def find_animals_groups(df):
    """given a dataframe, return animals and groups dataframes based on population of
    each row (> 1 == group)"""
    pop_sums = df[
        ["Population _Male", "Population _Female", "Population _Unknown"]
    ].sum(axis=1)
    groups = df[pop_sums > 1]
    animals = df[pop_sums == 1]
    return animals, groups