January 2023

In this VETgirl online veterinary continuing education blog, Amy Johnson, BS, LVT, RLATG, CVJ, VETgirl Manager of Content Development, reviews small exotic mammal information for veterinary professionals. Read on as she outlines some of the more important things that all veterinary professionals need to know about these species. Don’t forget to read PART 2 HERE to learn more about guinea pigs, ferrets, chinchillas, and rabbits too!

By Amy Johnson, BS, LVT, RLATG, CVJ
VETgirl Manager of Content Development

What You need to know about Small Exotic Mammals: Part 1

It is easy to think that working in small animal medicine means you won’t be seeing small little creatures (other than puppies and kittens, of course), but there will come a time when a small exotic mammal (a better term than pocket pet) will walk through your doors needing medical attention. In this VETgirl online veterinary continuing education blog, Amy Johnson, RLATG, LVT, CVJ outlines some of the more important things that all veterinary professionals need to know about these species.

Whether you are working in a small animal veterinary practice that sees some exotics, a veterinary emergency practice that may see a sick hamster or rat come through your doors on occasion, or a large animal vet out on a farm call asked to look at the sick 4H rabbit (rabbits covered in part 2) these little guys will come into your life and there are some basic things you need to know about rats, mice, hamsters, and gerbils to help treat them and educate their owners.

Here are some of the basics:


Portrait of a curious gray rat isolated on white background
• Life span: 2-4 years
• Gestation: 19-21 days
• Rats are highly intelligent and easily trainable animals and make great pets! If recommending a small exotic mammal as a pet for a family, I would recommend a rat over a hamster 100% of the time.
• They are also highly social creatures and either need a lot of attention from their human companions or they need another rat for companionship. Being lonely or neglected by their humans will cause aggression and other problems.
• Rats have a gland in the back of their eye orbit called Harder’s Gland (or the Harderian Gland). This gland secretes reddish/brown pigments called porphyrins. When porphyrins are secreted, they will drain through the eye and nasolacrimal duct, resulting in red color on or around their eyes, nose, or front limbs (due to grooming). This condition is known as chromodacryorrhea, commonly called “Red Tears,” and will cause alarm in owners who think it is blood. Although the secretion of porphyrins is not a disease condition, it is a sign that the rat is under some sort of immunological or environmental stress that must be addressed.
• Like many other rodents, rats have continually growing incisors. They need a hard pellet diet and things in their environment to chew on that will help file their teeth down naturally. If their incisors are allowed to overgrow, it will result in malocclusion, malnutrition, and if not corrected death. Teeth that get too long can be trimmed or filed down by someone who knows how to do it, but with the right diet and environmental enrichment this should not be necessary.
• Restraint and sexing video HERE


Brown mouse sitting on a white background
• Life span: 2-3 years
• Gestation: 19-21 days
• There are many similarities between mice and rats. Although mice are not as common as pets, they will potentially come into our practices.
• Just like rats, mice are very social creatures and do better in a small group, although avoid over-crowding, or you will have a whole different set of problems.
• Mice are very active animals and need some way to exert their energy. Wheels in the cage or balls to run around in are great options. Mice are also very prone to obesity, and this exercise helps with that as well.
• Mice also have continually growing incisors that need to be maintained like the incisors of rats.
• Restraint and sexing video HERE


Golden Hamster in front of white background
• Life span: 1-2 years
• Gestation: 14-18 days
• Hamsters have a flank gland on either side of their dorsal body, used for scent marking. These glands are black and commonly confused with tumors, especially melanomas. Don’t remove these and send out for histopathology!

Hamster in the bottom of a cage with the flank gland being pointed out.
• Hamsters, unlike other rodents, are solitary creatures. They do much better independently and will often kill their partners (females are notorious for this).
• Hamsters are the most likely small exotic mammal to bite when handled and they are carriers of Clostridium. For these reasons, they should not be recommended as pets for young children.
• Their incisors will also continually grow and need to be maintained like the teeth of rats and mice.
• Restraint and sexing can be found in this video HERE


Fluffy cute rodent - gerbil on neutral background
• Life span: 2-4 years
• Gestation: 24-26 days
• Gerbils have ventral scent glands that look like a small patch of hairless scar tissue mid-thorax. Although these glands are commonly associated with carcinomas in gerbils, do not mess with them unless they change in appearance – usually becoming enlarged or ulcerated if there is a problem.

A male gerbil being restrained so his ventral scent gland is visible.

• Tail degloving is a common injury in gerbils, which means their tails should be handled with care and gerbils only picked up by the BASE of the tail. If there is a degloving injury, it will not heal well and leave the gerbil open to infection. The tail should be amputated for best case results.
• Seizures are also common in gerbils. No need to intervene with drugs, just give them a quiet, dark room to recover.
• Like everyone else on the above list their incisors will continually grow and need the appropriate diet and environmental enrichment to maintain them.
• Restraint and sexing can be found in this video HERE

This is by no means a full list of what veterinary professionals need to know about these species, but this will give you the basics to help when they coming through your doors. Don’t forget to check out Part 2 next week HERE!

What do you wish you knew about these species before encountering them in practice? Tell us below in the comments!

*Life spans and gestation periods will vary slightly from source to source. 


Laboratory Animal and Exotic Pet Medicine, 3rd Edition by Margi Sirois, EdD, MS, RVT, CVT, LAT, VTES

Small Animal Pathology for Veterinary Technicians by Amy Johnson. BS, LVT, RLATG, CVJ



  1. As far as proper nutrition- what resources do you recommend for our education? Lafeber seems a little older (some species haven’t been updated since 2007, but maybe because there’s no new information?)

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