The influence of eco-geographical variables on Whale Shark Movements
Real-time tracking of marine megafauna with “Wildlife Tracker v0.3”
Satellite tags are being placed on a wide array of animals for scientists to track their movements around the globe. Tags are placed on land animals like tortoises, birds, and polar bears, and on marine animals like sea turtles, sea lions, and sharks. By following the animals’ movements scientists can learn about their life history, which environmental factors drive their movements and to learn what areas are most important for their survival.
For this purpose, the Galapagos Whale Shark Project has been tracking whale sharks from the Galapagos Marine Reserve out into the open ocean. Satellite tags have improved greatly in their technology which now allows us to follow these individuals in near real-time and with high accuracy. However, tracking marine animals presents a larger challenge than tracking land animals. Our tags only report via satellites when the tag comes out of the water, in our case it’s when the whale sharks’ dorsal fins break the surface of the ocean, making it harder to predict where the animals were beneath the surface. Also, because we cannot visually track them as we can land animals, conservation efforts are more complicated.
Whale sharks have been categorized as an endangered species with a currently declining population due to anthropogenic threats such as vessel strikes, industrial fisheries, and climate change. Understanding what drives their movements is essential for us to be able to predict habitat use to better protect them.
The Galapagos Whale Shark Project tagged 8 Rhincodon typus individuals in August and September of 2021 and has been tracking them until February of this year. The individuals all left the protection of the Galapagos Marine Reserve. The seven adults traveled towards the continental shelf of Ecuador and Peru, whilst the juvenile headed south and then back around as can be seen in the following image.
The “Wildlife Tracker v0.3” is a geo-framework that is being developed under GIS4 wildlife movement analytics, it provides us a unique opportunity to overlay the tracks of these animals over environmental data layers to visually observe in near real-time what may be affecting the movement of the animals.
Whale sharks seem to be highly driven by water temperatures and food availability when looking at their movement patterns around the globe. Like one of our collaborating scientists likes to say:
“they are the labradors of the ocean, mainly food driven”
For this reason, we are using the platform to look directly at how sea surface temperatures and the changes brought along by current systems throughout the year determine their movements and where they might be during different seasons.
The “Wildlife Tracker” was able to retrieve near real-time visualization of the tracks thanks to its connection to live feeds of Argos satellite. The most homogenous track collected was from “Sky” a juvenile 5m long female whale shark. The next map animation, executed with the geo-framework, shows the trajectory of “Sky” coloured by monthly periods from August until February 24th, 2022.
Online demo: Sky and its trajectory
The sea surface temperature (SST) was added to the movements of “Sky” following the date of its last location recorded.
This near real-time approach helps monitor her movements and allows us to predict what may be influencing them; information which in turn can be used for conservation purposes.
Note: The next map animation and demo show only the SSTs on February 24th, the last recorded location of “Sky” for demonstration purposes. However, the real application of wildlife tracker allows for direct correlation between date, time and location.
Online demo: Sky and SST
We are also using chlorophyll-a concentration data as a proxy for zooplankton productivity to see how their movements are related to food availability. The next map animation and demo represent her track, overlaid on the Chl-a concentrations of February 24th as well.
Online demo: Sky and Chl-a
These datasets were downloaded from Marine Copernicus Service and directly integrated into the program and thus display the most recent data collected for the variable of interest in the study region.
The world’s oceans are incredibly susceptible to climate change and are already being impacted with effects being noted such as rising water temperatures, ocean acidification, and alterations in ocean currents. Our changing oceans are already causing variations in the distribution and movements of marine animals. It is thus key for us to keep our eye on these deviations to properly implement mitigation strategies for the protection of this endangered species.
The “Wildlife Tracker” not only simplifies the data analysis processes for scientists and allows us to make predictions from real-time observations, but also allows us to use this data for environmental educations purposes, outreach, and fundraising since an image speaks a thousand words.
