Queen bees may get most of the glory, but there is another queen of the animal kingdom who is the linchpin of her entire society. Queen naked mole-rats (Heterocephalus glaber) reign over their underground kingdoms as the bearer of all children, while other rats build and maintain a complex system to tunnels, find food, and take care of the queen’s babies.  When a queen’s fertility declines or disappears, the colony fights a bloody succession battle. However, that violent fight for domination does not always occur. Peaceful succession between reigning queens and subordinate females is possible within an established naked mole-rat colony during times of stress. The findings are detailed in a study published today in the journal Science Advances and upends a lot of what we know about the rodent’s flexibility and resilience.  A special lab rat Native to eastern Africa, naked mole-rats have been particularly fascinating to scientists for over half a century. They were first brought into the lab in the 1960s due to their unusual adaptations to life underground. By the 1970s, scientists discovered that they are among the only eusocial mammals. Eusocial animals like bees and ants live in a colony with strict hierarchies and a single child-rearing queen.  Naked mole-rats also stick out for other reasons. They have a fairly long life-span, with some living up to 30 years, can thrive in dark and dank underground tunnels, do not feel inflammatory pain, and are resistant to age-related diseases like cancer.  In the wild, naked mole-rats live in a relatively stable environment. With this stability and not having to worry as much about food and other resources, they can spend energy on their typically aggressive and rigid reproductive strategy. Scientists believe that this strategy reduces reproductive conflict and infanticide, while keeping resources pooled towards one litter at a time. However, with this strategy comes the risk of injury and disruptions to social cohesion. The colony’s growth also hinges on the ability of  one queen’s reproductive system.  Triggering succession For this study, the team focused on their eusocial structure and the rodents’ resilience in the face of trouble.  “Resilience is the ability of biological systems to recover or return to their normal state after stress and is central for our understanding of health and disease,” Janelle Ayres, a study co-author and Salk Institute biologist, said in a statement. “While much research focuses on conflict, my lab studies cooperation as a fundamental organizing principle.” According to Ayres, investigating how group cooperation drives resilience can reveal what allows biological systems to recover and function after a challenge like a queen’s reign ending.  “For years we’ve known that only one female, the queen, reproduces, and that queen succession occurs through violent queen wars,” added study co-author and postdoctoral researcher Shanes Abeywarden. “We wanted to see if multiple queens could peacefully exist.” To learn how they balance the pros and cons of their rigid reproductive strategy, they observed a naked mole-rat colony for six years. During the first year, the team established a healthy, reproducing colony with one queen in their lab. Next, they introduced consecutive environmental stressors—increased density within the colony and moving it to a new location. Both of these stressors have been shown to destabilize reproduction in other rodents. After increasing colony density, the queen still conceived and gave birth, but the pups had poor survival outcomes. However, the queen still remained the sole reproductive naked mole-rat. Moving the colony to a new facility, the queen’s reproductive success was completely compromised. She could no longer produce litters, which triggered succession.   Over the next year, the team watched as one subordinate female from the colony slowly inched toward the crown. Surprisingly, the queen and this subordinate female cooperated, even maintaining partially overlapping pregnancies to help the colony in the face of environmental stress. A second subordinate eventually emerged, taking over the queen’s place. The queen slipped peacefully into a nonreproductive role in the colony, during a gradual, nonviolent succession. “Our study reveals a ‘hidden’ side of reproductive organization in naked mole-rat colonies, which opens an entirely new line of inquiry when studying naked mole-rats,” added study co-author and biologist Alexandria Schraibman. Related Naked Mole-Rat Stories 4 wild ways animals breed Like humans, naked mole-rats have regional accents 9 jaw-dropping facts about naked mole rats to celebrate the bloody ascent of their new queen The naked mole rat’s furry cousin also feels no pain Only the resilient survive For scientists, this peaceful queen succession in naked mole-rat colonies is a significant step toward understanding how they adapt and thrive as one of the only eusocial mammals on Earth. In future studies they hope to find out more about what determines if succession is aggressive or peaceful and what ecological or social factors influence that decision. This surprisingly peaceful finding also helps explain the importance of biological resilience that all species can benefit from. “Resilience is the core principle for health and disease,” said Ayres. “By studying resilience in various biological systems, the principles can be applied to other systems to better understand health and disease.” The post Not all naked mole-rat queens go out in a blaze of bloody violence appeared first on Popular Science. ...read more read less