Infer why it was "vitally necessary" to conceal that the animals were starving

It was a bitter winter. The stormy weather was followed by sleet and snow, and then by a hard frost which did not break till well into February. The animals carried on as best they could with the rebuilding of the windmill, well knowing that the outside world was watching them and that the envious human beings would rejoice and triumph if the mill were not finished on time.