115 Years Is Long Enough

Galpagos turtles can live for 150 years.  Two of them, Bibi and Poldi, have been partners for most of the 115 years they have been alive.  But now Bibi wants to call off the partnership.  She is so insistent on this point that she bit off part of Poldi's shell. Her keepers and other experts can't figure out why Bibi has gone from this

to this