My contribution will be general, as I am a biologist and do not know the particulars of the engineering field. A PhD is a degree earned when you establish you have mastered a portion of what is known in a field, and then you work to discover something more, something unknown to anyone else. It can be a long process, first to earn your bachelors degree, maybe a masters degree, and then several years (between 4 and 7 probably) to earn the PhD. In doing so, you learn about your subject and about the questions that are currently unanswered (you must be very curious!) as well as how to write grants, how to mentor younger students, how to work whatever equipment is useful in your field (that is my favorite part). There are many benefits to having a PhD, including good jobs (sometimes), travel (to conferences and collaborations and field sites), and occasionally you get well paid for it :) It's probably easier to get well paid in engineering than in animal behavior, but the critical thing is that you need to be passionate about what you choose to study. It is a LONG road if you are not invested, and if you don't like it, it can limit the jobs you are eligible for. So my recommendation is to do undergraduate research (the sooner the better!!!) and ask questions of the grad students working toward their PhD. If you love what you do, go for it! If you are not sure it is for you, there are lots are jobs that do not require a PhD, which can be very satisfying and well compensated as well.