Obesity is a common problem in many species of pet animals, from dogs to rabbits to reptiles. Species which seem particularly prone to unhealthy weight gain include rats, rabbits, guinea pigs, skunks, hedgehogs, and some reptiles such as leopard geckos. The primary causes are usually twofold: overfeeding of improper diets excessively high in calories (especially fats), and/or too little exercise.
Regardless of the species, obesity is a significant health problem when it occurs. The best approach is simple: provide regular exercise, and feed controlled amounts of nutritious, low-fat food.
Diets for exotic pets vary depending on species
Grazing herbivores such as rabbits, guinea pigs, and chinchillas do best with very high-fiber and low-calorie food. They should be maintained on a diet of mostly grass hay (timothy probably being the leanest variety) fed free-choice at all times, along with a smaller measured amount of pelleted feed, and small amounts of fresh vegetables.
The commercial feed should be pellets only, not a seed/nut/dried fruit mix. The mixes are too high in calories, not nutritionally balanced, and contain excessive amounts of sugars, protein and fat which promote weight gain and risk of severe digestive upsets. Even a good pelleted feed can cause obesity if overfed; the amount should be tailored to an animal’s needs. In general, the pellets are only fed free-choice with young growing animals, or with pregnant and nursing females.
The vegetables fed to grazing herbivores should be limited to mostly leafy greens, avoiding plants in the cabbage family which can cause gas and bloating (such as cabbage, kale, Brussels sprouts, Bok Choi, broccoli, and cauliflower). Items high in sugars (fruits, carrots, corn, peppers, etc.) should be minimized to avoid life-threatening digestive upsets and weight gain. The same goes for items high in protein, such as beans, grains, tofu and so on. In general, if it’s not a leafy part of the plant, don’t feed it to an herbivore.
Omnivores like pet skunks and rats will eat nearly anything, but the diets need to be balanced and low in fat content. Rats do best on a low fat commercial ‘lab block’ pelleted feed; healthy treats such as vegetables or non-sweetened cereal can be fed in small quantities. Skunks can be maintained on a mix of very low fat ‘diet’ dog food plus low calorie vegetables (especially leafy greens). Amounts must be carefully restricted with skunks, as they are extremely prone to obesity in captivity. Encouraging exercise can be helpful too; skunks tend to be inactive by nature and often become lazy if allowed to be.
Hedgehogs and sugar gliders are primarily insect-eating carnivores (insectivores) in the wild; the best captive diets are very low fat pelleted feeds designed for these species. Both gliders and hedgehogs now have good pellet diets available which reduce the tendency for obesity, while providing all the essential nutrients for good health.
Homemade diet mixes may lack key nutrients, and some are too high in calories as well. Insects sold as food for insectivores are often nutritionally poor and very fatty; examples include mealworms, king mealworms, ‘superworms’, and waxworms. These should be mostly avoided, although the common earthworm and garden slug are fairly nutritious, and can be used as live prey ‘treats’ for hedgehogs and gliders in captivity.
Gliders are active animals and need very large spacious cages to allow adequate exercise; having daily exercise time outside the cage is also recommended. Hedgehogs do well with an exercise wheel in the cage which allows them to run whenever they want; some rodents such as hamsters also will take advantage of a wheel.
Some carnivorous reptiles such as leopard geckos are voracious eaters and easily become obese. Leopard geckos primarily eat insects in captivity; this leads to problems when the insects are too fatty or if the animal is allowed to overeat. Earthworms, slugs, and calcium-enriched crickets are decent food choices; minimize mealworms (all varieties) and waxworms.
Obese reptiles can actually develop severe illness due to accumulation of excessive fat and cholesterol in their organs.