hackles up: erizado

To get your/their hackles up refers metaphorically to the literal act many mammals do when threatened, of raising their shoulders to protect their neck. On dogs it's particularly clear, as their hairs there stand up. I understand it to refer to how we can automatically puff up to defend ourselves,
without it being a thought out response. Gracias a Diana Ojeda for this fabulous suggestion of a Spanish equivalent. Nos erizamos, we get spiny like a sea urchin.