What’s the buzz on wasps?
With this current season’s wasp nests starting to be discovered in Zealandia, it feels timely to do a closer dive into one of the ultimate bees in our bonnet: wasps. While the impact of mammalian predators is well known throughout Aotearoa New Zealand, there are also invasive plants, fish, and insects which throw out the balance of our local ecosystems. But there are steps you can take to assist.
New Zealand is home to an estimated 2,000–3,000 species of wasps and bees, most of which are native. However, the introduced social wasps that you are most familiar with have a large impact on urban, rural, and natural ecosystems.
As with other invasive species, introduced wasp numbers get high as they don’t face the same pressure here as they would in their natural habitats. For example, we lack the cold winters that often kill off nests, meaning each spring the colony can continue building onto their nests rather than having to start over from scratch.
Introduced wasps don’t just feed on nectar, they also eat vast numbers of native insects, taking this resource away from the birds who eat them too. In beech forests, wasps also feed heavily on honeydew which is another important food source for insects and nectar-feeding birds such as kākā.
Compared to most countries, New Zealand has few native stinging wasp species—just 29, in two families. While they can sting, they’ll normally only do so when provoked. Introduced wasps, however, can be a hazard to people and animals due to their aggressive nature. They do not even need to be alive to have an impact on birds: necropsies on some deceased hihi/stitchbird chicks in Zealandia revealed perforations from stingers in their gizzards (part of the stomach) due to parents feeding their chicks wasps.
The fence surrounding Zealandia does a wonderful job at keeping out mammalian predators and keeping native species safe. However, wasps can simply fly over the fence which means finding different management solutions for this species.
A protein-based bait called Vespex has had great success in wasp-dense beech forests like those in Nelson Lakes. Unfortunately, Vespex was not successful at Zealandia, possibly because the forest here (unlike in beech forests) is sugar-limited rather than protein-limited, meaning wasps may not be interested in it. As the entire biology of social wasps is dependent on the nest, direct targeting of wasp nests in and around Zealandia is the most effective control method. However, finding nests is time-consuming and difficult.
In 2023, a conservation team intern investigated if there was a more efficient way to find nests. She created routes that she would walk slowly every two weeks, looking for signs of wasp nests. For example, when selecting a nest site, queen wasps prioritise areas that are sunny and sheltered relatively close to a stream or body of water. Because the majority of habitat in Zealandia is dense bushy forest, this theoretically limits the possible areas wasps would be nesting in.
Another sign of a nest is how wasps fly. When you see wasps generally, they tend to fly horizontally, foraging for food to bring back to their growing colony. However, when wasps exit their nest, they fly in a rapid vertical direction—if you see something exhibiting this unusual flight pattern, it may well indicate a wasp nest nearby.
As well as searching for nests, Zealandia’s rangers also keep their eyes and ears open as they go about their day, and any nests reported are quickly controlled. However, we can’t be everywhere at once, so we also rely on any sightings of potential nests from staff, volunteers, and members of the public. Wasps can forage as much as 4km away from their nest site, meaning many of the wasps in Zealandia may not even be nesting in the sanctuary. It is important to control wasps outside of the sanctuary too for the health of our native species and forest ecosystem.
If you have spotted or think you have spied a wasp nest in Zealandia, your property, or a Wellington reserve, please report it!
• In Zealandia: let a staff member know (with as specific a location as possible);
• In your backyard: contact a professional pest expert to control the nest;
• In a council reserve: Report it to your local council;
• In Wellington - log it though the Wellington City Council fixit app, online form, or call 04 499 4444. The more information you can give about the location of the nest the better for staff to be able to find it--you can even pin the location in the app/form!
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