Protecting and Prosecuting Your Copyrights
You always have the option of doing nothing. You may not care that the non-profit wolf society is using one of your wolf images. You may only want the society to give you proper credit. If so, write the society a letter officially giving it the right to use the image (be sure to designate the parameters of that use), but insist that you get a photo credit with a copyright notice. Also ask the society to add your website name. You may get additional work from the society or others.
Your most aggressive option is to pursue your legal remedies by filing suit. Remember, your copyright must have been registered with the Copyright Office. To file suit, get an attorney to help you because the legal procedures are complicated.
Usually, your most profitable and easiest road is the middle one. Since you have your proof of registration, you need only to contact the infringer to put him on notice. If the infringer is a business-savvy person, he will know that he's in trouble. If he doesn't understand the trouble he's in, he will as soon as he talks with his attorney. He will want to avoid the legal fees that will be imposed both by his and your attorney. So make your demand for statutory damages by letter and you will get your just rewards much more quickly.
The weight of your demand letter is dramatically increased if it comes from an attorney. The infringer will recognize that you mean business and are prepared to go forward with suit if the infringer doesn't respond appropriately.
Protecting and prosecuting your copyrights goes hand in hand. To best protect your rights, what you do after your copyright is infringed is as important as what you do beforehand.
Take my advice; get professional help.