Sand Puppies
Badly misnamed, “naked mole rats” live in the grasslands of East Africa. Their entire existence is subterranean.
The naked mole rat is more aptly called a sand puppy by the locals.
They are neither moles, nor rats; but they are naked. And they do look a bit like puppies if you are half blind, which they are.
Sand puppies have no fur. Fur would be a serious disability for a lifestyle living in the dirt.
The sand puppy has several adaptations that give the good life to be had from rooting around underground. The desert sand puppy is an excellent example of hand-in-glove adaptation to a habitat.
Sand puppies have no pain receptors in their skin, which is otherwise unknown for rodents.
Sand puppies have an almost ectothermic metabolism. Because they cannot regulate their body heat, sand puppies need a habitat with a highly stable temperature.
Sand puppy lungs are tiny, and their respiration rate extremely low: helpful for living inside tunnels, where air supply is limited. To compensate, sand puppy blood has a high affinity for oxygen, thereby making the most of stale air.
A sand puppy also has a modest metabolism. Low metabolism and breathing efficiency mean that aging by oxidative processes is minimized. One consequence is that cancer is unknown in these animals.
Sand puppies sleep a lot. Thanks to their lifestyle, sand puppies are especially long-lived for a rodent: only 3 years for hard-scrabbling workers, but up to 3 decades for breeders.
The sand puppy and the Damara mole rat are the only known eusocial mammals. A sand puppy colony has a single breeding queen, along with 1 to 3 breeding males among the 20 to 300 individuals in a colony; membership of 75 is average. Reproductivity in other females in the colony is suppressed by a pheromone secreted by the queen.
Food is hard to find in the parched terrain where sand puppies live. A solitary puppy would not survive. Eusociality solved several problems that ensured species survival.
Besides the queen, who sole task is procreation, sand puppies perform different roles at different ages, appropriate to their aptitude. (It was once thought that sand puppies have a strict caste system, like eusocial insects. Instead, Austrian zoologist Markus Zöttl explains, “mole rat social organization has more in common with the societies of other cooperative mammals, such as meerkats and wild dogs, than with those of social insects.”) The young attend to the queen.
Diligent and robust rats act as soldiers, standing watch against predators. Odor distinguishes friend from foe.
A solitary sand puppy is a snack to a desert snake, but a snake invading a sand puppy tunnel will meet a fierce defense.
Sand puppies nearby attack en masse. If one manages to sink its teeth into the snake, it will the drag the snake deeper into the tunnel, where the snake is gnawed to death.
The smallest adult sand puppies are laborers: digging for food and maintaining the burrows. Workers chew their way through hard soil in hopes of a robust root to feed the colony back home.
Eating dirt is no fun, even for a sand puppy – so a worker will tuck a block behind its teeth before gnawing its way to a tremendous tuber. The block acts as a barrier to dirt or other debris that could choke an industrious puppy.
For a barrier block a sand puppy picks a suitably sized wood sliver or bulb husk shaving. A puppy will pause to reposition his block as needed. A block is replaced when it becomes worn.
