Dolphins woo their mates with weeds and rocks

Amazon River dolphins use lumps of water weed, sticks or large pieces of rocks to impress their mates and establish territory. The ones who display them father the most off spring according to researchers.

Professor Tony Martin of St. Andrew University was exploring the Amazon basin in 2003, when he accidentally saw a dolphin in the Amazon River carrying a lump of wood in its mouth. Initially he ignored it but then a few hours later he came across the same behavior again. Then he decided there must be some connection and that led to this study.

Martin and his team recorded the data of the dolphins’ behaviors for a number of years and noticed about 57 instances of this display, a majority of them by adult males. The animals picked up sticks, lumps of grass from the river bed, rocks and in one case it was found showcasing a turtle.

Dr. Martin told National News about this unique behavior found nowhere else:

Dolphins will pick up thinks such as sticks and rocks from the river bed and slowly rise up out of the water holding them in their mouths while twisting on their axis…It is far more sophisticated and appears to be handed down the generations because we have seen younger male adults apparently learning from their masters…Just like men use Ferraris, gold chains and bunches of flowers to attract females, dolphins use sticks, rocks and lumps of clay to convey the same message."

Since the rivers are full of mud, it was difficult for them to observe under the river surface. But whenever they had a chance to observe they recorded the behavior.

The observations found that the biggest dolphin males carry the heaviest objects and they are the ones which father the most offspring according to Martin.

Dr Martin added:

Contrary to our earlier assumption, the context of this behavior indicates that its function is sociosexual display, not play.

The Indian Ocean bottlenose dolphin has been seen using marine sponges during foraging, but this is the first time an aquatic mammal has been seen using objects in social display. The behavior is rare in mammals, but more common in birds.

Martin is however worried about the dolphin population. The local fishermen are killing the dolphins in large numbers. Martin said the dolphin population has reduced by 50 percent during the last 5 years.