Mechanism

One of the best ways to understand what traits H. glaber utilize is to examine the changes that occur in subordinate helper females once the dominant female dies and similarly what shifts in subordinate males once breeders are made impotent. Because only one female mates in a colony that is 30-60 individuals, the death of a queen is a big event in a den, and the other females respond accordingly (9).

Behavior

The queen maintains her dominance by behavioral cues, mainly through shoving and walking all over the subordinate mole-rats (5). Instances where a mole-rat shoved another or walked over one indicated a higher social ranking of the mole-rat. Social rank was also based off of incidences of genital nuzzling, lordosis, or copulation (16). There are three basic ranks: the highest is the queen, the second are non working, non breeding females and the third are the working males and females.


The authors show that once a queen is removed, the females that in the higher part of the subordinate colony start acting like the queen, vying for reproductive status by trying to be the biggest bully of the bunch. These researchers show that although olfactory cues and gondatropins aid in establishing dominance, the strongest factor is that of behavioral cues (8, 16). This transition is rapid and violent (9). Those who begin to ovulate during that transition period will engage in fatal aggression. In naked mole-rat society, after all, there can be only one (18).

To learn more, see the Ontogeny page.

Morphology

The queen is larger and fatter than all the other females, and if she is removed, the metabolic changes in females are drastic. The second level begins to eat much more and gain 18.7% more body mass. They begin to show typical female rodent dimorphism, although only the new queen will develop a perforated vagina. Males also begin to gain mass, but their gain is not as drastic, although it is significant (5, 7).

One of the most amazing shifts that occurs is the lengthening of the new queen’s vertebrae during pregnancies (9). Body size is directly correlated to social standing in the hierarchy, and the largest workers are more likely to become the new queens because they can shove more (17).

However, even smaller female mole-rats can achieve reproductive with huge lumber growth that can allow for her to function in her society. As the researchers that discovered this phenomena explain, the queen provides is responsible for all reproduction, and so litter sizes are more favorable if they are large. However, the naked mole-rat queen depends on her behavioral cues to remain dominant and so she cannot be limited to her nest during pregnancy. Increasing lumbar length allows for all elements to be accounted for (9).

To learn more, see the Ontogeny page.

Horomonal

Although there is not much controlled experimentation of gonadal hormones on reproductive bonding or suppression of reproduction, observations and baseline measurements give an idea of how gondatropins and pheromones function in H. glaber society.


It’s not surprising to learn that the baseline levels of estrodiol and progesterone in females and testosterone in males is higher in breeding pairs, but the relationship between hormones and reproductive status is still very unclear (8). For example, queen females will start secreting large concentrations of luteinizing hormone (LH) when injected with gonadaltropin releasing hormone (GnRH) (18). When dominant pairs receive gondactomies, there is a increase in genital nuzzling and mating behaviors, although these instances are rare and the other morphological changes that occur when a queen dies or a naked mole-rat attempts to establish a new colony. Genital nuzzling was reduced through gondactomies in the dominant pair, but it was not eradicated, nor was the monogamity of mate choice (8). When subordinate pairs were removed from chemical and physical contact of the dominant pair, both male and female become sexually active and will begin breeding in around eight days after removal with levels of gonadotropins slowly increasing to the original breeding pair's levels (5,6).

To learn more, see the Ontogeny page.