I don't work in retail but I'd like to ask how you find it. My employment agent said one of the jobs she might get me would be retail. So, do you find it to be enjoyable, horrible, tolerable? Do you work the checkout or in the stock room? If the former, do you find it hard to interact with customers? Do they expect you to appear NT or "bubbly" all the time? Do they expect you to be friendly to people you don't care about or smile when you're not happy?
Also, don't give up on zoology. I hear Google are working on a driverless car. Maybe if they made a driverless off road vehicle you could be a park ranger.