Edit to add: I had 3 pretty decent coyotes I killed earlier this week laying in the yard out here at work. I just measured height to shoulder on them. 18", 18", and 19". The last one was a good size male.
Kirsh has very valid advice in his post above.
Once upon a time, a long time ago, I found a file on the internet that would print out a full size coyote silhouette using 11 sheets of paper. I still have that file saved somewhere on a thumb drive, but not sure where. I printed it and taped it together. I compared it to sizes of coyotes around here and found it to be very accurate. I used the taped together paper to cut some one piece carboard targets.
I did something else too. The place I work at we build water and foam tanks for fire trucks. Basically we take big sheets of plastic and cut and weld them together to make tanks. I took a piece of 3/8" thick copolymer plastic, cut out a life size coyote, and mounted it to a steel stand. It has a 4" steel swinging plate in the vital area. I named it Jezebel.
I have used Jezebel a lot practicing my shooting and teaching my young daughter how to shoot and hold on a coyote. I also have a decent size field we own across the street from our house. I use Jezebel out there some too, testing reticle subtensions against known distances, in both thermal and daylight scopes. That has helped me a bunch. My Thermion XQ50 has a particular reticle that matches up against known distances very well.
