The Great Prey Size Debate
by: Jason Ball
The size of prey items is a regular controversy amongst reptile keepers. Following the rule of thumb that prey items should be no larger than the space between a bearded dragon's eyes in order to avoid impaction. While the rule of thumb is a bearded dragon mainstay, some experienced keepers do not follow it and still raise bearded dragons to old age.
Despite successes both following and ignoring the rule of thumb, prey size is not an issue of mere preference.
Let's examine some justifications for offering large prey items before reviewing the benefits of following the rule of thumb.
Common Justifications for Offering Large Items
"Wild bearded dragons regularly eat large prey items."
You do not have a wild bearded dragon! OK, maybe if you live in Australia and acquired a wild animal there. Aside from that, bearded dragons have not been exported from the Australia for decades. Captive dragons pass down their genes based on human decisions about appearance, temperament, trends in the pet market or limitations in resources and accidents.
Even the majority of wild bearded dragons whose genes are passed on from parents who survived to adulthood will themselves die before reaching sexual maturity for reasons impossible and inappropriate to replicate. Most keepers would not intentionally expose their pets to chaotic shifts in weather, parasites, predation, or toxic plants and animals. You can't know if your dragon has the genetic "right stuff" for wild survival and you should not try to find out.
Wild bearded dragons die from eating inappropriate prey items (toxic, sharp, indigestible, or too large). Scarcity of food provides the need for wild bearded dragons to eat what is offered, when it's offered, lest they risk starving or slowing their growth rate thereby limiting their ability to compete. Captive bearded dragons will eat brightly colored toys or other indigestible items and die as a result. Regular availability of safe, healthy food and stable conditions that allow for digestion is one of the great advantages that captive bearded dragons enjoy.
No husbandry practice should be solely justified by "well it happens in the wild." Your home and the enclosure you keep your pet in is not "the wild" and you are not Mother Nature. If something happens in the wild, there should be a concrete reason why replicating it benefits your pet.
"Here's a video of captive bearded dragons eating some large things. See, they can eat big things" AND "I offer my bearded dragon large items so the rule of thumb is wrong"
Experienced keepers who follow prey size rule of thumb do not make the claim that "any and all violations will result in impaction and death." Moreover, the rule of thumb is not based on the
claim that bearded dragons can't fit prey into their bodies - rather what can happen when they try to squeeze large prey out.
Incidents of impaction are just as real as video footage of adult dragons that have been eating large prey throughout their lives, even if less common. Reports of impaction are not myths, not made up, not a conspiracy.
Simply pointing to the fact that impaction may be rare to dismiss incidents of impaction, almost as if they don't even happen, proves nothing and encourages inexperienced keepers to ignore the actual reasons why the rule of thumb does exist.
"If husbandry is correct, large prey items are no problem."
It is common to hear reptile keepers say "If husbandry is correct..." and these statements should be taken as a caution to be vigilant about conditions before engaging in a given practice. On this issue, however, the statement misses the point: the rule of thumb exists precisely because husbandry is not correct 100% of the time for the majority of keepers, and smaller food items can be passed safely even if not digested or only partially digested.
It is indisputably better to discover something is amiss by discovering a safely passed undigested small dubia roach in your pet's feces then it is to discover an impacted bearded dragon with a rotting mouse in its stomach.
"Bearded dragons have teeth and turn big items into small items" AND "The large version of a prey item is made of the same stuff as the small, if they can digest one they can digest the other."
While bearded dragons have teeth, they are just as likely to swallow prey whole as they are to bite through prey in the process of moving them down their throats.
Additionally, bearded dragons have weaker digestive enzymes than many other species of reptiles. Large pieces of chitin, larger bones means larger indigestible items have to make it through their bodies.
It is empirically wrong to claim that bearded dragons always break large prey items apart with their teeth and that if they can eat the small version of the thing they can eat the large version as well.
Why Do Keepers Offer Large Prey Items?
There are three primary reasons why keepers offer large prey items:
1. A keeper assumes that since they have offered large prey items in the past with no negative consequences that this is evidence that their practices are sound, that they will continue to be sound, and they can rest easy because bad things only happen to bad keepers.
2. A keeper is attracted to the spectacle of their predatory animal killing and eating another large animal. The benefit to the bearded dragon is an after-thought at best. The keeper may even upload footage to the internet displaying their dragons eating large things set to "bad ass" music to emphasize the "bad ass" nature of their "bad ass" predator. The dragon takes all the risk to reward a human audience with a show.
3. A keeper is experienced and vigilant in the maintenance and provision of ideal thermoregulatory conditions and correct in determining that providing large prey at a given time is reasonably safe. The keeper may believe (rightly or wrongly) that varying sizes in prey provides a source of additional stimulation for their bearded dragon.
Reasons to Follow the Rule of Thumb
Rule of thumb is a risk management strategy designed to simplify practices in a way that makes our mistakes less costly for our pets. Even after keeping reptiles for over twenty years, I still make mistakes. No keeper, despite their level of experience, is immune from mistakes.
Every once in a while I will be busy and distracted by daily tasks, not notice the time, and not realize that I've fed my reptiles too close to lights out until an undigested insect appears in the feces of my pet the next day.
Sometimes the power goes out and I don't always have the option of providing an alternate heat source. I may even be at work and only discover the outage when I come home and the digital clocks are blinking "12:00."
When these things happen, I am glad I follow the rule of thumb.
Not every keeper carries a heat bulb that can be quickly replaced in the event of a burnout. Not every keeper is even home when a burnout occurs. When a bulb goes out, it is better to have small items in your pet's stomach that can be easily passed if undigested.
Less experience keepers may not notice gradual shifts in enclosure conditions. They are more likely to feed at inappropriate times or handle their bearded dragons for too long a period after feeding. They may not account for the way shifts in ambient home temperature can change enclosure temperatures. They may be using unreliable and cheap thermometers that are common in pet stores and may be ignorant of their own ignorance.
Mistakes happen and the learning curve is real. Bearded dragons often won't show signs of improper conditions or poor health until a serious problem like impaction occurs. Learning to read the subtle cues of bearded dragon to behavior takes a lot of time and experience, and for many bearded dragon keepers their current pet is their first reptile. Impaction and the possibility of nerve damage, paralysis, death, and expensive veterinary bills is a high price to pay for a mistake. The rule of thumb exists to make sure our bearded dragons don't pay for our mistakes with their lives.