Friday, September 5, 2014

Mole Rats At Work

Animal Care Volunteer Maurice Warner is a perceptive observer of our naked mole rat colony. Recently, he submitted the following story that helps explain our colony’s curious behavior.

Most of us think our naked mole rats are cute as they hustle about in their plastic tube colony, but you might be surprised to discover they’re often hard at work, each with a specific job to do. When I began working as an animal care volunteer, I assumed our exhibit colony was too small and too different from a wild colony of mole rats to reveal much about mole rat behavior. Turns out I was wrong.

Scientists who have carefully studied both wild and exhibit colonies describe a three caste social system. The “reproductive” caste includes the queen (or in our case two queens) and each queen’s one to three male consorts. The “soldier” caste is made up of the larger, non-reproductive animals, both male and female. The third, or “housekeeper” caste is composed of the smaller adults, again, both males and females.

Sometimes when I watch closely I notice mole rats doing their caste “jobs”. Also, I sometimes make small changes to the colony system to enhance mole rat behavior. If you watch the colony via our web cam you may see some of our industrious naked mole rats at work.

The housekeepers are the easiest to spot. Their jobs include keeping the tunnels clear for safe passage, and discovering new food sources. When I place some loose bedding material into one of our colony’s plastic tunnels the small animals quickly removed it – usually by walking backward and pushing the material out of the tunnel with their hind feet. (Did you know naked mole rats have hairs between their toes that make them more effective shovelers?) Finding new food sources is another very important housekeeper job in wild colonies. When they find food, they communicate its location to the rest of the colony through both vocalizations and scent trails. The housekeepers also carry small bits of food back to the nest chamber where it is eaten by other animals. When I place bite-sized pieces of carrot or grapes in the plastic tunnels, watch what happens! The larger animals rarely carry food back to the nest – they eat it in place. Carrying food is a job for housekeepers, not soldiers.

The soldiers’ job is to defend the colony against intruding snakes or mole rats from other colonies. Our exhibit colony never faces the threat of dangerous intruders, so it’s very hard to see our soldier attack. However, soldiers do not shy away from the occasional intruding Animal Caretaker when it’s time for weighing or changing bedding. And since they’re the larger animals, soldiers are the strongest diggers. Our exhibit colony can’t dig new tunnels but if I place significant obstructions in the tunnels – like a large cork that completely blocks a tunnel – the housekeepers are likely to first discover it and initially attempt to clear it away. But soon the larger animals move in from both ends of the obstruction and chew away at it in a frenzy that lasts until the obstruction is removed.

The reproductive caste mole rats, the queens at least, have one other important role in addition to producing new pups. The queen is the work boss. You may notice her conducting inspection tours to see what work needs to be done, or shoving other animals around. Laboratory research has demonstrated that colonies with the most “pushy” queens actually function most effectively! So she’s not nasty, she’s just doing her job.

If the naked mole rat caste system sounds more like bees than rats, you’re right! It is very unusual for a mammal that lives in groups to have differing behavioral roles that are not based on gender or age. Think about lions for example. If you’re curious about how mole rats got that way, you might want to do some naked mole rat research of your own. “The Naked Mole-Rat Mystery” by Jarrow and Sherman is a good place to start.

Unusual behavior is just one of the things that delights me about our naked mole rats. They’re not naked, not moles, not rats, and not insects either, but I love them!

Maurice Warner

Volunteers like Maurice observe interesting phenomena every day at Pacific Science Center. If you love science and would love to share your enthusiasm with like-minded people, consider volunteering in our Science Interpretation Program. Training begins soon.

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