What are different vahanas of Goddess Durga, what do they signify?

It's believed that every year, Goddess Durga arrives on Earth on different 'vahanas (vehicles)' that signify good/bad times. She has five vehicles- lion, elephant, horse, boat and palanquin. This year the Goddess is said to have arrived in a palanquin (palki) and it's not considered auspicious as it signifies increased violence and pandemics. Elephant and boat are considered very auspicious.