Time-dependent memory and individual variation in Arctic brown bears (Ursus arctos)

Abstract

Background Animal movement modelling provides unique insight about how animals perceive their landscape and how this perception may influence space use. When coupled with data describing an animal’s environment, ecologists can fit statistical models to location data to describe how spatial memory informs movement. Methods We performed such an analysis on a population of brown bears (Ursus arctos) in the Canadian Arctic using a model incorporating time-dependent spatial memory patterns. Brown bear populations in the Arctic lie on the periphery of the species’ range, and as a result endure harsh environmental conditions. In this kind of environment, effective use of memory to inform movement strategies could spell the difference between survival and mortality. Results The model we fit tests four alternate hypotheses (some incorporating memory; some not) against each other, and we found a high degree of individual variation in how brown bears used memory. We found that 71% (15 of 21) of the bears used complex, time-dependent spatial memory to inform their movement decisions. Conclusions These results, coupled with existing knowledge on individual variation in the population, highlight the diversity of foraging strategies for Arctic brown bears while also displaying the inference that can be drawn from this innovative movement model.

Reinforced diffusions as models of memory-mediated animal movement

“…Explorations of such ideas could proceed mathematically by modifying the memory functional so that it was discontinuous with non-zero values only in some vicinity of each landmark. Another option would be to integrate reinforced diffusion models with parameter estimation approaches recently developed to gauge the importance of memory in a ‘time since last visit’ framework (see [52] for a case study involving seasonal movement of grizzly bears). Movement data are typically collected in discrete intervals (e.g.…”

Bridging human mobility to animal activity

“…It is very likely that such a strategy involves cognitive capabilities, because remembering both the location (spatial memory, 48) and the timing of the risk (temporal memory) is essential for bears to move in a human-dominated landscape of fear. Memory has already been proved to be fundamental for bears foraging activities (49), as well as for other species with much contrasted biology (roe deer, 50; chimpanzees, 51) and for flexibly adjusting their activity rhythm to human presence (chimpanzees: 52, 53). Coupling spatio-temporal dynamicity of human disturbance with memory-mediated behavioral responses by wildlife remains a fertile terrain of research for a better understanding on the effects of anthropogenic impacts on animal behavior and, eventually, population fate.…”

Simultaneous estimation of the temporal and spatial extent of animal migration using step lengths and turning angles

“…Brown bears in the Canadian Arctic are unique in comparison to their conspecifics worldwide, exhibiting many adaptations to harsh environmental conditions [ 23 ]. Brown bears are not considered migratory, but bears living in the Mackenzie River Delta region of northern Canada display annual home range shifts [ 25 ], and some perform temporally oriented navigations to food resources visited a year prior [ 88 ]. We used brown bear movement data from the Mackenzie Delta to evaluate if our model would identify any migratory patterns in what biologists view as a non-migratory species.…”