TITLE:
Modelling Animal Activity as Curves: An Approach Using Wavelet-Based Functional Data Analysis
AUTHORS:
Barbara Henning, Airton Kist, Alusio Pinheiro, Rafael L. Camargo, Thiago M. Batista, Everardo M. Carneiro, Sérgio F. dos Reis
KEYWORDS:
Functional Analysis of Variance, High-Frequency Data, Temporal Activity Pattern, Shrinkage, Wavelet Thresholding
JOURNAL NAME:
Open Journal of Statistics,
Vol.7 No.2,
April
20,
2017
ABSTRACT: Temporal activity patterns in animals emerge from complex interactions between choices made by organisms as responses to biotic interactions and challenges posed by external factors. Temporal activity pattern is an inherently continuous process, even being recorded as a time series. The discreteness of the data set is clearly due to data-acquisition limitations rather than a true underlying discrete nature of the phenomenon itself. Therefore, curves are a natural representation for high-frequency data. Here, we fully model temporal activity data as curves integrating wavelets and functional data analysis, allowing for testing hypotheses based on curves rather than on scalar and vector-valued data. Temporal activity data were obtained experimentally for males and females of a small-bodied marsupial and modelled as wavelets with independent and identically distributed errors and dependent errors. The null hypothesis of no difference in temporal activity pattern between male and female curves was tested with functional analysis of variance (FANOVA). The null hypothesis was rejected by FANOVA and we discussed the differences in temporal activity pattern curves between males and females in terms of ecological and life-history attributes of the reference species. We also performed numerical analysis that shed light on the regularity properties of the wavelet bases used and the thresholding parameters.