Dolphins Research

Dolphins in Central Peruvian Coast Dolphin Photo-Identification Project

First, of course, you need to take a picture. Dorsal fin photographs are taken from small research vessels with 35 mm cameras using color film or color slides.

Laboratory photo-analysis begins with the initial sorting and identification of a collection of negatives from a photographic survey. Only high quality photographs of distinctive dorsal fin notch patterns are included for analysis. These negatives are then scanned with a semiprofessional slide- and negative scanner. The name of each photo-file contains the location and date of the encounter.

The scanned images are then sorted into folders for the following categories:

A Dorsal Ratio (DR) is then calculated for all fins with 2 or more notches. The dorsal ratio is the distance b between the two largest notches A (above) and B (bottom) in the trailing edge of the fin, divided by the distance a from the lower notch B to the tip of the dorsal fin.

DR = b/a

As a relative measure the Dorsal Ratio is unaffected by the size of the fin when photographed, enlarged, or even under moderate cases of parallax, yielding a scale invariant parameter.

The disadvantage of the Dorsal Ratio is that it can only be calculated for fins with two or more nicks. In fins without nicks or other distinctive features like scratches or pigmentation and for all fins with out nicks taken against the sun, the shape of the fin becomes the most important feature to distinguish.

As the number of dolphins identified within a population increases, the physical process of "matching" individuals becomes labor intensive, and the probability of making errors increases significantly. Each new photograph obtained in the field must be compared to all previously cataloged photographs, a task requiring substantial effort and skill. Mundo Azul applies computer-based image recognition software (DARWIN) in order to improve the efficiency of the matching process and additionally has created its own comparative method in order to reduce misinterpretation.

This is a computer vision system that facilitates the comparison of digital images of the dorsal fins of new dolphins with a database of previously identified dolphin fins. If no match can be identified, we do compare the new fin with all identified fins manually. If this final check does not result in any match, the new fin is considered belonging to a new dolphin and is included in the data bases and in this Identification catalogue.

From all this it can be seen that the business of photo-identifying dolphins is time consuming and complicated. Nevertheless the result provides and valuable basic tool for any non-invasive ecological research of dolphins.

While photo-identifying dolphins' researchers also take notes of total group size observed and about the behaviors displayed by the dolphins. This research will also support the development of whale and dolphin watching guidelines assuring that no negative impacts are caused by the human activity.

Mundo Azuls photo-identification project aims to cover the entire area of the central Peruvian Coast between Chimbote and Paracas (approximately 700 km) during the next few years. This year we started with two first research areas: the coastline between Lima and Asia Island and the coastline north of the Paracas National Reserve.

You are able to take active part and financially support our research program by:

Adopting a dolphin
Give a name to your favorite dolphin
Become a dolphin conservation volunteer
Go dolphin watching