A winter milestone: our first full-range Māui dolphin survey

This winter, we hit a major milestone at MAUI63, one we’ve been working towards for a long time. 

For the first time, we completed a full-range winter aerial survey of Māui dolphin habitat, covering the west coast of the North Island from Raglan to Kaipara and extending up to 12 nautical miles offshore.  

It was our biggest fixed-wing survey yet, and the first time we had taken the full system we’ve been developing, including the aircraft, cameras, survey design, AI-assisted detection and data analysis, and applied it across the full survey area in winter. 

Why winter matters 

Winter has been an important gap in our understanding of Māui dolphins. 

Most previous Māui dolphin monitoring has taken place in summer, leaving much less information about where dolphins are during the colder months.  

One of the key questions has been whether Māui dolphins move further offshore during winter. 

This survey gave us the opportunity to investigate that across their full range. 

What the survey looked like 

Between 11 and 22 August 2025, we flew 164 line transects over seven survey days, covering approximately 4,000 km² of ocean.  

Our four-camera system captured around 160,000 high-resolution images, approximately 8 TB of data.  

For analysis, those images were grouped into 38,075 survey frames. Every frame was screened using our computer vision model to identify possible dolphins, with detections then manually reviewed and verified.  

What did we find? 

Across the survey, 26 individual Māui dolphins were captured in the imagery at least once, with 38 detections in total.  

Most detections were concentrated just south of Manukau Heads and just south of Port Waikato. 

Despite surveying as far as 12 nautical miles offshore, all confirmed detections were within approximately 4 nautical miles of the coast.  

Taken together, these results give us a clearer picture of winter distribution across the full survey range, with all confirmed detections close to shore. 

Estimating abundance 

We also asked independent ecological analysts Proteus to estimate Māui dolphin abundance from the aerial survey data. 

Their estimate was 47 Māui dolphins in the survey area, with a 95% interval of 21 to 103.  

That is broadly consistent with the most recent genetic mark-recapture estimate of 54 dolphins, with a 95% confidence interval of 48 to 66.  

For MAUI63, that is an important result: two completely different methods arriving at a similar estimate. 

It also demonstrates that our aerial survey system can do more than find dolphins. It can produce both distribution data and credible abundance estimates. 

Built over years 

If you’ve been following our work, you’ll know this didn’t happen overnight. 

Our early drone surveys provided the foundation. From there, we developed our four-camera fixed-wing system and completed sample surveys in March and April 2025 to test and refine the end-to-end process. 

In March, the fixed-wing system detected 14 Māui dolphins in a single day, followed by a further five during the April sample survey.  

The August winter survey was the next step, taking everything we had learned and applying the system across the full survey area. 

Why this matters 

The approach is repeatable. 

We can fly the same survey lines again, collect imagery in the same way and process it through the same pipeline. 

Repeating the survey over time will allow us to compare results and build a stronger evidence base on both Māui dolphin abundance and distribution. 

For MAUI63, that is an important part of what this survey represents: moving from smaller-scale testing to a monitoring system that can be used consistently across a much larger area. 

What’s next? 

We’re continuing to refine the system and build on what we learned from the winter survey. 

We’re also beginning to apply the same aerial survey capability beyond Māui dolphins. Test flights are underway in the Hauraki Gulf as we adapt the platform for different conditions and begin developing a multi-species detection model.  

A full-range winter survey like this has been a long time coming. 

For MAUI63, it marks an important step from testing the technology to demonstrating a practical, repeatable aerial monitoring capability at scale. 

And it gives us a strong foundation to keep building on, for Māui dolphins and for marine conservation more broadly.