def surf_vol(length, girth):
    """Calculate the surface volume of an animal from its length and girth

    Args
    ----
    length: float or ndarray
        Length of animal (m)
    girth: float or ndarray
        Girth of animal (m)

    Returns
    -------
    surf:
        Surface area of animal (m^2)
    vol: float or ndarray
        Volume of animal (m^3)
    """
    import numpy
    a_r = 0.01 * girth / (2 * numpy.pi)
    stl_l = 0.01 * length
    c_r = stl_l / 2
    e = numpy.sqrt(1 - a_r ** 2 / c_r ** 2)
    surf = 2 * numpy.pi * a_r ** 2 + 2 * numpy.pi * (a_r * c_r / e
        ) * 1 / numpy.sin(e)
    vol = 4 / 3 * numpy.pi * a_r ** 2 * c_r
    return surf, vol
