Análise da influência comportamental e ambiental na regulação térmica de botos-cinza utilizando modelos mistos

Abstract

Thermoregulation in aquatic mammals involves physiological, anatomical, and behavioral processes that contribute to heat conservation and dissipation in environments characterized by high rates of thermal exchange. In this study, the apparent temperature of Guiana dolphins (Sotalia guianensis) inhabiting an estuarine environment was analyzed using thermographic data associated with environmental, behavioral, and body-region variables. The dataset had a hierarchical and unbalanced structure, with repeated observations for the same individuals, which motivated the use of mixed-effects models with a random intercept. Initially, univariate and bivariate descriptive analyses were conducted to characterize the distribution of apparent temperature and identify patterns associated with water surface temperature, season, time of day, behavior, and body region. Gaussian and Gamma formulations were then compared, and the Gaussian mixed-effects model was selected as the reference model based on information criteria. Residual diagnostics indicated that the relationship between water temperature and apparent temperature was not adequately represented by a strictly linear term; therefore, the final model included polynomial terms up to the third degree for centered water temperature. The results indicated a strong influence of water surface temperature and seasonality on apparent temperature, as well as effects associated with behavior and the interaction between time of day and season. Sensitivity analyses, including nonparametric bootstrap resampling at the individual level, supported the stability of the main effects, although some contrasts among body regions showed greater uncertainty due to the unbalanced sample sizes. It is concluded that mixed-effects models provide an appropriate framework for analyzing thermographic data with a hierarchical structure, allowing environmental, behavioral, and individual factors to be jointly incorporated into the assessment of apparent thermal variation in Guiana dolphins.