Friday, September 16, 2011

Mole-rats Get Inked

If someone told you a naked mole-rat was getting a tattoo, would you imagine something like this?

Do you get images of pink rodents donning biker gear and going a bit wild? While this would make a colorful blog article, the truth is almost as interesting and a bit more plausible.

Why we needed a marking system

Pacific Science Center’s animal care staff keeps individual weight and health records for each naked mole-rat in the colony. This involves capturing and weighing them, but it also requires us to color mark each animal each time we weigh them. Over the course of a few weeks, the markings fade and identifying the mole-rats becomes a time consuming and stressful task for both the markers and the mole-rats. After a few years of the color marking method, we began to wonder if there were a more permanent marking system that would allowed us to recognize each animal at a glance.

What we chose

Tattooing fit the description, but there were some down-sides to it as well. It is more invasive than marking on the skin. Also, because most tattoo colors fade or look similar, we would be limited to only using black ink. The benefits, however, outweighed the risks. We chose a date during our annual closure in September and scheduled a mass inking session with our vet, Dr. Maas of The Center for Bird and Exotic Animal Medicine.

The tattooing process

After being weighed and positively identified, each naked mole-rat was briefly anesthetized for the procedure using isoflurane gas. Their skin was cleaned, and dots of ink were injected under the skin in key areas that would allow us to recognize the individual and give us details about his or her identity.

After tattooing, the animal’s skin was cleaned again and treated with antibiotic ointment. The mole-rats were monitored as they came out of anesthesia and then returned to the exhibit.

All seem to be doing well.

What each mark means

The animals in our colony range in age from over 15 years old, to pups born in August of this year. During that time, there have been several queens with successful offspring who are now part of the colony. We wanted our markings to help us keep track of which mole-rats came from which mother, and how old the various animals are.

The number of spots on the back of the neck indicates who the animal’s mother was. The spots on the rump allow us to identify which litter they are part of.

For individual identification, male mole-rats were marked on a left limb, females on the right. We used combinations of one or two spots on the front or hind limb, so that each animal could have a unique marking.

How the animals handled the experience

By day’s end, the naked mole-rats were fully recovered from anesthesia and were back in the colony chamber. Galinda had been briefly separated from her most recent pups, born in late August. But when she was returned to the colony, they recognized her immediately and started to nurse. We watched the mole-rats closely for signs that the ink sites were itchy or painful, but all appeared well.

By the next morning, the ink spots had spread slightly from when they were first injected. Dr. Maas predicted that they would first enlarge, and then fade slightly into distinct spots. We will monitor the colony closely for any complications, but for now it appears that the tattoos are healing well and will serve to identify the individuals in the colony for years to come.

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