Abstract :
[en] Most living beings move throughout their lives to meet all their needs and maximize their survival and the survival of their species. These movements take place on highly contrasting spatio-temporal scales, from the foraging of butterflies to the spectacular migration of Arctic terns (Sterna paradisaea). One of the major challenges of this the- sis is to better understand the relationships between physiology and movement, which are often governed by the environment in which individuals evolve. We have attempted to assess the main components of movement dynamics in the brown bear (Ursus arctos) population of Finland and Russian Karelia. These individuals are subject to external environmental factors, a combination of biotic and abiotic factors, as well as their physiological state, or internal state. We used the movement ecology paradigm of Nathan et al. (2008) to analyze the components that influence movement patterns within the home range, or during dispersal for subadults, for example. The factors behind movement can be multiple, such as the concentration of food for feeding related movements, the search for a partner for reproductive movements, or escape from a predator (in this case, human). This thesis uses telemetry data to analyze the movements of brown bears in their home ranges.
The brown bear is an interesting case study for two reasons. Firstly, although it has all the physical characteristics of a large carnivore (sharp canines, claws and a carnivorous digestive tract), it is an opportunistic omnivore. Their travel patterns and the study of their movements therefore merit attention. Secondly, brown bears can be extremely flexible in their primary diurnal activity patterns. They can be diurnal as well as crepuscular or nocturnal, depending on the conditions of their environment. In other words, habitat resources, human pressure and population density.
In this thesis, we focused on three themes that may impact on movement patterns. Firstly, we studied the behavior of this facultative carnivore through the prism of moonlight (variation in light intensity), (chapter 2). Indeed, when the moon is full, many strict carnivores such as cheetahs and ocelots see their hunting success increase. Their activity rates therefore increase with light intensity. Brown bears have a fruitrich diet and, consequently, the prey-predator relationships that drive carnivore dependence on moonlight appear to be weaker than in obligate carnivores.
Secondly, we studied feeding-related movements, and in particular movements in the vicinity of artificial feeding sites (chapter 3). This practice is frequently used for species conservation, to regulate human-wildlife conflicts or for tourism (ecotourism or hunting).
Finally, we investigated age-related differences in movement behavior and, more specifically, potential inter- and intra-individual variations between adult and subadult bears (chapter 4). The contribution of age to movement patterns seems irrelevant, as most observed movement patterns are mainly explained by season and body weight. We hypothesize that two mechanisms may lead subadults and adults to move in similar ways. Firstly, both need to hibernate and therefore need to store energy during hyperphagia. Secondly, although triggered by different factors, they both make erratic/long movements after hibernation, for dispersal (subadults) or mating (adults), which could help shape similar movement patterns. Different motivations could therefore be expressed by the same behavioral patterns, and equifinality (i.e. similarity of behavior) could be reinforced.
More generally, this study demonstrates the relevance of an ecophysiological approach to the study of movement. Chapter 5 closes the thesis with a general discussion of the factors influencing brown bear movements.
