drupal 7 menu items calling load() hook several times

foo_menu(){
  $items=array();
  $items['foo'] = array(
    'page callback' => 'foo_list',
...
    'type' => MENU_LOCAL_TASK,
  );
  $items['foo/list'] = array(
    'type' => MENU_DEFAULT_LOCAL_TASK,
  );
  $items['foo/add'] = array(
    'page callback' => 'drupal_get_form',
    'page arguments' => array('foo_add_form'),
...
    'type' => MENU_LOCAL_TASK,
  );
  $items['foo/%bar/edit'] = array(
    'page callback' => 'drupal_get_form',
    'page arguments' => array('foo_edit_form',1, 2)
...
    'type' => MENU_LOCAL_TASK,
  );
  $items['foo/%bar/clone'] = array(
    'page callback' => 'drupal_get_form',
    'page arguments' => array('foo_edit_form',1, 2)
...
    'type' => MENU_LOCAL_TASK,
  );
  $items['foo/%bar/delete'] = array(
    'page callback' => 'drupal_get_form',
    'page arguments' => array('foo_edit_form',1, 2)
...
    'type' => MENU_LOCAL_TASK,
  );

  return $items;
}

foo_list($form, &$form_state) {...}
foo_add_form($form, &$form_state) {...}
foo_edit_form($form, &$form_state, $bar, $action){...}
bar_load($barname) {
  dpm($barname, 'this called several times and should return a bar-object');
  ...
  return $barobject;
}

Problem: bar_load() is called several times even when requesting foo, foo/list or foo/add as long as menu items including %bar exist.