science project that collected public sighting records from residential backyards. Surveys undertaken in urban habitats captured four species of endemic skink: Oligosoma aeneum in Hamilton, O. polychroma, O. aeneum and O. ornatum in Wellington, O. polychroma in Nelson, and O. aff. polychroma Clade 5 in Dunedin. Site occupancy and number of captures were highly variable among the species and cities, with a very high proportion of sites occupied by skinks in Nelson and Wellington compared with Hamilton and Dunedin. Modelling showed O. polychroma catch per unit effort was positively related to rat tracking rates when grass cover was low but showed a negative relationship when grass cover was high. Higher proportions of urban land cover within 500 m were negatively associated with body condition.

The public sightings website gathered more than 100 records from around the Wellington region over one summer, suggesting citizen science may be a cost-effective solution for building knowledge about lizards in residential gardens that are otherwise difficult to survey. While skink sightings were reported from all over the city, gecko sightings appeared in clusters. Compared with a random sample of street addresses, both skink and gecko sightings were more common closer to forest land cover, but only skink sightings were more common in backyards that were north facing.

Finally, I administered a questionnaire survey to understand how socio- demographic characteristics relate to willingness to engage in three different pro-conservation activities that might benefit lizards: pest mammal trapping, biodiversity monitoring and pest mammal monitoring. Public willingness to engage in all three activities was positively related to respondents’ nature relatedness and nature dosage, while only the two monitoring activities were positively related to education. The relationship between willingness and nature relatedness was weaker for pest trapping than it was for the two monitoring activities, suggesting that willingness to trap may be determined by factors other than environmental concern.

Native lizards are an important component of New Zealand’s urban biodiversity. Despite cities having lost significant proportions of their original lizard fauna, a wide variety of habitats in cities still support numerous species. Some of these species seem well adapted to cope with the challenges of urban living, while further research is required to understand whether populations of other species are stable or in decline. To ensure the persistence of lizards in cities, further surveys using a variety of methods should be undertaken to assess lizard diversity and abundance in urban habitats and understand population trends of rare and sparsely distributed species. Public sightings may provide a useful starting point for assessing distribution patterns and allowing the targeting of surveys. In the future, through urban restoration, cities may offer opportunities to conserve a larger proportion of endemic species by reintroducing species that have become regionally extinct.