PhD defence Manh Cuong Ngo
Title: Modelling Marine Mammal Reactions
Abstract:
This PhD thesis consists of some works contributing to the field of ecology modelling for Arctic whales. Arctic cetaceans are facing challenges due to human activities, like changes of habitats, scarcity of prey due to fisheries and warmer water, pollution, anthropogenic noise, etc. Therefore, understanding their behavior is very important for conservation
management plans. Using several long-term datasets collected by tagging of individual animals, we apply different statistical and machine learning methods to understand the behavior of two endemic Arctic whales, bowhead whales and narwhals. We present new hidden Markov models, taking into account the correlation between maximum depth
and dive duration, to understand the diving behavior of a narwhal using dive data of 83 days. Our models relax the contemporaneous conditional independence assumption, which is often used in ecological modelling, leading to improvement of the model fit. We also establish machine learning models using deep learning, predicting the prey capture attempts from accelerometer data, without the need to use resource-heavy acoustic data.
Our models outperform the classical machine learning method random forest, and the statistical method logistic regression. Our results show that narwhals do not make instant change in acceleration which is often used as a proxy for prey captures in several other cetacean species. Finally, we propose Tweedie generalized linear models to understand the distribution of bowhead whales under warming water in the Arctic area. We exploit
GPU computing to boost up the model performance, thus, allowing to fit to a higher resolution of environmental data and daily whale positions.
Supervisor: Professor Susanne Ditlevsen, University of Copenhagen
Co-supervisor: Professor Mads Peter Heide-Jørgensen, Greenland Institute of Natural Resource
Assessment committee:
Professor Helle Sørensen (chair)
University of Copenhagen
Professor Roland Langrock
University of Bielefeld
Researcher Jacob Nabe-Nielsen
Aarhus University