Dolphin Tracking UAVs

This article was discussed in our Next Byte podcast. 

The full article will continue below.

Dolphin Tracking

Researchers at the University of Aberdeen and Duke University have a very important mission: understanding how bottlenose dolphin populations are affected by pollution, natural toxins, change in the availability of prey, etc. 

Unfortunately, it's not as easy as it sounds because most methods to study cetacean (marine mammals) populations are not efficient for the following reasons:

• Catch and release is time consuming and results are not reliable for estimating behavior of large populations

• Cetaceans spend a great deal of time underwater so they are mostly inaccessible

• Conclusions made on key factors - such as pregnancy success rates - are made after the fact which can lead to inaccurate generalizations

Help From Above

Utilization of unmanned aerial vehicles (UAVs) is the light bulb moment that began a research effort in 2017 to gauge the viability of this technology for studying cetacean populations.

UAVs with imaging and sensing technologies were deployed to monitor bottlenose dolphin populations in the Moray Firth Special Area of Conservation in Scotland with the goal of differentiating dolphins and determining their age, sex, and pregnancy status via analysis of gathered data. 

Researchers looked for unique identifiers to differentiate individual dolphins from one another and measured the length of the dolphin body (from the nose to the tail) along with the width at every 10% interval of the length. The goal was to use this data and see if there was any correlation between length and width that could help accurately determine the sex, age, and pregnancy status.

Image 1. Matching and measuring bottlenose dolphins during 2017 field tests (Cheney, 2022)

The Results

Here are some notable conclusions from the data gathered in the field studies:

• Sex - female dolphins were smaller than males on average; however, the difference was not significant enough to establish a baseline to confidently distinguish the sexes

• Age - there were significant length and width differences between the age classes but the width to length ratio remained the same across the ages. This was also not deemed as a reliable method to differentiate since ⅓ of the population was incorrectly classified into the wrong age group

• Pregnancy status - a noticeable change in the width of female dolphins was detected in the 40% and 50% portion of their length during a pregnancy

Putting this new knowledge into action resulted in correctly determining the pregnancy status of 14 out of 15 (~93%) female dolphins studied.

Image 2. Width to length ratio for pregnant female dolphins (red dots) and non-pregnant female dolphins (black dots)

Impact

Since successfully carrying a pregnancy to full term is an indicator of the health of a population and their growth trajectory, being able to accurately collect this data via UAVs will enable researchers to more accurately connect the impact of environmental changes to changes in the dolphin population. 

The link to the original article published on the University of Aberdeen's website can be found here.