def read_animals(filename):
    """
    Reads animal count file agreed upon at May 30, meeting.
    Must have 4 columns, and no header row.
    Columns are date, time, animal name, number seen.
    """
    f = open(filename, 'r')
    date = []
    time = []
    animal = []
    number = []
    
    # iterate over the file one line at a time
    for line in f:
        d, t, a, n = line.split()
        date.append(d)
        time.append(t)
        animal.append(a)
        number.append(int(n))
    return date, time, animal, number