I found the relevant research: https://www.pnas.org/doi/pdf/10.1073/pnas.0803650105

> Furthermore, there was no correlation between the position of roe deer and the time of day when the observation took place, meaning that the position of the sun had no influence on deer orientation.

Although I'm not sure how credible this information is given that they studied google images where who knows what time of day they are taking images at. Maybe there was a correlation.