When photographing a dark subject, like this young porcupine, against a brighter background, the exposure can be tricky. The background may eclipse the subject -- in other words, it may be relatively bright and therefore draw attention away from the subject. Or, the dark areas of the foreground subject may lose detail in deep shadow. Your exposure may be fine, but it's the gain in contrast that's characteristic of digital sensors that is most likely the culprit. Be prepared to work on the image in post-processing. In other words, in Adobe Camera Raw or Lightroom, use the shadows slider to lighten the dark portions of the picture and the highlight slider to tone down light areas of the background. That's exactly what I did for this picture.