Baa !

Sydney, Oct 3 (IANS) Sheep may have a reputation for being dumb, but when it involves recognising their own or their friends and foes, they have excellent memories.

Graeme Martin, professor at the University of Western Australia School for Animal Biology, says sheep are able to memorise the faces of up to 50 sheep and recognise them two years later.

Sheep use this capacity for long-term face recognition to distinguish between flocks and learn which sheep are friendly and which are aggressive - this helps sheep position themselves within their flock's dominance hierarchy.

More so than humans, the olfactory sense of sheep - particularly in ewes - is extremely developed and is the primary mechanism used by ewes to recognise their young, according to a Western Australia statement.

Ewes identify their young through a odour which is produced within the placenta and contained in the amniotic fluid in which the newborn is drenched.

The odour of the amniotic fluid is highly attractive to ewes only for the first two hours after birth and it is within this timeframe that ewes memorise their offspring's scent and are thus able to identify which lambs they allow to drink milk from their udders.

The lambs themselves remember their mothers because the colostrum they drink causes their stomach to fill with milk and stretch - this bodily sensation intensified by the warmth of the udder is stored in the lamb's memory.

Colostrum is yellow and thicker than normal ewe milk and is produced 48 hours immediately after the birth of a lamb. A new-born lamb must receive colostrum within 18 hours of birth, otherwise it has only a 50:50 chance of survival.

The colostrum along with the chemicals released from the ewe's teat become associated with the smell of their mother and the lamb remembers that particular ewe as the one from which food is provided.