Fig. 4

Number of peer-reviewed scientific papers on cortisol levels in Cervidae and Bovidae, between 1979 and 2024. The fitted line shows the expected response of a 3rd level polynomial autoregressive Poisson model; the shaded area indicates the 95% confidence level; the dashed line separates the first two decades from the last two decades (midyear 2000 was used as a midpoint)