Remote sensing of emperor penguin colony health and foraging success

• Applicant: Dr. Daniel Zitterbart
• Subject Area: Oceanography
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 443134677

Addressing the effects of human-induced changes on biodiversity is one of the most pressing scientific challenges we face today, and this is especially true for the accelerating changes occurring in marine environments. Investigating the effects of climate change on marine ecosystems, however, is both highly challenging and, despite its economic and societal priority, severely underfunded. While certain physical parameters (salinity, temperature, etc.) can be relatively easily and continuously measured by remote sensing, monitoring the ecosystem by oceanographic campaigns is logistically much more difficult. Of all marine environments, the fragile ecosystem of Antarctica is especially threatened. Thus, there is a recognized need to develop new methods to monitor oceanic ecosystem health, in particular the productivity of higher trophic levels, in and around Antarctica. An effective approach to investigate the effects of climate change on marine ecosystems is to monitor top-predator populations, such as seabirds. Top predators are highly sensitive bio-indicators as they are affected by a cascade of changes integrated along the food web. Emperor penguins, at the forefront of the impacts of climate warming, are a prime species for such studies, as they swim for thousands of kilometers while foraging, thus sampling a large oceanic area, while always returning to the same colony, where they can be measured. We recently showed that the huddling behavior of emperor penguins can be described as a phase transition from a fluid to a solid state. This transition depends sensitively on the apparent temperature that, like a windchill temperature for humans, is perceived by the penguins as a combination of ambient temperature, wind speed, solar radiation, and relative humidity. Emperor penguins change their huddling behavior in response to this perceived temperature and undergo a phase transition from "no huddling" to "huddling" at a particular transition temperature. This transition temperature depends foremost on the fat insulation of the animals. Here we propose to test the hypothesis that by continuously measuring the transition temperature of two emperor penguin colonies (at Atka Bay and Pointe Géology) throughout the year, we can estimate the average energy (fat) reserves of an entire penguin population at any given time point. Moreover, we will test the hypothesis that the baseline transition temperature (measured when the penguins arrive at the breeding site in late April after the hunting season) can be used to estimate the foraging success and hence the food supply of a large part of the southern ocean, as the foraging radius of Emperor penguins stretches for 300-500 km around the colony as measured by GPS-tracks.If our main hypothesis is confirmed, this would represent a milestone towards a remote sensing-based observation system for estimating the health of Emperor penguin colonies, without the need of potentially invasive human interventions.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1158: Infrastructure area - Antarctic Research with Comparative Investigations in Arctic Sea Ice Areas
• International Connection: Monaco
• Co-Investigator: Professor Dr. Ben Fabry
• Cooperation Partner: Dr. Celine Le Bohec