09/06/2006
Buck-Toothed Tunnelers
Remember in last week’s column my warning never to try to charge a nonrechargeable battery? OK, you’re right, there was no such warning; however, there should have been. This week I found in my October issue of Consumer Reports that a safety alert has been issued for the HP Photosmart R707 digital camera. If you put a nonrechargeable battery in the camera and put the camera in its docking station, a glitch in the “firmware” may result in charging of the battery. One case of a fire has been reported. HP says an update to the firmware will remedy the problem. (If you happen to own this camera, Consumer Reports gives a number, 866-304-7117, to call for information.)
Speaking of batteries, the battery in my trusty 1997 Volkswagen Jetta will have been in service precisely five years next Monday, September 11. I remember the date well, having had the battery installed between the times that the first and second planes hit the World Trade Center. I’m impressed the battery has lived these five years and wonder if I should be prudent and purchase a new one before winter sets in. Guess I’ll opt to go for six years.
Perhaps it’s my age but long lives seem to have been a recurrent theme recently. At our Old Guard meeting last week one member was celebrating his 103rd birthday. Then I read that the oldest person in the world, I believe she was in South America, died at the age of 116. An article by Joe Treen in the September/October AARP magazine discusses the science of aging and cites Edward Rondthaler, 101, as a centenarian who still writes songs, children’s books and a weekly letter to the editor for his local newspaper. The article has a picture of a man holding a turtle. I’m not sure if it’s Ed and, if so, why the turtle? The picture reminded me that I had failed to note the death within the past year of Harriet, at over 170 the world’s oldest known living animal. Harriet was a Galapagos tortoise that may have belonged to Charles Darwin at one time. She didn’t look a day over 100.
In the AARP article, Treen compares old Ed Rondthaler with the naked mole-rat. It seems that the naked mole-rat and Ed share the longevity thing. The mole-rat lives to 20 –30 years, up to 10 times longer than mice of the same size and scientists are trying to figure out why. Treen discusses various theories and studies on the factors that enter into living long. We’ve discussed some of these in earlier columns. For example, restricted diets and gene manipulation are two approaches that have significantly increased lifespans in various subjects ranging from mice to nematodes.
I was going to expand on the aging theme but then I searched for more on the naked mole-rat on the Web sites of the Smithsonian National Zoological Park, Cornell University and Davidson College. I found the naked mole-rat to be a fascinating critter with a lifestyle more like that of the ant or the bee than any rat or mole. Indeed, the naked mole-rat isn’t closely related to either a mole or a rat. Its closest relatives are porcupines, chinchillas and guinea pigs.
There are over 30 other species of animals known as mole-rats that hardly resemble the naked mole-rat, which is the only mole- rat that has virtually none of the typical rodent fur – hence, the “naked”. Jill Locantore, in an article on the National Zoo Web site, describes the naked mole-rat as resembling an “overcooked hot dog with buck teeth”. The four buck teeth, two upper and two lower, actually lie outside the mouth and are superbly adapted for digging tunnels. The naked mole-rat’s mouth can close behind the teeth so it doesn’t swallow dirt while digging. The wrinkled skin reminds me of one of those crinkly dogs, whose breed I’ve forgotten. The skin is so thin that you can see through it and make out some of the naked mole-rat’s organs. The animal itself can’t see worth a hoot. It has evolved in a world of darkness living in its underground tunnels.
The naked mole-rat is found in the wild only in arid regions in the horn of Africa in countries such as Ethiopia, Somalia and Kenya. In this part of Africa there are plants having large underground roots and tubers, some of which are the size of a soccer ball. The wise naked mole-rat eats out the center but leave the skin essentially intact. This lets the plant regenerate the tuber, providing another succulent meal for the mole-rat, which doesn’t drink water, getting all its water from the plants.
But it’s the social behavior of the naked mole-rat that is most interesting. The organization of a naked mole-rat colony is more like that of an ant or a bee colony than that of any other mammal. The naked mole-rat colony, which may number between 20 and 300 mole-rats, has a queen that rules with an iron hand. The queen has a harem, so to speak, of a few selected males. When she’s in the mood to mate, she’s the one who initiates the process. When she ascends to the throne, the queen becomes significantly larger than the other members of the colony. She needs this extra volume to handle the large number of offspring she will produce.
Paul Sherman at Cornell and his colleagues observed one naked mole-rat queen that gave birth to as many as 28 pups in one litter and had a total of over 900 in her lifetime! Only 10 to 11 weeks are required to bring a litter to term; thus a queen can produce 4 or 5 litters a year. My impression of the life of a bee queen is that she mostly lolls around laying eggs and being attended by her subjects. Not so the naked mole-rat queen. She takes an active interest in the detailed workings of the colony and will leave her nest to see how things are going. If she comes upon a blocked tunnel or if the food supply is running low, she’ll nudge and prod her subjects to get to work to remedy the situation.
She also actively discourages any hanky panky in the ranks by breaking up prospective romantic encounters among her subjects. Her strategy here seems to be to engage in a lot of nose-to-nose pushing and shoving with those members of the colony that are ready for sexual activity. The researchers don’t know how the queen enforces celibacy among her subjects but speculate the pushing and shoving create stress that may affect the hormone balance in both males and females.
The diet of the naked mole-rats is primarily the roots and tubers. When a tunnel-digging member of the colony finds a food source, it will bite off a chunk and carry it back to the colony, chirping and holding the food aloft for all to sniff. A stream of colony members then sets off, apparently following a scent trail, to bring back food for the colony. The mole-rats also have the distressing habit of re-ingesting their feces, presumably to get the maximum amounts of nutrients from their food. Also, if a pup dies, they depart from their vegetarian diet and eat the dead pup.
What happens when the queen dies? Things get messy and the high-ranking females, typically the soldier mole-rats, fight it out with each other. Sometimes females die in these fights, which may last weeks or months before one hardy female becomes the clear winner and becomes queen. I was intrigued by a less violent approach to becoming queen. It seems that occasionally a relatively fat and lazy naked mole-rat will one night decide to leave the colony and strike out on its own, searching for a similarly inclined mole-rat of the opposite sex. The two mate and start a new colony.
I think we may be having hot dogs tonight. I’ll try not to think of them as naked mole-rats!
Allen F. Bortrum
|