Using drone photogrammetry to assess demographic parameters in small delphinid populations

Written by Fabien Vivier

Last month (Oct 2018) we visited the Pacific Whale Foundation on Maui to initiate our project focusing on estimating small free-ranging delphinid population’ demographic parameters.

The main objective of this trip was to trial the use of Unoccupied Aerial Vehicles (UAVs) or drones in collecting aerial images of groups of delphinids to estimate length measurements for to infer age structure amongst these populations. The long-term goal of this research is to estimate population growth and survival rates as indicators of health and status for small delphinids.

Aerial picture of two mother-calf pairs and a single individual pantropical spotted dolphins (Stenella attenuata)

While on Maui we also visited the Hawaiian Islands Humpback Whale National Marine Sanctuary where Lars presented a talk to the general public entitled Integrating innovative technologies to study baleen whales. We are thankful to the Sanctuary for hosting this event.

While on the water we encountered three different species: Bottlenose dolphins (Tursiops truncatus), Pantropical spotted dolphins (Stenella attenuata) and short-finned pilot whales (Globicephala macrorhynchus). Pantropical spotted dolphins are amongst the smallest delphinids (average adult length = 2.5 m), while bottlenose dolphins and short-finned pilot whales represent intermediate sized species (3-4 m and 6 m, respectively).

Large male short-finned pilot whale (Globicephala macrorhynchus) surfacing the pristine waters of Maui

During this trial, we collected several measurements for these three delphinid species at different altitudes (up to 70 m) to assess which altitudes give us the best measurements to perform our analysis.

Good weather conditions are critical for our research and have a major influence on our UAV research. As you can see in these pictures, pristine water, sunshine and no wind considerably improve data collection, hence improving measurements and outcomes.

Aerial view of a small group of pantropical spotted dolphins (Stenella attenuata)

Our Maui trial has provided us with some initial data that is informing our next step: testing the precision of UAV-derived length estimates with hands-on measurements of dolphins housed Sea Life Park, Oahu, Hawaii. Later on, we will return to measuring free-ranging delphinid populations to start the second part of our project: using UAVs to assess demographic parameters in small delphinid populations.

All research has been conducted under NMFS take permit 20311 issued to PIFSC and is compliant with Federal and State regulations as well as University of Hawaii IACUC protocols.