def extract_mean_ci_score(rec):
    """
    

    Parameters
    ----------
    rec : dict
        Audio recording record.

    Returns
    -------
    Mean cacaophony index as float or -1 if it could not be found.

    """
    
    ci = -1.0
    
    try:
        caco_id = rec['additionalMetadata']['analysis']['cacophony_index']
        if len(caco_id) > 1 :
            ci = caco_id[0]['index_percent'] + caco_id[1]['index_percent'] 
            ci = ci/200.0  # convert to fraction and calculate mean
    except:
        pass
    
            
    return ci