Glider diet *has* been researched by professionals in the animal nutrition area, though interpreting it can be difficult and people tend to find faults in it that support their own cause, whatever that may be.
For example, during the discussion with Mr Rich from Wombaroo, one post here:
The Wombaroo High Protein Diet (Part One) (see bottom of post) lists four studies by professional animal nutritionists in his explanation of the approach Wombaroo takes to glider nutrition.
Some of the studies are old, some are partly on wild gliders, some of the studies are small, etc. etc. Pick your criticism, but I find it kind of strange folks who lack scientific training would feel justified criticizing studies created by people with the proper training to do this kind of work. The fact the study gets published means it was "peer reviewed", meaning a bunch of other scientists with the proper background reviewed the material and found it to be worthy.
It's probably also worth saying at this point that vets and animal nutritionists are different professions with different skill sets. Given a choice between what a vet says is a good diet, and what a nutritionist says is a good diet, it seems like the nutritionist would be the way to go.
But, while the statement "no studies have been done" is not correct, there is something to be said about hands on experience with diets, as Bourbon said above. If a diet has been around for 10 years, people get good results, and the diet does not directly defy what is generally known about animal nutrition, then it's hard to argue with.
Which leads us, seems to me, to the "tinkering" place, where people then take the foundation of a good diet and start messing around with it, because of personal preferences, because their gliders don't "like it” (um, do you feed your kids candy all the time because they like it?), because they want the diet to fit what they already buy for family, etc.
One of the best examples of this I think is the "day old chick" component of the original Taronga Zoo Diet, which includes the original Leadbeater's Mix.
Seems to me it's pretty hard to argue with a diet developed in a native zoo that has been taking care of gliders for years, especially when there is ongoing research by PhD students on the diet and health outcome of the gliders. Given the source, I find it hard to argue against this general approach as the best diet for gliders.
But then again, there's that "day old chick" problem - how many domestic households are going to feed a day old chick to their gliders once a week? How about fly pupae?
So what happens?
Domestic keepers asked around and substituted boiled chicken for day old chick.
And that's how these diets evolve.
I think the real question is this: what happens after 15 years of this evolution, when people keep substituting and substituting until the diets don't look anything like the originals? For example, the commonly used phrase "gliders are sap suckers" to defend certain diet and feeding approaches.
Folks, gliders do eat sap as a portion of the diet, when it’s is available. But these are the same animals that eat baby birds in the wild, were fed day old chicks in the zoo (makes sense if they eat baby birds, right?), and domestically eat mice if one wanders into their cage. Sap suckers? How did animal protein move from being a "staple" in the diet to a "treat"? Gliders are insectivores or omnivores, depending on who you ask. They’re clearly interested in eating a whole lot of different things. They’re not “sapivores”.
By the way, the Taronga Zoo Diet includes "dog kibble", and offering pelleted food is a standard practice in zoos, for a couple of reasons. Primarily, it’s because the food doesn’t spoil, so the animals can eat when they are hungry and not rely on some human to come around with the day old chick or the fly pupae. Gliders are free feeders and don’t have a “dinnertime” unless you teach them there’s only one time each day they can eat. Older gliders may not get up much during the day, but young gliders and especially breeding gliders will eat during the day as long as food is available.
Pellets also provide consistency in the diet, so if for some reason a glider is not getting the nutrients they need for what is available to eat (example: food stealing), they can always find these nutrients. Also, the pellets simply provide variety, and healthy alternative to whatever else is usually offered.
Which brings us to the idea of pellets as THE diet. Feeding pellets only, or “with a slice of apple for moisture”, is not a good idea either, for some of the same reasons mentioned above. Even if the “perfect pellet” existed, it would still be a bad idea to feed only pellets. Captive animals need stimulation, what they call in the zoos “enrichment”, and one of the best ways to provide enrichment is through diet. If you’ve ever seen a glider go for a mealie or a cricket, you know what I’m talking about – the excitement, the shear delight, the fun of it. Food as happiness, not just “staying alive” or surviving. Just because the glider doesn’t die when on a diet does not mean it’s a “good” diet.
So, on to specific pellets. I suppose one way to look at it is if it’s used in a zoo to feed gliders, and you believe the nutritionists in zoos are not in favor of abusing the animals they care for, that might be a good place to start. Reliable Protein and Mazuri mentioned above are zoo standards. Exotic Nutrition offers quite a few, and SunCoast offers two that are also used in zoos.
You can buy various brands at the big pet stores. Assuming those pet food companies are not trying to harm their customer’s pets, there must be some science behind those, I’d guess.
Then, comes down to what I mentioned in my first post above, personal preferences or beliefs, and many of these choices parallel the diet discussions in other animals and even humans. First up, do you want the pellet to have a lot of “fillers”, like corn? Or do you want the pellet to be mostly meat, animal protein? All the animal nutrition people we have worked with over the past 12 years say avoid the fillers, go for the animal protein. So both pellets we offer, one moist, the other hard, are based on animal protein.
Next, some people have a problem with pets consuming “meat by products”, as do some humans. The moist food SunCoast offers is made with pork byproducts, the hard food with human grade chicken. You decide.
Do you care about soy as a food, the potential for estrogen-related problems? Some people don’t want their pets eating soy, because they don’t want to eat it either. Decide.
Just to be clear, any of the pellet foods mentioned above that are routinely used in zoos are probably OK to use with your glider – the real issue is the nutrition they deliver, not what they are made from. For example, there are those that argue in the human world that vegetable protein in better for you, and for animals, than animal protein, even though vegetable protein lacks certain amino acids. So be it, if that is what you believe.
In the end, whether you feed a pellet or not is more of a lifestyle choice. If you have the time and resources to be very attentive and preparing a wide variety of fresh foods for your glider, and making sure they always have food that’s not spoiled to eat when they are hungry, then sure, do that. Some people do that for their dogs and cats. Great.
But please don’t go around shouting “pellets are bad” because it’s simply not true, unless:
1. People who do research on animal nutrition are in the habit of lying about what’s good and not good for the animals, including pellets for sugar gliders
2. Some of the most caring animal husbandry folks in the world, the people taking care of animals in zoos, are in the habit of routinely and intentionally hurting the animals they are responsible for, including feeding pellets to sugar gliders
Sorry for the length of this, wanted to have the whole story in one place for reference.