Ms Eszterhas used a long telephoto lens to photograph the mother and pup

'She did this so many times; it made me feel like a babysitter. It was adorable and it also really showed how vulnerable and trusting wild animals can be.'

There are almost 3,000 sea otters living along the California coast - all of which are descendants of a colony of 50 otters discovered in 1938.

Sea otters consume more than 100 different species, including crabs, mussels and even octopuses. 

Conservation efforts have boosted the population of sea otters worldwide, but the species is still classified as endangered by the International Union for Conservation of Nature.