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The Naked Mole-rat Pups Have Doubled in Size

  • Adult naked mole-rats and pups sleeping together in a pile.
    The naked mole-rats sleeping in a pile Jan. 30. The pups born in December are about the size of baby carrots and slightly darker in color.
  • The adults and pups in the naked mole-rat colony sleeping together in a pile Jan. 30. Naked mole-rats sleep in piles to stay warm.
    The adults and pups in the naked mole-rat colony sleeping together in a pile Jan. 30. Naked mole-rats sleep in piles to regulate their body temperatures and stay warm.
  • Adult naked mole-rats and their pups sleeping in a pile Dec. 25, 2019.
    The pups and adults sleeping together in a pile Dec. 25, when the pups were one-week-old.

We’re happy to welcome you back from our unscheduled break in naked mole-rat viewing! Life in our naked mole-rat colony has bustled on during the past three-and-a-half weeks. The four naked mole-rat pups are now six weeks old and they have doubled in size. When they were born they were about the size of jelly beans. Now, they are the size of baby carrots. If you tune into the naked mole-rat cam they will look and behave very differently than they did at even two weeks old. They have weaned and are no longer nursing. Though naked mole-rats are extremely long-lived for a species of rodent (they can live for up to 30 years), they still mature very quickly. They are also moving around on their own, and don’t depend on the workers in the colony to keep them near the queen.

Life in the colony has seemed to settle down significantly since the pups were born. Everyone seems to be following orders from the queen (long may she reign!) and doing their assigned jobs. As eusocial mammals, meaning they live in colonies with social structures similar to insects, every naked mole-rat has a job. The queen is the only female who breeds; she is larger than all the other mole-rats in the colony and she will only breed with certain males. The rest of the mole-rats in the colony protect and care for her. The workers dig tunnels and help care for pups and the queen, and soldiers are larger and help defend the colony from invaders.

It seems for now, the mole-rat wars to select a queen have finished. When the colony first arrived at the Zoo several months ago, they had not chosen a queen. One female seemed to be well-poised to take the throne, however, as she was much larger than the rest of the mole-rats. And take the throne she did. That process can be bloody sometimes. If a female mole-rat is vying to become queen, she must not only be the largest female in the colony, but she also must fight off any challengers. Those fights are often to the death. And a queen could potentially be challenged by another female at any time.

Since the queen has had pups, keepers expect that she will give birth again relatively soon. The average gestation for naked mole-rat pups is 70 days, and a previous colony’s queen at the Small Mammal House gave birth every 90 days. For the foreseeable future, keepers will always assume that the queen is pregnant or will be shortly. They also expect that the number of pups in the future litters will grow with each pregnancy. Naked mole-rats usually have between five and 10 pups in each litter, but experienced queens can have over 30! The queen can give birth to such large litters because she gets a little bigger after each pregnancy. Her spine (the actual space between her vertebrate) gets a very tiny bit longer, which allows her to grow longer and have more pups.

Keep watching the naked mole-rat cam! It is likely that the pups born in December and any new pups will be visible on the cam.