Sue McDonnell, PhD, Certified AAB

Sue M. McDonnell, PhD, is a certified applied animal behaviorist and the founding head of the equine behavior program at the University of Pennsylvania's School of Veterinary Medicine. She is also the author of numerous books and articles about horse behavior and management.

Articles by Sue McDonnell

Natural Stallion Behavior

Q: I own a Lusitano stallion that has been stabled at the same barn for four years. Within the past four to six months, he has shown increasingly aggressive displays toward two stallions that walk in front of his stall. He kicks an Read More

Training a One-Eyed Horse

Working with visually impaired horses has been mostly with those that lost vision as an adult, after they had been trained. And, in general, the horses I have worked with directly have impressed me with how adaptable they have been with losing vision Read More

Potty Problems

I have a serious problem with my 3-year-old Warmblood filly I recently purchased. I had her extensively vette Read More

Raising a Stud Colt

I have bred my first colt this year and thus far have followed handling practices we have used on our previous two filly foals with great success. We have a beautiful Welsh Section C colt who is unafraid of most things, is very people friendly, wil Read More

Becoming a Behaviorist


Veterinarians and nonveterinarians can pursue this growing field.

What does it require to pursue a career as an animal behavioral consultant? I've heard the question a number of times. Read More

Pawing Problem

Is there a humane method for breaking my 4-year-old Missouri Fox Trotter mare from pawing? Read More

Calming Mother Nature

Q: I have a 7-year-old Quarter Horse mare that is quite "the mare." When she is around the geldings (even if they are in different pastures) and in season, she will put her butt up to the fence and wink (the vulvar lips), etc. She Read More

Crossing Bridges

Q: My horse Dakota is not wanting to cross a wood bridge. I walked him across plywood for about three days and had no trouble. Then I rode back to the bridge, and he wouldn't have anything to do with it. Dakota goes crazy, start Read More

Bad-Asses

Q: Some friends and I were discussing the heightened "territorial" aspects of long-ears (mules and donkeys) vs. horses. While I've had horses that were bred and raised out West that were more protective against "predators" such Read More

Best Breeding Approach

Q: For a horse reproduction project in my equine seminar course, I was trying to find video clips of horses breeding. Well, there were many on YouTube, and it took awhile to find the decent ones. But once I found some that were Read More

Anabolic Steroid Effects

A colleague, Larry Soma, VMD, is an anesthesiologist/pharmacologist who conducts research for the Thoroughbred and Standardbred horse racing commissions in Pennsylvania. Basically, his lab develops and validates testing methods for detection of Read More

Oral Attacks

Q: We have an Arabian who, for some reason, has taken to chewing on the horse trailer when we are at a show. He has never done this before. He started gnawing on the fender. We tied him away from the fender, and he started chewing Read More

Defecation Behavior

Q: Why do some horses at our barn poop in the same place every time, then some others seem to go anywhere?


A: We certainly don't know the full answer, but I can tell you what we do Read More

Smart Mare, Smarter Vet

I am doing some positive reinforcement-based behavior modification for needle shyness in a draft broodmare. This mare is just too big and strong for the old-fashioned restraint methods of working around the problem. She has quite a repertoire of Read More

Unsettled Slumber

My horse might have sleeping problems. I have seen him almost fall over trying to sleep. Is this normal? Read More

Positive Reinforcement

Can you explain the concept of positive reinforcement training? What exactly does it mean? I was recently in New Zealand, where I was with a group that seems "converted" to what they call "all-positive training." It sounds like good old-fashioned Read More

In Living Color

Has it been sorted out whether horses can see in color? Read More

A Late Start

I have a 5-month-old colt that was never halter broken. According to the breeder, it appeared that at one point a halter had been put on him, and the experience was traumatic for him.

Since he came home with me, I have been spending time with Read More

Let Nature Work it Out (Shy Stud Colt)

I desperately need some advice about my new colt. He is a 2½-year-old Gypsy Cob named Geordie. He was raised in a herd, then separated as a yearling colt, and ran with a colt herd until I imported him to Australia. He is naturally gentle and not Read More

Herd Instincts: Sparring

My horse was seen biting another horse in the throat. They were up on their hind legs supposedly playing when all of a sudden my horse made a very unusual move, according to the witness, and bit the other horse in the throat. The other horse ran an Read More

Keeping Stallions Focused

I'm a veterinary student from the United Kingdom and have been riding with a stud farm veterinarian in America going from place to place. I am trying to figure out the art of handling stallions for breeding. Can you please enlighten me on the Read More

Orphans and Families

I wanted to share with you a horse behavior experience that I had after I lost my best broodmare. "Janet" died overnight on May 30, 2006, at age 22. She looked remarkably great for her age, so we were breeding her back to our stallion. She was Read More

Stallion-like Behaviors

I castrated my gelding at 17 months (November 2005). A veterinarian with 35 years of experience showed me the epididymides. My mare had her first heat cycle in March (2006). He mounted and bred her as if he was a stallion. Every time she is in heat Read More

Gelding Herding Mares

Is it possible to change a horse's aggressive behavior? Specifically, I am wondering if there is any information relating to reinforcement contingencies and transfer of learning from a "human-handled" situation to a free-running setting?

The Read More

Rearing and Flipping

We have a Quarter Horse mare whose mother was a bad flipper in the starting gate. She has two half-brothers that were also bad in the gate. All of these offspring were trained by different individuals. This spring, she had a filly that tried to fli Read More