A male donkey, called a jack, can injure or kill a baby donkey. This isn’t guaranteed behavior, but it’s a well-documented risk that donkey owners need to take seriously. Intact (uncastrated) male donkeys are the primary concern, and the danger is highest when the foal is not the jack’s own offspring or when the jack has been separated from the mare and foal for an extended period.
Why Jacks Can Be Dangerous to Foals
Intact male donkeys are driven by strong territorial and reproductive instincts. A jack may view a foal as a competitor, a threat to his position, or simply as an unfamiliar animal in his space. Unlike mares, jacks don’t have the hormonal bonding response that triggers protective behavior toward newborns. Their default reaction to a small, unfamiliar animal can range from indifference to outright aggression.
The aggression typically takes the form of biting, striking with the front hooves, or picking the foal up by the neck and throwing it. Donkeys are remarkably strong animals, and even a single strike or bite can be fatal to a newborn foal weighing only 20 to 30 pounds. The foal’s small size and inability to escape makes these encounters particularly dangerous in the first days and weeks of life.
When the Risk Is Highest
Several situations increase the likelihood of a jack harming a foal:
- Unrelated foals. Jacks are more likely to be aggressive toward foals that aren’t their own. This mirrors behavior seen in wild equids and other species where males may attack offspring sired by a rival.
- Separation and reintroduction. Even if the jack sired the foal, being separated from the mare and foal for a period of time and then reintroduced can trigger aggression. The jack may no longer recognize the foal or the mare-foal bond.
- First-time fathers. Jacks with no prior experience around foals are unpredictable. They haven’t learned to tolerate the foal’s presence.
- Confined spaces. In small pens or stalls where the mare can’t position herself between the jack and the foal, the risk of injury rises sharply.
Some individual jacks are calm and tolerant around foals, including foals that aren’t their own. But there’s no reliable way to predict this in advance. The consequences of guessing wrong are severe enough that most experienced donkey breeders treat every jack as a potential threat to foals until proven otherwise.
Geldings Are Safer, but Not Risk-Free
Castrated male donkeys (geldings) are significantly less aggressive than intact jacks. Removing the testes eliminates the testosterone-driven territorial and reproductive behavior that makes jacks dangerous. Most geldings coexist peacefully with mares and foals, and many donkey owners keep geldings in mixed herds without incident.
That said, geldings aren’t completely without risk. A recently castrated donkey can retain hormonal behavior for weeks or even months after the procedure. And any large animal can accidentally injure a fragile newborn through rough play or careless movement, even without aggressive intent. The safest approach is still to keep geldings separated from very young foals during the first couple of weeks, then introduce them gradually with supervision.
How to Keep Foals Safe
The most important step is physical separation. Jacks should never have direct access to newborn foals. This means solid fencing, not just a single rail or electric wire that a determined donkey could breach. For foal-safe enclosures, mesh fencing should use openings no larger than 2 by 4 inches and stand at least 54 inches high. If you’re using 48-inch mesh, add a top rail. Rail fencing works well but needs spacing of no more than 9 inches between rails to prevent a foal from slipping through gaps.
Give the mare and foal their own paddock for at least the first two weeks. A space of roughly 100 by 100 feet provides enough room for the foal to move and play without building up dangerous speed. Having calm, non-threatening animals in adjacent paddocks can actually help the mare feel more secure during this period, as donkeys are social animals that stress when completely isolated.
If you plan to eventually house the jack with the mare and foal, wait until the foal is old enough to move quickly and the mare is confident in protecting it. Introductions should happen in a large, open area where the mare has room to keep the foal away from the jack, and you should be present the entire time with a way to separate the animals if the jack shows any signs of aggression: pinned ears, lunging, bared teeth, or attempts to bite.
What the Mare Does to Protect Her Foal
Donkey mares are fiercely protective mothers. A mare will position herself between her foal and any perceived threat, and she won’t hesitate to kick or bite a jack that gets too close. In open pasture with plenty of space, an experienced mare can often defend her foal effectively. But in tight quarters or against a particularly aggressive jack, even a determined mare may not be able to prevent injury.
Relying on the mare as the sole line of defense is a gamble. Mares that are exhausted from a difficult birth, first-time mothers unsure of their protective role, or mares that are physically smaller than the jack are all at a disadvantage. Proper fencing and management are far more reliable than hoping the mare can handle the situation on her own.