In field captured social Damaraland mole-rats from Tswalu Kalahari Nature Reserve, physiological suppression amongst subordinate non-reproductive females eases markedly during the annual rains, despite the presence of the dominant female and in colonies containing no new immigrant males.
Non-reproductive females show substantially higher pituitary sensitivities to GnRH challenges during the wet period than compared to the dry while in the confines of the colony. These changes cannot be attributed to between female differences, variation in body mass or concomitant reductions in physiological stress. We suggest the findings reflect selection for reproductive readiness among subordinate females during periods of rainfall when ecological constraints on dispersal are relaxed.
For more information contact: Andy Young, Centre for Ecology & Conservation, University of Exeter, UK, A.J.Young@exeter.ac.uk
The Secret Societies of the Saber-toothed Sausage (Dr Andrew Young)
I raised the sand-caked door of the day’s last trap, to be greeted by the familiar toothsome grin of a Damaraland mole-rat, busy demolishing the sweet potato bait that I had set just an hour before. Having verified her identity and taken a range of measurements, I returned her to the burrow system and headed back to camp, pondering the lives of these remarkable creatures.
These endearing sabre-toothed sausages live in some of the most complex societies known, with a breeding system similar to that of the ants and bees, in which a single dominant female monopolises reproduction while a host of subordinates help to rear her young. My team and I have been following the fates of thirty such extended families in the red sands of Tswalu for the past three years, and our work is now yielding valuable new insights into the evolution and dynamics of cooperative societies. Most exciting is evidence that, like the bloated ‘egg-factory’ queens of many ants and termites, the bodies of dominant female Damaraland mole-rats are also specialized for their privileged breeding role within society - a phenomenon described only once previously outside the insects. Further, the dominant’s distinctive body shape appears to arise not from a pre-existing difference between females that become dominant and those that do not, but from a marked change in a female’s growth trajectory on dominance acquisition. These findings, recently published in the journal Evolution, reveal that such ‘morphological specialisation’ is more widespread among vertebrates than previously supposed, and highlight new depth to the remarkable parallels between insect and mammalian societies.
Dr Andrew Young is a Research Fellow at the University of Exeter’s Centre for Ecology & Conservation, and has been working in the Kalahari for over a decade studying cooperation and conflict in the societies of meerkats, mole-rats and white-browed sparrow weavers. His long-term research at Tswalu is supported by the Royal Society and the Natural Environment Research Council. |
